This invention is of a drilling fluid composition containing a liquid thixotrope, which thixotrope is free of solvents or any other diluent, and is in easily usable, liquid form, pourable at ambient temperatures, and which provides effective and efficient rheological properties when used at low levels in such compositions. In a specific aspect, the invention provides an oil or oil invert emulsion drilling fluid composition containing one or more organoclays, and in addition contains a additive which comprises the reaction product of an alkoxylated nitrogen containing compound or a diamine, and one or more polycarboxylic acids in a specified equivalent ratio.

The invention hereof relates to improved drilling fluids also known in the oil service industry as drilling muds, and, in particular, to oil and invert oil based emulsion types of drilling fluids in which water is dispersed in an oil-based medium. Such drilling fluid compositions when prepared at a mud plant are often called mud plant formulations.
Mud plant formulations contain special materials to enhance drilling fluids properties such as rheology, therefore providing a drilling fluid that is homogeneous and stable and which prevents the weighting material used from settling out during transportation and storage. Once the drilling fluid is used and circulated through the bore-hole it becomes known as a field mud, indicating the mud contains bore-hole cuttings and other contaminants. Additives used to enhance specific properties of the mud plant formulation should not adversely affect mud performance while in the bore-hole. However, these materials in a preferred manner also provide on-going beneficial properties and enhanced mud performance during circulation through the bore hole.
The invention is particularly directed to providing novel fluids with enhanced rheological and anti-settling properties; anti-settling is the ability of the fluids to retain in suspension in their structure, and to convey along with the fluid a variety of types of solid particles, the most important of which are weighting materials and bore-hole cuttings. These properties are particularly valuable when non-vertical directional drilling is undertaken.
The present invention particularly relates to drilling fluid compositions or systems containing a described liquid additive that also reduces or eliminates settling of the weighting material during storage and transportation to the rig and during the drilling operation. The present invention more particularly involves a drilling fluid containing an improved additive which additive is in a pourable, liquid form at ambient temperatures and which does not need a solvent to achieve its liquid state. Such an additive, when incorporated under low shear mixing typically encountered in the mud plant into a drilling fluid, provides improved suspension of weighting agents and other additives both during storage, during transport to the rig and during use in the bore hole.
Surprisingly the additive, described below at length, works in a most preferred embodiment in a synergestic and harmonious manner with organoclays in the fluid, to provide a system which effectively works at both low shear and ambient temperature and at high shear and elevated temperatures.
Drilling Fluid Compositions
United States oil industry rotary bit discovery drilling operations use xe2x80x9cdrilling mudsxe2x80x9d or drilling fluids. These muds are pumped under pressure down through a long string of drill pipe, then through the center of the drilling bit at the hole bottom, then back up through the annulus between the outside of the string of drill pipe and up the borehole wall to the surface. Oil-based drilling fluids, the liquid carriers of the mud, are often comprised of oils (diesel, poly alpha olefins or mineral, propylene glycol, methyl glycoside, and modified esters and ethers) and invert emulsions of oil in which water is dispersed in an oil-based medium.
Drilling muds provide a number of interrelated functions to satisfy the requirements of the oil industry for a commercial drilling fluid. These functions may be grouped as follows:
(1) The fluid must suspend and transport solid particles to the surface for screening out and disposal.
(2) It must transport a clay or other substance capable of adhering to and coating the uncased borehole surface, both (a) to exclude unwanted fluids which may be encountered, such as brines, thereby preventing them from mixing with and degrading the rheological profile of the drilling mud, as well as (b) to prevent the loss of downhole pressure from fluid loss should the borehole traverse an interval of porous formation material.
(3) It must keep suspended an additive weighting agent (to increase specific gravity of the mud), generally barytes (a barium sulfate ore, ground to a fine particular size), so that the entire column of drilling fluid is not interrupted upon encountering pressurized pockets of combustible gas, which otherwise would tend to reduce downhole pressure, as well as creating a xe2x80x9cblowoutxe2x80x9d in which the fluid and even the drill stem are violently ejected from the well, with resulting catastrophic damages, particularly from fires.
(4) It must constantly lubricate the drill bit so as to promote drilling efficiency and retard bit wear.
The interrelatedness of these functions can be seen by the fact that the unwanted materials to be removed at the surface can include not only xe2x80x9ccuttingsxe2x80x9d from the material through which the bit is passing, but also pieces of the drill bit itself, the barytes or other weighing materials, and substances particles such as gellants, dissolved gases, and salts created when other fluid constituents become xe2x80x9cspentxe2x80x9d under the high temperatures encountered in deeper wells, and sometimes fuse in agglomerative particles. Every substance added to achieve a desirable property, such as improved lubrication or pressure control, potentially results in the ultimate creation of a waste to be removed.
It should be noted that a drilling fluid must perform its various functions not only when the drill bit is actively encountering the bottom of the borehole, but also at times when the drill stem is inactive, or is being removed or re-inserted for some purpose. In particular, cuttings must be held in suspension in the event of shut-downs in drilling.
The Anti-settling Properties of Drilling Fluid Compositions
An ideal drilling fluid is a thixotropic system. That is, (1) it will exhibit low viscosity when sheared, such as during agitation or circulation (as by pumping or otherwise) but, (2) when the shearing action is halted, the fluid must set or gel to hold the cuttings in place, and it must become gelled relatively rapidly, reaching a sufficient gel strength before suspended materials fall any significant distance and (3) this behavior should be almost totally reversible. In addition, even when it is a free-flowing liquid, the fluid must retain a sufficiently high viscosity to carry all unwanted particulate matter from the bottom of the hole to the surface. Moreover, upon long-term interruption of circulation, such as when drilling fluid has been ejected from the borehole into a quiescent holding vessel or pond, the gel structure should be such as to allow the cuttings and other unwanted particulates over time to settle out from the liquid fraction.
A principal problem facing xe2x80x9cmud chemistryxe2x80x9d scientists and technicians is the production of drilling fluids, with the necessary thixotropic properties discussed above, which at the same time must possess critically important anti-settling properties. Drilling compositions have over the years involved the attention of both scientists and artisans, with scores of various improvements made and patented. The compositions of these various fluids may be considered a xe2x80x9cblack artxe2x80x9d to manyxe2x80x94in reality such fluids and their additives involve highly complex chemical, physical and rheological analysis using advanced scientific apparatus and intricate mathematical calculations and modeling.
xe2x80x9cAnti-settlingxe2x80x9d involves considerations of assurance of suspension and control of widely-varying matter including weighting materials during transportation of the fluid to the drilling site. It ideally entails the necessity of a measure of control when shear rate and force is high, low, or non-existent, and requires control of syneresis and deposition of such particles over wide ranges of a) temperature (from 0xc2x0 to as high as 300xc2x0 C.), b) time durations, c) pressures (from only a few bars to those exerted by a column of fluid that can extend for thousands of feet) and d) drilling directions (from vertical to horizontal).
A search has been going on for many years for an improved additive for modifying and controlling the suspension properties of drilling fluids that would be efficient, easily handled, and readily dispersible in a broad range of drilling muds, and usable under a broad range of conditions.
Oil and Oil Invert Emulsion Drilling Fluids
Drilling fluids or muds are typically classified according to their base fluid or continuous phase, as water base muds and oil base muds. Drilling muds may contain a mixture of base fluids, and are typically classified by the predominating or continuous base fluid, with the fluid present in lesser quantities becoming the internal or emulsified phase.
The use of oil and invert oil-based drilling fluids or muds in oil exploration is increasing rapidly owing to the more demanding requirements encountered in drilling deep and/or non-vertical and deviated wells. Compared with the longer-established water-based drilling muds, they possess a number of advantages, including reduced interaction with earth formations, and improved lubricity. While the drilling fluids and methods of this invention are particularly useful in invert emulsion systems, they also find use in other oil-based muds.
Oil base muds may have an aromatic or aliphatic oil, or a mixture of oils, as the continuous phase. These oils may include diesel, mineral or synthetic (PAO, esters, ethers) oil. They may be comprised entirely of oil, or more commonly may contain water ranging from 5% to upwards of 50%. In this mud, water becomes the internal phase, is emulsified into the oil, as a heterogeneous fine dispersion and the resulting system is referred to as a oil-based or oil-invert emulsion mud. Oil-invert emulsion drilling fluids are generally used throughout the world and consist of a three-phase system: oil, water and fine particulate solids. The aqueous phase may be a brine. The addition of brine reduces the overall price of the fluid, reduces the risk of combustion of the oil, and improves the water acceptance of the mud. The brine of choice is commonly an aqueous solution of an inorganic salt such as sodium chloride or calcium chloride.
Emulsifiers, weight agents, fluid loss additives, salts and numerous other additives may be contained or dispersed into the mud at the mud plant or during use to improve its performance with respect to one or more properties. These additives may be organic or inorganic in nature.
How Drilling Muds Work
As was noted above, the drilling fluid used is pumped under pressure down through the string of drill pipe, through the center of the drilling bit, then through the annulus between the outside of the drill stem and the borehole wall, back up to the surface. This circulation constantly removes the cuttings from the instantaneous bottom of the hole, and lifts them the entire distance from this bottom to the surface for disposal. Such a distance can be in the thousands or tens of thousands of feet.
Drilling fluids are designed to be shear thinning and possess less dynamic anti-settling properties when being circulated down the drill pipe and out the bit, and to exhibit a recovery to a high enough viscosity at low shear rate to provide higher anti-settling properties while rising back up through the annulus. The presence of unremoved cuttings in the fluid will decrease drilling penetration rates, with resultant increase in the overall costs of drilling the well. Once in the annulus, the cuttings, which are generally denser than the continuous phase of the drilling mud itself, tend to settle downward under the influence of gravity. Note that this means the upward velocity of the drilling fluid in the annulus must be higher than the settling rate, so as to bring the cuttings to the top of the hole.
As the bit cuts into the earth, the cuttings accumulate as drilling continues and the depth of the hole increases. A drilling fluid used to carry these cuttings to the surface for removal must allow the bit to continue functioning, and the ever-deepening bottom hole (where the bit is cutting) to be kept clean and free of cuttings at all times. As the hole deepens, the total amount of fluid involved will increase, and the difference between surface conditions and those experienced down-hole will increase. Even when a hammer drill or other non-rotary drilling system is used, a drilling fluid or the equivalent is still needed to remove the bore hole cuttings and to perform the other above-described functions normally performed in rotary drilling systems by drilling fluids.
Hydrocarbon drilling for exploratory and production wells has increasingly been done from platforms located in water settings, often called offshore drilling. Both deep-sea and shallow fresh and salt water drilling employ either floating barges or rigs fixed in some fashion to the submerged surface of the earth. Drill cuttings removed from the bore-hole must either be discharged to the surrounding body of water or transported to a remote location; the liquid phase of spent drilling fluid must similarly be disposed of. The disposal of cuttings may be inhibited by the presence of deleterious substances adhering to cuttings particles, whether oil from the fluid or a material encountered in the borehole. Cuttings can be cleaned to some extent by the use of vibrating screens or other mechanical separation devices, by washing techniques, and by chemical treatments. However, because of possible pollution to the environment, particularly the marine environment, the off-shore disposal of drilling fluids as well as of cuttings is increasingly discouraged. Rather, both the fluids and the cuttings are separately collected and transported to on-shore sites for rejuvenation or disposal.
Directional Drilling
The requirements for drilling fluids with enhanced properties have become more complex over the past decade as a result of improvements in directional drilling technology, in which at least a portion of the well is drilled at an angle other than vertical. Such wells are also known as deviated wells.
Procedures for deviating wells have improved greatly over recent years with the introduction of more powerful and reliable downhole motors, and the introduction of more accurate techniques utilizing wireline techniques as well as the latest computerized downhole, sensing and micro-reduction equipment, including improvements in sounding apparatus and microwave transmission. These techniques are collectively referred to as Measurement While Drilling (MWD) techniques, because they permit the obtaining of data relating to down-hole conditions without the need to remove the drill string.
There are, however, a number of inherent problems in this approach to directional drilling, which affect the anti-settling requirements of a drilling mud; namely:
(1) The annulus carrying the mud with cuttings to the surface is no longer vertical and extended in distance versus vertical wells.
(2) Gravity on a horizontal hole pulls cuttings, weighting material and particulate matter, not controlled by the drilling fluid, to the bottom side of the bore (not the bottom of the hole as in traditional drilling) and results in drag on the bore wall.
(3) Horizontal xe2x80x9cpay-outxe2x80x9d zones, in view of their substantial length, are more susceptible to settling formation damages and a resultant loss of flow efficiency.
(4) The amount of drilling mud required is increased since the distances are greater, and the time required for the cuttings to reach the earth""s surface also increases.
Two patents obtained by companies related to assignee describe drilling fluid additives which are not organoclays. U.S. Pat. No. 5,021,170 describes a viscosifying gellant for oil-based well bore fluids comprising a mixture of an organic clay and a sulfonated, ethylene/propylene/5-phenyl-2-norbornene terpolymer. U.S. Pat. No. 4,486,316 shows a drilling fluid comprising an aqueous dispersion of an emulsion polymerized latex comprised of an interpolymer of an olefinically unsaturated carboxylic acid monomer and at least one other, non-carboxylated polymerizable monomer, the latex being of a type which undergoes rapid increase in viscosity upon the addition of a sufficient amount of a basic material.
U.S. Pat. No. 5,254,531 describes oleophilic basic amine additives for invert drilling muds to regulate the flowability and pumpability of the drilling mud. The patent describes adding to the mud, containing an esterified oil, a basic amine compound having an oleophilic character and limited solubility in water and thereby forming in situ in the drilling mud an oil-soluble salt with said amine compound and a carboxylic acid formed by hydrolysis of the ester.
U.S. Pat. 4,781,730 describes an alkali metal or alkaline earth metal-containing composition (with or without a hydrocarbon-soluble dispersant) which are combined with the reaction product of a carboxylic acid and a polyhydroxyalkanolamine, with the preferred reaction product being an ester which forms between the hydroxyl moieties of the alkanolamine and the carboxylic acid (anhydride). The resultant compositions are discussed as useful for valve seat recession protection in internal combustion engines. The reaction product of the carboxylic acid and polyhydroxyalkanolamine acts as a demulsifier for the alkali metal or alkaline earth metal-containing composition. The patent describes a composition comprising a hydrocarbon-soluble or dispersible alkali metal or alkaline earth metal containing composition, and the reaction product of a polybasic acid and a polyhydroxyalkanolamine of the formula RN[(AO)xH][(DO)yH]. The polybasic acid may be either an acid or an anhydride, and is preferably a dicarboxylic acid.
As can be seen from the above brief review, the drilling fluid industry has constantly sought materials, alternatively referred to as thickeners, thixotropes, rheological additives or rheological control agents, which are used to control the rheological properties of drilling fluid compositions. Such rheological control agents must provide proper viscosity and rheological characteristics to the drilling fluid systems in which they are used. Depending on the composition of the system, the fluids made with these thickeners can be useful in a wide variety of oil-based drilling fluids.
Organophilic clays have long been known to be useful to thicken various drilling fluids and are used today in most drilling fluid compositions. Organoclays are very well known products and are the reaction product of smectite clay and quaternary amines. Exemplary U.S. Patents which describe various common kinds of such organically-modified clays are U.S. Pat. Nos. 4,208,218; 4,410,364; 4,412,018; and 4,517,112 which are incorporated by reference.
There are, however, drawbacks with the use of organically modified clays for thickening drilling fluid compositions. Most important of these drawbacks is that organoclays cause the fluid to increase in viscosity when subjected to the high shear and increased temperature encountered in a bore hole. This causes the mud to become very thick and much less useful.
Synthetic rheological thickeners have been used and include various amines and maleic acid and anhydride polymers in an attempt to avoid the use of organoclays. Two patents issued to Rheox Inc., assignee hereof show such productsxe2x80x94U.S. Pat. No. 5,034,444 to Han Bo Yun and U.S. Pat. No. 5,710,110 to Murray Cooperman.
While not in the drilling fluid art, U.S. Pat. No. 5,034,444 discloses a coating composition containing a rheological additive which is the reaction product of an alkoxylated aliphatic nitrogen containing compound or an aliphatic diamine with a polycarboxylic acid. The molar ratio of the two ingredients covers a broad rangexe2x80x94see col. 8, lines 10 to 15.
Two issued patents of one of the inventors hereof, i.e. U.S. Pat. Nos. 5,723,653 and 5,510,452 and U.S. pending patent application No. 09/023,064 filed Feb. 13, 1998 now U.S. Pat. No. 6,043,300 describe chemistry related to the chemistry described hereafter of the liquid additive used in the drilling fluid compositions of this invention.
Disadvantages of Current Systems
Organoclay thickeners for organic drilling systems are today prepared in solid form, and have been produced and used as thickeners in dry, solid form. Dispersion is critical to activation of the thickener and thickener efficiency is a direct function of dispersion into the system to be thickened. Problems associated with the use of solid thickeners, however, include poor dispersibility when added to organic systems under low shear conditions often encountered in the mud plant. When added to systems, solid thickeners by their nature tend to agglomerate to form clumps. Dispersion can be very slow, and can adversely affect the efficiency of specific manufacturing operations.
Particularly in formulations comprising other chemicals and ingredients, extended agitation and aging periods are required before proper incorporation and activation is attained. Even when such additives are furnished as solutions, they are still difficult to disperse uniformly, so as to avoid the production of local areas of high concentration. This difficulty requires users and formulators to develop crude empirical methods for estimating the final rheological properties of the drilling fluid formulations.
Manufacturers have long searched for a fast, effective and simple way of incorporating such thickeners into organic drilling systems. To satisfy this desire, some commercial solid thickeners and rheological additives are today sold for drilling compositions as liquids. Such thickening compositions are prepared by dissolving a solid rheological additive in an organic solvent, which solvent is Newtonian. The reason for the utilization of such an organic solvent is to lower the viscosity of the rheological additive, which is non-pourable and solid, to provide ease in handling as a liquid. The choice of type and percentage of solvent depends on the desired viscosity of the thickening composition mixture. Typically, the viscosity of the pourable thickening composition mixture should be less than about 250-300,000 cP (at 10 RPM with a Brookfield RVT viscometer) so that it will readily pour from the storage container as a liquid, and rapidly incorporate into the system to be thickened at room temperature. The solvent selected for each such commercial composition has, up to this time, almost exclusively been a volatile organic solvent. Ranges of ratios of 20% to 50% rheological additive to 50%-80% solvent are common for such commercial liquid products.
A liquid thickening composition having little or no VOC contributes little or zero VOC to the system being thickened, while having the advantage of being pourable.
The manufacture of drilling fluid compositions using a pourable thickener, which thickener is substantially 100% active, containing no or very little solvent, has been perceived heretofore as presenting daunting technical difficulties that led many scientists to conclude that it would be impossible to achieve. Rheological additives must provide high levels of viscosity or thickening, as well as anti settling properties to systems, which prior to such addition are often less viscous. Some systems, must in fact become very viscous as a result of the addition. The rheological additives must be efficientxe2x80x94when added at very small relative weight levelsxe2x80x94and must, therefore, have the ability, at such levels, to impart significant increases in viscosity to much larger volumes of organic drilling systems. Rheological additives in fact often must impart to drilling fluid systems at very low shear rates a behavior that approaches that of a solid which remains in place in the drilling hole. These requirements led scientists to wrongly conclude that such additives must themselves have very high viscosity levels, and that they must be either solid or solid-like.
In summary, in the manufacturing of oil and oil based emulsion drilling fluids, despite the numerous types of rheological additives known in the art, research has been independently and simultaneously conducted toward both 100% active liquid thickeners that are in pourable, pumpable forms, and which are highly efficient and are readily dispersible in the composition to be thickened; and, in addition, toward non-VOC-containing rheological additives which overcome the deficiencies associated with prior art volatile solvent-mixed thickeners.
Obiects of the Invention
It is a specific object of the present invention to provide an invert emulsion drilling fluid which contains organoclays and one or more additives as described herein which has very rapid viscosity increase under low shear conditions. When incorporated into a fresh or new drilling fluid the viscosity build is effective at suspending solids such as weighting materials during transport to a drilling rig and provides the drilling fluid during use in the bore hole with enhanced properties over a wide temperature and shear range.
It is a further object of the present invention to provide an additive to an invert emulsion drilling fluid, which can contain or not contain an organoclay, which will prevent settling of the other additives in the drilling fluid, during the transfer of the drilling fluid from the mud plant to the drilling site.
It is a further object of the present invention to provide a drilling fluid using a rheological thixotrope which thixotrope is either entirely free of volatile solvents, or contains a greatly reduced amount of such solvents, is easily incorporated into the fluid and is in a pourable, pumpable form fluid at ambient temperatures.
Summary of the Invention
The invention discloses new drilling fluids, particularly oil invert drilling muds, which are distinguished by improved anti-settling properties, high ecological acceptability, and at the same time exhibit good storage, transportation and application properties. Invert emulsion drilling fluids are described at length in U.S. Pat. No. 4,436,636, obtained by NL Industries, Inc., a predecessor of the assignee herein.
One important area of application for the new drilling fluid systems is in both on and off-shore wells for the development of hydrocarbon deposits, the aim of the invention being particularly to make available industrially usable drilling fluids with enhanced anti-settling properties over wide temperatures and shear ranges. The use of the new drilling fluid systems has particular significance in the marine environment, but is not limited to this field. The new mud system also can be put to use in land-based drilling operations beyond hydrocarbons, for example, in geothermal wells, bore-holes for water, deep waste injection-disposal wells, geoscientific bores, and solution-extraction mining bores such as those for common salt.
In addition to organoclays and the additives described herein, the inventive drilling fluid may contain other additives providing other properties, so as to obtain desired application properties, such as, for example, emulsifiers or emulsifier systems, weighting agents, fluid loss-prevention additives and wetting additives.
This invention is of drilling fluid system containing a liquid thixotrope, which thixotrope free of solvents or any other diluent, is in easily usable, liquid form, pourable at ambient temperatures, and provides effective and efficient rheological properties when used at low levels in such systems.
In one specific aspect, the present invention provides an oil or oil invert emulsion drilling fluid composition, which contains a rheological additive which comprises the reaction product of a) an alkoxylated nitrogen containing compound or a diamine, and b) one or more polycarboxylic acids. This additive is liquid and pourable at or at nearly 100% active material without the need of a volatile solvent, and provides acceptable rheology and viscosity to a large variety of organic and other systems at low levels of use.
Further advantages and features of the invention, as well as the scope, nature and utilization of the invention, will become apparent to those of ordinary skill in the art from the description of the preferred embodiment of the invention set forth below.
This invention in a most preferred embodiment is of drilling fluid system containing in addition to one or more organoclays a specific liquid thixotrope/anti settling additive. When such thixotrope is incorporated under low shear conditions into a drilling fluid, such as by typical mud plant mixing devices, sufficient viscosity to suspend solids such as weighting agents is developed. This increased viscosity is sustainable during drilling fluid transportation so to allow a homogeneous fluid to be transported from a mud plant to a drilling rig.
Downhole conditions of drilling, particularly high shear as when a fluid is pumped through a drilling bit and increased temperature, substantially reduce the viscosity built by the additives of the present invention. This is of surprising benefit as organophilic clays presently used in invert emulsion drilling fluids tend to build viscosity when subjected to high shear and increased temperature when circulated through a drilling bit.
The increase in viscosity for the organoclay coupled with the viscosity losses from the additives of the present invention allow the drilling fluid to maintain a constant viscosity with respect to circulating a new mud through a drilling bit. The fall of viscosity provided by the additives of this invention sustains flat rheology and prevents the mud from becoming excessively thick and difficult to pump, due to the increased viscosity provided by the organoclay at high shear especially in cold water. If the defined additives did not provide this viscosity reduction, the mud would become very thick.
One aspect of the present invention relates to drilling fluid compositions comprising:
a) an oil or invert oil drilling fluid base formulation containing one or more organoclays and;
b) one or more rheological additives which when free of diluent are pourable at room temperature comprising the reaction product of:
i) one or more polycarboxylic acids; and
ii) a chemical selected from the group consisting of one or more liquid alkoxylated nitrogen containing compounds and polyether diamines which contain xe2x89xa72 active hydrogen groups;
wherein the ratio of the equivalents of carboxylic acid groups to the equivalents of active hydrogen groups is between 1.05 to 2.10.
It is important to control the stoichiometry of the reactants in order to prepare ester-terminated polyamide according to the invention. In the following discussion regarding the reactant stoichiometry, the term xe2x80x9cequivalent(s)xe2x80x9d will be used, and is intended to have its standard meanings as employed in the art. However, for additional clarity, it is noted that equivalents refer to the number of reactive groups present in a molar quantity of a molecule, such that a mole of a dicarboxylic acid (e.g., sebacic acid) has two equivalents of carboxylic acid. Furthermore, it is emphasized that the diacid has only two reactive groups (both carboxylic acids), and that diamine has only two reactive groups (preferably both primary amines), and these are preferably, although not necessarily, the only reactive materials present in the reaction mixture.
The compositions of the present invention are drilling fluids containing organoclay additives and, in addition, the additives more clearly defined below, which effectively impart thixotropic properties to the systems in which they are utilized. These properties are equal or better than previously known and are effective over wide ranges of shear and temperature. When used, the additives contain no solvent, or may optionally contain substantially reduced solvent. Organic or other solvent can be used at less than about 25% by weight if convenient for either manufacture or use. Compared to recent solid additives disclosed in the art, the rheological additives of this invention can be incorporated in the drilling system as liquids.
Compound a), the oil or invert oil drilling fluid base formulation, is broadly defined to mean any combination of chemicals used to prepare oil and oil inert emulsion drilling fluids as well known in the industry. In the most preferred embodiment such base formulation includes one or more organoclays. Some representative chemicals often contained in such base formulation are weighting agents, barytes, emulsifiers, fluid loss additives, salts, anti-fracture additives, and so forth.
Compounds useful for element b)i), include one or more polycarboxylic acid or acids. Such acids can be selected from the dicarboxylic acid oligomers of fatty acids having carbon chain length of from 16 to 20 carbon atoms. Exemplary fatty acids are those derived from soybean oil, tall oil, corn oil, linseed oil, cottonseed oil, castor oil, kapok seed oil, rice bran oil and mixtures thereof. Even further preferred are oligomers of fatty acids, which are substantially comprised of the dimerized fatty acid. These are normally called xe2x80x9cdimer acids.xe2x80x9d These dimerized fatty acids constitute at least 75% by weight of dibasic acid.
The oligomerized fatty acid used preferably also may have a low monomer content such as less than about 8% by weight. The dimerized fatty acids also preferably should have a low polybasic acid content, such as less than about 20% by weight. Useful dimer acids are commercially available under the trade names Empol Dimer Acids from Henkel Corporationxe2x80x94Emery Group and Pripol Dimer Acids from Uniqema International. Illustrative useful preferred examples of dimer acids are Pripol 1015, Pripol 1025, Empol 1008, Empol 1018, Empol 1016, and the like. The term xe2x80x9cdicarboxylic acidsxe2x80x9d is also used to include hydroxyl substituted dicarboxylic acids.
In addition to the dicarboxylic acids, polybasic acids, which contain more than two carboxylic acid groups are also useable. Representative examples of these polybasic acids are trimellitic acid, trimesic acid, citric acid, 1,2,3,4-butane tetracarboxylic acid and the like. Polymerized polybasic acids, which contain more than two carboxylic acid groups are also included in the definition of polybasic acids. Especially preferred polymerized polybasic acids are fatty acids having carbon chains from 48 to 60. The polymeric polybasic acids with 3 carboxylic acid groups are known as xe2x80x9ctrimer acidsxe2x80x9d. These trimer acids are commercially available under the trade name Empol from Henkel Corporationxe2x80x94Emery Group, Pripol from Uniqema International and Unidyme from Union Camp Corporation. Representative examples of these trimer acids are Pripol 1040, Empol 1043, Empol 1052, and Unidyme 60. More preferred trimer acids are Pripol 1040 and Empol 1043, and a most preferred trimer acid is Pripol 1040. Pripol 1040 is substantially comprised (by weight) of polybasic acid (67%), dibasic acid and (31 %), and monobasic acid (2%). The amount of tri- and higher polybasic acids selected for use can be important. The amount of trimers and polybasic acids should preferably not be excessive.
Compounds useful for element b)ii) include liquid alkoxylated nitrogen containing compounds containing xe2x89xa72 active hydrogen groups such as alkoxylated aliphatic amine diols and alkoxylated aliphatic amide diols, which are liquids at ambient temperatures. These compounds can normally be selected from tertiary amines with one alkyl group and preferably two hydroxyalkyl or polyoxyalkylene groups attached to the nitrogen atom and have a general chemical structure represented by the following formula (I):
where:
(1) R1, which also provides another one of the important functions of the invention, is a pendent straight or branched chain aliphatic alkyl or alkenyl or amido radical having 6 to 40 carbon atoms, preferably 8 to 20 carbon atoms, and most preferably 10 to 18 carbon atoms. Especially preferred is where R1 is either Rn or Rnxe2x88x921Cxe2x95x90O where n is 12 to 18 carbon atoms such as coco, stearyl, soya, tallow, hydrogenated tallow, oleyl and mixtures thereof.
(2) R2 and R3 are independently selected from hydrogen or methyl.
The oxyalkylene group, which also provides one of the important functions of the invention, is represented by
where R2 and R3 are independently selected from hydrogen or methyl group and z=x or y from the previous formula and the oxyalkylene group is preferably ethoxy, propoxy or a mixture thereof. At least one of x or y is at least 1, preferably both x and y are at least 1 and the sum of x+y is from 1 to 40, preferably 2 to 30, and most preferably 2 to 20. Illustrative examples of such alkoxylated aliphatic amine diols useful in this invention and represented by formula (I) are available under the trade name Varonic, from Witco Corporation, and Ethomeen from Akzo Chemie America, and include polyoxyethylene(5)cocoamine, polyoxyethylene(10)cocoamine, polyoxyethylene-(15)cocoamine, polyoxyethylene(5)octadecylamine, polyoxyethylene(10 )octadecylamine, polyoxyethylene(15)octadecylamine, polyoxyethylene(5)tallowamine, polyoxyethylene-(15)tallowamine, polyoxyethylene(5)oleylamine, polyoxyethylene(15)oleylamine, polyoxyethylene(5)soyaamine, polyoxyethylene(10)soyaamine, polyoxyethylene-(15)soyaamine, wherein the number in parentheses is the sum of x+y. Useful alkoxylated aliphatic amides are also available from Akzo Chemie America under the trade name Ethomid. The use of one or more liquid alkoxylated nitrogen-containing compounds assists in making a rheological additive which is an easily pourable or pumpable liquid at ambient temperatures, but which when dispersed will provide substantial viscosity to the system to be thickened. The presence of an unsaturated moiety or moieties of the fatty chain in the liquid alkoxylated compound provides the additional benefit of lowering the melting point of the resulting rheological additive, thereby assisting in assuring a liquid rheological additive at room temperature.
Also useful for element are b)ii) polyglycol polyamines. These polyamines contain primary amino groups attached to the termini of the polyether backbone. They are also known, and referred to hereafter, as polyetherdiamines. The polyetherdiamines make up a family of products having repeating polyether backbone structures containing repeating propylene oxide, ethylene oxide, or mixed ethylene oxide/propylene oxide units such as polyoxyalkylene diamines of the formula
H2Nxe2x80x94R1xe2x80x94(OR2)xxe2x80x94NH2xe2x80x83xe2x80x83(II)
And
H2Nxe2x80x94R1xe2x80x94(OR2)axe2x80x94(OR3)bxe2x80x94(OR2)cxe2x80x94NH2xe2x80x83xe2x80x83(III)
where R1 is the alkylene group, R2 and R3 are ethylene or propylene groups, x, a, b, and c indicate number of repeating units of ethylene oxide and propylene oxide groups. These repeating units are present on average more than once.
Polyetherdiamines can also be derived from random copolymers of the formula:
H2Nxe2x80x94R1xe2x80x94[xe2x80x94(OR2)acxe2x80x94(OR3)bcxe2x80x94]cxe2x80x94OR4xe2x80x94NH2xe2x80x83xe2x80x83(IV)
where R1 and R4 are the alkylene groups, R2 and R3 are ethylene or propylene groups, a, b and c are integers.
Polyetherdiamines known in the trade as polyglycol polyamines of various molecular weights are sold under the trade name xe2x80x9cJeffaminesxe2x80x9d by Huntsman Corporation, are also useful. Representative examples of such diamines are Jeffamine D-230, Jeffamine D-400, Jeffamine D-2000, Jeffamine ED-600 and Jeffamine ED-900.
Suitable polyetherdiamines also include the urea condensates of Jeffamine-D series products of the formula
where R1 is the alkylene group and n is, on the average 5.6, such as Jeffamine DU-700.
Formula II and formula III represent preferred polyetherdiamines with molecular weights ranging from 200-6000. According to the present invention a mixture of diamines is also preferred so that the average effective molecular weights range from 300-2000.
Most preferred polyetherdiamines are Jeffamine D-400 and Jeffamine ED-600. The most preferred polyetherdiamine according to this present invention is Jeffamine D-400.
The rheological compounds used in the inventive drilling fluids made according to this invention are preferably formed as the condensation reaction product of b)i) and b)ii). It is important to this invention that the reactive moieties of compound b)i) be in stoichiometric excess of the active moieties of compound b)ii) within the ratio defined above in an amount so that no substantial unreacted compound b)ii) remains after the reaction is completed. It is important to note in this regard for example that the ratio of the equivalents of carboxylic acid groups in component b)i) to the equivalents of active hydrogen groups in component b)ii) be between 1.05 and 2.1. The reaction product of b)i), and b)ii) results in a polymer with termini that contain carboxylic acid units and which functions as a rheological and anti settling additive in a similar manner to that previously described.
The product of this reaction is a liquid polymer preferably with a molecular weight of  less than 50,000 and most preferably from 2,000-15,000. Higher molecular weight products often produce solid materials. The rheological additives of the present invention are preferably fully liquid without a diluent and of a molecular weight that permits pourability.
The useful rheological additive may be prepared according to the known polycondensation reaction. The order of the addition of the co-reactants is not generally important and these can be added either at ambient temperature or at reaction temperature. For example, the reactants may be charged in increments to a suitable reaction vessel equipped with a mechanical stirrer, a thermometer, a Dean-Stark adapter or other water collector and a nitrogen inlet. The vessel containing the reactants is heated under a blanket of nitrogen. The reaction may be carried out under atmospheric pressure or under vacuum. The reaction temperature to be used in the synthesis may be varied, but preferably ranges from ambient temperature to 300xc2x0 C. under normal pressure. More preferably, the temperature ranges from ambient to 250xc2x0 C., and most preferably from 120xc2x0 to 220xc2x0 C. Water is removed as condensate as the reaction progresses. After the completion of the reaction, the additive is cooled and discharged.
The rheological additive of the present invention may be used to thicken a variety of organic and solvent-based drilling fluid compositions. The additive is particularly useful, for example, in thickening aliphatic and aromatic solvent-based and synthetic oil-based drilling fluid compositions, and may also be used in polar (ketones, alcohols, esters) based compositions.
The liquid rheological additives are preferably used in oil-mud formulations. By the use of small amounts of these liquid additives in conjunction with organoclays improved drilling mud formulations are obtained. These additives produce higher yield points, and higher low shear rheology, while maintaining relatively constant plastic viscosities over a wide range of temperatures and shear ratios.
Since the additive is an easily pourable or a pumpable rheological liquid it can be incorporated very easily into a variety of drilling fluid compositions at various stages of their preparation. It can be added at the beginning of processing, during processing, as a post-add, or during drilling operations.
The amount of rheological additive used in a specific instance is determined by numerous factors, including the type of the drilling fluid composition to be thickened, and the level of thickening desired. However, a general range is from about 0.5 to about 30 pounds per barrel of composition. On a weight basis, the amount of the rheological additive is generally from about 0.1 to about 10% by weight, preferably from about 0.1 to about 8% by weight, more preferably from about 0.1 to about 5% by weight and most preferably from about 0.2% to about 3% by weight of the system to be thickened.
The rheological additives used in the present invention may be synthesized with or without a catalyst. The catalyst, if used, may be selected from those, which are normally used for condensation reactions. Examples of such catalysts include, but are not limited to, sulfuric acid, p-toluene sulfonic acid, dibutytin dilaurate, tetraalkyl tin or titanium compounds, metal hydrides and the like. A preferred catalyst is p-toluene sulfonic acid. The catalyst should generally be used in an amount of from about 0.001 to 2.5 percent by weight based on the total weight of the reactants.
The additive useful in the present invention may be manufactured with or without an organic solvent. Since the form of the rheological control agent is a solvent-free diluent-free pourable liquid, it is preferable to synthesize the product in a solvent-free environment. Since the solvent-free product may be a viscous liquid, it may be appropriate to use a solvent at the let down stage during the synthesis to make the product even more pourable. When a solvent is used during synthesis, the type of solvent is not critical except that it be unreactive with the reactants. If it is appropriate to use a solvent during the synthesis, the same solvent used into the drilling mud composition in which the rheological additive could be incorporated may be preferred.
Solvents, if used, for synthesizing the rheological additive useful in the drilling fluids of this invention are preferably aromatic solvents, such as toluene, xylene, aromatic petroleum distillates and mixtures thereof, aliphatic solvents such as hexane, heptane, cyclohexane and aliphatic petroleum distillates and mixtures thereof. The most preferred such solvents are aromatic petroleum distillates such as being sold under the trade name Aromatic 100 by Exxon Chemical Company. A combination of solvents could be employed as long as the solvents are compatible with the addition to the total mud formulation. The solvent should generally be used from 0 to 25 percent by weight of the reaction mixture, most preferably 0 percent.
The useful rheological additives described are preferably solvent-free (zero VOC) or contain substantially reduced solvent (low VOC) and they are thus easily incorporated with all drilling fluid including deepwater systems regardless of VOC specification. Since the rheological additives are easily pourable liquids, they are easily incorporated at low activation temperatures in almost all drilling fluid systems.
Rheological additives generally are used in drilling fluids to provide viscosity needed to suspend weighting material and cuttings in a drilling fluid. Organoclay and polymeric viscosifier, for example, are added at the mud plant and on the rig under low shear mixing conditions. In the laboratory, such organoclays and polymeric vicosifiers are incorporated into the drilling mud using a Hamilton Beach or Multimixer mixers. Typically, the materials are added at low to medium speed to simulate mud plant mixing conditions. The rheological additives described for this invention similarly can be added at any point in the mixing procedure, providing there is sufficient base fluid to insure good mixing.
The liquid additives to be used in the inventive drilling fluids of this invention may be made using a variety of materials and by a variety of methods either disclosed herein, or which will appear obvious when the disclosure of this patent occurs. Applicants do not intend to limit the materials or methods of manufacture of such additives by the description above.
The rheological additives described in this invention can be added to a base fluid consisting of brine and emulsifiers preferably prior to weighting materials being added. The additive is then mixed to uniformly distribute the material in the drilling fluid. Mixture is preferably at low speed. After or before the rheological additives are incorporated, other additives including weighting materials and fluid loss additives can be incorporated completing the drilling fluid. We define an oil or invert oil base drilling formulation to be everything in the drilling fluid composition except the rheological additive.
Description of Tests

Oil and oil invert emulsion drilling fluids with improved anti-settling properties


The phosphor according to the invention has the following composition:

The invention is based on a phosphor for light sources and an associated light source in accordance with the preamble of claim 1. It relates in particular to a garnet phosphor which emits in the long-wave range of the visible spectral region and is to be excited by short wavelengths in the visible spectral region. Suitable light sources are in particular a lamp (primarily a fluorescent lamp) or an LED (light-emitting diode), which overall generates white light, for example.
WO 98/05078 has already disclosed a phosphor for light sources and an associated light source. In that document, the phosphor used is a garnet of the structure A3B5O12, the host lattice of which, as first component A, comprises at least one of the rare earths Y, Lu, Sc, La, Gd or Sm. Furthermore, one of the elements Al, Ga or In is used for the second component B. The only activator used is Ce.
A very similar phosphor is known from WO 97/50132. The activator used in that document is either Ce or Tb. While Ce emits in the yellow spectral region, the emission from Tb is in the green spectral region. In both cases, the complimentary color principle (blue-emitting light source and yellow-emitting phosphor) is used to achieve a white luminous color with a semiconductor element.
Finally, EP-A 124 175 describes a fluorescent lamp which, in addition to a mercury fill, contains a plurality of phosphors. These are excited by UV radiation (254 nm) or also by short-wave radiation at 460 nm. Three phosphors are selected in such a way that they add up to form white (color mixture).
The object of the invention is to provide a phosphor in accordance with the preamble of claim 1 which is able to withstand high thermal loads and is eminently suitable for excitation in the short-wave visible spectral region.
This object is achieved through the characterizing features of claim 1. Particularly advantageous configurations are given in the dependent claims.
In detail, according to the invention, a phosphor is proposed for excitation by a radiation source whose emission is in the short-wave optical spectral region. The phosphor has a garnet structure A3B5O12, and it is doped and activated with Ce, the second component B representing at least one of the elements Al and Ga. The first component A contains a rare earth RE selected from the group Y, Sc, Gd, Tb, La and/or Lu, with an amount of at most 5 mol % of A being replaced by praseodymium (Pr). Because of the concentration quenching to be observed with Pr, above all an amount of at most 5 mol % is to be recommended. Particularly favorable is an amount of at most 1 mol %. In this case praseodymium acts as second activator in addition to Ce according to the formula A3B5O12: (Ce, Pr).
Advantageously, the first component A is predominantly (more than 75 mol %) formed by yttrium and/or lutetium, in order to achieve a high efficiency. In addition thereto, it is possible to use amounts of Tb, Sc, Gd and/or La for fine-tuning. Particularly advantageous is the addition of Tb to the component A in small quantities (0.1 to 20 mol %) , since Tb improves the temperature quenching. Good results are furnished, in particular, by a garnet (Y, Tb)3Al5O2: (Ce, Pr).
The phosphor according to the invention can be excited in a wide range of the blue spectral region by radiation in the range from 420 to 490 nm, in particular 430 to 470 nm. A particularly good matching can be achieved to a light source, the peak wavelength of which is in the range 440 to 465 nm.
The phosphor has in particular a garnet structure
(RE1xe2x88x92xxe2x88x92yPrxCey)3(Al, Ga)5O12,
where
RE=Y, Sc, Tb, Gd, La and/or Lu.
The concentration of the two activators should be selected in the following ranges:
0.00005xe2x89xa6xxe2x89xa60.05;
0.01xe2x89xa6yxe2x89xa60.2.
The second component B contains advantageously both Ga and Al and may additionally contain In.
It has become evident that the addition of Pr to the YAG:Ce host crystal must be accurately dimensioned, since, when the concentration is too high, the luminous efficacy deteriorates significantly, while, when the dimensioning is too low, a marked effect of the red improvement no longer occurs. A good indication for the calculation of the Pr are its lines which occur in the emission spectrum. In particular the amount of the praseodymium and the condition of the host lattice (selection of the components A and B) should be selected in such a way that, essentially, lines of the Pr below 650 nm appear in the emission spectrum, in particular the two lines of the Pr at 609 and 611 nm. The shorter-wave the red component can be selected, the higher the visual useful effect, since the sensitivity of the eyes decreases very strongly towards long wavelengths. A red component which is obtained by an emission at a wavelength above 650 nm, that is, in a range 650 to 700 nm, is therefore considerably less favorable.
In particular the amount of the praseodymium should be less than 0.3 mol % and should, in particular, be selected to be so small that the two lines of the Pr at 609 and 611 nm appear separated from one another in the emission spectrum. In addition, if the Pr amount is suitably dimensioned, the Pr line at 637 nm can also appear in the emission spectrum. Advantageously the amount of the praseodymium should be greater than 0.2 mol % and should be selected to be so high that the Pr line at 637 nm distinctly appears in the emission spectrum. For, as a result of this, an additional contribution in the red spectral region is obtained, in addition to the two other main lines of the Pr at 609 and 611 nm. It should, in particular, amount to at least 10% of the contribution of the other two lines.
The present invention also comprises a light source which primarily emits radiation in the short-wave blue range of the optical spectral region, this radiation being partially or completely converted into longer-wave radiation by means of a phosphor as specified above. In particular, the primary radiation emitted lies in the wavelength range from 420 to 490 nm, in particular 430 to 470 nm. The primary radiation source used is advantageously a blue-emitting light-emitting diode, in particular based on InGaN, in order to produce a white LED. A particularly good matching of phosphor to primary light source is obtained in the range of a peak emission of the LED in the range 440 to 465 nm. This is achieved by combining a blue LED (primary light source) with a phosphor as specified above, which is excited by the radiation from the LED and the emission (secondary radiation source) from which supplements the remaining blue primary LED radiation to form white light. In the case of using a single Pr-containing phosphor, this phosphor should emit mainly in a broad band in the yellow region of the spectrum and should emit additionally in a narrow band in the red region of the spectrum. In the case of using two Pr-containing phosphors, one of the phosphors should emit mainly in a broad band in the yellow region of the spectrum and should emit additionally in a narrow band in the red region of the spectrum (relatively low Pr content), while the second phosphor has an emission curve which is shifted, relatively to this, towards longer wavelength and has a relatively high Pr content (more than 50% higher than the first phosphor). In particular, the concentration of the Pr in the first phosphor should be selected in such a way that only the two Pr lines at 609 and 611 nm appear, while the concentration of the second phosphor may be selected in such a way that the additional line at 637 nm appears also and furnishes a contribution.
A process for producing the phosphor comprises the following process steps:
Comminution of the oxides and adding a flux;
First annealing in forming gas (mixture of H2 and N2);
Milling and screening;
Second annealing.
According to the invention, for light sources whose emission lies in the short-wave blue spectral region, the phosphor used has a garnet structure A3B5O12 and is doped with Ce, the second component B representing at least one of the elements Al and Ga, the first component A containing praseodymium. Surprisingly, it has emerged that praseodymium (Pr) is eminently
0.00005xe2x89xa6xxe2x89xa60.05;
0.01xe2x89xa6yxe2x89xa60.2.
The phosphor absorbs in the range from 400 to 500 nm, preferably between 430 and 470 nm, and can thus be excited by radiation from a blue light source which is in particular the radiation source for a lamp or LED. Good results were achieved with a blue LED with a maximum emission at 420 to 465 nm. When using pure YAG:Ce as base, in particular a range from 440 to 465 nm has proved useful; when using amounts of Lu and Ga, a peak wavelength between 420 and 450 nm is recommended.
This phosphor is particularly suitable for use in a white LED, based on the combination of a blue LED with the garnet phosphor which is excited by absorption of some of the radiation from the blue LED and the emission from which supplements the remaining radiation from the LED to form white light.
A particularly suitable blue LED is a Ga(In)N-LED, although any other way of generating a blue LED with emission in the range from 420 to 490 nm is also suitable. The principal emission range recommended is in particular 430 to 470 nm, since this is when efficiency is highest.
By selecting the type and quantity of rare earths RE, it is possible to finely adjust the position of the absorption bands and the emission bands.
In connection with light-emitting diodes, a range for X which is between 0.0005 and 0.01 is particularly suitable. The preferred range for y is 0.03 to 0.1.
The phosphor according to the invention is also suitable for combination with other phosphors, above suitable as an additional activator in the host lattice (first component A of the garnet), for example under blue excitation in the range from 420 to 490 nm. The standard emission range of the base phosphor of the type YAG:Ce material, the dopant of which is cerium, represents a broad band in the yellow spectral region. Due to the presence of the Pr3+ in the material of the type YAG:Ce3+, additional red light is emitted, with the result that the color locus can be controlled within a wider range and the color reproduction is improved compared to standard YAG:Ce materials. The red emission by Pr3+ is possible because the Pr ion absorbs light which is emitted by the first activator, the Ce ion (above all at the wavelengths 480 to 500 nm), and emits light again. A second transfer mechanism which is surprisingly present is the direct transfer of energy from the Ce ion to the Pr ion. In this case, the Ce ion acts as a sensitizer for the second activator Pr.
The white light is generated, for example, by the combination of an Ga(In)N-LED with the phosphor YAG:Ce. In this case, apart from Pr, it is possible in particular for yttrium to be used as principal constituent of the first component A of the garnet on its own or together with at least one of the rare earths Tb, Gd, Sc, La and/or Lu.
The second component used is at least one of the elements Al or Ga. The second component B may additionally contain In.
In a particularly preferred embodiment, a garnet of the formula A3B5O12: (Ce, Pr) having the stoichiometric structure
(RE1xe2x88x92xxe2x88x92yPrxCey)3(Al, Ga)5O12 is used,
where
RE=Y, Gd, Sc, Tb, La and/or Lu;
all green-emitting phosphors, for example, with a green-emitting phosphor such as thiogallate, in which case above all gallium is under consideration as a constituent of the metallate, as well as, in particular, with other YAG:Ce phosphors, in particular a type which emits more (red) in the long-wave range. However, a particular advantage is that the addition of Pr often makes the use of a further phosphor which, in terms of its centroid, tends to emit more in the red spectral region superfluous.

Phosphor for light sources, and associated light source

Abstract: where

Abstract: RE=Y, Sc, Tb, Gd, La and/or Lu;

Abstract: 0.00001 less than x less than 0.05;

Abstract: 0.01 less than y less than 0.2.

Patent-Treuhand-Gesellschaft fuer elektrische Gluehlampen mbH


A method for treating migraine is disclosed in which a composition consisting essentially of pharmacologically effective amounts of both an antiemetic compound and tramadol is administered to a patient in need thereof.

The present invention relates to a new process for using pharmaceutical compositions containing tramadol, and an antiemetic-antinauseant substance for the treatment of migraines and migraine-like headaches.
Migraine is a disease with recurring attacks of headaches, which last between 4 and 72 hours. Migraine attacks predominantly are unilateral, dull at the beginning and then pulsing headaches occur with moderate to severe intensity. Typical accompanying symptoms of migraines are hypersensitivity towards light and sound, pallor, nausea and vomiting and without neurological focal attack, as a prodromal stage.
The (usual) migraine without aura is differentiated from the (classical) migraine with aura, which always commences with a characteristic scintillating scotoma. A complicated migraine exists if the visual disorders last for days or other neurological focal symptoms occur with the known special forms of the retinal, basilar, ophthal-moplegic, aphasic or hemiplegic migraine.
There are different ideas concerning the pathomechanism of the migraine. Earlier hemodynamic ideas, according to which the initial neurological attacks are triggered by regional, intracranial vasoconstriction and the subsequent pulsing headache by extracranial vasodilation with pain conduction over the nervus opththalmicus and nervus trigeminus, explain the processes during the migraine only inadequately.
The regional cerebral blood flow is reduced during a migraine with aura occipital, the slow migration of the cortical oligemia with crossing over of the supply regions of individual arteries suggesting that not only vasomotor, but also electrophysiological phenomena corresponding to the so-called xe2x80x9cspreading depressionxe2x80x9d participating (Spierings ELH (1988); Recent advances in understanding of migraine. Headache 28; 655-658).
Other findings suggest that the accompanying headaches are triggered not only by an extracranial vasodilation, but also by a central lowering of the pain threshold, IEGs (immediate early genes) being activated in the cells of the spinal cord and of the brain stem after noxic stimulation (M. Zimmermann (1955); Neurobiology of the Pain System, Neuroforum 1/95; 34-45).
A different theoryxe2x80x94the neurogenic inflammation modelxe2x80x94offers a possibility of explaining the blood flow change as well as the increased pain sensitivity of the vessels during migraine attacks. According to this theory, the increased pain sensitivity is brought about by an increased sensitization of the sensory perivascular fibers of the trigeminovascular system. Vascular pulsations, which normally are not capable of initiating painful sensations, are potent pain stimuli due to this increased sensitization, and bring about the pulsing, throbbing migraine pain. The neurogenic inflammation is initiated by noxic stimulation of the perivascular nerve fibers of the meningeal blood vessels. From the nerve ends, which probably are nociceptors at the same time, neuropeptides such as P. neurokinin A and CGRP (calcitonin-gene related peptides), which are capable of initiating the neurogenic inflammation, are secreted. During a migraine attack, CGRP can also be detected in increasing amounts in the venous blood of the head.
A vicious circle is set in motion due to the secretion of the neuropeptides, wherein a peptide release leads to vasodilation and to an increase in capillary permeability, resulting in an increased stimulation of nociceptors which, in turn, leads to a yet increased release of peptides. The known antimigraine actives, such as sumatriptan and ergot alkaloids inhibit the release of the neuropeptides and interrupt the pain-initiating cycle (M. Zimmermann: Chronic Pain and its Causes, Deutsches Arzteblatt 93, vol. 43, 1996 A-2749-2752).
Other findings suggest a primary neurogenic hypothalamic dysfunction, during which the vasoactive serotonin, which is secreted in a reduced amount from the nuclei of the raphe of the brain stem during the migraine attack, plays a key role (Ferrari M D et al. (1989): Serotonin metabolism in migraine. Neurology 39: 1239-1242; R. Pramod et al. (1989): 5-HT1-like receptor agonists and the pathophysiology of migraine. Trends in Pharmacological Sciences 10, 200-204).
Regardless of many hypotheses and complicated models, the patho-mechanisms of the migraine are not understood as yet. The migraine has a multifactorial genesis with a genetic disposition and external (such as alcohol) and internal (such as hormone) trigger mechanisms. It is not a psychosomatic disease, although psychic factors can trigger an attack.
Frequent side effects of ergotamine and dihydroergotamine which are the drugs of choice for treating migraines, are nausea, retching, vomiting, headaches, muscle pain and a general sensation of coldness. These are symptoms which, under a false assumption of a continuing migraine attack, may cause the compositions to be taken repeatedly and thus can lead to an overdosage. Persistent headaches may result from frequent use, and this fosters ergotamine abuse. Circulation disorders, coronary heart disease, occlusive arterial disease, hypertension and anginal disorders occur as serious side effects. Ergot alkaloids must not be used during pregnancy, while nursing or by children below the age of 12.
Sumatriptan and its derivatives (almotriptan, eletriptan, naratriptan, rizatriptan, zolmitriptan) are very effective migraine remedies which, when used orally, are superior to individual substances, such as ergotamine, acetylsalicylic acid or metoclopramide. Sumatriptan is contraindicated for children, during pregnancy, while nursing, and for patients above the age of 65 or having coronary heart disease. A sensation of pressure and heart, a general sensation of weakness, a sensation of tightness in the chest, hypertension, coronary heart disease, a myocardial infarction and angina pectoris can occur as undesirable effects.
Thus, although it has been known to combine some analgesics with antiemetics, these are either weak analgesics (e.g. paracetamol or salicylates) that are not useful against moderate to severe migraine pain. Strong analgesics, such as ergot compounds or sumatriptan, are unreliable, because they are known to have adverse cardiac and other undesirable side effects, and also to cause nausea.
Metoclopramide and domperidone have been used in combination with ergot compounds because of their prokinetic effects, and also because of their effect on symptoms such as nausea and vomiting, which frequently occur as symptoms that accompany a migraine.
The medicinal treatment of migraines is symptomatic in nature and does not represent a cure. Mixed preparations of non-opioid analgesics and mixed preparations of ergot alkaloids are not recommended, since they themselves can cause headaches when used for a prolonged period and particularly when used daily. Furthermore, liver and kidney damage, such as analgesic nephropathy are possible consequences of the long-term use of analgesic combination. Because of the possibility that they will be misused or result in dependence, opioid analgesics are generally not suitable for the treatment of migraines.
The following specific combinations, in particular, are known from the patent literature for the treatment of migraines: paracetamol and metoclopramide (EP 011 489, EP 011 490, U.S. Pat. No. 5,437,874, EP 695 546, EP 774 253); acetylsalicylic acid or the 1-lysine derivative thereof and metoclopramide (EP 605 031); and analgesics (such as acetylsalicylic acid), antiemetics (such as metoclopramide) and an antacid (CA 20 20 018). The above analgesic combinations are generally suitable for the treatment of mild migraine attacks. They are not suitable, however for the treatment of moderately severe to severe migraines. In the case of severe migraines, ergot alkaloids, in combination with an antiemetic or sumatriptan, are generally indicated.
It is a disadvantage that, under treatment with ergot alkaloids or sumatriptan, a large number of, in some cases, serious cardiovascular side effects, such as angina pectoris, coronary heart disease, hypertension and myocardial infarction can occur.
An alternative class of analgesics, the opioid analgesics are generally also unsuitable for such use, partly because of their dependence-creating effect, and also their tendency to cause constipation which works against the desired fast analgetic effect.
Tramadol is a centrally acting analgesic having a weak opioid binding activity and a complimentary weak inhibition of reuptake of norepinephrine and serotonin. Unlike morphine, tramadol does not show a histamine release. It was, however, not considered to be used in preference to opioids, because it is known to cause nausea, vomiting, sweating, dryness of the mouth, dizziness and drowsiness can occasionally occur. Gastrointestinal complaints or different types of mental effects are infrequently also observed. Therefore, tramadol has not been successfully used against migraine pain.
WO 97/18801 describes the combination of tramadol with antinauseant substances, particularly in a controlled release dosage form. There is, however, no prior suggestion of using such combinations for the treatment of migraines.
There is therefore a great need for a reliable analgesic, which has few side effects and a good activity in the case of moderately severe to severe migraine attacks.
It is an object of the present invention to prepare an improved therapeutic agent for the treatment of moderately severe to severe migraine attacks.
The present invention is a composition containing tramadol and an antiemetic antinauseant substance, including dopamine antagonists, phenothiazine, 5HT3 antagonists, and antihistamines (hereinafter singly and collectively referred to as xe2x80x9cantiemeticsxe2x80x9d). It has been surprisingly found that in accordance with the present invention tramadol was also found to be an exception among opioid analgesics, which does not produce the serious side effects which are typically seen in the use of opioids. Not only is the constipation-causing side effect of opioid analgesics effectively suppressed by combining tramadol with such an antiemetic, but additionally the analgesic action is also unexpectedly potentiated by the antiemetic, and the absorption and compatibility of tramadol is increased by the combination of the present invention. Yet further analgesic activity can be provided by a further combination with one or more conventional analgesics, such as an NSAID, thus also to provide an antiinflammatory effect.
As used throughout the specification and the claims, xe2x80x9ctramadolxe2x80x9d means 2-[(dimethylamino)methyl]-1-(3-methoxyphenyl)cyclohexanol, or its pharmaceutically acceptable salts, esters, and enantiomers. Tramadol is an analgesic, which is pharmacologically effective in the case of moderately severe to severe pain. It belongs to the group of opioids with a weak activity. In comparison to other opioids, tramadol is distinguished by a lesser development of tolerance with respect to the analgesic effect and by the fact that the side effects, typical of an opiate, are largely absent and that the potential for developing a dependence is very slight. The analgesic effect of tramadol includes opioid as well as non-opioid components, the latter by way of the release of serotonin (5-HT) and the inhibition of the resorption of serotonin and noradrenalin in the central nervous system (CNS). These non-opioidal components provide a significant contribution to the analgesic effect of tramadol. Noradrenaline resorption is inhibited predominantly by the (xe2x88x92)-enantiomer and the release of serotonin, as well as the inhibition of the resorption of serotonin from the synaptic cleft is produced predominantly by the (+) enantiomer. Both enantiomers contribute to the analgesic effect in man.
As used throughout the specification and the claims, compounds the main representatives of which include metoclopramide, domperidone, prochlorperazine, trifluoroperazine, promethazine, dimenhydrinate, cinnarizine, cyclizine, ondansetron, granisetron, and tropisetron, in addition to their role as antiemetics in the present invention, also potentiate the analgesic efficacy of tramadol. They are also pharmacologically active to increase the tonus of the lower gastroesophageal sphincter and to stimulate and accelerate the emptying of the stomach and the passage through the small intestine, which emptying is otherwise disturbed or otherwise hindered by the migraine, and also as antiemetics to suppress nausea, retching and vomiting. The antiemetics are conventionally also indicated in the case of gastroparesis, which can occur postoperatively, and also in the case of some basic diseases (such as diabetes mellitus, etc.). They are also given in the case of functional dyspepsia (irritated stomach), as the cause of the latter is suspected to be a disorder of gastrointestinal motility. Any reference in the disclosure and the claims to an xe2x80x9cantiemeticxe2x80x9d is meant to include its pharmaceutically acceptable salt and esters.
It was noted with surprise that, as a result of the use of the combination of tramadol and an antiemetic, the migraine attacks can be effectively cut short and the occurrence of nausea and vomiting are be prevented. This was all the more surprising, since tramadol itself can cause nausea and vomiting or intensify these symptoms that accompany migraines. For this reason, tramadol was regarded in the past as being unsuitable as a sole active for the treatment of migraines.
By combining tramadol with an antiemetic, most suitably with metoclopramide, it is possible to make the more highly effective analgesic tramadol available for the treatment of moderately severe to severe pain, including the treatment of migraines. With the combination of the present invention the compatibility of tramadol can be improved, the absorption of tramadol in the gastrointestinal tract can be accelerated and the occurrence of accompanying symptoms of migraines, namely nausea and vomiting, can be prevented.
Tramadol and antiemetics, are also suitable as partners in using these compositions from the point of view of their pharmacodynamic and pharmacokinetic properties. The duration of the analgesic effect of tramadol is about 4 to 7 hours, with a terminal elimination half life of about 5-6 hours. The duration of the prokinetic effect of e.g. metoclopramide and domperidone is about 1 to 2 hours and that of the antiemetic effect about 3 to 5 hours. The half life time is about 4 to 6 hours.
In a further embodiment of the process of the present invention, the combinations can additionally be used with suitably from about 1% wt. to about 15% wt. of a non-steroidal antiinflammatory drug (NSAID) such as acetylsalicylic acid, ibuprofen, naproxen and paracetamol. By these means, on the one hand, a different analgesic mechanism is created by an effect of tramadol on the central nervous system, and the analgesic and antiinflammatory effect of non-steroidal antiinflammatory drugs on both the central and peripheral nervous systems. Therefore, these combinations with an NSAID can be of particular importance in the case of therapy-resistant forms of migraines. On the other hand, the total dose of tramadol or of the additional combination partner having analgesic activity can be reduced without loss of effect on the pain, without undesirable side effects such as gastrointestinal disorders in the case of the NSAIDs.
The composition of the present invention can be administered in any suitable dosage form such as tablets, effervescent tablets, capsules, granulates, powders, sustained release tablets, sustained release capsules (single and multiple unit formulations), ampoules for intravenous and intramuscular injection and in the form of infusion solutions, suspensions, suppositories or in any other suitable dosage form.
The sustained release dosage forms of the present invention can contain the active ingredient completely or partly in the sustained release form with or without an initial, immediate dosing of the actives.
The active ingredients can be present jointly or partially or completely in separate formulations, so that it is possible to administer them separately as well as at different times. If the active ingredients are present only in separate formulations, these formulations are suitably matched to one another and each contains a respective active ingredient within the dosage unit in the same amounts and corresponding ratios by weight, in which they can and would be present in a combined dosage form. The active ingredients can also be present in the form of their pharmaceutically usable salts in any of these pharmaceutical dosage forms. Oral pharmaceutical compositions, dosage forms which contain a combination of the actives, are deemed to be most suitable.
Pharmaceutical preparations containing these combinations in their given amounts, are suitably formulated with physiologically compatible carriers and/or diluents and/or inactive ingredients in the desired manner. Examples of carriers and inactive ingredients include gelatin, natural sugars such as cane sugar or lactose, lecithin, pectin, starch (such as corn starch or amylose), cyclodextrins and cyclodextrin derivatives, dextran, polyvinylpyrrolidone, polyvinyl acetate, gum arabic, alginic acid, tylose, talcum, lycopodium, silica, calcium hydrogen phosphate, cellulose, cellulose derivatives such as methyloxypropyl cellulose, methyl cellulose, hydroxypropylmethyl cellulose, hydroxypropylmethyl cellulose phthalate, C12-22 fatty acids, emulsifiers, oils and fats, particularly also vegetable glycerin esters and polyglycerin esters of saturated fatty acids, monohydric or polyhydric alcohols and polyglycols, such as polyethylene glycols, esters of aliphatic saturated or unsaturated C2-22 fatty acids with monohydric, C1-20 aliphatic or polyhydric alcohols, such as glycols, glycerin, diethylene glycol, 1,2-propylene glycol, sorbitol, and mannitol.
Further inactive ingredients can suitably include materials, which bring about disintegration (so-called disintegrants), crosslinked polyvinylpyrrolidone, sodium carboxymethyl starch, sodium carboxymethyl cellulose and microcrystalline cellulose. Known coating agents can likewise be used. Polymers, as well as copolymers of acrylic acid and/or methacrylic acid and/or their esters, zein, ethylcellulose, ethylcellulose succinate and shellac are particularly suitable.
As plasticizers for coatings, citrate and tartrate esters, glycerin and glycerin esters and polyethylene glycol of different chain lengths can be used. Water or physiologically compatible organic solvents, such as alcohols and fatty alcohols, can be suitably employed for the preparation of solutions or suspensions.
For liquid preparations, it may be necessary to use preservatives, such as potassium sorbate, methyl-4-hydroxy benzoate or propyl 4-hydroxybenzoate, antioxidants, such as ascorbic acid, and a taste improver such as peppermint oil.
Customary solubilizers or emulsifiers, such as polyvinylpyrrolidone and polysorbate 80 can be used in preparing the compositions. Further examples of carriers and inactive ingredients include those described, for example in H. P. Fiedler xe2x80x9cLexikon der Hilfsstoffe fxc3xcr Pharmazie, Kosmetik und Angrenzende Gebiete (Encyclopedia of Inactive Ingredients for Pharmaceuticals, Cosmetics and Adjoining Fields)xe2x80x9d.
Anti-migraine preparations, which contain the combinations of antiemetics with prokinetic effect and of tramadol, the composition can suitably contain from about 5% wt. to about 30% by weight of the antiemetic. Suitably the weight ratio of the compounds is from about 1:4 to about 1:10. Individual doses of these pharmaceutical preparations can contain from about 5 to about 50 mg of an antiemetic, and from about 50 to about 400 mg of tramadol. Moreover, the daily dose should suitably contain from about 20 to about 80 mg of antiemetic and from about 200 to about 400 mg of tramadol. Depending on the therapeutic indication, the daily dose can be administered all at once, or in the form of from about 2 to about 4 partial doses per day. In general, the administration in from about 2 to about 4 partial doses per day is most suitable.

Pharmaceutical compositions containing tramadol for migraine