High-Pressure, High-Temperature Technologies

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1 High-Pressure, High-Temperaure Technologies E&P aciviy increasingly involves operaions in high-pressure, high-emperaure downhole condiions. This environmen inroduces difficul echnical concerns hroughou he life of a well. Scieniss and engineers are developing advanced ools, maerials and chemical producs o address hese challenges. Gunnar DeBruijn Craig Skeaes Calgary, Albera, Canada Rober Greenaway Souhampon, England David Harrison Mike Parris Sugar Land, Texas, USA Simon James Clamar, France Fred Mueller Corpus Chrisi, Texas Shanonu Ray Aberdeen, Scoland News repors coninually remind us abou he cos and availabiliy of energy from fossil fuels and renewable sources. Despie remarkable growh in renewable-energy echnology during he pas 2 years, i is well acceped by he scienific and engineering communiy ha he world s energy needs will coninue o be saisfied primarily by fossil fuels during he nex few decades. Aggressive exploraion and producion campaigns will be required o mee he coming demand. Finding and producing new hydrocarbon reserves may be a difficul proposiion, ofen requiring oil and gas producers o conend wih hosile downhole condiions. Alhough highpressure, high-emperaure (HPHT) wells are fundamenally consruced, simulaed, pro duced and moniored in a manner similar o wells wih less-demanding condiions, he HPHT environ - men limis he range of available maerials and echnologies o exploi hese reservoirs. The oil and gas indusry has conended wih elevaed emperaures and pressures for years; however, here are no indusry-wide sandards ha define HPHT condiions and he associaed inerrelaionship beween emperaure and pressure. In an effor o clarify hose definiions, Schlumberger uses guidelines ha organize HPHT wells ino hree caegories, seleced according o commonly encounered echnology hresholds (below). 1 Mark Riding Gawick, England Lee Temple Houson, Texas Kevin Wuherich Hannover, Germany For help in preparaion of his aricle, hanks o Trevor Bouchard, Calgary; Mary Jo Caliandro, Marha Duon, Grechen Gillis, John Sill and Don Williamson, Sugar Land, Texas; and Lisa Sewar, Cambridge, Massachuses, USA. AIT, CemCRETE, CemSTRESS, CNL, FlexSTONE, FlexSTONE HT, Liho-Densiy, Quicksilver Probe, REDA Holine55, Sensa, SlimXreme, SLT, ThermaFRAC, WellWacher, WellWacher BrieBlue, WellWacher Ulra and Xreme are marks of Schlumberger. Chemraz is a rademark of Greene, Tweed & Co., Ld. INCONEL and Monel are rademarks of Special Meals Corporaion. Teflon is a regisered rademark of E.I. du Pon de Nemours and Company. Vion is a rademark of DuPon 1. Belani A and Orr S: A Sysemaic Approach o Hosile Environmens, Journal of Peroleum Technology 6, no. 7 (July 28): Saic reservoir emperaure, F C 25 C 15 C 5, 69 MPa 1, HPHT 15, 2, 25, Saic reservoir pressure, psi 3, 35, 4, > HPHT classificaion sysem. The classificaion boundaries represen sabiliy limis of common well-service-ool componens elasomeric seals and elecronic devices. 138 MPa Ulra-HPHT HPHT-hc 241 MPa 46 Oilfield Review

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3 HPHT Ulra-HPHT HPHT-hc > HPHT projecs around he world. During he pas decade he number of HPHT projecs has increased significanly; neverheless, hese projecs represen only abou 1% of producing reservoirs worldwide. The principal HPHT areas are found in he Unied Saes (deepwaer Gulf of Mexico and deep, ho onshore wells), Norh Sea, Norwegian Sea, Thailand and Indonesia. In addiion, hermal-recovery projecs o exrac heavy oil are locaed in Canada, California, Venezuela and easern Europe. In his sysem, HPHT wells begin a 15 C [3 F] boomhole emperaure (BHT) or 69 MPa [1, psi] boomhole pressure (BHP). The raionale for his hreshold is relaed o he behavior of sandard elasomeric seals. Engineers who run downhole equipmen in his environmen have found i pruden o replace he seals before reusing he ools. Ulra-HPHT wells exceed he pracical operaing limi of exising elecronics echnology greaer han 25 C [4 F] or 138 MPa [2, psi]. A presen, operaing elecronics beyond his emperaure requires insalling inernal hea sinks or placing he devices inside a vacuum flask o shield he elecronics from he severe emperaures. The HPHT-hc classificaion defines he mos exreme environmens wells wih emperaures and pressures greaer han 26 C [5 F] or 241 MPa [35, psi]. 2 Such pressure condiions are unlikely o be seen in he foreseeable fuure. However, boomhole empera ures in geohermal and hermal-recovery wells already exceed 26 C. I is imporan o emphasize ha he Schlumberger HPHT classificaion scheme is no limied o wells ha simulaneously saisfy he emperaure and pressure crieria. If eiher parameer falls wihin one of he hree HPHT regions, he well is classified accordingly. Thus, a low-pressure, shallow seamflood projec o exrac heavy oil lies in he HPHT-hc region because of he high seam emperaure. Conversely, reservoirs associaed wih lowemperaure, high-pressure sal zones in he Gulf of Mexico fi an HPHT classificaion because of he high pressure. A vial HPHT-well parameer is he lengh of ime ha ools, maerials and chemical producs mus wihsand he hosile environmen. For example, logging and esing ools, drilling muds and simulaion fluids are exposed o HPHT environmens for a limied ime, bu packers, sand screens, reservoir monioring equipmen and cemen sysems mus survive for many years even beyond he well s producive life. Accordingly, his ime facor has a major impac on how scieniss and engineers approach produc developmen. Oilfield Review las reviewed he HPHT domain in Since hen, he number of HPHT projecs has grown, and he severiy of operaing condiions has seadily increased (above). For example, a recen proprieary survey by Welling and Company on he direcion of subsea sysems and services repored ha 11% of wells o be drilled in he nex hree o five years are expeced o have BHTs exceeding 177 C [35 F]. In addiion, 26% of respondens expec BHPs beween 69 and 13 MPa [1, and 15, psi], and 5% predic even higher pressures. Today, scieniss and engineers push he limis of maerials science o mee he echnical challenges posed by HPHT wells. This aricle surveys ools, maerials, chemical producs and operaing mehods ha have been developed for successful HPHT well consrucion, simulaion, producion and surveillance. Case sudies illusrae he applicaion of some soluions. 48 Oilfield Review

4 Tesing and Qualificaion of HPHT Technologies HPHT condiions amplify risks ha exis in convenional wells. In HPHT wells, he margin for error is grealy reduced, and he consequences of failure may be more cosly and far reaching. Therefore, before field applicaion, new producs and services designed for hosile environmens mus be rigorously esed and qualified o wihsand he ougher downhole condiions. 4 This qualifi caion includes acceleraed degradaion esing aimed a calculaing ulimae service life wihou performing several years of esing. To mee his need, he indusry has buil sae-of-he-ar faciliies ha allow engineers o conduc realisic evaluaions (righ). Many ess are performed according o sandard indusry mehods; however, increasingly severe downhole condiions are rapidly approaching he limis of documened esing procedures. 5 Laboraory evaluaions fall ino hree principal caegories: fluids, mechanical devices and elec - ronics. Engineers pump a plehora of fluid sysems ino wells hroughou heir producive lives. Tesing under simulaed downhole condi - ions answers wo basic quesions. Can he fluid be prepared and properly placed in he well? Will he fluid be sufficienly sable o perform is inended funcions? The esing proocol is ofen complex, involving rheology, filraion, corrosion and mechanical-properies evaluaions. 6 Mechanical devices include seals, screens and packers, along wih roaing and reciprocaing pars such as shafs, pisons, valves and pumps. In addiion o HPHT exposure, qualificaion esing also includes conac wih hazards such as mechanical shocks, hydrogen sulfide [H 2 S], carbon dioxide [CO 2 ] and erosive paricle-laden fluids. Elecronic componens and sensors, he hird elemen, are paricularly vulnerable o high emperaures. The key challenge involves he sabiliy of plasic or composie maerials ha provide modern elecronics wih srucural inegriy and insulaion. Elecronics manufac - urers do no perform exensive R&D in he HPHT domain because he size of he HPHT elecronics marke is iny compared o consumer elecronics such as mobile phones. As a resul, oilfield-equipmen engineers mus deermine he operaional ime limi of exising elecronics under simulaed downhole condiions. The availabiliy of sophisicaed es faciliies, coupled wih an inense R&D effor, has resuled in he developmen of new HPHT producs and services ha span all he sages of well opera - ions. Several of hese advances are highlighed in he following secions. > HPHT esing. Special equipmen and faciliies are required o evaluae fluids, mechanical devices and elecronics a realisic downhole condiions. Logging ools and associaed elecronics can be operaed in an HPHT casing simulaor (op lef) a emperaures and pressures up o 316 C and 27 MPa. HPHT consisomeers (op cener) can evaluae he hickening and seing behavior of cemen slurries up o 371 C [7 F] and 27 MPa. (Phoograph couresy of Cemen Tesing Equipmen, Inc.) A similar device for measuring he rheological behavior of drilling fluids can operae a 316 C and 276 MPa [4, psi] (op righ). (Phoograph couresy of AMETEK, Inc.) For flow-assurance measuremens, HPHT pressure-volume-emperaure (PVT) cells (cener) deec fluid-phase changes and bubblepoins a condiions up o 25 C and 172 MPa. For safey, engineers place he equipmen in individual reinforced esing bays (boom lef) and conrol i remoely from a cenral faciliy (boom cener). Before shipmen o he field, inegraed soluions can be esed in he well a he Schlumberger Sugar Land, Texas faciliy (boom righ), raed o 316 C and 241 MPa. 2. The hc erm comes from he seepes mounain-grade classificaions used by he Tour de France bicycle race. In he French language, hc sands for hors caégorie, essenially meaning beyond classificaion. 3. Adamson K, Birch G, Gao E, Hand S, Macdonald C, Mack D and Quadri A: High-Pressure, High- Temperaure Well Consrucion, Oilfield Review 1, no. 2 (Summer 1998): Baird T, Fields T, Drummond R, Mahison D, Langseh B, Marin A and Silipigno L: High-Pressure, High- Temperaure Well Logging, Perforaing and Tesing, Oilfield Review 1, no. 2 (Summer 1998): Arena M, Dyer S, Bernard LJ, Harrison A, Lucke W, Rebler T, Srinivasan S, Borland B, Was R, Lesso B and Warren TM: Tesing Oilfield Technologies for Wellsie Operaions, Oilfield Review 17, no. 4 (Winer 25/26): Organizaions governing he esing and qualificaion of oilfield producs and services include he American Peroleum Insiue (API), Inernaional Organizaion for Sandardizaion (ISO), NACE Inernaional (NACE) and ASTM Inernaional (ASTM). 6. For more on laboraory esing of fluids: Dargaud B and Boukhelifa L: Laboraory Tesing, Evaluaion and Analysis of Well Cemens, in Nelson EB and Guillo D (eds): Well Cemening 2nd Ediion. Houson: Schlumberger (26): Gusler W, Pless M, Maxey J, Grover P, Perez J, Moon J and Boaz T: A New Exreme HPHT Viscomeer for New Drilling Fluid Challenges, paper IADC/SPE 999, presened a he IADC/SPE Drilling Conference, Miami, Florida, USA, February 21 23, 26. Laboraory Techniques for Fracuring-Fluid Characerizaion, in Economides MJ and Nole KG (eds): Reservoir Simulaion. Houson: Schlumberger Educaional Services (1987): C-1 C-3. Auumn 28 49

5 Drilling and Formaion Evaluaion While drilling HPHT wells, engineers frequenly encouner overpressured formaions, weak zones and reacive shales. In addiion, boreholes are ofen slim and highly deviaed. To mainain well conrol, he drilling-fluid hydrosaic pressure mus be high enough o resis he formaion pore pressure, ye low enough o preven formaion fracuring and los circulaion. As a conse - quence, he accepable fluid-densiy range is ofen small, requiring careful conrol of fluid circulaion o avoid pressure surges ha exceed formaion-fracure pressures. To preven forma - ion damage or borehole collapse, he drilling fluid mus inhibi clay-mineral swelling. The drilling fluid mus also be chemically sable and noncorrosive under HPHT condiions. During he pas decade, drilling fluids based on formae sals have been displacing convenional halide-base fluids in HPHT wells. 7 Fluids conaining halides are highly corrosive o seel a elevaed emperaures and pose environmenal hazards. Corrosion raes associaed wih formae soluions are low, provided he fluid ph remains in he alkaline range. For his reason, formae muds are usually buffered wih a carbonae sal. Unlike halides, formaes are readily biodegradable and may be used wih confidence in environmenally sensiive areas. Formaes are exremely soluble in waer and can be used o creae inver emulsions or solidsfree brines wih densiies up o 2,37 kg/m 3 [19.7 lbm/galus], reducing he need for weighing agens. 8 Lower solids concenraions Maximum TVD, f 33, 31, 29, 27, 25, 23, 21, 19, 17, 15, ofen improve he rae of drillbi peneraion and allow beer conrol of rheological properies. Formae brines also have low waer aciviy; consequenly, hrough osmoic effecs, hey reduce he hydraion of formaion clays and promoe borehole sabiliy. 9 Saoil repored success wih formae-base fluids when drilling high-angle HPHT wells in he Norh Sea. 1 The wells are in he Kviebjørn, Krisin and Huldra fields, wih reservoir pres sures up o 8.7 MPa [11,7 psi] and emperaures up o 155 C [311 F]. Long sequences of inerbedded reacive shales are also presen. Despie he challenging environ men, Saoil experienced no well-conrol incidens in all 15 HPHT drilling operaions in hose fields during a five-year period. In addiion, conrol of formaion clays and drilling cuings helped mainain a low solids concenraion, allowing he operaor o rouinely recycle and reuse he drilling fluid. HPHT condiions presen abundan chal - lenges o scieniss and engineers who design and operae formaion-evaluaion ools. As menioned earlier, he mos vulnerable ool compo nens are seals and elecronics. Measuremen physics dicaes direc exposure of mos logging-ool sensors o wellbore condiions; hus, hey are buil ino a sonde. Mos sonde secions are filled wih hydraulic oil and incorporae a compen - saing pison ha balances he inside and ouside pressures o mainain srucural inegriy and preven ool implosion. Curren sondes are rouinely operaed a pressures up o 27 MPa [3, psi] Year > Trend of maximum well deph in he Gulf of Mexico. A significan acceleraion of he rend has occurred since he mid 199s. Unprecedened boomhole condiions are expeced wihin he nex few years, wih BHTs exceeding 26 C and BHPs approaching 241 MPa. The elecronics are separaed and proeced inside a specially engineered carridge secion. 11 Unlike sonde secions, carridges are no pressurecompensaed because high pressures would crush he elecronics inside. During a logging rip, elecronic componens remain a amospheric pressure inside he carridge housing, which mus resis he exernal pressure. Housing collapse no only would desroy he elecronics, bu also migh disor he ool o an exen ha fishing would be necessary. Pressure proecion is provided by ianium-alloy housings. Leaks a seal surfaces or joins may also lead o flooding and carridge desrucion. Therefore, O-rings are sraegically placed along he oolsring o seal connecions and inernal comparmens. To avoid caasrophic failure of he enire oolsring, individual ools are also isolaed from each oher by pressure-igh bulkheads in a manner similar o hose in a submarine. O-rings for HPHT applicaions are composed of fluoropolymeric elasomers. Vion elasomer, he mos common example, is raed o 24 C [4 F]. A higher emperaures, he Vion formulaion breaks down and loses elasiciy. For hese exreme siuaions, Schlumberger engineers have quali fied O-rings fabricaed from Chemraz elasomer an advanced maerial ha is sable o abou 316 C [6 F] bu is significanly more expensive han is Vion counerpar. 12 Curren elecronic sysems for HPHT logging can operae coninuously a emperaures up o 177 C. The emperaure inside he carridge is a funcion of he downhole emperaure and inernal hea generaed by he elecronics. When higher exernal emperaures are anicipaed, engineers place he ool inside an insulaing Dewar flask a vacuum sleeve ha delays hea ransmission. Depending upon he duraion of he logging run, Dewar flasks allow operaions a emperaures up o 26 C. Recenly, exended run imes have become possible wih he inro - ducion of low-power elecronics ha generae less inernal hea. Since he mid 199s, well dephs in he Gulf of Mexico have increased rapidly, and BHTs and BHPs have followed sui (lef). 13 Conversely, borehole size usually decreases wih deph. In response o his rend, Schlumberger engineers inroduced he SlimXreme well logging plaform a miniaurized version of he Xreme HPHT logging sysem (nex page). 14 This service offers he same suie of measuremens as is larger counerpar, packaged in a 3-in. diameer oolsring. As a resul, he sysem can be run inside openings as small as in. drillpipe or in. open hole. In addiion, hanks in par o 5 Oilfield Review

6 he lower exernal surface area of he ianium housing, he SlimXreme oolsring can operae a pressures up o 27 MPa. Chevron applied SlimXreme echnology in he Gulf of Mexico while logging deepwaer exploraory wells a he Tonga prospec in Green Canyon Block 727. During logging runs o 31,824 f [9,7 m], he sysem experienced pres - sures up o 26, psi [18 MPa] and coninued o operae successfully. Anoher Chevron exploraory well, he Endeavour 2 in souh Texas, esed SlimXreme performance a elevaed empera ures. The oolsring, incorpo raing porions enclosed wihin a Dewar flask, was able o provide reliable daa o 21,8 f [6,645 m] and 489 F [254 C]. Deep HPHT wells presen addiional wirelinelogging challenges. Muliple runs are usually necessary o acquire he informaion, and small boreholes, long cables and heavy oolsrings increase he risk of he ools becoming suck. Telemery and gamma ray carridge CNL compensaed neuron log ool Liho-Densiy ool Caliper sonde Temperaure, C Tool limi Exernal Inernal 2 4 Time, min High-srengh wireline cable High-srengh dual-drum capsan Deph, f 3 o 6 f recommended Sandard Schlumberger wireline uni 7. Formae sals are based on formic acid HCOOH. Sodium, poassium and cesium formae (and combina - ions hereof) are used in drilling-fluid applicaions. 8. An inver emulsion conains oil in he coninuous, or exernal, phase and waer in he inernal phase. 9. Waer aciviy (a w ) is he equilibrium amoun of waer available o hydrae maerials. When waer ineracs wih solues and surfaces, i is unavailable for oher hydraion ineracions. An a w value of one indicaes pure waer, whereas zero indicaes he oal absence of free waer molecules. Addiion of solues (such as formae sals) always reduces he waer aciviy. Byrne M, Paey I, George L, Downs J and Turner J: Formae Brines: A Comprehensive Evaluaion of Their Formaion Damage Conrol Properies Under Realisic Reservoir Condiions, paper SPE 73766, presened a he SPE Inernaional Symposium and Exhibiion on Formaion Damage Conrol, Lafayee, Louisiana, USA, February 2 21, Berg PC, Pedersen ES, Laurisen A, Behja N, Hagerup-Jenssen S, Howard S, Olsvik G, Downs JD, Harris M and Turner J: Drilling, Compleion and Openhole Formaion Evaluaion of High-Angle Wells in High-Densiy Cesium Formae Brine: The Kviebjørn Experience, 24 26, paper SPE/IADC 15733, presened a he SPE/IADC Drilling Conference, Amserdam, February 2 22, The sonde is he secion of a logging ool ha conains he measuremen sensors. The carridge conains he elecronics and power supplies. 12. Vion elasomer is a copolymer of vinylidenfluoride and hexafluoroisopropene, (CH 2 CF 2 ) n (CF(CF 3 )CF 2 ) n. Chemraz elasomer is a similar compound ha conains more fluorine. Boh are relaed o he well-known Teflon fluoropolymer. 13. Sarian S: Wireline Evaluaion Technology in HPHT Wells, paper SPE 97571, presened a he SPE High Pressure/High Temperaure Sour Well Design Applied Technology Workshop, The Woodlands, Texas, May 17 19, Inroduced during he lae 199s, Xreme well-logging ools record basic perophysical measuremens a condiions up o 26 C and 172 MPa [25, psi]. The measuremens include resisiviy, formaion densiy, neuron porosiy, sonic logging and gamma ray specroscopy. Henkes IJ and Praer TE: Formaion Evaluaion in Ulra-Deep Wells, paper SPE/IADC 5285, presened a he SPE/IADC Drilling Conference, Amserdam, March 9 11, SLT sonic logging ool AIT array inducion imager ool 1, 2, Weakpoin > Equipmen and sofware for wireline logging and sampling in HPHT wells. The SlimXreme plaform (lef), designed for slimhole drilling in HPHT and high-angle wells, provides a complee suie of downhole measuremens in boreholes as small as in. Engineers run he ools a speeds up o 1,97 m/h [3,6 f/h], and daa can be ransmied o he surface hrough wireline as long as 1,97 m [36, f]. Temperaure planning sofware simulaes he logging job and predics exernal (red) and inernal (blue) ool emperaures versus ime (op righ). In his example, he exernal ool emperaure rises and falls as he ool is lowered ino he well and hen rerieved. However, he inernal ool emperaure remains well below he 16 C limi (green), indicaing ha he elecronics will be proeced. These simulaions are useful for opimizing he operaion and ensuring ool survival. The applicaion considers several job parameers, including well condiions, logging speed and he presence of Dewar flasks. The risk of suck oolsrings increases when logging and sampling from deep, slim HPHT wells. A high-ension deploymen sysem (boom righ) miigaes he risk by combining a sandard Schlumberger wireline uni, a high-srengh dual-drum capsan and highsrengh wireline cable. The capsan increases he pulling force ha can be exered on he wireline, allowing rerieval of heavy oolsrings and reducing he risk of sicking. Auumn 28 51

7 Linear expansion, % Sal cemen Foamed cemen FlexSTONE HT cemen > FlexSTONE HT cemen properies a 2 C compared wih hose of convenional cemens. To ensure proper bonding beween he cemen/casing and cemen/formaion inerfaces, FlexSTONE cemens can be formulaed o provide significanly more expansion afer seing han convenional sysems (lef). FlexSTONE HT sysems also offer improved zonal-isolaion properies, including lower Young s modulus and lower permeabiliy (righ). Fishing operaions o rerieve ools from deep holes are expensive, ime-consuming and precarious possibly resuling in suck drillpipe, ool damage or ool loss. To minimize he danger, Schlumberger engineers developed an improved ool-deploymen mehod using high-ension cable and a capsan. The sysem allows rapid deploymen of he logging sring and much higher pulling capaciy, reducing he risk of ool sicking. Anoher imporan wireline operaion involves acquiring fluid samples from hydro - carbon reservoirs and analyzing hem downhole or a he surface. Tes resuls provide oil companies wih informaion necessary o decide how o complee a well, develop a field, design surface faciliies, ie back saellie fields and commingle producion beween wells. 15 HPHT condiions increase he difficuly of downhole sampling. In addiion, pressurized live-fluid samples mus be safely ranspored o he surface and hen o nearby laboraories. Sampling operaions in HPHT wells are cosly, especially offshore; herefore, collecing highqualiy samples is crucial o jusify he expense. In 24, Chevron began drilling exploraory wells ino he Lower Teriary play in he deepwaer Gulf of Mexico (see The Prize Beneah he Sal, page 4). These wells can be difficul o drill and complee, wih waer dephs o 9,8 f [3, m], oal well dephs exceeding 25, f [7,6 m], and BHPs and BHTs ofen approaching 2, psi [138 MPa] and 392 F [2 C]. In 26, Chevron decided o inves considerable resources and rig ime o perform an exended well es (EWT) on he Jack 2 well, souhwes of New Orleans and 2. Well-isolaion properies Young s modulus, MPa x 1, Convenional cemen FlexSTONE HT cemen Permeabiliy o waer, µd 175 mi [282 km] offshore. The long-erm drillsem es (DST) was necessary o acquire vial reservoir and producion informaion ha would reduce uncerainy and risk involving reservoir compar - menalizaion, fluid properies and produciviy. A 28,175 f [8,588 m], he Jack 2 es would be he deepes ever aemped in he Gulf of Mexico. Before performing he DST, Chevron seleced he Quicksilver Probe fluid-sampling ool o exrac high-puriy formaion-fluid samples. This sysem employs a unique muliple fluid-inake sysem o minimize formaion-fluid sample conaminaion, and i operaes in condiions o 35 F. Samples acquired by he Quicksilver Probe module conained less han 1% conami - naion afer 4 hours of pumping. Fluid-properies daa provided by he samples allowed he operaor o make drilling and well-esing proce - dure adjusmens ha reduced he overall risk. The Jack 2 EWT also required an HPHT perforaing sysem. Consuling wih Chevron personnel, Schlumberger engineers buil a ool combinaion ha is raed o 25, psi [172 MPa]. The Jack 2 perforaing sysem incorporaed a 7-in. gun capable of firing 18 shos per foo, as well as a perforaing shock absorber and a redundan elecronic firing head. Approximaely nine monhs of engineering, manufacuring and esing were required o achieve full qualificaion. A final 9-day performance es ook place a he Schlumberger Reservoir Compleions (SRC) Cener in Rosharon, Texas, inside a es vessel ha simulaed he anicipaed downhole condi - ions. The equipmen funcioned properly, and Chevron engineers approved deploymen of he perforaing equipmen o he rig. The EWT was a success, and he Jack 2 well susained a flow rae exceeding 6, bbl/d [95 m 3 /d] of crude oil from abou 4% of he well s ne pay. This resul led Chevron and is parners o reques various sizes of HPHT perforaing sysems for addiional appraisal wells nearby and fuure field developmens elsewhere in he deepwaer Gulf of Mexico. 16 Cemening and Zonal Isolaion Providing zonal isolaion in deep oil and gas wells such as Jack 2 requires use of cemen sysems ha are sable in HPHT environmens. Thermally sable cemens are also necessary in seamflood wells and geohermal wells. 17 The physical and chemical behavior of well cemens changes significanly a elevaed emperaures and pressures. Wihou proper slurry design, he inegriy of se cemen may deeriorae, poenially resuling in he loss of zonal isolaion. Unlike many oher HPHT echnologies, well cemens are permanenly exposed o downhole condiions and mus suppor he casing and provide zonal isolaion for years. Porland cemen is used in nearly all wellcemening applicaions. The predominan binding minerals are calcium silicae hydraes (CSH). A emperaures above abou 11 C [23 F], mineralogical ransformaions occur ha may cause he se cemen o shrink, lose srengh and gain permeabiliy. This deerio - raion can be minimized or even prevened by adding a leas 35% silica by weigh of cemen. The composiional adjusmen causes he formaion of CSH minerals ha preserve he desired se-cemen properies. Alhough silicasabilized Porland cemen sysems can be used a emperaures up o abou 37 C [7 F], hey are suscepible o oher challenges posed by hermal wells. A hermally sable cemen sysem may iniially provide adequae zonal isolaion; however, changes in downhole condiions can induce sresses ha compromise cemen-sheah inegriy. Teconic sresses and large changes in wellbore pressure or emperaure may crack he sheah and can even reduce i o rubble. Radial casing-size flucuaions induced by emperaure and pressure changes can damage he bond beween he se cemen and he casing or he formaion, creaing a microannulus. These problems are of paricular concern in deep, ho wells and hermal-recovery wells employing cyclic-seam-simulaion (CSS) or seamassised-graviy-drainage (SAGD) processes Oilfield Review

8 Unil recenly, he well cemening indusry focused on one mechanical parameer unconfined uniaxial compressive srengh o qualify a cemen design. The longer-erm diffi - culies described above led Schlumberger scieniss o more horoughly invesigae he mechanical properies of se cemen, along wih models governing he mechanical behavior of seel pipe and rocks. They adaped he models o he geomery of a well and inroduced CemSTRESS sofware an applicaion ha analyzes he behavior of a cemen sheah exposed o anicipaed downhole condiions. This sofware analyzes radial and angenial sresses experi - enced by he cemen sheah resuling from pressure ess, formaion-propery changes and emperaure flucuaions. Along wih compressive srengh, he CemSTRESS algorihms consider Young s modulus, Poisson s raio and ensile srengh and help engineers deermine he appropriae cemen mechanical properies for a given applicaion. 19 CemSTRESS analysis usually indicaes ha cemen sheahs in CSS and SAGD wells should be more flexible han in convenional sysems. This can be achieved by using cemens wih lower Young s moduli (previous page). 2 In addiion, he cemen sheah should expand slighly afer seing o ensure firm conac wih he casing and formaion. These requiremens led o he developmen of FlexSTONE HT high-emperaure flexible cemen. 21 This cemen is par of a family ha combines he engineered paricle-size concep of CemCRETE echnology wih flexible paricles ha lower he Young s modulus. 22 In addiion, expansion afer seing can be significanly higher han ha of convenional cemen sysems, promoing bonding wih he casing and formaion. 23 The emperaure limi of FlexSTONE HT cemen is abou 25 C [482 F]. An operaor in he UK region of he Norh Sea had an ambiious goal of producing gas a a susained 6.8-million m 3 /d [24-MMcf/d] produc - ion rae from hree wells wih a BHT of 193 C 15. Akkur R, Bowcock M, Davies J, Del Campo C, Hill B, Joshi S, Kundu D, Kumar S, O Keefe M, Samir M, Tarvin J, Weinheber P, Williams S and Zeybek M: Focusing on Downhole Fluid Sampling and Analysis, Oilfield Review 18, no. 4 (Winer 26/27): Beancour S, Davies T, Kennedy R, Dong C, Elshahawi H, Mullins OC, Nighswander J and O Keefe M: Advancing Fluid-Propery Measuremens, Oilfield Review 19, no. 3 (Auumn 27): Aghar H, Carie M, Elshahawi H, Ricardo Gomez J, Saeedi J, Young C, Pingue B, Swainson K, Takla E and Theuveny B: The Expanding Scope of Well Tesing, Oilfield Review 19, no. 1 (Spring 27): Nelson EB and Barle-Gouédard V: Thermal Cemens, in Nelson EB and Guillo D (eds): Well Cemening 2nd Ediion. Houson: Schlumberger (26): Alboudwarej H, Felix J, Taylor S, Badry R, Bremner C, Brough B, Skeaes C, Baker A, Palmer D, Paison K, Beshry M, Krawchuk P, Brown G, Calvo R, [38 F]. 24 Meeing his goal would require unusually high drawdown pressures, exering signi fican mechanical sress on he casing, cemen sheah and formaion. Using CemSTRESS sofware, Schlumberger engineers deermined ha placing FlexSTONE HT cemen across he producion zone would provide a gaske-like seal capable of wihsanding he severe environmen. Afer cemen placemen, he producion srings were subjeced o pressure ess up o 69 MPa and drawdown ess exceeding 41 MPa [6, psi]. The cemen sheah remained inac. Afer more han wo years of producion, here have been no wellinegriy problems. Heavy-oil projecs involving SAGD wells also employ FlexSTONE HT cemen exensively. An easern European reservoir conained a paricularly hick crude oil 12,-MPa-s [12,-cP] viscosiy and a 17 API graviy. Oil mining had been he sandard recovery mehod. To reduce producion coss, he operaor eleced o ry he SAGD mehod in a pilo well. This approach presened muliple well-consrucion concerns: 3-m [984-f] horizonal secions a a TVD of 228 m [748 f], emperaures approaching 25 C and sresses on he cemen sheah resuling from hermal producion cycles and a sof formaion. FlexSTONE HT cemen success - fully wihsood he producion condiions wih no loss of zonal isolaion, and he operaor has planned addiional SAGD insallaions. CSS and SAGD wells in Canada, Venezuela, Egyp, Indonesia and California, USA, have also benefied from FlexSTONE HT cemen. CSS and SAGD wells require specialized, highperformance compleion equipmen o handle he exreme emperaure cycles. Common elasomeric seals ofen fail, allowing pressure and fluids o escape up he casing, reducing seaminjecion efficiency and increasing he poenial for casing corrosion. Recenly, Schlumberger engineers began using seals fabricaed from a yarn of carbon fibers conained wihin an INCONEL alloy jacke. These seals are capable of Cañas Triana JA, Hahcock R, Koerner K, Hughes T, Kundu D, López de Cardenas J and Wes C: Highlighing Heavy Oil, Oilfield Review 18, no. 2 (Summer 26): Thiercelin M: Mechanical Properies of Well Cemens, in Nelson EB and Guillo D (eds): Well Cemening 2nd Ediion. Houson: Schlumberger (26): James S and Boukhelifa L: Zonal Isolaion Modeling and Measuremens Pas Myhs and Today s Realiies, paper SPE 1131, presened a he SPE Abu Dhabi Inernaional Peroleum Exhibiion and Conference, Abu Dhabi, UAE, November 5 8, Young s modulus, also called he modulus of elasiciy, is he raio beween he sress applied o an objec and he resuling deformaion, or srain. Lower Young s moduli correspond o more flexible maerials. 21. Abbas R, Cunningham E, Munk T, Bjelland B, Chukwueke V, Ferri A, Garrison G, Hollies D, Laba C and Moussa O: Soluions for Long-Term Zonal Isolaion, Oilfield Review 14, no. 3 (Auumn 22): Upper ieback sealbore Permanen hold-down slip Heavy-oil-hermal (HOT) seal Permanen hanging slip Liner connecion > Schlumberger high-emperaure liner hanger. Developed for seamflood applicaions, he liner hanger feaures seals made from carbon fiber and INCONEL alloy. The ool has permanen slips and a one-piece mandrel o minimize possible leak pahs and can be roaed while running in he hole. To dae, Schlumberger engineers have insalled more han 15 unis in Canada, wih no pressure-es failures. Some of he sysems have survived up o 1 hermal cycles o 343 C [649 F]. operaing a cycled-seam emperaures up o 34 C [644 F] and pressures up o 21 MPa [3, psi], allowing reliable deploymen of hermal liner sysems (above). Siles D: Effecs of Long-Term Exposure o Ulrahigh Temperaure on he Mechanical Parameers of Cemen, paper IADC/SPE 98896, presened a he IADC/SPE Drilling Conference, Miami, Florida, February 21 23, For more on engineered-paricle-size cemens: Nelson EB, Drochon B and Michaux M: Special Cemen Sysems, in Nelson EB and Guillo D (eds): Well Cemening 2nd Ediion. Houson: Schlumberger (26): Cemen sysems ha expand slighly afer seing are a proven means for sealing microannuli and improving primary cemening resuls. Improved bonding resuls from ighening of he cemen sheah agains he casing and formaion. 24. Palmer IAC: Jade Norh Sea HPHT Developmen: Innovaive Well Design Generaes Bes in Class Performance, paper SPE/IADC 92218, presened a he SPE/IADC Drilling Conference, Amserdam, February 23 25, 25. Auumn 28 53

9 Schlumberger high-emperaure hermal liner hangers have been used in he Cold Lake field, where a major operaor in Canada is conducing a horizonal-well CSS program. 25 Wih cusomized liners and carbon-fiber and INCONEL seals a he op of he liner, he operaor has been able o achieve good seam conformance seam inake spread evenly over he lengh of he horizonal well verified by ime-lapse seismic surveys over he pilo area. Reservoir Simulaion and Producion Reservoir simulaion encompasses wo major echniques: marix acidizing and hydraulic fracuring. Boh procedures bypass formaion damage incurred during drilling, cemening and perforaing, and hey also provide an enhanced connec ion beween he formaion rock and he wellbore. The goal is o increase hydrocarbon producion o levels far exceeding wha would be possible under naural-flow condiions. 26 > Wormholes formed during a laboraory-scale marix acidizing reamen of a carbonae-formaion sample. The lengh, direcion and number of wormholes depend on he formaion reaciviy and he rae a which acid eners he formaion. Once formed, he wormholes carry virually all of he fluid flow during producion. Marix acidizing consiss of pumping a low-ph fluid hrough naurally exising channels in he rock, a raes ha are sufficienly low o avoid creaing fracures in he formaion. The acid dissolves soluble componens of near-wellbore formaion rock and damaging maerials deposied by previous well-service fluids, hereby creaing a more permeable pah for hydrocarbon flow. Acidizing fluids are formulaed o simulae carbonae or sandsone formaions. Mos carbonae acidizing involves reacing hydrochloric acid (HCl) wih formaions com - posed of calcium carbonae (calcie), calcium magnesium carbonae (dolomie) or boh. As he acid flows hrough perforaions and dissolves he carbonae rock, highly conducive channels called wormholes are creaed in he formaion. Wormholes radiae from he poin of acid injecion and carry virually all of he fluid flow during producion (lef). For efficien simulaion, he wormhole nework should penerae deeply and uniformly hroughou he producing inerval. HCl is an effecive simulaion fluid a low emperaures, bu i can be problemaic when used a emperaures exceeding abou 93 C [2 F]. A higher emperaures, his mineral acid aacks he formaion oo rapidly, mini mizing he deph and uniformiy of he wormholes. These condiions also promoe excessive ubular corrosion and require engineers o add high concenraions of oxic corrosion inhibiors. Recenly, Schlumberger chemiss solved hese problems by developing acidizing fluids based on hydroxyehylamino - carboxylic-acid (HACA) chelaing agens. Common commercial HACA compounds such as era - sodium EDTA and risodium HEDTA have been used in he oil field for decades, mainly as scaleremoval agens and scale inhibiors. 27 A variey of HACA compounds underwen laboraory esing a emperaures up o 2 C. The evaluaion consised mainly of coreflood ess in limesone and corrosion-rae measure - mens involving common ubular meals. The bes performer was risodium HEDTA, buffered o a ph value of abou 4. Less acidic han a carbonaed beverage, his formulaion is far less corrosive han convenional mineral acids, and very low ubular corrosion raes can be achieved by adding small amouns of milder, environ - menally accepable corrosion inhibiors. Wih is higher ph, risodium HEDTA reacs more slowly and creaes an exensive, farher-reaching wormhole nework raher han a shor dominan 54 Oilfield Review

10 one (righ). In addiion, HEDTA fluid is far more efficien han HCl a HPHT condiions. A comparable level of simulaion may be achieved by pumping less han one-enh he fluid volume (below righ). 28 Hydraulic fracuring involves pumping large volumes of fluid hrough perforaions and ino he formaion a raes and pressures sufficien o no only creae a fracure, bu also propagae i far beyond he near-wellbore region. The final fluid sage fills he fracure wih proppan silicae, ceramic or bauxie granules wih high sphericiy leaving a high-permeabiliy condui beween he producing formaion and he wellbore. 29 Fracuring-fluid viscosiy is a criical param - eer ha governs fracure iniiaion and propagaion, as well as proppan ranspor down he ubulars, hrough perforaions and ino he fracure. A HPHT condiions, sufficien fluid viscosiy is usually achieved by preparing mealcrosslinked soluions of guar-base polymers. The mos common meal crosslinkers are boron and zirconium. 3 However, viscosiy aainmen alone is no sufficien o perform a successful HPHT fracuring reamen. To minimize fricionpressure losses as he fluid is pumped downhole, he crosslinking reacions should be delayed unil jus before he fluid eners he perforaions. In addiion, he viscosiy should no be unduly sensiive o he high-shear-rae environmen commonly found in he ubulars and perfora ions; oherwise, he fluid will be ill equipped for fracure propagaion and proppan ranspor, increasing he likelihood of a premaure screenou. 31 The characerisics of borae- and zirconaecrosslinked fluids are fundamenally differen. Borae crosslinking arises from ionic bonds ha can break under high-shear condiions; however, he bonds heal and fluid viscosiy recovers when a low-shear environmen is resored. Zirconaecrosslinked fluids are no as forgiving because he linkage resuls from covalen bonds ha form only once. If he fluid crosslinks and experiences elevaed shear oo early, he bonds will break > Acidizing coreflood es wih 2% Na 3 HEDTA. Technicians pumped he acid hrough a 2.54-cm [1-in.] diameer, 3.5-cm [12-in.] long limesone core a 177 C [35 F]. The Na 3 HEDTA soluion creaed numerous wormholes ha formed a complex nework. The phoograph of he core enrance (lef) shows he formaion of many wormholes. The CT-scan sequence (righ) confirms ha he wormhole nework exends hroughou he core lengh. The upper-lef CT-scan image displays he core enrance, and subsequen core secions coninue from lef o righ. Pore volumes o breakhrough 1, % HCI 2% Na 3 HEDTA Flow rae, bbl/min > Comparing he acidizing efficiency of 15% HCl (purple) and Na 3 HEDTA (green) a 177 C. This graph shows he amouns of acidizing fluid (expressed in pore volumes) required o radially penerae 3.5 cm [12 in.] ino a 3.5-m [1-f] inerval of 1-mD carbonae formaion wih 2% porosiy. The resuls indicae ha, regardless of pumping rae, risodium HEDTA is more han one order of magniude more efficien han HCl. 25. Smih RJ and Perepeleca KR: Seam Conformance Along Horizonal Wells a Cold Lake, paper SPE/ PS-CIM/CHOA 799, presened a he SPE Inernaional Thermal Operaions and Heavy Oil Symposium and Inernaional Horizonal Well Technology Conference, Calgary, November 4 7, For more on reservoir simulaion: Economides MJ and Nole KG (eds): Reservoir Simulaion, 3rd Ediion. New York Ciy: Wiley, Chelaing agens, also known as sequesering agens, are compounds used o conrol undesirable reacions of meal ions (such as Ca, Mg and Fe). For example, hey form chemical complexes ha do no precipiae during acidizing reamens, hereby prevening formaion damage. EDTA and HEDTA are acronyms for ehylene - diamineeraaceic acid and hydroxyehylene diamineriaceic acid. Frenier WW, Fredd CN and Chang F: Hydroxyamino - carboxylic Acids Produce Superior Formulaions for Marix Simulaion of Carbonaes a High Temperaures, paper SPE 71696, presened a he SPE Annual Technical Conference and Exhibiion, New Orleans, Sepember 3 Ocober 3, Frenier WW, Brady M, Al-Harhy S, Arangah R, Chan KS, Flaman N and Samuel M: Ho Oil and Gas Wells Can Be Simulaed Wihou Acids, paper SPE 86522, presened a he SPE Inernaional Symposium and Exhibiion on Formaion Damage Conrol, Lafayee, Louisiana, February 18 2, For more on hydraulic fracuring: Economides and Nole, reference Crosslinks are bonds ha link one polymer chain o anoher. Boron and zirconium inerac wih guar-base polymers, forming linkages ha increase he effecive polymer molecular weigh by several orders of magniude and dramaically increase he fluid viscosiy. 31. Screenou occurs when proppan paricles bridge he perforaions and block furher fluid ingress. This condiion is accompanied by a sudden reamenpressure increase. A premaure screenou occurs when he fracure volume is insufficien, when less han he desired amoun of proppan is placed in he fracure, or boh. Auumn 28 55

11 irreversibly, fluid viscosiy will decrease, and he screenou probabiliy will increase (below). Therefore, i is vial o conrol he iming and he locaion of crosslinking. Viscosiy a 1 s 1, cp Viscosiy a 1 s 1, cp 1,6 1,4 1,2 1, Borae-Crosslinked Fluid Zirconae-Crosslinked Fluid 1, Time, min Unsheared Sheared a 1,35 s 1 for 5 min Alhough less forgiving, zirconae-crosslinked fluids have been used almos exclusively in HPHT fracuring reamens, mainly because hey are hermally more sable han borae fluids. Despie seady advances in fluid design, achieving Time, min > Shear-hisory behavior of guar fluids crosslinked by borae and zirconae compounds. Rheological esing of fracuring fluids involves wo principal devices: a shear-hisory simulaor and a viscomeer. The shear-hisory simulaor exposes fracuring fluids o shearing condiions hey would experience while raveling down he ubulars oward he perforaions. The viscomeer measures he fracuringfluid viscosiy a various shear raes, emperaures and pressures. Shear-hisory sudies deermine how shearing in he ubulars would affec fluid viscosiy. Technicians measure and plo he rheological behavior of wo idenical fluids one ha has undergone prereamen in he shear-hisory simulaor (blue) and one ha has no (pink). Tes resuls show ha, afer prolonged exposure o a high-shear-rae environmen in he shear-hisory simulaor, he borae-crosslinked fluid recovered and achieved he same viscosiy as is counerpar ha did no experience prereamen (op). The viscosiy plos evenually overlapped. On he oher hand, he zirconae-crosslinked fluid permanenly los viscosiy afer prereamen in he shear-hisory simulaor (boom). This effec would increase he poenial for screenou. The baseline viscosiies on he plos correspond o a 1-s 1 shear rae. The periodic spikes denoe shear-rae ramps in he viscomeer up o abou 3 s 1. Viscosiy measuremens a various shear raes allow calculaion of addiional rheological parameers ha engineers use o opimize fracuring-fluid designs. sufficien crosslink conrol wih zirconae fluids has remained elusive. The crosslinking reacions are emperaure-sensiive, and predicing circu - laing emperaures inside ubulars of HPHT wells is ofen difficul. Chemiss solved hese problems by com - bining he bes feaures of boraes and zirconaes ino one sysem ThermaFRAC fracuring fluid. The new dual-crosslinker fluid, based on carboxymehylhydroxypropyl guar (CMHPG), feaures wo crosslinking evens an early low-emperaure reacion involving borae, and a secondary emperaure-acivaed one involving zirconae. Borae crosslinking provides low shear sensiiviy, and zirconae bonding conribues hermal sabiliy (nex page). 32 Fluid preparaion is simpler and more reliable because addiives previously used o sabilize and conrol radiional zirconae-only fluids are no longer necessary. Laboraory ess have demonsraed suiable performance a emperaures from 2 o 375 F [93 o 191 C]. Souh Texas has long been a major cener of HPHT aciviy, and operaors here have come o rely heavily on new echnologies o solve problems. Producing reservoirs are deep and mus frequenly be simulaed hrough long ubing srings or slimhole compleions. This well geomery is problemaic for wo main reasons. Firs, reamen pump raes mus be reduced o minimize fricion-pressure losses and decrease he number of pump rucks a he wellsie. 33 Lower flow raes limi he fluid pressure ha engineers may apply o iniiae and propagae a hydraulic fracure. Second, fracuring fluids experience high amouns of shear as hey flow hrough small-diameer ubulars, and zirconaebase fluids are paricularly suscepible o premaure deerioraion. Dual-crosslinker fluids have successfully addressed hese problems. One example involves a well ha suffered casing collapse afer a fracuring reamen. Workover operaions o resore communicaion and producion were unsuccessful, and he operaor s only remaining opion was o siderack he wellbore and insall a slimhole compleion. The operaion involved lowering 12,2 f [3,719 m] of in. ubing from surface o he producing inerval and hen cemening i in place. Wellbore inegriy was a serious concern because of damage resuling from he workover operaions. In addiion, he operaor was worried abou fricion-pressure losses and high leakoff raes arising from fluid diversion ino he exising fracure. The hickness of he producing sandsone inerval was 46 f [14 m], and he BHT was 31 F [154 C]. 56 Oilfield Review

12 The operaor approved a ThermaFRAC rea - men ha addressed he anicipaed difficulies. The pad volume was unusually large 65% of he oal job and he CMHPG concenraion was high 45 lbm/1, galus [5.4 kg/l] o compensae for he high leakoff rae. 34 To mini - mize fricion pressure, he maximum pump rae was 12 bbl/min [1,98 L/min]. The proppan slurry placed 62, lbm [28,12 kg] of 2/4-mesh resin-coaed bauxie a concenra - ions up o 8 lbm/galus [961 kg/m 3 ] of fracuring fluid. Following he success of his reamen, he operaor applied dual-crosslinker fluids in addiional slimhole applicaions, including one in which 295, lbm [133,81 kg] of 2/4-mesh ceramic and resin-coaed ceramic proppan were placed ino a 74-f [22.6-m] inerval hrough 11,6 f [3,536 m] of in. ubing. A his wriing, more han 6 ThermaFRAC reamens involving 11 operaors have been successfully performed in souh Texas, a boomhole empera - ures beween 121 and 191 C [25 and 375 F]. The new fracuring fluid has also been used o simulae a gas-bearing HPHT sandsone reservoir in norhern Germany. The average formaion deph is 4,55 m [14,93 f] TVD, and he BHT is approximaely 15 C. BHPs vary from 25 o 3 MPa [3,63 o 4,35 psi], and he formaionpermeabiliy range is.1 o 5 md. In his area, engineers usually perform fracuring reamens hrough a dedicaed ubing sring wih he rig in place. To save money, he operaor waned o begin simulaing wells wihou he rig, pumping he reamen hrough he final well-compleion sring. Fracuring fluids are usually prepared wih ambien-emperaure mix waer. However, pump - ing a cool fluid hrough a finished compleion would cause sufficien ubular conracion o exer excessive sress on packers and jeopardize zonal isolaion. Therefore, o minimize hermal effecs, i would be necessary o prehea he mix waer o 5 C [122 F]. Zirconae crosslinking is emperaure-dependen, and i was unlikely ha reliable rheological conrol would be possible wih a radiional single-crosslinker sysem. To develop a soluion, engineers conduced fluid-design experimens a he Schlumberger Clien Suppor Laboraory in Aberdeen, Scoland. This faciliy has esing equipmen ha can simulae boh he hermal environmen and he shear environmen anici paed in he German well. Tes resuls showed ha he dualcrosslinker fluid would allow sufficien leeway o design a reamen compaible wih he operaor s cos-saving goal. Viscosiy a 1 s 1, cp ThermaFRAC Fluid 1, Time, min Unsheared Sheared a 1,35 s 1 for 5 min > Shear-hisory behavior of ThermaFRAC fluid a 135 C [275 F]. Afer prolonged exposure o a high shear rae in he shear-hisory simulaor, he viscosiy of ThermaFRAC fluid does no change significanly. 32. Guar gum, a powder consising of he ground endosperm of guar beans, is used exensively as a food hickener. Guar-gum derivaives are purified and funcionalized producs wih good hermal sabiliy. Common derivaives for hydraulic-fracuring applicaions include hydroxypropyl guar (HPG) and carboxymehyl - hydroxypropyl guar (CMHPG). 33. Fricion-pressure loss is he pressure decrease arising from fricional losses ha occur as a fluid passes Engineers performed he ThermaFRAC rea - men in a well wih a 3-m [98-f] producing zone, pumping 184 m 3 [48,6 galus] of fluid wih a CMHPG loading of 4.8 kg/m 3 [4 lbm/1, galus], and placing 32 meric ons [7,5 lbm] of 2/4 resin-coaed high-srengh proppan in he frac - ure. The resuling fracure conduciviy in his well was 25% higher han hose of offse wells reaed wih convenional single-crosslinker fluids, and he producion rae was 3% higher han he operaor s predicion. Consequenly, he operaor has chosen his fluid o simulae seven more wells in his region. Cerain ypes of HPHT reservoirs would no benefi significanly from marix-acidizing or hydraulic-fracuring reamens. Perhaps he bes examples are heavy-oil deposis, in which he preferred simulaion mehod involves oilviscosiy reducion by seam injecion. Seam generaion comprises approximaely 75% of he SAGD operaing expenses. Reducing he seam/oil raio (SOR) and mainaining an opimal producion rae are keys o improving profiabiliy. Reducing seam inpu saves energy coss, decreases produced-waer volume and reamen expenses, and curails associaed CO 2 emissions. A 1 o 25% SOR reducion may be achieved by using elecric submersible pump (ESP) sysems. ESPs allow reservoirs o be produced a pressures ha are independen of wellhead or separaor pressures, hereby increasing seaminjecion efficiency and decreasing he produc ion cos by a leas US $1. per barrel of produced oil. Numerous Canadian operaors, including Encana, Suncor, ConocoPhillips, Nexen, TOTAL, Husky and hrough pipe. The pressure decrease is mainly a funcion of pipe diameer, pipe lengh, fluid rheological properies and flow rae. High fricion reduces he available fluid pressure a he pipe oule. 34. Fracuring reamens consis of wo fluid sages. The firs sage, he pad, iniiaes and propagaes he fracure. The second sage, he proppan slurry, ranspors proppan down he ubulars, hrough he perforaions and ino he fracure. Auumn 28 57

13 Pump Inake Moor > REDA Holine55 ESP arificial lif sysem. The mulicomponen oolsring can be used in wells wih BHTs up o 218 C (cener). The hear of he sysem is he cenrifugal pump, equipped wih silicon- or ungsen-carbide bearings for durabiliy a exreme emperaures (lef). The number of sages can also be adjused according o he compleion requiremens. The pump moor employs meal-o-meal seals o provide a hea-resisan mechanical barrier o fluid enry (righ). Cables ha ransmi power o he moor and daa o surface are proeced by insulaing armor composed of heavy galvanized seel, sainless seel and corrosion-resisan Monel alloy (inse). As of November 28, he Holine55 sysem is operaing in more han 1 Canadian hermal wells. Blackrock, have insalled he REDA Holine55 high-emperaure ESP sysem in seam-injecion wells (lef). Raed o operae coninuously a up o 288 C [55 F] inernal moor emperaure, or 218 C [425 F] boom hole emperaure, he equipmen employs high-emperaure hermo - plasic moor-winding insulaion and is designed o compen sae for variable expansion and conracion raes of he differen maerials in he pump. Many of hese insallaions have operaed coninuously for more han wo years. Surveillance Mainenance of an opimal reservoiremperaure disribuion is vial o efficien heavy-oil producion from SAGD or CSS wells; herefore, engineers need o acquire real-ime emperaure informaion o make necessary seam-injecion or producion-rae adjusmens. For more han a decade, WellWacher disribued emperaure sensing (DTS) sysems have been capable of ransmiing daa o surface by laser signals ha ravel hrough Sensa fiber-opic cable. 35 However, convenional DTS sysems do no funcion properly in an HPHT environmen. Mos opical fibers begin o degrade when exposed o hydrogen, which occurs naurally in wellbores. This degradaion acceleraes a high emperaures, derimenally affecing signal ransmission and measuremen accuracy. A emperaures above 2 C, convenional opical fibers exposed o a hydrogen-pressured environ - men may become unusable wihin days. Schlumberger and Sensa engineers responded by developing WellWacher BrieBlue mulimode opical fiber from a maerial ha is more hermally sable and chemically resisan o hydrogen (below). 36 An improved version, WellWacher Ulra DTS sysem, is equipped wih Sandard single-mode fiber Pure core single-mode fiber WellWacher BrieBlue fiber Ligh loss Ligh loss Time, min Wavelengh, nm > Hydrogen effecs on opical-fiber performance afer HPHT exposure. Acceleraed esing mehods deermine he high-emperaure performance of WellWacher BrieBlue mulimode fiber (blue) compared wih ha of convenional single-mode opical fibers (red and orange). Ligh ransmiance of he mulimode fiber deerioraes a a significanly lower rae (lef), allowing he fibers o ransmi daa for years afer insallaion. Unlike he single-mode fibers, he new fiber maerial mainains he abiliy o ransmi ligh hroughou he useful wavelengh range (righ). 58 Oilfield Review

14 Seam injecion Oil recovery > WellWacher BrieBlue fiber insallaion in a heavy-oil well. Engineers pump he fiber hrough a condui inside a coiled ubing sring (inse) ha is hung from he surface across he producing inerval. he new fiber and can measure emperaures wih ±.1 C [±.18 F] accuracy over disances up o 15 km [9.3 mi] wih a 1-m [3.3-f] spaial resoluion. Since 27, he new fiber-opic sysem has been insalled in Canadian seamflood comple - ions wih BHTs up o 3 C [572 F] (above). So far, no discernable reducion in fiber or measuremen performance has been observed, and he emperaure daa are providing operaors wih reliable guidance for deciding how o adjus seam injecion and oil producion o achieve maximum efficiency (righ). 35. Al-Asimi M, Buler G, Brown G, Harog A, Clancy T, Cosad C, Fizgerald J, Navarro J, Gabb A, Ingham J, Kimminau S, Smih J and Sephenson K: Advances in Well and Reservoir Surveillance, Oilfield Review 14, no. 4 (Winer 22/23): Mulimode opical fiber is mainly used for communica - ion over relaively shor disances, such as wihin a building or a campus. Typical mulimode links suppor daa raes up o 1 Gbis/s over disances up o a few kilomeers. Mulimode fiber has a higher ligh-gahering capaciy han single-mode opical fiber and allows he use of lower-cos elecronics such as ligh-emiing diodes or low-power lasers ha operae a he 85-nm wavelengh. Temperaure, C Temperaure 166 o o o o o o 53 3 o , 1,5 Sampling posiion, m 2, > SAGD-well emperaure profile acquired by he WellWacher BrieBlue sysem. Opical fibers ransmi emperaure daa o surface a a 1-m [3.3-f] resoluion. The sharp emperaure increase indicaes ha seam injecion is effecively confined o he horizonal inerval beween abou 9 and 1,5 m [2,95 and 4,92 f]. Time, s Auumn 28 59

15 Drilling and Evaluaion Developmen Producion Drilling Evaluaion Cemening Simulaion Compleions Arificial lif Service Domains RSS Formae drilling fluids MWD Perophysics Reservoir Geology Geophysics Tesing Addiives Tes Evaluaion Upper Lower Perforaing Monioring ESP LWD Wireline (SlimXreme plaform) LWD Wireline LWD Wireline LWD Wireline (SlimXreme plaform) DST Tubing conveyed perforaing Quicksilver Probe ool Rearder Fluid loss FlexSTONE HT cemen Fluids Hydraulic-fracuring monioring HEDTA acidizing fluid ThermaFRAC fluid Subsurface safey and isolaion valves Packers Flow conrol Screens Fluids Tools Thermal liner hanger Permanen WellWacher Ulra sysem Producion logging REDA Holine55 ESP Maximum emperaure 15 C 155 C 26 C 15 C 26 C 15 C 15 C 26 C 215 C 2 C 26 C 249 C 249 C 316 C 26 C 25 C 23 C 25 C 19 C 2 C 218 C 15 C 34 C 26 C 3 C 2 C 218 C HPHT >15 C or 1 Ulra-HPHT >25 C or 2 HPHT-hc >26 C or 35 > HPHT producs and services summary. The range of producs and services for HPHT wells spans he producive life of a well. The color codes indicae how echnologies fi ino he HPHT, ulra-hpht and HPHT-hc schemes. Producs and services highlighed in his aricle are shown in boldface. Fuure HPHT Technology Developmens Significan echnologies inroduced during he pas decade are allowing operaors o confidenly address numerous challenges posed by HPHT projecs (above). As HPHT aciviy coninues o grow and well condiions become more severe, more advanced devices and maerials will be required. Engineers are working o ranslae he advances realized wih HPHT wireline logging o he MWD/LWD environmen. The measuremen sysems mus no only wihsand elevaed emperaure and pressure, bu also perform reliably when exposed o shocks and vibraions associaed wih drilling operaions. The goal is o reduce drilling risk by enabling beer well placemen, improved borehole sabiliy and a decreased number of required rips. Curren chemical research involves exending he useful range of addiives for primary and remedial cemening, as well as simulaion fluids, ino he HPHT-hc realm. This work includes developing novel sealans for plugging and abandoning HPHT wells a he end of heir useful lives, and ensuring long-erm isolaion o preven fluid flow beween suberranean zones or o he surface. In addiion, research is under - way o develop compleion equipmen fabricaed from maerials wih beer resisance o corrosive fluids and gases. Exensive operaor involvemen in equipmen design and manufacure, as well as chemicalproduc developmen, is no ypical for sandard wells; however, operaor paricipaion will be crucial o he success of fuure ulra-hpht and HPHT-hc operaions. Cooperaion beween operaors and service companies will be vial for proper quali ficaion esing, manufacuring, assembly, esing and insallaion. Schlumberger scieniss and engineers are commied o paricipaing in his cooperaive process, helping he indusry a large advance he echnologies necessary o mee he world s growing demand for energy. EBN 6 Oilfield Review


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