Improved methods of coating dry proppant particles with a hardenable resin composition, suspending the coated proppant particles in a fracturing fluid and consolidating the proppant particles after being placed in fractures into high strength permeable masses are provided. As the fractures are formed, a liquid hardenable resin component is mixed with a liquid hardening agent component to form a hardenable resin composition. The hardenable resin composition is coated onto dry proppant particles conveyed from a source thereof to form resin composition coated proppant particles, and the resin composition coated proppant particles are suspended in the fracturing fluid.

1. Field of the Invention
The present invention relates to improved methods and compositions for consolidating proppant in subterranean fractures formed by a gelled liquid fracturing fluid.
2. Description of the Prior Art
Hydrocarbon producing wells are often stimulated by hydraulic fracturing treatments. In hydraulic fracturing treatments, a viscous fracturing fluid which also functions as a carrier fluid is pumped into a producing zone to be fractured at a rate and pressure such that one or more fractures are formed in the zone. Particulate solids, e.g., graded sand, for propping the fractures, commonly referred to in the art as xe2x80x9cproppantxe2x80x9d are suspended in a portion of the fracturing fluid so that the particulate solids are deposited in the fractures when the fracturing fluid is broken. That is, a breaker is included in the fracturing fluid whereby the fracturing fluid reverts to a thin fluid which is returned to the surface. The proppant deposited in the fractures functions to prevent the fractures from closing so that conductive channels are formed through which produced hydrocarbons can readily flow.
In order to prevent the subsequent flow-back of proppant as well as loose or incompetent sand in the fractured zone with fluids produced therefrom, a portion of the proppant introduced into the fractures has heretofore been coated with a hardenable resin composition which is caused to harden and consolidate the proppant particles in the zone. Typically, the hardenable resin composition coated proppant is deposited in the fractures after a large quantity of uncoated proppant has been deposited therein. That is, the last portion of the proppant deposited in each fracture, referred to in the art as the xe2x80x9ctail-endxe2x80x9d portion, is coated with the hardenable resin composition. When the viscous fracturing fluid which is the carrier fluid for the proppant is broken and reverts to a thin fluid as described above, the hardenable resin coated proppant is deposited in the fractures and the fractures close on the proppant. The partially closed fractures apply pressure on the hardenable resin coated proppant particles whereby the particles are forced into contact with each other while the resin composition hardens. It has heretofore been thought that the hardening of the resin composition under pressure brings about the consolidation of the resin coated proppant particles into a hard permeable pack having sufficient compressive and tensile strength to prevent unconsolidated proppant and formation sand from flowing out of the fractures with produced fluids. However, it has been found that as the fracturing fluid containing proppant without a hardenable resin composition coating thereon is carried into the fractures by the fracturing fluid, some of the proppant is continuously deposited in the bottom of the fractures adjacent to the well bore. This unconsolidated accumulation of non-resin coated proppant remains in the fractures adjacent to the well bore and when the hardenable resin coated proppant enters the fractures at the end of the proppant deposit, it does not displace the uncoated proppant at the bottom of the fractures. Instead, the hardenable resin coated proppant flows over the uncoated proppant. This results in unconsolidated proppant at the bottom of the fractures adjacent to the well bore. During the subsequent production of formation fluids through the propped fractures, the unconsolidated proppant at the bottom of the fractures flows back with the formation fluids. The flow-back of the proppant with the formation fluids is very detrimental in that it erodes metal goods, plugs piping and vessels and causes damage to valves, instruments and other production equipment.
Another problem encountered in the use of prior hardenable resin compositions for coating proppant particles is that the hardenable resin composition components, i.e., the liquid hardenable resin component and the liquid hardening agent component, have heretofore had very short shelf lives. That is, the shelf lives of the hardenable resin composition components have heretofore been as short as about four days or less. In addition, the hardenable resin composition components have heretofore had very low flash points, i.e., flash points of about 60xc2x0 F. or below making them very dangerous to use.
Thus, there are needs for improved methods of consolidating proppant particles in subterranean fractures whereby all of the proppant particles are consolidated into high strength permeable packs in the fractures which do not permit the flow-back of proppant, formation sand and the like. Further, there are needs for improved hardenable resin compositions and/or the components thereof that have long shelf lives and high flash points, i.e., flash points above 125xc2x0 F.
The present invention provides improved methods of coating dry proppant particles with a resin composition and suspending the coated proppant particles in a fracturing fluid as well as improved hardenable resin compositions and components thereof which meet the needs described above and overcome the deficiencies of the prior art. The resin compositions of this invention harden and consolidate resin coated proppant particles into high strength permeable packs in fractures formed in subterranean zones which do not allow proppant flow-back. The methods are basically comprised of the following steps. A liquid hardenable resin component is provided comprised of a hardenable resin and optionally, a solvent for the resin. A liquid hardening agent component is provided comprised of a hardening agent, a silane coupling agent, a hydrolyzable ester for breaking gelled fracturing fluid films on the proppant particles, a surfactant for facilitating the coating of the resin on the proppant particles and for causing the hardenable resin to flow to the contact points between adjacent resin coated proppant particles, a liquid carrier fluid and optionally, a viscosifying agent for viscosifying the carrier fluid and dispersing the hardening agent when the hardening agent is a particulate solid. In addition, a source of dry proppant particles and a gelled liquid fracturing fluid are provided. The gelled liquid fracturing fluid is pumped into a subterranean zone to form one or more fractures therein and to place the hardenable resin composition coated proppant particles in the fractures. As the fractures are formed by the fracturing fluid, the liquid hardenable resin component is mixed with the liquid hardening agent component to form a liquid hardenable resin composition. The liquid hardenable resin composition is continuously coated on dry proppant particles conveyed from the source of the dry proppant particles. The resulting hardenable resin composition coated proppant particles are continuously mixed with the fracturing fluid whereby the hardenable resin composition coated proppant particles are suspended in the fracturing fluid and are deposited in the one or more fractures formed wherein they are caused to harden and consolidate into a high strength permeable pack which prevents proppant flow-back. When the hardenable resin composition coated proppant particles have been placed in the one or more fractures, the pumping of the fracturing fluid, the mixing of the liquid hardenable resin component with the liquid hardening agent component, the coating of the dry proppant particles with the hardenable resin composition and the mixing with and suspending of the resin composition coated proppant particles with the fracturing fluid are terminated. The hardenable resin composition on the coated proppant particles is allowed to harden and to consolidate the proppant into one or more high strength permeable packs which prevent proppant flow-back.
Another improved method of the present invention for coating dry proppant particles with a resin composition and suspending the coated proppant particles in a fracturing fluid, the resin composition hardening and consolidating the resin coated proppant particles into a high strength permeable mass which prevents proppant flow-back after being placed in one or more fractures formed in a subterranean zone is comprised of the following steps. A liquid hardenable resin component as described above and a liquid hardening agent component as described above are provided along with a source of dry proppant particles and a gelled liquid fracturing fluid. The gelled liquid fracturing fluid is pumped into the subterranean zone to form one or more fractures therein and to place the hardenable resin composition coated proppant particles in the fractures. The liquid hardenable resin component is mixed with the liquid hardening agent component to form a hardenable resin composition. The volume ratio of the liquid hardening agent component to the liquid hardenable resin component is varied from an initial volume ratio to a lower volume ratio and then back to the initial volume ratio in order to consolidate all of the proppant particles in the fractures while conserving the amount of the liquid hardening agent component used. The hardenable resin composition is continuously coated onto dry proppant particles conveyed from the source thereof to form hardenable resin composition coated proppant particles. The hardenable resin composition coated proppant particles are continuously mixed with the fracturing fluid so that the hardenable resin composition coated proppant particles are suspended in the fracturing fluid and are deposited in the fractures. Thereafter, the pumping of the fracturing fluid into the subterranean zone, the mixing of the liquid hardenable resin component with the liquid hardening agent component, the coating of the hardenable resin composition onto the dry proppant particles to form hardenable resin composition coated proppant particles and the mixing with and suspending of the resin composition coated proppant particles in the fracturing fluid are terminated. The hardenable resin composition on the coated proppant particles is allowed to harden and to consolidate the proppant into one or more high strength permeable packs which prevent proppant flow-back.
Yet another improved method of the present invention for coating dry proppant particles with a resin composition and suspending the coated proppant particles in a fracturing fluid, the resin composition hardening and consolidating the resin coated proppant particles into a high strength permeable mass which prevents proppant flow-back after being placed in one or more fractures formed in a subterranean zone by way of a perforated interval or intervals in a well bore penetrating the subterranean zone is comprised of the following steps. A liquid hardenable resin component as described above and a liquid hardening agent component as described above are provided along with a source of dry proppant particles and a gelled liquid fracturing fluid. The gelled liquid fracturing fluid is pumped into the subterranean zone to form one or more fractures therein and to place proppant particles in the fractures. The liquid hardenable resin component is mixed with the liquid hardening agent component to form a hardenable resin composition. The hardenable resin composition is intermittently coated onto dry proppant particles continuously conveyed from the source thereof to form hardenable resin composition coated proppant particles and uncoated proppant particles. The hardenable resin composition coated proppant particles and uncoated proppant particles are continuously mixed with the fracturing fluid so that the hardenable resin composition coated proppant particles and the uncoated proppant particles are suspended in the fracturing fluid and are deposited in the fractures. Thereafter, the pumping of the fracturing fluid into the subterranean zone, the mixing of the liquid hardenable resin component with the liquid hardening agent component, the intermittent coating of the hardenable resin composition onto the dry proppant particles to form hardenable resin composition coated proppant particles and uncoated proppant particles and the mixing with and suspending of the resin composition coated proppant particles in the fracturing fluid are terminated. The hardenable resin composition on the coated proppant particles is allowed to harden and to consolidate the proppant into one or more high strength permeable packs which prevent proppant flow-back.
The liquid hardenable resin compositions for coating proppant particles of this invention are comprised of a hardenable resin, a hardening agent for causing the hardenable resin to harden, a silane coupling agent, a hydrolyzable ester for breaking gelled fracturing fluid films on the proppant particles, a surfactant for facilitating the coating of the resin on the proppant particles and for causing the hardenable resin to flow to the contact points between adjacent resin coated proppant particles and a liquid carrier fluid having a flash point above about 125xc2x0 F.
The objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
As mentioned above, the prior art methods of consolidating proppant in subterranean fractures have generally included the placement of a large quantity of uncoated proppant in the fractures followed by a tail-end portion of proppant coated with a hardenable resin composition. When the viscous fracturing fluid which is the carrier for the proppant is broken and reverts to a thin fluid, the proppant is deposited in the fractures. The tail-end portion of the proppant which is coated with a hardenable resin composition is consolidated into a hard permeable mass by the resin composition, but the uncoated proppant previously deposited in the bottom of the fractures as the large quantity of uncoated proppant was transported into the fractures is not consolidated. As a result, when the well is placed on production, flow-back of the uncoated proppant takes place.
Another problem which is encountered in consolidating the proppant to prevent flow-back involves the strength of the consolidated resin coated proppant packs in the fractures. Heretofore, it has been a common practice to utilize proppant that is precoated with a resin composition and stored. When the precoated proppant is required for use at a job site, it is transported to the job site. While such precoated resin coated proppant is consolidated after being placed by a hardening agent, the resulting consolidated proppant pack often does not have enough strength to prevent deterioration and proppant flow-back.
In accordance with the methods of the present invention, all or part of the proppant transported into the fractures is coated with a resin composition (preferably on-the-fly) and is suspended in the fracturing fluid as the fracturing fluid is pumped into the well bore and into the fractures. As a result, the resin coating on the proppant is fresh and when it hardens and consolidates the proppant, high strength permeable proppant packs are formed in the fractures which prevent proppant flow-back. In addition, the hardenable resin composition components of this invention have long shelf lives, e.g., four months and longer. The components, i.e., the liquid hardenable resin component and the liquid hardening agent component are stored separately until they are mixed in a weight ratio of 1.5 parts liquid hardenable resin component to 1 part liquid hardening agent component just prior to being coated onto proppant. The mixing of the components can be by batch mixing or the two components can be metered through a static mixer to obtain a homogeneous mixture before being coated on dry proppant particles while the proppant particles are conveyed in a sand screw. The amount of mixed liquid hardenable resin composition coated on the proppant ranges from about 0.1% to about 5% by weight of the proppant with about 3% being preferred.
As will be described further hereinbelow, in order to conserve the amount of hardening agent utilized for curing the hardenable resin which has been deposited on all of the proppant in the fractures, the volume ratio of liquid hardening agent component to liquid hardenable resin component utilized in accordance with this invention can be varied. In a preferred technique, the volume ratio of the liquid hardening agent component to the liquid hardenable resin component is varied from an initial volume ratio at the beginning of the proppant suspended in the fracturing fluid to a lower volume ratio as the middle portion of the proppant is suspended in the fracturing fluid and then back to the initial volume ratio at the end portion of the proppant suspended in the fracturing fluid. This technique results in consolidated proppant packs in the fractures which have high strength at the forward ends of the packs, less strength at the middle portions of the packs and high strength at the end portions of the packs. The middle portions of the packs tend to be placed deeply in the fractures far away from the well bore. Since all of the proppant is consolidated, there is no unconsolidated proppant remaining in the bottoms of the fractures and as a result proppant flow-back does not occur.
When it is desirable or necessary to conserve a major portion of the hardenable resin composition, the hardenable resin composition can be applied to an initial portion of the proppant particles deposited in one or more fractures, not applied or intermittently applied to the middle portion of the proppant particles deposited in the fractures and applied to the last portion of the proppant particles deposited in the fractures.
In accordance with one improved method of this invention, dry proppant particles are coated with the hardenable resin composition, preferably on-the-fly, the coated proppant particles are suspended in the fracturing fluid, preferably on-the-fly, and the resulting hardenable resin composition coated proppant particles are placed in one or more fractures formed in a subterranean zone. The method is basically comprised of the following steps. A liquid hardenable resin component is provided comprised of a hardenable resin and optionally, a solvent for the resin having a high flash point. When used, the solvent is added to the resin to reduce its viscosity for ease of handling, mixing and transferring. However, as will be understood by those skilled in the art, the solvent can be omitted and the liquid hardenable resin can be heated to reduce its viscosity. A liquid hardening agent component is provided comprised of a hardening agent, a silane coupling agent, a hydrolyzable ester for breaking gelled fracturing fluid films on the proppant particles, a surfactant for facilitating the coating of the resin on the proppant particles and for causing the hardenable resin to flow to the contact points between adjacent resin coated proppant particles, a liquid carrier fluid having a high flash point and optionally, a viscosifying agent for viscosifying the carrier fluid and dispersing the hardening agent when the hardening agent is a particulate solid. When the hardening agent is a particulate solid, it can be added separately to the resin composition and the viscosifying agent can be omitted. Also, when a liquid hardening agent is used, the viscosifying agent can be omitted. In addition to the liquid hardenable resin component and the liquid hardening agent component, dry proppant particles and a gelled liquid fracturing fluid are provided. The gelled liquid fracturing fluid is pumped into a subterranean zone to form one or more fractures therein and to place the resin composition coated proppant particles in the fractures. As the fractures are formed by the fracturing fluid, the liquid hardenable resin component is mixed with the liquid hardening agent component, preferably on-the-fly, to form the hardenable resin composition. The hardenable resin composition is continuously coated on the dry proppant particles which are conveyed from the source thereof, preferably on-the-fly, to form hardenable resin composition coated proppant particles. The hardenable resin composition coated proppant particles are continuously mixed with the fracturing fluid, preferably on-the-fly, whereby the hardenable resin composition coated proppant particles are suspended therein. Thereafter, the hardenable resin composition coated proppant particles are carried into the fractures whereupon the pumping of the fracturing fluid and other related steps are terminated. As is well understood by those skilled in the art, the gelled liquid fracturing fluid can include a breaker which causes it to revert to a thin fluid so that the resin composition coated proppant particles are deposited in the fractures and the fracturing fluid is returned to the surface.
The term xe2x80x9con-the-flyxe2x80x9d is used herein to mean that a flowing stream is continuously introduced into another flowing stream so that the streams are combined and mixed while continuing to flow as a single stream. While the mixing of the liquid hardenable resin component with the liquid hardening agent component to form the hardenable resin composition, the coating of the dry proppant particles with the hardenable resin composition and the mixing of the hardenable resin coated proppant particles with the fracturing fluid are all preferably accomplished on-the-fly, as is well understood by those skilled in the art such mixing can also be accomplished by batch mixing or partial batch mixing.
As is also well understood, when the fracturing fluid is broken and the hardenable resin composition coated proppant particles are deposited in the fractures formed, the fractures close on the proppant particles. The partially closed fractures apply pressure on the hardenable resin composition coated proppant whereby the proppant particles are forced into contact with each other while the resin composition hardens. The hardening of the resin composition under pressure helps bring about the consolidation of the resin coated particles into a hard permeable pack having sufficient compressive strength to prevent unconsolidated proppant and formation sand from flowing out of the fractures with produced fluids. In fracture treatments carried out in unconsolidated formations, good consolidation of proppant is required in the perforations which extend from the inside of the well bore through casing and cement into the unconsolidated formation as well as in the fractured portions of the unconsolidated formation surrounding the well bore. The last portion of the proppant which is deposited in the perforations and in the fractures is coated with a hardenable resin composition and is caused to harden. The resulting consolidated proppant in the perforations and fractures contributes to the prevention of proppant flow-back. However, there is often little closure pressure applied to the hardenable resin coated proppant in the fractures close to the well bore and there is no closure pressure applied to the hardenable resin coated proppant particles in the perforations. In addition, the hardenable resin coated proppant particles can be separated from each other by films of the gelled fracturing fluid and because of the presence of the fracturing fluid films, the proppant particles do not sufficiently consolidate. As a result, the consolidated permeable packs formed in the perforations and fractures often have less than sufficient compressive strength to prevent unconsolidated proppant and formation sand from flowing out of the perforations and fractures. These problems are solved by including in the hardenable resin composition one or more hydrolyzable esters which function to break gelled fracturing fluid films on the particles, and a surfactant for facilitating the coating of the resin composition on the proppant particles and for causing the hardenable resin composition to flow to the contact points between adjacent resin coated proppant particles so that the particles are consolidated into a high strength permeable mass.
In accordance with the above described method all of the proppant particles are coated with the liquid hardenable resin composition. In order to conserve the liquid hardening agent component used and to reduce the cost of the fracturing procedure, the volume ratio of the liquid hardening agent component can be varied. That is, in a preferred technique, the volume ratio of the liquid hardening agent component to the liquid hardenable resin component is varied from an initial volume ratio which produces a high strength permeable pack to a lower volume ratio which produces a lower strength resilient permeable pack and then back to the initial volume ratio which produces a high strength permeable pack adjacent to the well bore. As mentioned, because all of the proppant particles are coated with the liquid hardenable resin, there are no unconsolidated proppant particles in the bottoms of the fractures and consequently, the consolidated permeable pack does not allow flow-back to occur. The initial volume ratio of the liquid hardening agent component to the liquid hardenable resin component is generally in the range of from about 1:10 to about 1:1 and the lower volume ratio is in the range of from about 1:20 to about 1:5. Preferably, the initial volume ratio of the liquid hardening agent component to the liquid hardenable resin component is about 1:1.5 and the lower volume ratio is about 1:5.
Thus, another method of the present invention includes the following steps. A liquid hardenable resin component is provided comprised of a hardenable resin and optionally, a solvent for the resin having a high flash point. A liquid hardening agent component is provided comprised of a hardening agent, a silane coupling agent, a hydrolyzable ester for breaking gelled fracturing fluid films on the proppant particles, a surfactant for facilitating the coating of the resin on the proppant particles and for causing the hardenable resin to flow to the contact points between adjacent resin coated proppant particles, a liquid carrier fluid having a high flash point and optionally, a viscosifying agent for viscosifying the carrier fluid and dispersing the hardening agent when the hardening agent is a particulate solid. In addition, a source of dry proppant particles and a gelled liquid fracturing fluid are provided. The gelled liquid fracturing fluid is pumped into the subterranean zone to form one or more fractures therein and to place the resin composition coated proppant particles in the fractures. As the fractures are formed, the liquid hardenable resin component is mixed with the liquid hardening agent component, preferably on-the-fly, to form the resin composition. The volume ratio of the liquid hardening agent component to the liquid hardenable resin component is varied, and the hardenable resin composition formed is continuously coated onto dry proppant particles conveyed from the source thereof, preferably on-the-fly, to form hardenable resin composition coated proppant particles. The hardenable resin composition coated proppant particles are continuously mixed with the fracturing fluid being pumped, preferably on-the-fly, whereby the hardenable resin composition coated proppant particles are suspended therein. After the hardenable resin composition coated proppant particles have been placed in the one or more fractures formed in the subterranean zone, the pumping of the gelled liquid fracturing fluid and other related steps are terminated. Thereafter, the gelled liquid fracturing fluid breaks into a thin fluid, the hardenable resin composition coated proppant particles are deposited in the fractures and the resin composition hardens and consolidates the proppant particles in the one or more fractures into high strength permeable packs which do not allow proppant flow-back.
Yet another method of this invention for coating dry proppant particles with a liquid hardenable resin composition and suspending the coated proppant particles in a fracturing fluid, the resin composition hardening and consolidating the resin coated proppant particles into a high strength permeable mass which prevents proppant flow-back after being placed in one or more fractures formed in a subterranean zone by way of a perforated interval or intervals in a well bore penetrating the subterranean zone is comprised of the following steps. A liquid hardenable resin component is provided comprised of a hardenable resin and optionally, a solvent for the resin having a high flash point. A liquid hardening agent component is provided comprised of a hardening agent, a silane coupling agent, a hydrolyzable ester for breaking gelled fracturing fluid films on the proppant particles, a surfactant for facilitating the coating of the resin on the proppant particles and for causing the hardenable resin to flow to the contact points between adjacent resin coated proppant particles, a liquid carrier fluid having a high flash point and optionally, a viscosifying agent for viscosifying the carrier fluid and dispersing the hardening agent when the hardening agent is a particulate solid. In addition, a source of dry proppant particles and a gelled liquid fracturing fluid are provided. The gelled liquid fracturing fluid is pumped into the subterranean zone to form one or more fractures therein and to place the proppant particles in the fractures. As the fractures are formed, the liquid hardenable resin component is mixed with the liquid hardening agent component, preferably on-the-fly, to form the hardenable resin composition. The hardenable resin composition formed is intermittently coated onto dry proppant particles conveyed from the source thereof, preferably on-the-fly, to form hardenable resin composition coated proppant particles and uncoated proppant particles. The hardenable resin composition coated proppant particles and uncoated proppant particles are continuously mixed with the fracturing fluid being pumped, preferably on-the-fly, whereby the hardenable resin composition coated proppant particles and uncoated proppant particles are suspended therein. After the hardenable resin composition coated proppant particles and uncoated proppant particles have been placed in the one or more fractures formed in the subterranean zone, the pumping of the gelled liquid fracturing fluid and other related steps are terminated. Thereafter, the gelled liquid fracturing fluid breaks into a thin fluid, the hardenable resin composition coated proppant particles and the uncoated particles are deposited in the fractures and the resin composition hardens and consolidates the proppant particles in the one or more fractures into high strength permeable packs which do not allow proppant flow-back.
In a preferred technique, when the well bore includes a single perforated interval having a length of less than about 50 feet or several perforated intervals having a combined length of less than about 50 feet, hardenable resin composition coated proppant particles are suspended in the fracturing fluid during the initial time period of pumping the fracturing fluid, uncoated proppant particles are suspended in the fracturing fluid during the middle time period of pumping the fracturing fluid and hardenable resin composition coated proppant particles are suspended in the fracturing fluid during the last time period of pumping the fracturing fluid. This technique results in hardenable resin composition coated proppant particles entering the fractures first and depositing hardenable resin composition coated proppant in the bottom of the fractures and additional hardenable resin composition coated particles entering the fractures last which moves uncoated proppant particles to the middle of the fractures and prevents uncoated proppant particles from flowing back with produced fluids.
Most preferably, the resin composition coated proppant particles suspended in the fracturing fluid pumped during the initial time period constitute about 15% of the total proppant particles pumped, the uncoated proppant particles suspended in the fracturing fluid pumped during the middle time period constitute about 60% of the total proppant particles pumped and the resin composition coated proppant particles suspended in the fracturing fluid pumped during the last time period constitute about 25% of the total proppant particles pumped.
When the well bore includes multiple perforated intervals having a length greater than about 50 feet, hardenable resin composition coated proppant particles are suspended in the fracturing fluid during the initial time period of pumping the fracturing fluid, a mixture of resin composition coated proppant particles and uncoated proppant particles are suspended in the fracturing fluid during the middle time period of pumping the fracturing fluid and hardenable resin coated proppant particles are suspended in the fracturing fluid during the last time period of pumping the fracturing fluid.
Most preferably, the resin composition coated proppant particles are suspended in the fracturing fluid pumped during the initial time period constitute about 15% of the total proppant particles pumped, the mixture of the resin composition coated proppant particles and the uncoated proppant particles pumped during the middle time period constitute about 60% of the total proppant particles and the resin composition coated proppant particles suspended in the fracturing fluid pumped during the last time period constitute about 25% of the total proppant particles pumped.
Examples of hardenable resins which can be utilized in the liquid hardenable resin component include, but are not limited to, organic resins such as bisphenol A-epichlorohydrin resin, polyepoxide resin, novolak resin, polyester resin, phenol-aldehyde resin, urea-aldehyde resin, furan resin, urethane resin, glycidyl ethers and mixtures thereof. Of these, bisphenol A-epichlorohydrin resin is preferred. The organic resin utilized is included in the liquid hardenable resin component in an amount in the range of from about 70% to about 100% by weight of the liquid hardenable resin component, preferably an amount of about 85%.
Examples of solvents having high flash points (above about 125xc2x0 F.) which can optionally be used for the hardenable resin in the liquid hardenable resin component include, but are not limited to, dipropylene glycol methyl ether, dipropylene glycol dimethyl ether, dimethyl formamide, diethyleneglycol methyl ether, ethyleneglycol butyl ether, diethyleneglycol butyl ether, propylene carbonate, d""limonene and fatty acid methyl esters. Of these, dipropylene glycol methyl ether is preferred. The amount of the solvent utilized in the liquid hardenable resin component is in the range of from about 0% to about 30% by weight of the liquid hardenable resin component, preferably in an amount of about 15%.
Examples of the hardening agents which can be used in the liquid hardening agent component include, but are not limited to, amines, aromatic amines, polyamines, aliphatic amines, cyclo-aliphatic amines, amides, polyamides, 4,4xe2x80x2-diaminodiphenyl sulfone, 2-ethyl-4-methyl imidazole and 1,1,3-trichlorotrifluoroacetone. Of these, 4,4xe2x80x2-diaminodiphenyl sulfone is preferred. The hardening agent is included in the liquid hardening agent component in an amount in the range of from about 40% to about 60% by weight of the liquid hardening agent component preferably in an amount of about 50%.
Examples of silane coupling agents which can be used in the liquid hardening agent component include, but are not limited to, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane and n-beta-(aminoethyl)-gamma-aminopropyl trimethoxysilane. Of these, n-beta-(aminoethyl)-gamma-aminopropyl trimethoxysilane is preferred. The silane coupling agent is included in the liquid hardening agent component in an amount in the range of from about 0.1% to about 3% by weight of the liquid hardening agent component.
Examples of hydrolyzable esters which can be utilized in the liquid hardening agent component for facilitating the coating of the resin composition on the proppant particles and for breaking gelled fracturing fluid films thereon include, but are not limited to, a mixture of dimethylglutarate, dimethyladipate and dimethylsuccinate, sorbitol, catechol, dimethylthiolate, methyl salicylate, dimethyl salicylate, dimethylsuccinate and ter-butylhydroperoxide. Of these, a mixture of dimethylglutarate, dimethyladipate and dimethylsuccinate is preferred. The ester or esters are present in the liquid hardening agent component in an amount in the range of from about 0.1% to about 3% by weight of the liquid hardening agent component, preferably in an amount of about 2%.
The surfactants which can be utilized in the liquid hardening agent component for facilitating the coating of the resin on the proppant particles and for causing the hardenable resin to flow to the contact points between adjacent resin coated proppant particles include, but are not limited to, an ethoxylated nonyl phenol phosphate ester, mixtures of one or more cationic surfactants and one or more non-ionic surfactants and an alkyl phosphonate surfactant. The mixtures of one or more cationic and nonionic surfactants are described in U.S. Pat. No. 6,311,733 issued to Todd et al. on Nov. 6, 2001 which is incorporated herein by reference. Of the surfactants that can be used, a C12-C22 alkyl phosphonate surfactant is preferred. The surfactant or surfactants utilized are included in the liquid hardening agent component in an amount in the range of from about 2% to about 15% by weight of the liquid hardening agent component, preferably in an amount of about 12%.
The liquid carrier fluid having a high flash point (above about 125xc2x0 F.) in the liquid hardening agent component is selected from the group consisting of dipropylene glycol methyl ether, dipropylene glycol dimethyl ether, dimethyl formamide, diethyleneglycol methyl ether, ethyleneglycol butyl ether, diethyleneglycol butyl ether, propylene carbonate, d""limonene and fatty acid methyl esters. Of these, dipropylene glycol methyl ether is preferred. The liquid carrier fluid is present in the liquid hardening agent component in an amount in the range of from about 20% to about 40% by weight of the liquid hardening agent component, preferably in an amount of about 30%.
Examples of viscosifying agents that can optionally be utilized in the liquid hardening agent component, include, but are not limited to hydroxypropyl cellulose and organophilic clays. Of these, organophilic clay is preferred. Organophilic clays are the reaction product of purified smectite clay (either hectorite or bentonite) and a quaternary ammonium salt. The viscosifying agent is present in the liquid hardening agent component in an amount in the range of from about 0% to about 3% by weight of the liquid hardening agent component, preferably in an amount of about 1%.
As mentioned above, during the time that the liquid hardenable resin component and the liquid hardening agent component are continuously mixed and coated on the dry proppant particles, the rate of the liquid hardening agent component can be varied while the rate of the liquid hardenable resin component is held constant. Stated another way, the volume ratio of the liquid hardening agent component to the liquid hardenable resin component is varied. Preferably, the volume ratio of the liquid hardening agent component to the liquid hardenable resin component is varied from an initial volume ratio to a lower volume ratio and then back to the initial volume ratio. This procedure causes all of the proppant particles to be consolidated with the proppant particles adjacent to the well bore and the proppant particles at the front of the fracture being strongly consolidated and the proppant particles in between being moderately consolidated. This arrangement effectively prevents proppant flow-back. The procedure is based on the discovery that reductions in the amount of the liquid hardening agent component from the amount that produces a very hard and strong cured resin causes the resin to become more rubbery or flexible, but it still functions to consolidate the proppant particles. Thus, the middle portion of a consolidated proppant particle pack in a fracture can be resilient and have less compressive strength so long as the end portions of the pack are consolidated with high strength rigid resin.
A variety of fracturing fluids can be utilized in accordance with the present invention including aqueous gels, emulsions and other fluids utilized for forming fractures in subterranean zones and carrying resin composition coated proppant particles into the fractures. The aqueous gels are generally comprised of water and one or more gelling agents. The emulsions can be comprised of two immiscible liquids such as an aqueous gelled liquid and a liquefied, normally gaseous fluid, such as nitrogen.
The preferred fracturing fluids for use in accordance with this invention are aqueous gels comprised of water, a gelling agent for gelling the water and increasing its viscosity, and optionally, a cross-linking agent for cross-linking the gel and further increasing the viscosity of the fluid. The increased viscosity of the gelled or gelled and cross-linked fracturing fluid reduces fluid loss and allows the fracturing fluid to transport significant quantities of suspended proppant particles. The water utilized to form the fracturing fluid can be fresh water, salt water, brine or any other aqueous liquid which does not adversely react with the other components utilized in accordance with this invention.
A variety of gelling agents can be utilized including hydratable polymers which contain one or more functional groups such as hydroxyl, cis-hydroxyl, carboxyl, sulfate, sulfonate, amino or amide. Particularly useful such polymers are polysaccharides and derivatives thereof which contain one or more of the monosaccharide units galactose, mannose, glucoside, glucose, xylose, arabinose, fructose, glucuronic acid or pyranosyl sulfate. Examples of natural hydratable polymers containing the foregoing functional groups and units which are particularly useful in accordance with the present invention include guar gum and derivatives thereof such as hydroxypropyl guar and cellulose derivatives such as hydroxyethyl cellulose. Hydratable synthetic polymers and copolymers which contain the above mentioned functional groups can also be utilized. Examples of such synthetic polymers include, but are not limited to, polyacrylate, polymethacrylate, polyacrylamide, polyvinyl alcohol and polyvinylpyrrolidone. The gelling agent used is generally combined with the water in the fracturing fluid in an amount in the range of from about 0.1% to about 1% by weight of the water.
Examples of cross-linking agents which can be utilized to further increase the viscosity of a gelled fracturing fluid are alkali metal borates, borax, boric acid and compounds which are capable of releasing multivalent metal ions in aqueous solutions. Examples of the multivalent metal ions are chromium, zirconium, antimony, titanium, iron, zinc or aluminum. When used, the cross-linking agent is generally added to the gelled water in an amount in the range of from about 0.01% to about 1% by weight of the water.
The above described gelled or gelled and cross-linked fracturing fluids typically also include internal delayed gel breakers such as those of the enzyme type, the oxidizing type, the acid buffer type and the temperature activated type, all of which are well known to those skilled in the art. The gel breakers cause the viscous carrier fluids to revert to thin fluids that can be produced back to the surface after they have been used to place proppant particles in subterranean fractures. The gel breaker used is generally present in the fracturing fluid in an amount in the range of from about 1% to about 5% by weight of the gelling agent therein. The fracturing fluids can also include one or more of a variety of well known additives such as gel stabilizers, fluid loss control additives, clay stabilizers, bacteriacides and the like.
The proppant particles utilized in accordance with the present invention are generally of a size such that formation particulate solids which migrate with produced fluids are prevented from being produced from the subterranean zone. Various kinds of proppant can be utilized including graded sand, bauxite, ceramic materials, glass materials, walnut hulls, polymer beads and the like. Generally, the proppant particles have a size in the range of from about 2 to about 400 mesh, U.S. Sieve Series. The preferred proppant is graded sand having a particle size in the range of from about 10 to about 70 mesh, U.S. Sieve Series. Preferred sand particle size distribution ranges are one or more of 10-20 mesh, 20-40 mesh, 40-60 mesh or 50-70 mesh, depending on the particular size and distribution of formation solids to be screened out by the consolidated proppant particles.
The liquid hardenable resin compositions of this invention for coating proppant particles are basically comprised of a hardenable resin, a hardening agent for causing the hardenable resin to harden, a silane coupling agent, a hydrolyzable ester for breaking gelled fracturing fluid films on the proppant particles, a surfactant for facilitating the coating of the hardenable resin composition on the proppant particles and for causing the hardenable resin composition to flow to the contact points between adjacent resin coated proppant particles and a liquid carrier fluid having a flash point above about 125xc2x0 F.
Examples of the hardenable resins which can be utilized in the hardenable resin compositions of this invention include, but are not limited to, bisphenol A-epichlorohydrin resin, polyepoxide resin, novolac resin, polyester resin, phenol-aldehyde resin, urea-aldehyde resin, furan resin, urethane resin, glycidyl ether and mixtures thereof. Of these, bisphenol A-epichlorohydrin resin is preferred. The hardenable resin is included in the liquid hardenable resin composition in an amount in the range of from about 70% to about 100% by weight of the composition, more preferably in an amount of about 85%.
Examples of hardening agents which can be utilized include, but are not limited to, amines, aromatic amines, polyamines, aliphatic amines, cyclo-aliphatic amines, amides, polyamides, 4,4xe2x80x2-diaminodiphenyl sulfone, 2-ethyl-4-methyl imidazole and 1,1,3-trichlorotrifluoroacetone. Of these, 4,4xe2x80x2-diaminodiphenyl sulfone is preferred. The hardening agent is included in the liquid hardenable resin composition in an amount in the range of from about 40% to about 60% by weight of the composition, more preferably in an amount of about 50%.
Examples of silane coupling agents which can be utilized include, but are not limited to, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane and n-beta-(aminoethyl)-gamma-aminopropyl trimethoxysilane. Of these, n-beta-(aminoethyl)-gamma-aminopropyl trimethoxysilane is preferred. The silane coupling agent is included in the liquid hardenable resin composition in an amount in the range of from about 0.1% to about 3% by weight of the composition, more preferably in an amount of about 1.5%.
Examples of hydrolyzable esters which can be used include, but are not limited to, a mixture of dimethylglutarate, dimethyladipate and dimethylsuccinate, sorbitol, catechol, dimethylthiolate, methyl salicylate, dimethyl salicylate, dimethylsuccinate and terbutylhydroperoxide. Of these, a mixture of dimethylglutarate, dimethyladipate and dimethylsuccinate are preferred. The hydrolyzable ester is included in the liquid hardenable resin composition in an amount in the range of from about 0.1% to about 3% by weight of the composition, more preferably in an amount of about 2%.
Examples of surfactants which can be utilized include, but are not limited to, ethoxylated nonyl phenol phosphate ester, mixtures of one or more cationic surfactants and one or more non-ionic surfactants and a C12-C22 alkyl phosphonate surfactant. Of these, a C12-C22 alkyl phosphonate surfactant is preferred. The surfactant is included in the liquid hardenable resin composition in an amount in the range of from about 2% to about 15% by weight of the composition, more preferably in an amount of about 12%.
Finally, examples of the liquid carrier fluid that can be utilized include, but are not limited to, dipropylene glycol methyl ether, dipropylene glycol dimethyl ether, dimethyl formamide, diethyleneglycol methyl ether, ethyleneglycol butyl ether, diethyleneglycol butyl ether, propylene carbonate, d""limonene and fatty acid methyl esters. Of these, dipropylene glycol methyl ether is preferred. The liquid carrier fluid is included in the liquid hardenable resin composition in an amount in the range of from about 20% to about 40% by weight of the composition, more preferably in an amount of about 30%.
A preferred improved method of this invention for coating dry proppant particles with a hardenable resin composition and suspending the coated proppant particles in a fracturing fluid, the resin composition hardening and consolidating the resin coated proppant particles into a high strength permeable mass which prevents proppant flow-back after being placed in one or more fractures in a subterranean zone comprises the steps of: (a) providing a liquid hardenable resin component comprised of a hardenable resin and optionally, a solvent for the resin; (b) providing a liquid hardening agent component comprised of a particulate solid hardening agent, a silane coupling agent, a hydrolyzable ester for breaking gelled fracturing fluid films on the proppant particles, a surfactant for facilitating the coating of the resin on the proppant particles and for causing the hardenable resin to flow to the contact points between adjacent resin coated proppant particles, a liquid carrier fluid and optionally, a viscosifying agent for viscosifying the carrier fluid and dispersing the hardening agent when the hardening agent is a particulate solid; (c) providing a source of dry proppant particles (d) providing a gelled liquid fracturing fluid; (e) pumping the gelled liquid fracturing fluid into the subterranean zone to form the one or more fractures therein and to place the hardenable resin composition coated proppant particles in the fractures; (f) as the fractures are formed in step (e), mixing the liquid hardenable resin component with the liquid hardening agent component to form the hardenable resin composition; (g) coating the hardenable resin composition produced in step (f) onto dry proppant particles conveyed from the source thereof to form resin composition coated proppant particles; (h) mixing the resin composition coated proppant particles produced in step (g) with the fracturing fluid pumped in accordance with step (e) whereby the resin composition coated proppant particles are suspended therein; (i) terminating steps (e), (f), (g) and (h) when the resin composition coated proppant particles have been placed in the one or more fractures; and (j) allowing the hardenable resin composition on the resin composition coated proppant particles to harden and consolidate the proppant particles into one or more high strength permeable packs which prevent proppant flow-back.
Another preferred improved method of coating dry proppant particles with a hardenable resin composition and suspending the coated proppant particles in a fracturing fluid, the resin composition hardening and consolidating the resin coated proppant particles into a high strength permeable mass which prevents proppant flow-back after being placed in one or more fractures formed in a subterranean zone comprises the steps of: (a) providing a liquid hardenable resin component comprised of a hardenable resin and optionally, a solvent for the resin; (b) providing a liquid hardening agent component comprised of a particulate solid hardening agent, a silane coupling agent, a hydrolyzable ester for breaking gelled fracturing fluid films on the proppant particles, a surfactant for facilitating the coating of the resin on the proppant particles and for causing the hardenable resin to flow to the contact points between adjacent resin coated proppant particles, a liquid carrier and optionally, a viscosifying agent for viscosifying the carrier fluid and dispersing the hardening agent when the hardening agent is a particulate solid; (c) providing a source of dry proppant particles; (d) providing a gelled liquid fracturing fluid; (e) pumping the gelled liquid fracturing fluid into the subterranean zone to form the one or more fractures therein and to place the resin composition coated proppant particles in the fractures; (f) as the fractures are formed in step (e), mixing the liquid hardenable resin component with the liquid hardening agent component to form the hardenable resin composition; (g) varying the volume ratio of the liquid hardening agent component to the liquid hardenable resin component during step (f); (h) coating the hardenable resin composition produced in steps (f) and (g) onto dry proppant particles conveyed from the source thereof to form resin composition coated proppant particles; (i) mixing the resin composition coated proppant particles produced in step (h) with the fracturing fluid pumped in accordance with step (e) whereby the resin composition coated proppant particles are suspended therein; (j) terminating steps (e), (f), (g), (h) and (i) when the resin composition coated proppant particles have been placed in the one or more fractures; and (k) allowing the hardenable resin composition on the resin composition coated proppant particles to harden and consolidate the proppant particles into one or more high strength permeable packs which prevent proppant flow-back.
Yet another preferred method of coating dry proppant particles with a liquid hardenable resin composition and suspending the coated proppant particles in a fracturing fluid, the resin composition hardening and consolidating the resin coated proppant particles into a high strength permeable mass which prevents proppant flow-back after being placed in one or more fractures formed in a subterranean zone by way of a perforated interval or intervals in a well bore penetrating the subterranean zone comprises the steps of: (a) providing a liquid hardenable resin component comprised of a hardenable resin and optionally, a solvent for the resin; (b) providing a liquid hardening agent component comprised of a particulate solid hardening agent, a silane coupling agent, a hydrolyzable ester for breaking fracturing fluid films on the proppant particles, a surfactant for facilitating the coating of the resin on the proppant particles and for causing the hardenable resin to flow to the contact points between adjacent resin coated proppant particles, a liquid carrier fluid and optionally, a viscosifying agent for viscosifying the carrier fluid and dispersing the hardening agent when the hardening agent is a particulate solid; (c) providing a source of dry proppant particles; (d) providing a gelled liquid fracturing fluid; (e) pumping the gelled liquid fracturing fluid into the subterranean zone to form the one or more fractures therein and to place the proppant particles in the fractures; (f) as the fractures are formed in step (e), mixing the liquid hardenable resin component with the liquid hardening agent component to form the liquid hardenable resin composition; (g) intermittently coating the hardenable resin composition produced in step (f) onto dry proppant particles continuously conveyed from the source thereof to form resin composition coated proppant particles and uncoated proppant particles; (h) mixing the resin composition coated proppant particles and uncoated proppant particles from step (g) with the fracturing fluid pumped in accordance with step (e) whereby the resin composition coated proppant particles and uncoated proppant particles are suspended therein; (i) terminating steps (e), (f), (g) and (h) when the resin composition coated proppant particles and uncoated proppant particles have been placed in the one or more fractures; and (j) allowing the hardenable resin composition on the resin composition coated particles to harden and consolidate the proppant particles into one or more high strength permeable packs which prevent proppant flow-back.
A preferred liquid hardenable resin composition for coating proppant particles comprises a hardenable resin; a hardening agent for causing the hardenable resin to harden; a silane coupling agent; a hydrolyzable ester for breaking gelled fracturing fluid films on the proppant particles; a surfactant for facilitating the coating of the hardenable resin composition on the proppant particles and for causing the hardenable resin composition to flow to the contact points between adjacent resin coated proppant particles; and a liquid carrier fluid having a flash point above about 125xc2x0 F.
In order to further illustrate the methods of the present invention, the following examples are given.

Methods and compositions for consolidating proppant in subterranean fractures


A method and apparatus are disclosed for supervising a communication link in a cellular mobile radio system between a base station and a mobile station on a digital voice channel by utilizing digital voice color codes. The base station transmits bursts of communication data, which have an associated digital voice color code, to the mobile station. The mobile station, upon receiving the bursts and decoding the digital voice color code, compares the digital voice color code with a reference digital voice color code received during a call setup or handoff operation. A timer is initiated to time out the communication link after a predetermined period of time in response to the reference digital voice color code not being equivalent to a first predetermined number of the digital voice color codes received with the bursts. The timer is reset and deactuated in response to the reference digital voice color code being equivalent to the first predetermined number of consecutively received digital voice color codes of the bursts received by the mobile station. The communication link is disconnected when the reference digital voice color code is not equivalent to the first predetermined number of consecutive digital voice color codes received during the predetermined period of time clocked by the timer. After the timer is reset and deactivated, the received digital voice color codes are again compared with the stored digital voice color code. In the event that a second predetermined number of consecutively received digital voice color codes are not equivalent to the stored digital voice color code, the timer will be initiated again to possibly time out the communication link as described above.

In cellular mobile radio systems it is fundamental that a mobile station with an established connection on a radio channel should be able to maintain the established connection when moving from one cell served by one base station to another cell served by another base station. The process by which a mobile station maintains an established connection when moving between cells in a cellular radio system is generally called handoff. It is also highly desirous that a mobile station with an established connection on a radio channel be able to maintain the connection when moving within the same cell, even if the radio channel being used is subject to increased interference. If the quality of the established connection falls below specified parameters it is further desirable to automatically disconnect the connection in the event that handoff or other signal processing fails to improve the quality of the connection.
In general, radio communication is only possible when the desired information-carrying radio signals have sufficient signal strength at the receiver and are sufficiently strong in relation to noise and interfering radio signals at the receiver. The minimum strength of course depends on the particular features of the system, e.g., the kind of modulation and receiver used. In order to make sure an established connection may continue on a selected radio channel between a mobile station and a base station, handoff and disconnect processes perform various measurements on radio signals at the intended base and/or mobile stations.
The first cellular mobile radio systems in public use were analog systems for speech or other analog information. The systems comprised multiple radio channels for transmitting analog information between base and mobile stations by transmitting analog-modulated radio signals. These first cellular mobile radio systems had comparably large cells. In general, the signal measurements during the handoff and disconnect processes in such systems were performed by the base stations. One such system is the Nordic Mobile Telephone system NMT 450. Another known cellular mobile radio system, of particular interest as background to the present invention, is the AMPS mobile radio system utilized in the U.S.A.
Recently, digital cellular mobile radio systems for public use have been designed. Digital cellular mobile radio systems comprise digital radio channels for transmitting digital or digitized analog information between base and mobile stations by transmitting digitally modulated radio signals. Digital cellular mobile radio systems may offer substantial advantages over analog cellular mobile radio systems. To achieve these advantages there are certain demands. In particular, channel supervision must be frequent and the handoff and disconnect processes must be rapid and be allowed to be frequently carried out in relation to conventional analog systems.
One digital mobile radio system intended to be a common system for many European countries is the GSM system. In European countries already having an analog cellular mobile system, the new digital GSM system is intended to be introduced as a new system independent of any conventional existing analog systems. The GSM system base and mobile stations are not designed to be compatible with conventional existing systems, but give optimum performance in various aspects by themselves. Accordingly, there has been a comparatively great freedom of choice in technical matters when designing the GSM system. In particular, this is true with the handoff method in the GSM system. In the GSM system, measurements for the purpose of handoff and disconnect are done both by base and mobile stations.
In contrast to the introduction of a new independent digital cellular mobile radio system like the GSM system, in an area with an existing analog cellular system it has been proposed to introduce a digital cellular mobile radio system designed for cooperation with the existing analog cellular mobile radio system. To obtain digital radio channels within the frequency band allotted to cellular mobile radio systems, it is proposed to withdraw a number of radio channels allotted to present analog mobile radio systems and use them in the digital cellular mobile radio system. Due to the proposed design of the digital mobile radio system, three or possibly six digital radio channels may use, in time division multiplex, the frequency band of one previous analog radio channel. Accordingly, replacing some analog channels by multiplex digital radio channels in time division multiplex may increase the total number of radio channels in the joint analog and digital systems.
The intention in this regard is to gradually introduce the digital system and with time gradually increase the number of digital channels and decrease the number of analog channels in the coexisting cellular systems. Analog mobile stations already in use will be able to continue their use of remaining analog channels. New digital mobile stations will be able to use new digital channels. New dual-mode mobile stations will be able to use both remaining analog channels and new digital channels. In such a system, the handoff and disconnect processes for digital radio channels cannot simply be selected to be identical with the handoff and disconnect processes for a strictly digital system, e.g., the GSM system. The handoff and disconnect processes for digital channels must not interfere with the handoff and disconnect processes of the existing analog system and must not require changing of signals in the analog system.
In a dual-mode mobile station, it is desirable to provide the user with the same or comparable functionality in the digital mode as that which is available in the analog mode, since the user is often not aware of whether he is using an analog or a digital voice channel during any particular call. For example, one feature that is available in analog systems is the ability to continue a call without an automatic disconnect even though an interruption of the signal on the channel occurs for a short period of time, such as that which is occasioned by driving through a tunnel or the like. It is desirable to provide this same capability in the digital mode of operation. To this end, it would be further desirable to employ some of the existing equipment in the mobile station, which is used to provide this capability for the analog mode of operation, during the digital mode of operation as well.

Mobile station link supervision utilizing digital voice color codes


The present invention relates to a field-effect transistor which is improved such that the linearity of mutual conductance g.sub.m is flattened over a wider range of gate bias. This field-effect transistor is a MESFET comprising a channel layer and a cap layer in Schottky-contact with a gate electrode. In particular, between the channel layer and the cap layer, one or more auxiliary layers having a doping concentration lower than that of the channel layer and higher than that of the cap layer are provided. The doping concentration of one or more auxiliary layers is set such that the doping profile of a laminated structure constituted by the channel layer, one or more auxiliary layers, and cap layer exponentially lowers from the channel layer toward the cap layer. According to this configuration, the depletion layer can effectively be controlled over a wider range of gate bias, the long gate effect and the like are suppressed, and the linearity of mutual conductance g.sub.m is improved.

1. Field of the Invention
The present invention relates to structures of field-effect transistor (FET).
2. Related Background Art
As FETs realizing ultrafast operations, there have been known those employing a pulse-doped structure in a channel layer. The pulse-doped structure is a structure in which a channel layer with a high doping concentration is formed directly under an undoped layer (cap layer). The cap layer has a predetermined thickness from the substrate surface on which a gate electrode is formed on the cap layer. FETs having the pulse-doped structure are disclosed, for example, in U.S. Pat. No. 4,163,984 or Japanese Patent Application Laid-Open No. HEI 6-310535.
In n-type FETs having the pulse-doped structure, a long gate effect may occur. The long gate effect is a phenomenon in which, the effective gate length enhances due to a depletion layer on the drain electrode side (where the gate bias is a small negative value). For suppressing the long gate effect, the FET disclosed in Japanese Patent Application Laid-Open No. HEI 4-225533, for example, employs a double-pulse-doped layer structure. The double-pulse-doped layer structure is a structure further comprising a pulse-doped layer (additional doped layer) which is disposed over a channel layer. The channel layer and the additional doped layer are separated from each other by a predetermined distance by an undoped layer (a part of a cap layer). The additional doped layer inhibits the depletion layer from spreading toward the channel layer.


A computer program for routing a service call from a calling party to a service network having a plurality of service network locations, the program stored in a computer-readable medium. The program includes receiving a service call request to connect the calling party to one of the service network locations, determining a location of the calling party by searching a Number Plan Area (NPA) table to determine an NPA of the calling number of the calling party, identifying one of the service network locations for receiving the service call request, and identifying routing information for routing the service call request to the receiving service network location, and completing the service call request to the receiving service network location.

1. Field of the Invention
The present invention generally relates to the field of telecommunications. More particularly, the present invention relates to a telecommunications network environment having intelligent call routing and call return capabilities for routing service calls, such as emergency or poison assistance calls, to an appropriate service or control center.
2. Acronyms
The written description provided herein contains acronyms which refer to various telecommunications services, components and techniques, as well as features relating to the present invention. Although some of these acronyms are known, use of these acronyms is not strictly standardized in the art. For purposes of the written description herein, acronyms will be defined as follows:                10-Digit (10D)        Action Control Point. (ACP)        Advanced Intelligent Network (AIN)        Common Channel Signaling (CCS)        Central Office (CO)        Call Processing Record (CPR)        Data and Reporting System (DRS)        End Office (EO)        Integrated Service Control Point (ISCP)        Integrated Services Digital Network (ISDN)        Multi-Frequency (MF)        Number Plan Area (NPA)        Central Office Code (NXX)        Poison Control Answering Point (PCAP)        Poisoned Party Number (PPN)        Primary Rate Interface (PRI)        Public Service Answering Point (PSAP)        Service Creation Environment (SCE)        Service Control Point (SCP)        Service Management System (SMS)        Signaling System 7 (SS7)        Service Switching Point (SSP)        Signaling Transfer Point (STP)        Terminating Attempt Trigger (TAT)        Transaction Capabilities Applications Part (TCAP)        Transmission Control Protocol/Internet Protocol (TCP/IP)
3. Background Information
In recent years, a number of new telephony service features have been implemented and provided by an Advanced Intelligent Network (AIN). The AIN evolved out of a need to increase the capabilities of the existing telephone network architecture and meet the growing needs of telephony customers. The AIN architecture generally comprises two networks, a data messaging network and a trunked communications network. The trunked communications network handles voice and data communications between dispersed network locations, whereas the data messaging network is provided for controlling operations of the trunked communications network.
An illustration of the basic components of an AIN network environment is shown in FIG. 1, which is provided to facilitate communication between a plurality of network locations or stations 72-86. As shown in FIG. 1, Central Offices (COs) 64-70 are provided for sending and receiving data messages from a Service Control Point (SCP) 56 via one or more Signaling Transfer Points (STPs) 51, 53 and 59. The data messages are communicated to and from the COs 64-70 and the SCP 56 along a Common Channel Signaling (CCS) network 88. Each CO 64-70 serves as a network Service Switching Point (SSP) to route telephone calls between a calling station (e.g., station 72) and a called station (e.g., station 84) through the trunked communications network 90-93.
Additional information regarding AIN and AIN-related network environments, see Berman, Roger K., and Brewster, John H., "Perspectives on the AIN Architecture," IEEE Communications Magazine, February 1992, pp. 27-32, the disclosure of which is expressly incorporated herein by reference in its entirety.
A number of features provided by prior AIN or AIN-type intelligent networks relate to specialized call processing of incoming calls. For example, U.S. Pat. Nos. 4,611,094 and. 4,611,096, both to ASMUTH et al., disclose a system for providing custom incoming telephone call processing services to a subscriber operating at geographically diverse locations. A subscriber program stored in a central database is accessed to provide instructions to the SSPs to complete incoming calls to one of the subscriber locations in accordance with special services defined by the subscriber. The subscriber program controls the Action Control Points (ACPs) to string together the desired call processing capabilities to process each call. Specified parameters stored in the program, such as time of day, caller location, and data inputted by the caller may be utilized to determine the final destination to which each call should be completed.
U.S. Pat. No. 4,788,718, to McNABB, discloses centralized recording of call traffic information. The system provides a data gathering and recording function to the centralized database which stores the subscriber's call routing program. The subscriber's call routing program performs several functions, including presenting various announcements to callers, prompting callers for inputting information digits and collecting the resulting information digits, routing the call to a number provided by the subscriber, and performing final call dispositions other than routing to the telephone number provided by the subscriber. Processing of the call traffic information dynamically changes the subscriber's call routing program to reduce the number of blocked calls to the subscriber's telephone numbers.
U.S. Pat. No. 5,247,571, to KAY et al., discloses an Area Wide Centrex system to provide specialized calling features to stations connected to a plurality of central offices. Each of the central office switching points connects to a number of local telephone lines. The features are extended to the local telephone lines by taking the programming intelligence out of the central offices and moving it into a database located at a centralized location, such as an SCP. Service features are, controlled by the central database and are changed by reprogramming the service logic located at the central database. A variety of service features are provided including a work at home service that enables a user of a private network access from a home telephone and access authorization to increase the security of the private network.
U.S. Pat. No. 5,353,331, to EMERY et al., discloses an AIN system which connects to, and controls processing of, calls to a subscriber's wireless handset via a home base station or wireless communication network. In response to calls directed to the subscriber's wireless handset, the AIN determines where the handset is located using a central database and routes the call to that location. The incoming call can be routed directly to the handset, blocked, or routed to an alternate termination point. In response to calls from the handset, the central database provides data instructions to the landline network to extend a requested special service to the subscriber.
U.S. Pat. No. 5,592,541, to FLEISCHER, III et al., discloses an AIN network environment for forwarding incoming calls by utilizing a subscriber defined routing list. The routing list may comprise alternate telephone numbers to which calls placed to the subscriber's number(s) will be routed. The routing lists may be defined for forwarding incoming calls to other numbers for either all of the numbers or for selected groups of one or more numbers. Incoming calls may also be routed according to the time-of-day, day-of-week, percentage allocation, specific date, originating location of calling party, or calling party selection.
While prior AIN or AIN-type intelligent network applications have provided various call forwarding and routing features as indicated above, such prior attempts have not provided intelligent call routing capabilities for routing service calls to predetermined service or control centers. For instance, with the development of emergency and poison assistance control centers by state and local governments, there is an increasing need to provide intelligent call routing capabilities to facilitate the handling and routing of emergency or poison assistance calls, so that calls may be directed to the most appropriate or nearest control center. It would be desirable, for example, to provide an intelligent network environment that is capable of routing calls based on the location of the calling party and the availability of designated service or control centers. Prior attempts have also not provided system flexibility in terms of providing various routing and/or call return options that may be combined with routing based on the location of the calling party.
Such features would be highly desirable for service or control centers that provide assistance to individuals or members of the general public who dial a single publicized telephone number. With intelligent routing capabilities, calls could be automatically directed to the most appropriate control or service center, without requiring additional information or assistance from the calling party. Further, with flexible routing options, calls could be routed away from under-staffed or closed centers (e.g., based on the time-of-day, day-of-week, percentage allocation, etc.) so that reliable service or assistance may be provided to end users.

This patent is subject to a terminal disclaimer.

Apparatus and method for intelligent call routing and call return


A failure detection circuit for a motor vehicle electronic computer, including: a main microcontroller having at least two microcontroller cores configured to execute the same instructions in parallel, and at least one first software module providing a critical function of a motor vehicle. The first software module includes a predetermined input point and a predetermined output point a supervision microcontroller and a synchronous communication interface for coupling the main microcontroller and the supervision microcontroller so as to enable mutual supervision. The detection circuit makes it possible to detect systematic and random failures.

The development of electronic computers in the motor vehicle sector has to take into consideration numerous functional safety constraints, such as those stipulated by the ISO 26 262 standard.
In the framework of this standard, it is necessary in particular to be able to detect what are called systematic failures that are linked to development errors in the software modules of computers (for example blocking of the execution of a function, erasure of part of a memory space).
The requirements of this standard apply particularly to electronic computers involved in implementing what are called critical functions of a motor vehicle, such as the ABS, ESP, EPS, EPB or airbag functions.
To meet these requirements, patent application EP 2 685 379 A1, which is incorporated by reference, proposes to integrate, into the electronic computers, a main microcontroller and a supervision microcontroller that are designed to supervise one another via a bus-type communication interface. This layout makes it possible to detect numerous failures of the critical functions of a motor vehicle.
However, document EP 2 685 379 A1 does not contemplate the configuration in which the main microcontroller comprises at least two microcontroller cores that are designed to execute the same instructions in parallel.
In this scenario, systematic failures are not able to be detected by the supervision microcontroller, as the two cores of the main microcontroller will execute the same software code and therefore produce the same results. The supervision microcontroller is therefore not able to deduce a failure linked to the execution of the software on the basis of the identical results produced by the two microcontroller cores.
Furthermore, what are called common-cause random failures are not able to be detected by the supervision microcontroller either. Common-cause random failures stem from a fault common to at least two redundant elements of the electronic computer, such as the microcontroller cores, the power supplies or the clocks. For example, when the main microcontroller comprises two peripherals, such as analog-to-digital converters (called ADCs hereinafter), the detection of a failure of the ADCs is able to be deduced by comparing the results produced by each of the ADCs. Now, generally speaking, the two ADCs, just like the two cores, have the same power supply, are supplied by the same clock, and often form part of the same module. It may then be the case that a fault common to the two ADCs, or to the two cores, may occur such that the results from the ADCs are not able to be utilized to detect a possible failure. Specifically, there may very possibly be a failure caused by a power supply fault and/or clock fault or a fault resulting from an electrostatic discharge (ESD) from the module comprising the ADCs and the cores. The supervision microcontroller is therefore not able to deduce a common-cause random failure on the basis of the results produced by the two peripherals.
This is unacceptable for the application under consideration, as numerous critical failures are not detected.

Circuit for detecting systematic and random faults


A thin film transistor array panel is provided that includes: a gate electrode that is disposed on an insulating substrate; a gate insulating layer that is disposed on the gate electrode; an oxide semiconductor that is disposed on the gate insulating layer; a blocking layer that is disposed on the oxide semiconductor; a source electrode and a drain electrode that are disposed on the blocking layer; a passivation layer that is disposed on the source electrode and drain electrode; and a pixel electrode that is disposed on the passivation layer. The blocking layer includes a first portion that is covered by the source electrode and drain electrode and a second portion that is not covered by the source electrode and drain electrode, and the first portion and the second portion include different materials.

1. Field of the Invention
The present invention relates to a thin film transistor array panel and a manufacturing method thereof.
2. Description of the Related Art
Liquid crystal displays are currently one of the most widely used type of flat panel displays. A liquid crystal display includes two display panels, on which electrodes are formed to control liquid crystal molecules disposed there between, by applying the voltage to the electrodes.
A thin film transistor (TFT) array panel is one of the two display panels constituting the liquid crystal display and is used as a circuit board for independently driving each pixel in the liquid crystal display or in an organic electro luminescence (EL) display device. The thin film transistor array panel includes a scanning signal wire or a gate wire that transmits a scanning signal, an image signal line or a data wire that transmits an image signal, a thin film transistor that is connected to the gate wire and the data wire, a pixel electrode that is connected to the thin film transistor, a gate insulating layer that covers the gate wire, and an interlayer insulating layer that covers the thin film transistor and the data wire.
Each layer of a thin film transistor array panel is formed using a photosensitive film. The pattern of each layer is formed by etching the films and then using the etched film as a mask.
An oxide semiconductor is generally used to form components of an array panel. In order to reduce damage of the oxide semiconductor by an etching solution, when a source electrode and a drain electrode are formed, an etching prevention layer is formed on the semiconductor layer, and a mask for forming the etching prevention layer is needed. As such, manufacturing costs are increased and a manufacturing process is complicated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not constitute prior art.

Thin film transistor array panel and manufacturing method thereof


The new blueberry plant variety ‘ZF06-079’ is provided. ‘ZF06-079’ is an ornamental variety intended for nursery, landscape, and home garden use. The plant has striking blue/green foliage with pink new growth throughout spring and summer and turns an attractive lavender color in the fall. The new variety ripens in mid-July in Oregon and produces mildly sweet berries in loose clusters. The plant is vigorous, with an estimated chilling requirement of 500 hours.

The present invention relates to the discovery of a new and distinct cultivar of northern highbush blueberry hybrid known as a Vaccinium corymbosum hybrid and referred to as 'ZF06-079', as herein described and illustrated.
The new blueberry plant variety 'ZF06-079' was selected in Lowell, Oreg., in 2006. 'ZF06-079' is an ornamental variety intended for nursery, landscape, and home garden use. The new variety has striking blue/green foliage with pink new growth throughout spring and summer and turns an attractive lavender color in the fall. The new variety ripens in mid-July and produces mildly sweet berries in loose clusters. The plant is vigorous, with an estimated chilling requirement of 500 hours.
The new blueberry plant originated from a cross of 'Toro' (female parent, unpatented) by 'FLX-2' (pollen parent, U.S. Plant Pat. No. 19,381). The female parent was produced by a cross between 'Earliblue' (unpatented) and 'Ivanhoe' (unpatented). The pollen parent was produced by a cross between 'FL92-9' (unpatented) and 'Sunshineblue' (unpatented). The new blueberry plant variety 'ZF06-079' has been planted in replicated trials since 2007.
The new variety differs from the unpatented female parent 'Toro' in that 'ZF06-079' has smaller leaves, is smaller in size, and has pronounced pink and red new growth.
'ZF06-079' differs from the patented male parent 'FLX-2' in that 'ZF06-079' is smaller in size and has more pronounced pink and red new growth.
The new blueberry plant variety 'ZF06-079' has maintained its distinguishing characteristics throughout successive asexual propagations. The variety has been repeatedly asexually reproduced through softwood cuttings in Lowell, Oreg., and the clones are phenotypically identical to the original plant.


An apparatus for a flat panel is disclosed. The apparatus comprises a flat panel assembly and a hinge mechanism coupled to the flat panel assembly. The hinge mechanism is adaptable to an industry standard mount and a non-industry standard mount. A system and method in accordance with the present invention allows for the replacement of a non-VESA standard compatible display mount with a display mount that is compatible with the VESA standard. Utilizing the system and method in accordance with the present invention, such a replacement can be accomplished with minimal effort, and in an efficient manner.

Flat panel displays have advanced to the point of being comparable with CRTs with respect to resolution, color capabilities and image quality. In most environments, flat panel displays are more desirable than CRTs due to their compact, portable size and low weight.
In an integrated computer system environment it is desirable to be able to mount and remove the display from an integrated computer system in an easy and convenient manner. In addition, due to the proliferation of different and incompatible flat panel display interfaces, it is difficult, costly and time consuming to integrate flat panel displays into notebook computers, instrumentation and other devices with integrated displays.
The Video Electronics Standards Association (VESA) has developed a flat panel display interface standard that standardizes mounting specifications. Accordingly, it is desirable that a flat panel display have a VESA compliant mounting system and also be able to be adapted to a non-VESA compliant mounting system.
Accordingly, what is desired is a flat panel display which can rotate in a variety of directions, be easily mounted in an integrated computer environment, and which is also VESA compliant yet able to be adapted to a non-VESA compliant mounting system. The flat panel display should be cost effective, easily adapted to existing integrated computer environments and be easily removed from and mounted in such an environment. The present invention addresses such a need.

Flat panel display including a hinge assembly


An electrical device and method are presented, the device having an enclosure defining an interior volume sealed from the environment and an electronic lighting apparatus, which may include a heat generating element such as a light source, a heat sink, and a fluid flow generator, and optionally a support offsetting the fluid flow generator form the heat sink. The heat sink may be positioned adjacent the heat generating element and transfer heat there from. The fluid flow generator may create a flow of fluid to transport heat away from the heat sink and to the enclosure. The electronic lighting apparatus may be carried by the enclosure and partially disposed within the interior volume of the enclosure. The electrical device may further include an optic carried by the enclosure.

Cooling systems for digital devices have traditionally employed a heat sink thermally coupled to the digital device. In some other systems, a fan has also been employed to direct a flow of air through the heat sink, thereby accelerating the dissipation of heat from the heat sink and, therefore, from the digital device.
However, traditional cooling systems for digital devices have also relied upon a supply of relatively cool air from the environment to blow onto and transfer heat away from the digital device. As a result, proposed solutions in the prior art have included vents, apertures, or other openings generally into the housing of the digital device to provide a supply of cool air from the environment.
The introduction of air from the environment into the housing of a digital device may also results in the introduction of contaminants. Substances carried along with the environmental air can inhibit and impair the operation of the digital device, causing faulty performance by or early failure of the digital device. Moreover, the accumulation of contaminants in the cooling system can result in a reduction in efficacy of the cooling system. Accordingly, there is a need in the art for a cooling system that can operate in a system sealed from the environment, hence without a supply of air external the sealed system.
Sealed cooling systems are known in the art. As an example, a Peltier device can be used to cool a digital system without a supply of external air. However, Peltier devices are expensive to produce and use electricity inefficiently in comparison to more traditional cooling systems. Accordingly, there is a need for a cooling system in a sealed environment that is inexpensive to produce and is energy efficient.
Other proposed solutions have included the use of a sealed system containing a fluid thermally coupled to the digital device in association with a radiator where fluid warmed by the digital device radiates the heat into the environment. However, these systems require significant amounts of space in order to pipe the fluid between the radiator and the thermal coupling with the digital device. Accordingly, there is a need for a cooling system that can operate in a space-limited sealed system.

Sealed electrical device with cooling system and associated methods


This invention relates to an electron multiplier unit and others enabling cascade multiplication of electrons through successive emission of secondary electrons in multiple stages in response to incidence of primary electrons. The electron multiplier unit has a first support member provided with an inlet aperture for letting primary electrons in, and a second support member located so as to face the first support member. The first support member is provided with a focusing electrode functioning to alter trajectories of the primary electrons, in order to guide the primary electrons to the inlet aperture. These first and second support members hold an electron multiplication section for the cascade multiplication and an anode. The electron multiplication section comprises at least a first dynode of a box type and a second dynode having a reflection type secondary electron emission surface located so as to face the first dynode and arranged to receive secondary electrons from the first dynode and to emit secondary electrons to a side where the first dynode is located. The anode is located at a position where the secondary electrons emitted from the first dynode do not directly arrive, and the second dynode alters a travel path of secondary electrons so as to be kept in a space between the first and second support members.

1. Field of the Invention
The present invention relates to an electron multiplier unit enabling cascade multiplication of electrons through successive emission of secondary electrons in multiple steps in response to incidence of primary electrons, and to a photomultiplier including the same.
2. Related Background Art
The following conventional technologies are known as techniques prior to the electron multiplier unit and the photomultiplier including it according to the present invention.
Japanese Patent Application Laid-Open No. 7-245078
Japanese Patent Application Laid-Open No. 4-315758
WO98/33202
U.S. Pat. No. 5,914,561

Electron multiplier unit including first and second support members and photomultiplier including the same


A hydroponics apparatus includes a housing; two or more channels provided vertically on one side of the housing to be spaced apart from each other; brackets coupled to the channels; and cultivation modules seated on the brackets, wherein a plurality of cultivation modules is fitted and coupled to each other to have an extended form and water channels are formed to communicate with each other, the cultivation modules in the extended form are coupled to each channel and seated through a plurality of brackets disposed in a horizontal direction, and the plurality of brackets are coupled to the channels so that heights are gradually increased or decreased from one-side bracket in the horizontal direction to the other bracket in the horizontal direction to form an inclination of the water channel.

A plant factory is a technique for producing plants in a closed or semi-closed space that regulates an internal environment, and may refer to an environmental conservation production system for the purpose of safe grocery supply and anniversary supply of planting.
The plant factory is not affected by a hypothetical variation such as cold summer or warm winter, typhoon, and not damaged by pathogens or pests. Accordingly, plants can be supplied with quality such as a constant amount, a constant shape or taste, nutritious, and a stable price, and a stable price without bad harvest. Further, the plant factory is not invaded with pathogens or pests and not required for pesticide application to prevent and exterminate pathogens or pests. As a result, eco-friendly production by non-pesticides is enabled.
However, the plant factory developed far mainly consists of small plant factories, and it is difficult to replace a large-area farm. As described in prior arts, up to now, the problem is caused in that a cultivation module of the plant factory can not help having certain length and area. Therefore, there is a need for technologies that maximize the length and area of the cultivated module of the plant factory.


A high performance reflection type photocathode for use in a photomultiplier tube is formed by sequentially depositing three layers on a substrate made of nickel. The first layer is made of either one of chromium, manganese and magnesium as a major component and is deposited over the substrate. The second layer is made of aluminum as a major component and is deposited over the first layer. The third layer is made of antimony and at least one kind of alkaline metals and is deposited over the second layer.

1. Field of the Invention
The present invention relates to a reflection type photocathode and a photomultipler using the same.
2. Description of the Prior Art
The photomultiplier is a very versatile and sensitive detector of radiant energy in the ultraviolet, visible, and near infrared regions of the electromagnetic spectrum. In the photomultiplier, the basic radiation sensor is the photocathode which is located inside a vacuum envelope. Photoelectrons are emitted and directed by an appropriate electric field to an electrode or dynode within the envelope. A number of secondary electrons are emitted at the dynode for each impinging primary photoelectron. These secondary electrons in turn are directed to a second dynode and so on until a satisfactory gain is achieved. The electrons from the last dynode are collected by an anode which provides the signal current that is read out.
One type of the photomultipliers uses a reflection type photocathode and another type thereof uses a transmission type photocathode. The reflection type photocathode is typically made up of a nickel substrate, an aluminum layer deposited over the substrate, a layer of antimony and alkaline metal such as cesium (Cs), natrium (Na) deposited over the aluminum layer.
Various properties of the reflection type photocathode changes considerably depending on how the layer structure is determined or what kind of materials is used for each layer.

4-layer structure reflection type photocathode and photomultiplier using the same