58 Oilfield Review Testing Oilfield Technologies for Wellsite Operations Michele Arena Stephen Dyer Rosharon, Texas, USA Larry J. Bernard Allen Harrison Walter Luckett Thomas Rebler Sundaram Srinivasan Sugar Land, Texas Brett Borland Rick Watts ConocoPhillips Houston, Texas Bill Lesso Houston, Texas T ommy M. Warren Tesco Corporation Houston, Texas For help in preparation of this article, thanks to Claire Bullen, Luanda, Angola; Robert Edmondson, Joe Fuentes and Teresa Garza, Cameron, Texas; and John Hobbins, Randy LeBlanc, Thomas Querin and Don Shapiro, Sugar Land, Texas. EcoScope, FIV (Formation Isolation Valve), InterACT, PowerDrive, StethoScope and TeleScope are marks of Schlumberger. Casing Drilling is a mark of Tesco Corporation. At full-scale test facilities, new drilling, logging and completion technologies can be tested under actual wellsite conditions in a controlled and confidential environment, before they are utilized in the field. The industry is now taking the ultimate step in quality assurance by providing full-scale system integration tests and testing while drilling. The knowledge gained by this rigorous assessment helps create tools that perform as designed, even under the most demanding conditions. Demand for resources is driving our industry to seek oil and gas in increasingly difficult locations. Operators want new capabilities in downhole tools, but do not want to risk failure of a new tool in a high-cost wellbore. Predeployment testing has become a critical step in the introduction of new tools. Identification of problems with a new technology is best when done early in the development process, because solutions tend to be more expensive when implemented later. Early testing is therefore crucial and forms an integral part of product development, from conception to design to deployment in the field. Tests should examine general usability, applic- ability , measurement accuracy and repeatability , product safety , manufacturability , and delivery configuration and logistics. Service companies are interested in testing a tool under conditions that are as close as possible to those likely to be experienced in the field, but without the logistical and external operational constraints of the field. In a controlled environment, a test can be focused, concise and complete. As a result, unanticipated usage scenarios and measurement issues, as well as hardware reliability , can be thoroughly investi- gated and worked through on site during the testing phase. Having the ability to address problems when they are first encountered greatly improves the development process. Oil and gas companies, on the other hand, want to minimize the financial risk resulting from a tool malfunction or failure. In a test facility , they can explore tool functionality or system interface issues in a controlled and well-characterized environment without the constraints of rig-time costs or safety problems. Some of the latest advances in drilling technology, including drilling with casing in high-angle wells, can be evaluated in settings that mimic the actual well conditions. Equally important for both the operator and the service provider is the need to compare tests on new tools with previously proven technologies performed under similar conditions. The interpretation results of the comparison are more accurate and reliable when test conditions can be controlled and monitored under identical operating conditions, rather than trying to extrapolate between different fields or well conditions. Various kinds and levels of testing are performed at a number of centers around the world. 1 This article discusses qualification testing, which ranges from components to system integration, and collaborative experiments between oil and gas companies and service providers. Of particular interest are the final tests and performance measurements made just prior to field deployment or before a customized complex product configuration is deployed in a commercial well. The Schlumberger Cameron Texas Facility (CTF) is designed to accommodate such advanced tests. 1. Schlumberger test centers include, among others, the Abingdon Technology Center, England; Beijing Geoscience Center, China; Cameron Texas Facility, T exas; Gatwick Technology Center, England; Integrated Productivity & Conveyance Center, Singapore; Oslo T echnology Center, Norway; Princeton Technology Center, New Jersey; Schlumberger Conveyance and Delivery Center, Sugar Land, Texas; Schlumberger European Learning Center, Melun, France; Schlumberger Kabushiki Kaisha, Fuchinobe, Sagamihara, Kanagawa, Japan; Schlumberger Reservoir Completions Technology Center, Rosharon, Texas; Schlumberger Reservoir Fluids Center, Edmonton, Canada; Schlumberger Riboud Product Center, Clamart, France; Schlumberger Stonehouse Technology Center, Gloucestershire, England; and Sugar Land Technology Center, Texas. For additional information on other test facilities: Lang K: “Oilfield Testing Centers: Nurseries for New Ideas,” Petroleum Technology Transfer Council Newsletter 9, no. 4 (2003): 6–9.
For help in preparation of this article, thanks to Claire Bullen,Luanda, Angola; Robert Edmondson, Joe Fuentes and TeresaGarza, Cameron, Texas; and John Hobbins, Randy LeBlanc,Thomas Querin and Don Shapiro, Sugar Land, Texas.EcoScope, FIV (Formation Isolation Valve), InterACT,PowerDrive, StethoScope and TeleScope are marksof Schlumberger. Casing Drilling is a mark ofTesco Corporation.
At full-scale test facilities, new drilling, logging and completion technologies can be
tested under actual wellsite conditions in a controlled and confidential environment,
before they are utilized in the field. The industry is now taking the ultimate step in
quality assurance by providing full-scale system integration tests and testing while
drilling. The knowledge gained by this rigorous assessment helps create tools that
perform as designed, even under the most demanding conditions.
Demand for resources is driving our industry toseek oil and gas in increasingly difficultlocations. Operators want new capabilities indownhole tools, but do not want to risk failureof a new tool in a high-cost wellbore.Predeployment testing has become a critical stepin the introduction of new tools.
Identification of problems with a newtechnology is best when done early in thedevelopment process, because solutions tend tobe more expensive when implemented later.Early testing is therefore crucial and forms anintegral part of product development, fromconception to design to deployment in the field.Tests should examine general usability, applic-ability, measurement accuracy and repeatability,product safety, manufacturability, and deliveryconfiguration and logistics.
Service companies are interested in testing atool under conditions that are as close aspossible to those likely to be experienced in thefield, but without the logistical and externaloperational constraints of the field. In acontrolled environment, a test can be focused,concise and complete. As a result, unanticipatedusage scenarios and measurement issues, as wellas hardware reliability, can be thoroughly investi-gated and worked through on site during thetesting phase. Having the ability to addressproblems when they are first encountered greatlyimproves the development process.
Oil and gas companies, on the other hand,want to minimize the financial risk resulting froma tool malfunction or failure. In a test facility, theycan explore tool functionality or system interfaceissues in a controlled and well-characterizedenvironment without the constraints of rig-timecosts or safety problems. Some of the latestadvances in drilling technology, including drillingwith casing in high-angle wells, can be evaluatedin settings that mimic the actual well conditions.
Equally important for both the operator andthe service provider is the need to comparetests on new tools with previously proventechnologies performed under similarconditions. The interpretation results of thecomparison are more accurate and reliable whentest conditions can be controlled and monitoredunder identical operating conditions, rather thantrying to extrapolate between different fields orwell conditions.
Various kinds and levels of testing areperformed at a number of centers around theworld.1 This article discusses qualificationtesting, which ranges from components to systemintegration, and collaborative experimentsbetween oil and gas companies and serviceproviders. Of particular interest are the finaltests and performance measurements made justprior to field deployment or before a customizedcomplex product configuration is deployed in acommercial well. The Schlumberger CameronTexas Facility (CTF) is designed to accommodatesuch advanced tests.
1. Schlumberger test centers include, among others, theAbingdon Technology Center, England; BeijingGeoscience Center, China; Cameron Texas Facility,Texas; Gatwick Technology Center, England; IntegratedProductivity & Conveyance Center, Singapore; OsloTechnology Center, Norway; Princeton TechnologyCenter, New Jersey; Schlumberger Conveyance andDelivery Center, Sugar Land, Texas; SchlumbergerEuropean Learning Center, Melun, France; SchlumbergerKabushiki Kaisha, Fuchinobe, Sagamihara, Kanagawa,Japan; Schlumberger Reservoir Completions TechnologyCenter, Rosharon, Texas; Schlumberger Reservoir FluidsCenter, Edmonton, Canada; Schlumberger RiboudProduct Center, Clamart, France; SchlumbergerStonehouse Technology Center, Gloucestershire,England; and Sugar Land Technology Center, Texas.For additional information on other test facilities: Lang K:“Oilfield Testing Centers: Nurseries for New Ideas,”Petroleum Technology Transfer Council Newsletter 9,no. 4 (2003): 6–9.
Winter 2005/2006 59
From Components to SystemIntegration TestingReliability is a key factor in the success andprofitability of any wellsite product. Althoughany new equipment or tool may be a wonderfulinnovation, it is destined to fail if it cannotwithstand the harsh environment of downholeoperations or drilling. Good engineering coupledwith rigorous performance and environmentaltesting is an effective means to success.2
For example, each component of a loggingtool is tested for a wide variety of factors such asthe operating environment, deployment methodsand measurement dynamic range. Environ-mental conditions in the oil field, both upholeand downhole, are quantified for extremes oftemperature, pressure, shock, vibration anddifficult logging conditions. Deployment andcontingency methods tested include wireline,
slickline and coiled tubing. Real-time interactionand control through each deployment methodare also tested. The absolute and relativeaccuracy of the measurement dynamic range andits repeatability are tested in different mud typesand lithologies.
Within Schlumberger, the rigorous productdevelopment process begins when the feasibilityof a project is first examined. Based on the tool’splanned operational environment, a requirementand specification document details the expecteduse and life of the product and the conditions itwill be subjected to over its lifetime. Thisdocument provides the basis for a plan thatspecifies the tests to be performed at thecomponent, subassembly, assembly and systemlevels to verify that the product’s design meetsquality and reliability requirements. The finallevel of tests is system integration testing (SIT),when multiple tools and pieces of equipment
from Schlumberger and third-party suppliers aretested in actual wellsite operating conditions.
Also during the project feasibility phase, thephysics of the measurements are verified in thelaboratory, in external test facilities or downhole.Once the project is shown to be technicallyfeasible and to have sufficient business justifi-cation to warrant further investment, the productmoves on to the development phase, in which testsare performed every step of the way (below).
During the development phase, component-level testing starts at the earliest possible stage.At this point, test costs are the lowest, yet designimprovements at this stage yield the mosteffective results. During component testing, testmachines and laboratory conditions producestresses on individual components similar to, orin excess of, what can occur in an actual well.
60 Oilfield Review
> Stages of testing—from components to system integration—during the development phase of tools or equipment.
Component setup for high-temperature testVibration test of subassembly
High-pressure, high-temperature test vessel for system testingCompression test of a tool assembly
Winter 2005/2006 61
The test conditions typically range from lowtemperature during transportation and storageto very high temperature at the bottom of a welland also include shock, vibration, low and highpressure, bending, corrosion and erosion.
Subassembly testing begins when theindividual components are qualified and multiplecomponents are assembled and combined.Verifications of performance and reliability areperformed. This is accomplished in a mannersimilar to component-level testing but requireslarger test machines. Each engineering center hascustomized test machines corresponding to thetype of subassemblies developed at that center.
The next stage is subsystem or assembly-leveltesting, when a downhole tool is built to a pointwhere it can stand alone and provide one or morefunctions at a wellsite. Subsystem testing may bechallenging because of equipment size andusually requires special facilities. Surface testsinclude mud flow through and around the tool,pressure, shock, vibration and rotation ofcomplete downhole tool sections.
In system-level testing or precommercialevaluation, measurements are verified foraccuracy and repeatability, especially withrespect to variations that occur during themanufacturing process. Many of these test
parameters can be examined under controlledconditions, for example, by drilling throughhardened well cement (left). Several questionsare addressed at this stage of testing. Doesthe production tool perform according to thespecifications of the engineering prototype? Do all the tools perform in a consistent manner? Are there unanticipated tool-to-toolproduction variations? What is the sensitivity of aspecific tool parameter to the overall measure-ment performance?
Finally, in the SIT phase, multiple toolcombinations are tested. For instance, the SITmay involve long well-completion assemblies;these strings may come from different centersand suppliers. Verification of system interop-erability and performance is crucial and isvirtually impossible to determine withoutassembling and testing the entire system at a testfacility that provides a complete dress rehearsal.In the past, rig qualification was performed on anoperator’s rig. Today, test facilities equipped withdrilling rigs are available to perform the samefunction without the constraints of costly rigtime and safety issues.
About Test FacilitiesSchlumberger offers several facilities for systemintegration testing, each with differentcapabilities. Beginning with the first test well in1956, the four test wells at the SchlumbergerReservoir Completions (SRC) Technology Centerin Rosharon, Texas, have been used for devel-opment and testing of perforating guns, wirelinelogging tools, tubing-conveyed perforatingequipment and, more recently, drillstem test andcoiled tubing equipment. The facility also has asmall artificial lake that has been used byWesternGeco to conduct tests with marineseismic sources.
The Schlumberger European Learning Center(SELC) in Melun, France, provides cased hole,openhole, downhole and surface well testingprimarily for wireline and some well services. Wellsat the Sugar Land Technology Center are used forcustomer acceptance testing of wireline andcertain logging- and measurements-while-drilling(LWD and MWD, respectively) tools. The GenesisDrilling Test Facility is a full-size drilling rig thatcan duplicate many conditions that occur at thewellsite in cased vertical boreholes. The rig notonly is an excellent facility for performing drillingtests, but also serves as a training facility.2. At Schlumberger, quality and safety assurance are
based on industry standards such as the InternationalOrganization for Standardization (ISO) 9001certificationfor engineering and manufacturing, Det Norske Veritas(DNV) certification, International Air TransportAssociation (IATA) qualification for transportation of
> Genesis Drilling Test Facility. Genesis is a 142-ft [43.3-m] cantilever-type,skiddable land-drilling rig with 1,250,000-lbf [5,560-kN] derrick capacity. Inservice at the Sugar Land Technology Center since 1988, Genesis is used toreproduce downhole field conditions for various types of tests. Mud flow,pressure, shock, vibration and rotation of downhole tools can be performedunder controlled conditions, either by drilling through cement or by using ashock-inducing device, also known as cam sub.
explosives and batteries, third-party safety audits,American Petroleum Institute (API) recommendedpractices for industry standards in hardware tests,NACE International and American Society of MechanicalEngineers standards for completion equipment, andrigorous quality control both on site and off site.
The Schlumberger Cameron Texas Facility(CTF) has a full-capability drilling rig forperforming drilling, borehole measurement andsystem integration tests. The CTF, whichencompasses several hundred acres, becameoperational in 2004 (below left). The CTF drillingrig provides boreholes with more than 6,000 ft[1,829 m] of horizontal reach. The formationspenetrated by CTF wells have a wide diversity ofporosities, permeabilities and mineralogies.Drilling, LWD, MWD and wireline tools may berun in carbonate and sandstone lithologies.Because the site covers such a large area, manydifferent borehole trajectories can be drilled topenetrate the various formations.
As a Schlumberger facility, CTF serves as aconfidential test bed for the latest downhole anduphole technologies. The high-bandwidthconnection within the Schlumberger firewallallows for easy, secure movement of confidentialdata and enables the involvement of remote
witnesses in extensive tests while drilling. Thefacility also provides hands-on experience forSchlumberger employees and clients, includingtesting of rig-up and transport logistics, andtraining of rig crews for complex deployment.
Wide arrays of tests have been run at CTF,ranging from feasibility to precommercializationand system integration. Tests associated with thelatest generation LWD tools—TeleScope high-speed telemetry-while-drilling service, EcoScopemultifunction logging-while-drilling service andStethoScope formation pressure-while-drillingservice—have been run at CTF. The tests run onthese tools were compared with results fromprevious generation LWD tools over the sameintervals in the same well and also with wirelinelogs run over the same intervals. Full-scalequalification tests of the newest while-drillingtools prior to field testing enabled earlydebugging of the tools and helped to preparethese services for successful introduction on
commercial wells.3 Clearly, this fast-track tooldevelopment would not have been feasiblewithout CTF.
Testing Integrated SystemsSIT is especially beneficial for critical develop-ment projects that must integrate many types ofwells and tools. The increasing number ofcomplex, deep offshore wells has heightened thevalue of performing SIT, potentially making SITan integral part of a risk-management plan forhigh-profile critical projects.
Completion SIT has been performed severaltimes over the past year at CTF and SRC,simulating as closely as possible actual wellconditions in different parts of the world.Completion SIT objectives include assemblyprocedures, interface verification, installationoptimization, intervention testing and contin-gency planning. An important goal is to reducethe learning curve through customized personnel
62 Oilfield Review
3. Adolph B, Stoller C, Archer M, Codazzi D, El-Halawani T,Perciot P, Weller G, Evans M, Grant BJ, Griffiths R,Hartman D, Sirkin G, Ichikawa M, Scott G, Tribe I andWhite D: “No More Waiting: Formation Evaluation WhileDrilling,” Oilfield Review 17, no. 3 (Autumn 2005): 4–21.
5. The customized changes to the completion assemblyincluded a proprietary seal system, allowing bypass ofmultiple control lines and multiple-choke-position flow-
control valves that are set hydraulically. The gravel-packer circulating housing allowed slurry to be pumpedinto the annulus between the screen and the casing. Ithas a sleeve designed to close when the gravel-packpumping operation is completed.
6. The customized gravel-pack system features a single-trip service tool that provides a mechanism for packersetting and testing, fluid circulation and gravel-pack (GP)operation in a highly deviated wellbore. The GPcirculating housing is specially modified toaccommodate the inner completion string without therisk of opening the port sleeve.
> Cameron Texas Facility. This facility is equippedwith a drilling rig for performing drilling,borehole-measurement and system integrationtests. The rig is capable of handling three-jointstands of drillpipe and is equipped with high-volume mud pumps. The rig is mounted on railsfor convenient access to different well slots witha wide variety of directional wells that can beused for both openhole and cased-hole tests.
> Slack-off and pickup weight data during completion installation. The chart shows the effect of dragon the lower completion installation (left). A maximum overpull—the difference between the slack-offttand pickup weights—of more than 200,000 lbf observed at TD would have caused tubing stress abovethe specified rating. Based on the information gained during the SIT and data collected for the lowercompletion slack-off and pickup weight, the wellbore was cleaned out and the annular fluid waschanged to reduce friction. These steps reduced overpull to less than half the lower-completion value(right). The measurement of drag encountered during the inner completion installation was used tottimplement procedural changes both during the test and in the extended-reach offshore well.
Simulated slack-off weightsSimulated pickup weightMeasured slack-off dataMeasured pickup data
Winter 2005/2006 63
training and experience across service providers,third parties and client operations.
In one SIT example, the first of its kind for anextended-reach well, an intelligent flow-controldevice was placed within a triple-zone, cased-holegravel pack in a test well at SRC (right).4 Thecompletion assembly incorporated a number ofnewly customized items, including proprietaryseal assemblies, reduced outside-diameter flow-control valves and a hydraulically set, single-trip,step-bore gravel-pack system with a dedicatedservice tool and modified circulating housing.5 TheSIT plan for this well also included a full downholesystem test at SRC, followed by verification of thewellhead and control-line interfaces on locationprior to equipment mobilization offshore. Thesetests provided the optimum method for identifyingkey installation risks and were used tosubsequently modify procedures to reducenonproductive time or failures.
Several specific issues were addressed inthis SIT. The issue was interface testing of thelower sandface completion with the intelligentinner completion, particularly the frictionaleffects of multiple long-seal assemblies, theircorrect positioning—space out—within thewellbore, equipment eccentricity alignment, andminimization of seal-bore scratching and fatigueprior to landing the completion. Second, dragand wear issues for the inner completion whilerunning through a highly deviated environmentwere examined. Third was testing of a modifiedsingle-trip hydraulically set gravel-pack systemutilizing a step-bore and dedicated service tool.6
Finally, SIT was used to optimize runningmultiple hydraulic and electric-control lineswhile minimizing the number of splices to reduceinstallation time and risk.
SIT proved the feasibility of the completiondesign, the capability to install the equipmentsuccessfully and the device’s reliability for zonalisolation. A total of 35 recommendations basedon the SIT were incorporated into thepreparation and installation procedures as bestpractices, contingencies or special-attentionitems during the actual well installation. Asubsequent offshore installation was completedwith minimal nonproductive time, especiallyconsidering the high-drag environmentencountered during gravel packing, with amaximum difference of more than 200,000 lbf[890 kN] between slack-off and pickup weightat total depth (TD) (previous page, right).Knowledge gained during the SIT was used tocalibrate the installation drag model thatensured successful space out and landing.
> A three-zone, cased-hole gravel-pack (GP) intelligent completion layout used for system integrationttesting (SIT) (left). Installation of the inner completion string during the SIT was conducted at thettSchlumberger Reservoir Completions Technology Center in Rosharon, Texas (bottom right). The GPttpacker system includes the isolation packer and circulating housing. As part of the SIT, additionalttests on the wellhead called “stack-up tests” were performed in collaboration with the wellheadsupplier on location (top right).tt
Production packer
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Flow-control valve
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The three zones were individually stimulatedand tested using the flow-control valves, provingzonal isolation. Downhole production data,which are used for allocation of production, arecurrently captured by using InterACT real-timemonitoring and data delivery. The project—from inception through planning, testing andexecution—was accelerated for completion withina 12-month time frame.
In another example, a month-long SIT ofseveral newly designed completion tools wasperformed at the CTF in a purpose-built casedwell with an extended horizontal leg to simulateas closely as possible the conditions anticipatedduring an offshore installation (right). Theobjective of this test was to investigate anyinterface issues and to verify quality assuranceand quality control, assembly procedures,operating procedures and the accuracy of thecontingency plans. Additionally, it was importantto identify and implement lessons learned,including changes to the design and proceduresthat would result in increased efficiency,reliability or functionality in the operator’s field application.
Knowledge gained during the tests led toimprovements in the intervention phase. A newnipple profile used in conjunction with theexpandable shifting tool for the tubing-isolationvalve was redesigned to overcome an incom-patibility with the previously chosen config-uration. Additional tests with tractors forconveyance were also explored in conjunctionwith various intervention methods to avoid thecoiled tubing lockup, or helical buckling,anticipated at compressive loads greater than2,500 lbf [11.1 kN] that were observed during SIT.Additionally, more than 60 different action itemsrelated to safety, outlined procedures, equipmentmodifications and best practices were recorded toincrease efficiency, reliability and functionality.
Testing integrated systems has providedproven long-term cost savings, both by solvingproblems prior to first field installation and bylessons learned to improve efficiency and toreduce installation and nonproductive time.Despite detailed pre-engineering studies thathad been performed, SIT clarified the limitationsof what could be planned and verified in advanceand demonstrated the importance of conductinga field trial in a confidential manner and withoutrig-time constraints.
The ability to tailor integration tests in acontrolled and relatively low-cost environmentallows operators and service companies alike tosignificantly reduce the learning curve and risk.Test facilities, especially those equipped with a
8. A retrievable system for drilling with casing is requiredfor directional wells because of the need to recoverexpensive directional drilling and guidance equipment,to replace failed equipment before reaching casingpoint, and to quickly and cost-effectively accessformations below a casing shoe. A wireline retrievabledirectional-drilling assembly, positioned in the lowerend of the casing, replaces the directional tools used
> A subsea openhole gravel-pack (GP) completion used in a system integrationttest at CTF. The upper (green) and lower (blue) completion assembliesincorporated a number of newly designed completion tools—a gravel-packservice tool for gravel-pack operation (not shown here), single-assemblyintegrated products with permanent gauge and chemical injection, and threedifferent types of isolation valves.
Tubing hanger
Landing string
Surface-isolationvalve
Safety valve
Production packer
Nipple profile
Contraction joint
Seals
FIV Formation IsolationValve system
Casing extension
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in a conventional bottomhole assembly. For more onretrievable tools for drilling with casing operations:Tessari R, Warren T and Houtchens B: “Retrievable ToolsProvide Flexibility for Casing Drilling,” presented at theWorld Oil 2003 Casing Drilling Technical Conference,Houston, March 6–7, 2003.
9. Borland B, Watts R, Warren T and Lesso B: “Drilling HighAngle Casing Directionally Drilled Wells with Fit-for-Purpose String Sizes,” paper IADC/SPE 99248, presentedat the IADC/ SPE Drilling Conference, Miami, Florida,USA, February 21–23, 2006.
Winter 2005/2006 65
full-scale drilling rig, such as the CTF, expand thehorizons of what can be achieved in simulatingcomplex well plans and testing new technologiesin collaboration with oil and gas companies andother third-party contractors.
A Collaborative Project: Directional Drillingwith CasingIn recent years, drilling with casing has steadilygained acceptance because it offers increasedwell control and safety, enhanced efficiency anddemonstrated cost savings.7 Although the mostsignificant savings can be achieved in offshoreenvironments, drilling with casing in matureassets presents significant challenges. Wellsdrilled from a platform are typically directional,and drilling deviated wells with casing mayrequire modifications to rig or platform equip-ment that could affect production at aprohibitive cost in an offshore operationalenvironment. Also, a learning curve typicallymust be developed with the first few wells drilledin a new application area.
ConocoPhillips, an industry leader in applyingretrievable Casing Drilling technology, hasmultiple offshore assets in which drilling withcasing has the potential to help deal with knownwell-construction problems.8 In mature fields,such as the Eldfisk field offshore Norway, reservoirdepletion leads to well-stability concerns. Drillingwith standard drillpipe may require extra casingstrings to avoid well-stability problems that arecaused by depleted formation pressures. Inaddition to solving drilling problems, thetechnology of drilling with casing has thepotential to reduce the number of casing strings,which could lead to improved well-constructionefficiency and substantial cost savings.
A collaborative project of ConocoPhillips,Tesco and Schlumberger was undertaken todesign and test directional drilling with casingfor two wells planned for Eldfisk field in 2006.The planned wells were to be drilled from acommon wellhead with 103⁄3⁄⁄ -in. and 73⁄3⁄⁄ -in. casing.At the start of the project, drilling with casingtools did not exist in these sizes and operationalproblems related to directional wells requiredredesign of the existing hardware.
The high risks associated with setting,directionally drilling and retrieving these newtools with modifications in untested boreholesizes warranted testing this technology indirectional wells in an onshore field. But therewere additional concerns about this approach.First, with multiple partners, it was difficult toconduct a test that would benefit the operatorbut potentially have little or no benefit to the
other partners. Quantifying the costs and riskswas complicated.
Second, because pay-zone targets and accom-panying directional-well trajectories frequentlychange as new information is learned about thefield, a directional build profile in one casingsection may be moved to another section becauseof a change in a geological model. These changesin the well plan severely constrained the testobjectives. Third, commercial wells are drilled tocompletion. The very nature of testing a drillingprocess, such as drilling with casing, may lead toproblems that are significant enough to abandonthe test or well. Once a section of directionaldrilling with casing is started, it must be finished.If there are problems with the tools, the ability torevert to directional drilling with drillpipe has tobe an available option. This fail-safe nature ofwell construction required extensive planningand budgeting of costs.
These issues, common in well construction,made it difficult to test new technologies for onebusiness unit in the fields of another business
unit, even for large multinational operatororganizations. Several months were spent inmodifying well designs before the decision wasmade to look for a different approach. Thealternative was to utilize CTF.
Two tests were planned. The wells at CTFwould mirror the directional sections, build ratesand operational parameters such as mud flowrates that are required for Eldfisk wells.9 Thefirst well would test setting and retrieving the75⁄5⁄⁄ -in.-casing bottomhole assembly (BHA) toolsin horizontal drilling operations. The secondwould test the 10 ⁄3⁄⁄ -in. system with multiple buildrates, kicking off a directional well from thevertical section.
The first test took place in July 2005 in apreviously drilled, high-angle borehole at CTFwith 133⁄3⁄⁄ -in. casing, which included about 600 ft[183 m] of horizontal section (below). Tests wereconducted for setting and retrieving the BHA inthe vertical section and at well deviations of 45°and 90°. A directional drilling with casing BHAincorporating a rotary steerable system (RSS)
>Well profile of the horizontal well at the Cameron Texas Facility for testing directional drilling withcasing (bottom). Four bottomhole assembly (BHA) setting and retrieval operations at vertical andvarious inclinations are shown. Test 5 included about 850 ft of horizontal drilling. Rig personnel havetthe ability to break equipment down and make minor design changes based on the test taking placeon the nearby rig, such as the Tesco crew here (top). Briefings that include safety guidelinesare held each day of the tests to outline procedures for the next 12 hours. During these and otherdirectional drilling with casing tests, two daily briefings included ConocoPhillips, Tesco andSchlumberger personnel (right).tt
Test 1
Test 2
Test 3 Test 4Test 5
Drill 850 ft horizontally
BHA setting and retrieval testsplanned at 0°, 45° and 90°
Previously drilled well with10 3⁄4-in. casing to 3,769 ft
Dept
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was tested (below).10 The test also included thedirectional performance of this equipment. Acommand was sent to the RSS to turn the wellpath to the right, at 1.0°/100 ft [1.0°/30 m]. After300 ft [91.4 m], a second command was sent toturn to the left, at 3.0°/100 ft [3.0°/30 m]. Finally,
a command was sent to maintain a constantinclination and azimuth until the end of the test.The first turn was accomplished at 1.4°/100 ft[1.4°/30 m], the second turn had a 4.3°/100-ft[4.3°/30-m] rate and the third command resultedin a constant azimuth. About 850 ft [259 m] ofnew horizontal borehole was drilled.
Setting and retrieving the drilling with casingBHAs were achieved using wireline. However,because of the high well inclination, pumping thetools down the borehole was also tested. TheBHA was successfully set and retrieved. It wasthen reset and then released using a pumpdown
66 Oilfield Review
> Directional drilling with casing BHA used in the 7 ⁄5⁄⁄ -in. test (left). The PowerDrive rotary steerable assembly included a motor that was run inside thettshoe joint of the casing to provide adequate drilling rotational speed while minimizing casing rotation to control wear and fatigue. The directional drillingwith casing BHA has a stick-out, or length, below the casing shoe of 85 ft [25.9 m], whereas a typical vertical BHA has a stick-out of only 15 ft [4.6 m]. Thedirectional performance of the rotary steerable system for three PowerDrive settings is shown (bottom right). Test results indicate the degree of successttof the horizontal drilling test. Tesco and Schlumberger personnel are seen making up the BHA (top right).tt
Motor bit box
Internal tandemstabilizer
Vibration sensorsub9 7⁄7 8⁄⁄ -in. underreamer
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releasing tool without a wireline attachment. Ata targeted depth, the releasing tool landed in theprofile nipple, releasing the drill lock andallowing BHA retrieval, thus completing a fullfunctional test of the hardware.
A downhole vibration sensor sub was runabove the underreamer to monitor lateral andtorsional accelerations. Shocks during theearlier part of the run were of greater intensity,but tapered off later. These shocks have thepotential of causing damage to the RSS. A fullinspection of the tools demonstrated that theysuffered none of the damage seen previously,probably because of the modifications to therotary steerable tool to make it more robust. Thesmall-diameter BHA used in drilling with casingis still susceptible to excessive vibrations andshocks and will continue to be monitored.However, modeling to mitigate shocks andimprovements in tool robustness have greatlyreduced this problem.
The 103⁄3⁄⁄ -in. test took place in November 2005.A previously installed 133⁄3⁄⁄ -in. casing had been setvertically at about 2,000 ft [609.6 m]. Thewireline installation for the 75⁄5⁄⁄ -in. test used anupper wireline sheave suspended below the rig’sconventional traveling block, whereas the 103⁄3⁄⁄ -in. test used a fixed crown sheave and splitblock to match the equipment on the Eldfisk rig.The directional BHA design was similar to thatused in the 75⁄5⁄⁄ -in. test. An RSS and MWD toolwere used for directional control in the pilotsection of the BHA (left).
Downhole vibration measurements—shockcounts—were transmitted uphole in real timefrom the MWD tool. Shock counts were alsorecorded downhole in the RSS. Additionally, threesensor packages were placed in the BHA; oneabove the underreamer and two below it, betweenthe MWD tool and RSS. Downhole recordedmeasurements included annular pressure;lateral, axial and torsional shocks; rotationalspeed; torque; and weight-on-bit. Two BHAs ofdifferent lengths were used to test differences invibration response.
The dataset from this test is the mostextensive recording of downhole data evercollected during an operation involving drillingwith casing. Data were recorded while kicking offa sidetrack plug, traversing through a maze ofother bores drilled from the same parentborehole and drilling to about 850 ft whilebuilding angle to about 20°. The well wasdirectionally drilled, first with a low build rateof 0.5°/100 ft [0.5°/30 m] and then a higher rateof 3.0°/100 ft.
The drilling mechanics and dynamics datagathered during these tests have led torecommendations in tactical changes that willimprove well designs for the ConocoPhillipsNorway operations at Eldfisk.
Expanding Horizons in Quality AssuranceDesigning equipment that can withstand theextreme environmental and drilling conditions ofglobal oil fields while making highly sensitivemeasurements continues to be incrediblychallenging. As tools become more complex andhydrocarbons hide in ever more difficult settings,the risk and costs associated with applying newtechnologies will only increase in the future.Therefore, qualifying oilfield technologies priorto their introduction in the field is essential.
With the need to mitigate exposure tohazardous oilfield environments and keep costsin check, remote testing involving clients andengineering and test facilities personnel hasbeen a growing trend. The high-bandwidthconnectivity within the Schlumberger networkfirewall provides the ability to conduct testsconfidentially and involve experts who might bethousands of miles away.11
The benefits of maintaining and operatingtest centers, including full drilling capability,are well-established. Rapid deployment of high-performance enabling technologies in thefield and an increasing demand for complex,multidisciplinary, turnkey completion projectsare some of the reasons for the necessity of test facilities such as SRC and CTF. In fact, thelimits of testing are prescribed only by the creativity boundaries of the technology developers.
The future is likely to see an increased numberof collaborative projects between operators,service companies and third-party suppliers totest new limits of technology and provide bothquality and safety assurance in tough, geologicallycomplex drilling environments. —RG
10. Copercini P, Soliman F, Gamal ME, Longstreet W, Rodd J,Sarssam M, McCourt I, Persad B and Williams M:“Powering Up to Drill Down,” Oilfield Review 16, no. 4(Winter 2004): 4–9.
11 Aldred W, Belaskie J, Isangulov R, Crockett B,Edmondson B, Florence F and Srinivasan S:“Changing the Way We Drill,” Oilfield Review 17, no. 1(Spring 2005): 42–49.
> Directional drilling with casing BHA used in the103⁄3⁄⁄ -in. test. The BHA used in the 103⁄3⁄⁄ -in.-casingttest is the heaviest and longest BHA ever usedin directional drilling with casing. The BHA hasa stick-out of 122 ft [37.2 m], and the BHA weighstthree times the weight of a BHA used in the7 ⁄5⁄⁄ -in. test.
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