How much does a company spend each year on chemicals to ensure offshore oil production stays up and running? For most, chemical injection is an unavoidable cost of doing business. Since many of the chemicals injected are proprietary formulations and consequences of underinjection can be catastrophic, questioning the dollars spent can be challenging. But in today’s low oil-price environment, a critical examination of a chemical injection system and practices may yield tremendous operating expense (OPEX) savings.
Chemical injection, as a cost of doing business, has a huge impact on a producer’s bottom line. Chemicals are a necessary expense. Without chemicals, problems can occur in the pipeline that can severely affect production. For example, scales and waxes could plug tubing indefinitely, or hydrates could block production, costing up to $1 million per day in shut-in production to dissociate. Without a corrosion inhibitor, a complete loss of well or infrastructure could occur over time. With such severe consequences, producers consistently inject more than the recommended quantity of chemical. A sampling of producers interviewed showed that chemicals such as demulsifiers are typically overinjected by up to 20 percent in attempts to ensure that an emulsion does not form and shut down production facilities. The annual cost of overinjection for a single chemical run at 20 percent excess could be as high as $400,000. Figure 1 details the additional OPEX impact of that single chemical cost as a percent of overinjection.
Consider a single offshore platform and the annual amount spent for injecting chemicals for six to eight wells. For a representative platform, four to six chemicals would be injected including scale, wax and corrosion inhibitor as well as monoethylene glycol or methanol for hydrate inhibition. In this case, one would inject more than 9,000 gallons (34,000 liters) of chemical per hour for eight wells. In total, this hypothetical platform could consume $175 million in annual operational costs just in chemical injection. And if all that chemical is overinjected at just 5 percent, that is potentially 4 million gallons (15 million liters), or $8.75 million worth, of wasted chemical injected in a single year for a single platform because of uncertainty in measurement and control. Chemical injection represents a tremendous cost, and in today’s environment, such an operational cost deserves more scrutiny.
In addition to poor chemical injection control, several other obstacles to good system operation hamper performance. Often the primary obstacle to system reliability is injection rate drift, either mechanically from the pump or from the valve that controls flow. Rate change can be caused by changes in back-pressure in the system or wear of their parts and seals. As temperatures change, chemical viscosity can change, resulting in a drift in the actual chemical injected versus indicated rate. One operator in the Gulf of Mexico noted that he or she needed to employ dedicated personnel just to monitor and adjust chemical injection rates every four hours. This presented a resource cost — not to mention additional bed space and health, safety and environment risks — that could be utilized elsewhere on the platform.
In the past, injection control devices have been maintenance-intensive, especially at startup and shutdown. Plugging issues with these devices, whether caused by chemical quality and precipitates or failed filters, added to the risk of underinjection of chemical and potential shutdowns. Another challenge noted for proper chemical monitoring and control is the wide turndown required over the life of the well. Many valves and mechanical flowmeters have limited turndowns that do not serve the range of expected flow rates over the life of the well, particularly as the asset declines or enters secondary or tertiary recovery. Lastly, space and weight for offshore systems are large considerations since they are at a premium for offshore platforms. Any reduction in equipment size and weight can result in significant upfront capital expenditure savings.
As a final complication, target reservoirs are deeper than ever, resulting in operating pressures for chemical injection equipment in excess of 10,000 psi (690 Bar), which limits the instrumentation and control options available.
Achieving significant savings in chemical injection requires confidence in the accuracy and reliability of chemical injection monitoring and control devices. With an accurate flow control device and a repeatable, accurate mass flowmeter, a closed loop can be created that constantly monitors and adjusts the chemical rate to ensure the right amount is injected at all times.
Recent advancements in Coriolis technology allow its use in emerging high-pressure chemical injection systems with operating pressures up to 15,000 psi (1,034 Bar).
So, what are the benefits of using a Coriolis meter with an accurate flow control valve compared to traditional mechanical meters and valves for chemical injection systems? First, Coriolis meters are extremely accurate and repeatable, with accuracies down to 0.1 percent of flow rate. This enables operators to account for all the chemicals used to a high level of confidence and can drastically reduce overdosing chemicals by ensuring the proper amount is being delivered every time. Next, unlike other meters such as positive displacement or turbine, Coriolis meters have no moving parts. This means that no parts are present that will wear out over time and need replacing. The lack of moving parts also greatly reduces the need to stock spare equipment for maintenance, which helps ensure that downtime is reduced and can drastically lower operating costs. Additionally, Coriolis mass flowmeters do not require straight runs to condition the flow profile, which provides a smaller footprint for space and weight savings on the platform.
Also, Coriolis meters are true mass meters. Mass meters measure the amount of flow, regardless of changes in fluid properties such as density and viscosity. This is important because it allows a single meter to be used to measure multiple chemicals. Conversely, volumetric meters have errors associated with changing fluid characteristics like pressure or temperature. Also, some meters need to be calibrated directly to the fluid being measured in the process to meet their stated accuracies. This is not true for a Coriolis flowmeter. Coriolis meters provide accurate measurement, even if the fluid characteristics change, providing certainty that the flow rate is correct.
Additionally, Coriolis meters are multivariable devices capable of measuring density and temperature. Density is important because it is a great quality control measurement that can monitor changes in composition of the chemicals being injected. The density output can be used to monitor product density or concentration measurement. Concentration limits can be set for fluids and to provide indication and alarm if the chemical concentration or fluid properties change over time. This ensures the chemical is within specification and that the correct chemical is injected downhole. Additionally, the density measurement can be used for interface detection.
Furthermore, advances in diagnostics allow for better maintenance practices. For example, some meters are offered with diagnostics. Coriolis meters have no moving parts and are not expected to degrade over time, but many technicians have entrenched work practices that may have them question the integrity of the instrumentation. Others may have internal procedures in place to calibrate equipment at a specific time interval. One verification tool can be run remotely and automatically or by a touch of a button to provide confidence that the meter is in its original factory condition.
The tool works by using an established baseline that is programmed into each new meter from the factory. This baseline is stored in the electronics and can be referenced at any time in the field. Once in the field, a user can run a test to compare its present value to its original baseline and see if any changes have taken place in the meter. This diagnostic can extend or eliminate calibration intervals and give confidence that the meter operates accurately. The complete meter is checked, including sensor (coils, resistance thermometer and tube integrity) and transmitter (zero, configuration and alarms).
Finally, the advanced Coriolis meter can be combined with an accurate chemical injection flow control valve that utilizes an integrated, microprocessor-based proportional-integral-derivative controller that brings precise, algorithmic control to chemical injection systems. This technology provides responsive control that allows the valve to adapt to an ever-changing system and accuracy to 0.1 percent, which reduces downtime and maintenance associated with clogging.
Through use of a flow control valve and Coriolis mass meter, the space and weight of the chemical injection system can be dramatically reduced. Figure 2 demonstrates how a single tank and pump per chemical can be used to reliably supply each of the wells on a platform. This significantly reduces maintenance requirements with fewer pumps and filters to maintain while reliably and accurately delivering the exact amount of chemical that each well requires.
Traditional flow control methods have large amounts of variation, poor repeatability and injection rate drift that drive operators to overinject chemical to ensure protection of their assets while incurring significant OPEX in excess chemical. Variation in flow can be a result of the device design that does not account for variation in the process parameters. Precision chemical injection flow control that retains consistency regardless of downstream pressure fluctuations, changes in chemical properties or other changing conditions, is necessary to bring injection rates closer to the required rate. Coriolis and flow control technology advancements enable more reliable operation of the chemical injection system, which reduces maintenance and overinjection while keeping production up and running with a smaller footprint.
Timothy Drost is a global product manager for Emerson Automation Solutions. He has been with the company for more than 13 years. He holds an MBA and Bachelor of Science in mechanical engineering from the University of Colorado, Boulder.
Wendell Love is an oil and gas industry manager for Emerson Automation Solutions. His background includes 10 years of oil and gas experience with downhole tools, frac equipment and production systems. Love joined Emerson in 2013 to expand pressure control product lines. He has a Bachelor of Science in mechanical engineering from Texas Tech and an MBA from Southern Methodist University.
Laura Schafer is vice president of oil and gas for Emerson Flow. With more than 15 years of oil and gas experience, she joined Emerson in 2012 with a focus on extending flow measurement applications in oil and gas. Schafer holds Bachelor of Science and Master of Science degrees in chemical engineering from the Colorado School of Mines.
Kampuni hutumia kiasi gani cha pesa kila mwaka kwa kemikali ili kuhakikisha kwamba mafuta ya pwani yanaendelea kutokezwa? Kwa wengi, sindano za kemikali ni gharama isiyoweza kuepukika ya kufanya biashara. Kwa kuwa kemikali nyingi zinazowashwa ni za kipekee na matokeo ya kutoweka kwa kiasi cha kutosha yanaweza kuwa mabaya, kuhoji dola zilizotumiwa inaweza kuwa changamoto. Lakini katika mazingira ya leo ya bei ya chini ya mafuta, uchunguzi muhimu wa mfumo wa sindano ya kemikali na mazoea yanaweza kuzalisha akiba kubwa ya gharama za uendeshaji (OPEX). Injection kemikali, kama gharama ya kufanya biashara, ina athari kubwa juu ya mstari wa chini ya mtayarishaji. Kemikali ni gharama muhimu. Bila kemikali, matatizo yanaweza kutokea katika bomba ambayo yanaweza kuathiri sana uzalishaji. Kwa mfano, vipimo na waxes zinaweza kuziba mabomba kwa muda usiojulikana, au hydrates inaweza kuzuia uzalishaji, ikigharimu hadi $ 1 milioni kwa siku katika uzalishaji wa kufungwa. Bila kizuizi cha kutu, hasara kamili ya kisima au miundombinu inaweza kutokea kwa muda. Kwa sababu ya matokeo mabaya kama hayo, wazalishaji huingiza kemikali nyingi kuliko kiasi kinachopendekezwa. Kwa mfano, katika uchunguzi wa majaribio ya kemikali, kemikali kama vile demulsifiers ni kawaida overinjected kwa hadi 20% katika majaribio ya kuhakikisha kwamba emulsion haina kuunda na kufunga vifaa vya uzalishaji. Gharama ya kila mwaka ya over-injection kwa ajili ya moja kemikali kukimbia katika 20% ziada inaweza kuwa kama juu kama $ 400,000. Picha ya 1 inaonyesha athari ya ziada ya OPEX ya gharama hiyo ya kemikali moja kama asilimia ya overinjection. Fikiria jukwaa moja la baharini na kiasi cha kila mwaka kinachotumiwa kwa kuingiza kemikali kwa visima sita hadi nane. Kwa mfano, kwa ajili ya jukwaa, kemikali nne hadi sita itakuwa injected ikiwa ni pamoja na kiwango, wax na corrosion inhibitor pamoja na monoethylene glycol au methanol kwa hydrate kuzuia. Katika hali hii, mtu angeweza kuingiza zaidi ya galoni 9,000 (litri 34,000) za kemikali kwa saa kwa visima nane. Kwa jumla, jukwaa hili la dhana linaweza kutumia $ 175 milioni katika gharama za uendeshaji wa kila mwaka tu katika sindano ya kemikali. "Na ikiwa kemikali zote hizo zimeingizwa kwa kiasi cha asilimia 5 tu, hiyo ni uwezekano wa galoni milioni 4 (litri milioni 15), au thamani ya dola milioni 8.75 za kemikali zilizotupwa kwa mwaka mmoja kwa jukwaa moja kwa sababu ya kutokuwa na uhakika katika kipimo na udhibiti. """ Injection kemikali inawakilisha gharama kubwa, na katika mazingira ya leo, gharama kama hiyo ya uendeshaji inastahili uchunguzi zaidi. Mbali na udhaifu wa udhibiti wa sindano ya kemikali, vizuizi vingine kadhaa kwa utendaji mzuri wa mfumo huzuia utendaji. Mara nyingi kizuizi kikuu kwa kuegemea mfumo ni mtiririko wa kiwango cha sindano, ama mechanically kutoka pampu au kutoka valve kwamba udhibiti mtiririko. Mabadiliko ya kiwango yanaweza kusababishwa na mabadiliko katika backlash- shinikizo katika mfumo au kuvaa ya sehemu zao na seals. Kama joto mabadiliko, viscosity kemikali inaweza kubadilika, na kusababisha drift katika kemikali halisi injected dhidi ya kiwango cha alionyesha. Mfanyakazi mmoja katika Ghuba ya Mexico alisema kwamba alihitaji kuajiri wafanyakazi wa pekee ili tu kufuatilia na kurekebisha viwango vya sindano za kemikali kila baada ya saa nne. Hii iliwasilisha gharama ya rasilimali - bila kutaja nafasi ya kitanda cha ziada na afya, usalama na hatari za mazingira - ambayo inaweza kutumika mahali pengine kwenye jukwaa. Katika siku za nyuma, vifaa vya kudhibiti sindano vimekuwa vya matengenezo, hasa wakati wa kuanza na kuzima. Matatizo ya kuziba na vifaa hivi, iwe yalisababishwa na ubora wa kemikali na precipitates au filters kushindwa, aliongeza kwa hatari ya underinjection ya kemikali na uwezekano shutdowns. Changamoto nyingine iliyotajwa kwa ajili ya ufuatiliaji sahihi wa kemikali na udhibiti ni turndown pana inayohitajika juu ya maisha ya kisima. Valves nyingi na flowmeters mechanical kuwa na turndowns mdogo kwamba si kutumika mbalimbali ya viwango vya mtiririko inatarajiwa juu ya maisha ya kisima, hasa kama mali inashuka au kuingia uponyaji wa sekondari au wa tatu. Mwishowe, nafasi na uzito kwa ajili ya mifumo ya pwani ni kuzingatia kubwa tangu wao ni katika premium kwa ajili ya majukwaa ya pwani. Kupunguzwa yoyote katika ukubwa wa vifaa na uzito inaweza kusababisha kiasi kikubwa cha mapato ya awali ya gharama za mtaji. Kwa sababu ya hali ya hewa, mabwawa ya lengo ni ya kina zaidi kuliko hapo awali, na kusababisha shinikizo la uendeshaji kwa vifaa vya sindano ya kemikali zaidi ya 10,000 psi (690 bar), ambayo hupunguza chaguzi za vifaa na udhibiti zinazopatikana. Kufikia akiba kubwa katika sindano ya kemikali inahitaji uaminifu katika usahihi na kuegemea ya kemikali sindano ufuatiliaji na vifaa vya kudhibiti. Kwa kifaa sahihi cha kudhibiti mtiririko na kipimaji cha mtiririko wa wingi cha mara kwa mara, mzunguko uliofungwa unaweza kuundwa ambao unasimamia na kurekebisha kiwango cha kemikali ili kuhakikisha kiasi sahihi cha dawa inawekwa wakati wote. Maendeleo ya hivi karibuni katika teknolojia ya Coriolis inaruhusu matumizi yake katika mifumo ya kuingiza kemikali ya shinikizo la juu na shinikizo la uendeshaji hadi 15,000 psi (1,034 Bar). Kwa hiyo, ni faida gani za kutumia mita ya Coriolis na valve sahihi ya kudhibiti mtiririko ikilinganishwa na mita za jadi za mitambo na valves kwa mifumo ya sindano ya kemikali? Kwa mfano, mita za Coriolis ni sahihi sana na zinaweza kurudia kwa asilimia 0.1 ya kiwango cha mtiririko. Hii inawawezesha waendeshaji kuelezea kemikali zote zinazotumiwa kwa kiwango cha juu cha uaminifu na inaweza kupunguza sana kemikali za kupita kiasi kwa kuhakikisha kiasi sahihi kinatolewa kila wakati. Kisha, tofauti na mita nyingine kama vile positive displacement au turbine, mita za Coriolis hazina sehemu zinazohama. Hilo lamaanisha kwamba hakuna sehemu zozote ambazo zitazidi kuharibika na kuhitaji kubadilishwa. Ukosefu wa sehemu zinazohama pia hupunguza sana haja ya kuhifadhi vifaa vya ziada kwa ajili ya matengenezo, ambayo husaidia kuhakikisha kwamba wakati wa kushuka hupunguzwa na inaweza kupunguza gharama za uendeshaji. Kwa kuongezea, Coriolis mass flowmeters haihitaji mbio moja kwa moja ili hali ya mtiririko wa profile, ambayo hutoa alama ndogo kwa nafasi na kuokoa uzito kwenye jukwaa. Pia, mita za Coriolis ni mita za kweli za wingi. Vipimo vya wingi hupima kiasi cha mtiririko, bila kujali mabadiliko katika mali ya kioevu kama vile wiani na viscosity. Hii ni muhimu kwa sababu inaruhusu mita moja kutumika kupima kemikali nyingi. Kinyume chake, mita volumetric kuwa na makosa kuhusishwa na kubadilisha sifa ya kioevu kama shinikizo au joto. Pia, baadhi ya mita zinahitaji kuwa calibrated moja kwa moja kwa kioevu kuwa kipimo katika mchakato wa kukutana na usahihi wao alitangaza. Hii si kweli kwa ajili ya Coriolis flowmeter. Coriolis mita hutoa vipimo sahihi, hata kama tabia ya kioevu kubadilika, kutoa uhakika kwamba kiwango cha mtiririko ni sahihi. Kwa kuongezea, mita za Coriolis ni vifaa vya multivariable vinavyoweza kupima wiani na joto. Uwiano ni muhimu kwa sababu ni kipimo kikubwa cha udhibiti wa ubora ambao unaweza kufuatilia mabadiliko katika muundo wa kemikali zinazowashwa. Uzalishaji wa wiani unaweza kutumika kufuatilia wiani wa bidhaa au kipimo cha mkusanyiko. Vipimo vya mkusanyiko vinaweza kuwekwa kwa kioevu na kutoa dalili na kengele ikiwa mkusanyiko wa kemikali au mali ya kioevu inabadilika kwa muda. Hii inahakikisha kemikali ni ndani ya vipimo na kwamba kemikali sahihi ni injected downnhole. Aidha, kipimo wiani inaweza kutumika kwa ajili ya kugundua interface. Isitoshe, maendeleo katika utambuzi huruhusu mazoea bora ya matengenezo. Kwa mfano, baadhi ya mita hutolewa na utambuzi. Coriolis mita haina sehemu zinazohama na hazitarajiwa kuharibika kwa muda, lakini wataalamu wengi wana mazoea ya kazi ambayo yanaweza kuwafanya waulize uadilifu wa vifaa. Wengine wanaweza kuwa na taratibu za ndani mahali pa kupima vifaa katika muda maalum wa muda. Vifaa vya ukaguzi vinaweza kuendeshwa kwa mbali na moja kwa moja au kwa kugusa kifungo ili kutoa uaminifu kwamba mita iko katika hali yake ya awali ya kiwanda. Chombo kazi kwa kutumia msingi imara ambayo ni programu katika kila mita mpya kutoka kiwanda. Hii baseline ni kuhifadhiwa katika umeme na inaweza kurejeshwa wakati wowote katika uwanja. Mara baada ya katika uwanja, mtumiaji anaweza kukimbia mtihani kulinganisha thamani yake ya sasa na msingi wake wa awali na kuona kama mabadiliko yoyote yamefanyika katika mita. Hii utambuzi inaweza kupanua au kuondoa vipindi calibration na kutoa ujasiri kwamba mita inafanya kazi kwa usahihi. Mita kamili ni kukaguliwa, ikiwa ni pamoja na sensor (coils, thermometer upinzani na uthabiti bomba) na transmitter (zero, Configuration na Alarms). Mwishowe, mita ya Coriolis ya hali ya juu inaweza kuunganishwa na valve sahihi ya kudhibiti mtiririko wa sindano ya kemikali ambayo hutumia mtawala wa jumla wa microprocessor-based, ambayo huleta udhibiti sahihi wa algorithmic kwa mifumo ya sindano ya kemikali. Teknolojia hii hutoa udhibiti wa kujibu ambao unaruhusu valve kurekebisha mfumo unaobadilika daima na usahihi wa asilimia 0.1, ambayo hupunguza wakati wa kushuka na matengenezo yanayohusiana na kuziba. Kupitia matumizi ya valve kudhibiti mtiririko na Coriolis mass meter, nafasi na uzito wa mfumo wa sindano ya kemikali inaweza kupunguzwa sana. Picha ya pili inaonyesha jinsi tank moja na pampu kwa kila kemikali inaweza kutumika kwa kuaminika kusambaza kila moja ya visima juu ya jukwaa. Hii hupunguza kwa kiasi kikubwa mahitaji ya matengenezo na pampu chache na vichungi kudumisha wakati kuaminika na kwa usahihi kutoa kiasi sahihi cha kemikali kwamba kila vizuri inahitaji. Mbinu za kawaida za kudhibiti mtiririko zina kiasi kikubwa cha kutofautiana, kurudia vibaya na kuhamisha kiwango cha sindano ambayo huendesha waendeshaji kuingiza kemikali kupita kiasi ili kuhakikisha ulinzi wa mali zao wakati wa kuathiri OPEX kubwa katika kemikali ya ziada. Tofauti katika mtiririko inaweza kuwa matokeo ya kubuni kifaa kwamba haina akaunti kwa ajili ya tofauti katika vigezo mchakato. Utaratibu wa usahihi wa mtiririko wa sindano ya kemikali, ambayo inahifadhi uthabiti bila kujali mabadiliko ya shinikizo la chini, mabadiliko katika mali ya kemikali au hali nyingine zinazobadilika, ni muhimu kuleta viwango vya sindano karibu na kiwango kinachohitajika. Coriolis na maendeleo ya teknolojia ya kudhibiti mtiririko huwezesha uendeshaji wa kuaminika zaidi wa mfumo wa sindano ya kemikali, ambayo hupunguza matengenezo na overinjection wakati wa kuweka uzalishaji na kuendesha na alama ndogo. Timothy Drost ni meneja wa bidhaa ya kimataifa kwa Emerson Automation Solutions. Amekuwa akifanya kazi katika kampuni hiyo kwa zaidi ya miaka 13. Ana shahada ya kwanza ya uhandisi na shahada ya kwanza ya uhandisi wa mashine kutoka Chuo Kikuu cha Colorado, Boulder. Wendell Upendo ni oil na gesi sekta meneja kwa Emerson Automation Solutions. Yeye ni mtaalamu wa miaka 10 ya mafuta na gesi na vifaa vya chini ya shimo, vifaa vya fracking na mifumo ya uzalishaji. Love alijiunga na Emerson mnamo 2013 kupanua safu za bidhaa za kudhibiti shinikizo. Ana shahada ya kwanza ya uhandisi wa mashine kutoka Texas Tech na MBA kutoka Chuo Kikuu cha Methodist Kusini. Laura Schafer ni makamu wa rais wa mafuta na gesi kwa Emerson Mtiririko. Akiwa na uzoefu wa zaidi ya miaka 15 katika sekta ya mafuta na gesi, alijiunga na Emerson mnamo 2012 na lengo la kupanua matumizi ya kipimo cha mtiririko katika sekta ya mafuta na gesi. Schafer ana Shahada ya Sayansi na Shahada ya Sayansi katika uhandisi wa kemikali kutoka Shule ya Madini ya Colorado.