RESERVOIR MANAGEMENT EMPHASIZES PEOPLE …€¦ · engineering and drilling and workover ... Guidelines and Standards Manual). ... The mission of reservoir management at Saudi Aramco

Al-Faddagh is supervisor for the Hawiyah and‘Uthmaniyah Unit of the Gas Reservoir ManagementDivision. In 1984 he graduated from the University ofTulsa in Oklahoma, with a BSc in petroleum engineering.Al-Faddagh has completed assignments in productionengineering and drilling and workover engineering. He wasthe team leader in charge of the development of Shaybahfield. In 1995-1996 he was chairman of the Saudi ArabiaSection of the Society of Petroleum Engineers (SPE).

Tobert is a petroleum engineer in the ReservoirManagement Department. In 1980 he graduated fromTexas A&M University with a BSc in petroleumengineering. His assignments have included Berri field,Abqaiq field and Khurais Complex development. In1998-1999 Tobert was chairman of the Saudi ArabiaSection of the SPE. Prior to joining Saudi Aramco in1991, Tobert worked for Tenneco and Fina on their Gulf Coast gas properties.

ABSTRACT

Saudi Arabia owns 25 percent of the world’s oil reserves and is a reliable supplier ofenergy. Economists predict world oil demand will rise from 76 million barrels perday (MMBPD) in 2002 to 90 MMBPD by 2010. Saudi Aramco supplies 12 percentof the world oil demand with a capacity to produce 10 MMBPD. Saudi Arabia’spolicy is to use its large oil reserves to ensure market stability as world demandincreases. In addition, economists predict the Kingdom’s internal demand fornatural gas will increase substantially during the decade. A gas program is in placeto discover and develop reserves to meet gas demand and advance nationaleconomic growth. Saudi Aramco’s energy reserves are its primary assets. Assetteams engaged in the reservoir management process undertake a stewardship rolefor those reserves. The reservoir management process is a set of decisions andoperations by which an asset team characterizes, evaluates, develops, produces and

RESERVOIR MANAGEMENTEMPHASIZES PEOPLE,TECHNOLOGY AND INNOVATION

Hussain A. Al-Faddaghand Gordon Tobert

Hussain A. Al-Faddagh

Gordon Tobert

SAUDI ARAMCO JOURNAL OF TECHNOLOGY SPRING 2003 11

monitors a hydrocarbon reservoir from discovery untilabandonment. Saudi Aramco’s reservoir managementstandards guide decisions and plans throughout thereservoir life (Saudi Aramco E&P, Reservoir ManagementGuidelines and Standards Manual). The main objectives ofthe reservoir management process at Saudi Aramco are to:

• Meet supply commitments;• improve hydrocarbon recovery; and• increase upstream efficiency.Asset team members include geoscientists, lab

scientists, information technology (IT) specialists, aswell as engineers experienced in safetyand the environment,drilling,production,reservoirsimulation andreservoirmanagement. Thelatter undertake thecoordination role withinthe multidisciplinary team,by defining reservoirdepletion strategies and devising fielddevelopment plans. This text presents thereservoir management process from theirperspective.

PLANNING FOR A BRIGHT TOMORROW

Reservoir strategies and development plans set theframework for managing a reservoir. Reservoir strategiesset out long term goals and objectives. Development plansfill in the implementation details of where and when todrill wells, expected production and injection rates andanticipated reservoir pressures. Asset teams updatestrategies and plans when new information supports anenhanced geological interpretation or engineering analysis. Creative ideas and innovation are rewarded asways to achieve reservoir management objectives withincreased efficiency.

Knowledge about a reservoir’s behavior increasescontinuously throughout its productive life. Seismic,

wireline logs, well testing and production andinjection data all provide descriptive information

about a reservoir. A proactive dataacquisition program, including

This is a visualization of the Arab C reservoir in Qatif field with wells entering the reservoir. Qatif field development is the story of an asset team integratingtechnology into a comprehensive plan. Visualization capabilities are an important part of a platform that enable team members to share multidisciplinaryinformation. Shared information enriches contributions from every team member.

Horizontal and multilateral wells put a largerfootprint into a reservoir than do vertical wells.

Long reservoir contact increases productivityand reduces field development costs by requiringfewer wells, and it also improves sweep and

recovery. Progress is impossible without changeand asset teams apply horizontal well innovations as

they emerge. Saudi Aramco’s reservoir managementprocess encourages innovation.

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12 SAUDI ARAMCO JOURNAL OF TECHNOLOGY SPRING 2003

Saudi Arabia is a reliable supplier of energy. Saudi Aramco’s state-of-the-art technology surface facilities, such as Zuluf GOSP-3 (Gas/Oil Separation Plant) shownhere, support this reputation. Oil wells flow to a GOSP where the produced fluid is separated into oil, gas and salt water. The reservoir management processbridges subsurface and surface engineering requirements. It does this by providing engineering parameters, such as production rates, wellhead pressures and plateaulife, which are included in the design of large capital expenditure items like this offshore GOSP.

The area of Saudi Aramco’s operations encompasses the entireKingdom of Saudi Arabia including territorial waters in the ArabianGulf and Red Sea. This operational area is equal to twice the size ofEgypt or three times the size of Texas. The map shows thecompany’s oil and gas fields. Most of the fields are located in theEastern Province. Recently discovered fields are located in theCentral Province near Riyadh.

Active fields include Ghawar and Safaniya, the largest onshoreand offshore fields in the world, respectively. The geological types ofreservoirs range from platform carbonate reservoirs in Ghawar fieldto deltaic sandstone reservoirs in Safaniya field.

Field developments include deep, high pressure, low permeabilityand sour non-associated gas reservoirs. The broad array anddifferent types of reservoirs cover the full spectrum of rock and fluidproperties.


The mission of reservoir management at Saudi Aramco is to maximize the economic recovery of the company’s energy assets by optimizing reservoir strategies anddevelopment plans over the reservoir life cycle. Multidisciplinary asset teams use state-of-the-art technologies to develop and reliably produce energy for SaudiAramco in an efficient, safe and environmentally responsible manner.

The discovery dates of the six oil producing areas are:• ‘Ain Dar 1948• Haradh 1949• ‘Uthmaniyah 1951• Shedgum 1952• Hawiyah 1953• Fazran 1957

Vertical fractures and aleached stratiforminterval show in thisoutcrop of the Arab Dmember. These featuresflow at high rates atdepth and influencereservoir strategies.

Integration of well log,core and 3D seismicresults contribute to acomprehensive geologicalmodel of the reservoir.

A geological model withrobust characterizationimproves the accuracy ofreservoir performancepredictions by reservoirsimulation.

A geocellular geologicalmodel shows the variabledistribution of porosity inGhawar field.

Seismic interval velocityvolume reflects thegeological interpretation.

supervisory control and data acquisition (SCADA) systems,serves as the eyes and ears of the reservoir managementteam to monitor reservoir behavior. The reservoirmanagement process transforms reservoir data intointegrated geological and reservoir simulation models to

predict productive capacity and to improve hydrocarbonrecovery in planning for a bright tomorrow.

BUILDING ON SUCCESS

Exciting opportunities exist at Saudi Aramco to apply a

Workflow among engineers and geoscientists occurs in feedback loops to provide comprehensive and integrated reservoir management. Information technology andthe Internet are having a beneficial impact on the reservoir management process as integration of real time information into the reservoir management processimproves decision quality.

Lab scientists conduct rock and fluid studies in Saudi Aramco’s state-of-the-art Research and Development Center. Reservoir management teams use lab studyresults to update reservoir characterization, refine the initial reserves evaluation and plan field development in a best practices manner.


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comprehensive and integrated approach to reservoirmanagement in the development of giant fields. SaudiAramco commissioned Shaybah field in 1998 and thedevelopment of Qatif field started in 2001. The Qatif assetteam utilized lessons learned from the successfuldevelopment of Shaybah field when it formulated itsdevelopment plan.

Asset teams provide solutions that achieve businessresults by applying carefully selected technologyaccelerators (Collins, J., Technology and Creativity).Dedicated professionals work together and build on atradition of success. They are the heart of the reservoirmanagement process at Saudi Aramco. It is an effortfocused to manage Saudi Arabia’s reservoirs for the benefitof the Kingdom and the world.

STEWARDS OF A VITAL RESOURCE

Saudi Arabia possesses the largest oil accumulation in theworld and Saudi Aramco manages all but a small fractionof the Kingdom’s energy reserves. Reserves at the end of2001 totaled 260 billion barrels of oil and 224 trillioncubic feet of gas. Saudi Aramco managed 81 fields and 315reservoirs in the first half of 2002.

Reservoir management plays an important role in thecompany’s stewardship of the Kingdom’s reserves.Consistent with this role, the reservoir management vision atSaudi Aramco is to be an industry leader in the applicationof best-in-class reservoir management practices. The visionguides professionals to create business value by buildingemerging technologies into the reservoir managementpractices (Saleri, N. G., Innovative Technologies).

RESERVOIR MANAGEMENT PROCESS

The extrapolation of current and emerging trends inreservoir management points to a process that isincreasingly multidisciplinary, integrated, technology based,information loaded and real time. The process createsbusiness value for Saudi Aramco by leveraging these trendsto meet challenges that include developing difficult-to-produce reservoirs and improving hydrocarbon recovery inmature reservoirs.

Key sub-processes of the reservoir management process(RMP) are:

• Reservoir characterization• Reserves evaluation• Reservoir simulation• Development and optimization• Reservoir monitoringThe sub-processes are active in each stage of the

reservoir life cycle. Reservoirs in Saudi Arabia are in one ofthree stages: field appraisal, development or production.The following sections outline the three stages andselectively highlight the five sub-processes.

FIELD APPRAISAL STAGE

The field appraisal stage starts when explorationgeoscientists discover oil or gas and it ends when companymanagement approves a development plan. An asset teamparticipates in field delineation and makes an initialevaluation of reserves. Field appraisal moves to thedevelopment stage if Saudi Aramco needs a new field’sproduction to meet supply commitments. During the field

Reservoir visualization included an integrated geocellular model. The Khurais teamused the tool to match wellbore options to the depositional environment andstructure, thereby improving the probability of achieving development plan rates.

ECC is equipped with the energy industry’s most advanced computing systems.The energy industry and Saudi Aramco are power users of computers to findand develop energy, as well as to increase upstream efficiency.


appraisal stage, the reservoir management process providesengineering parameters that are included in the design ofsurface facilities.

PROPERTIES AND RESERVES

Lab scientists conduct rock and fluid studies to gather thefull spectrum of reservoir properties of a new energyresource. Saudi Aramco’s state-of-the-art Research andDevelopment Center is equipped to make the required rockand fluid measurements. The asset team uses the results toupdate the initial reserves’ evaluation. This updatedevaluation and the geological model serves as thefoundation for reservoir simulation.

Data acquisition is important in each reservoir stage.During field appraisal it is critical for an asset team to developan accurate catalog of initial reservoir properties. Basic datarequirements serve as input and a baseline for subsequentreservoir engineering and reservoir simulation studies.

RESERVOIR SIMULATION

Khurais Complex consists of Abu Jifan, Khurais andMazalij fields and is the field example for this stage.Khurais field is 56 miles (90 km) long and 7 miles (11 km)wide and is the largest of the three fields. The Khurais teamdevised a comprehensive development plan in 2001 forthese underdeveloped fields.

Due to the large scale of Saudi Arabia’s fields, reservoir

simulation is important for optimizing plans in the fieldappraisal stage. Because a field is new, however, thechallenge is having sufficient production data for ameaningful history match. Without the calibration of agood history match, simulation in prediction mode providessensitivities with considerable uncertainty. Several decadesof low rate production reduced this risk in the case ofKhurais Complex.

The technical basis for the Khurais development planwas a simulation study run on Saudi Aramco’s in-housedeveloped Parallel Oil Water & Gas Reservoir Simulator(POWERS) utilizing Massive Parallel Processing (MPP)technology. The 4 million cell Khurais simulation modelwas the world’s largest active model in 2001. Multimillioncell models are under development for Ghawar, Safaniyaand all active fields.

The 4 million cell Khurais full field simulation modeland the geological model had the same resolution. ThePOWERS simulator has the ability to incorporate fullresolution geocellular models. This improves the historymatch and increases predictive accuracy. POWERS alsoprovides rapid turnaround in the analysis of complexdevelopment scenarios, running Khurais history and 25years of prediction in 16 hours.

Saudi Aramco maintains reservoir simulation modelsfor its active oil and gas reservoirs and for reservoirsunder appraisal for development. Asset teamscontinuously refresh active field models with updatedgeological, laboratory, seismic and production data.POWERS creates business value by providing accurate

Members of the Khurais team use 3D visualization to review reservoir depletion and pressure maintenance strategies for the field development plan.



and rapid analysis of reservoir management options acrossthe reservoir life cycle.

COMPUTING REQUIREMENTS

Asset teams centered in the Exploration and PetroleumEngineering Center (EXPEC) have large reservoirsimulation and seismic data processing requirements. TheEXPEC Computer Center (ECC) provides the computingpower to meet the requirements of both reservoirsimulation and seismic data processing. ECC hadcomputing capabilities of 15 million floating operations persecond (FLOPS) and 20 billion bytes of online storage in1983. By 2002, the ECC raised its processing and onlinestorage capacity to one trillion FLOPS and 600 trillionbytes, respectively. The first supercomputer was a Crayacquired in 1984. A series of ever-faster Cray, IBM and SGIsupercomputers followed over the years.

ECC is equipped with the energy industry’s most advancedcomputing systems. A respected website (www.top500.org)that tracks the world’s 500 most powerful computer systemsranks ECC as one of the foremost facilities of its type in theworld. This comparison includes the giant computer facilitiesat Lawrence Livermore National Laboratory, SandiaNational Labs and Los Alamos National Laboratory.

ENHANCED SEISMIC IMAGES

Supercomputers make enhanced images of reservoirs,located a mile or more underground, by processing vastamounts of seismic data. Advanced and resource intensiveprocessing techniques are required to accurately imagereservoirs that are deep, or are located in areas of complexgeology. The increase in seismic data at Saudi Aramco hasbeen truly astounding. The number of seismic traces (theform in which data is delivered from seismic field crews)grew from approximately 150 million traces per month in1998 to two billion in 2002. More seismic data means highresolution images of the subsurface, which in turnmaximizes the probability of drilling successful wells.

MEGA-CELL MODELS

Mega-cell simulation models require immense computerprocessing power and the upward direction of this trendwithin the industry is clear. The 4 million cell Khuraismodel was the largest active model in the world at the endof 2001. It is reasonable to forecast reservoir simulationmodels with 25 million cells in the near future and topredict reservoir simulation models having 100 million cellswithin five to ten years. Saudi Aramco intends to be aleader in this trend. POWERS enables the analysis of giantreservoirs in fine detail. POWERS accomplishes 50 year

The illustration shows the sequence stratigraphic framework of the Shu’aiba carbonate reservoir in Shaybah field. It depicts the correlation of the major depositional cyclesand the distribution of reservoir rock types within each cycle. The formation was deposited on gentle ramp margins of an intrashelf basin. Subtle basement tectonicscreated several northeast trending depositional blocks with rudist buildups. Rudists, related to modern day oysters and clams, lived in the Mesozoic and became extinctwith the dinosaur. The depositional framework ranges from lagoonal (blue), through the rudist barrier complex (orange), to open marine rock types (green).

(and longer) prediction runs in hours, without the need toscaleup reservoir attributes. This allows reservoirmanagement engineers to use improved reservoir character-izations, which model actual reservoir heterogeneities,thereby increasing predictive accuracy.

VISUALIZATION AND INTEGRATION

Saudi Aramco utilizes a multidisciplinary and integratedasset team approach in the reservoir management process.Reservoir management teams include geoscientists, labscientists, IT specialists, as well as engineers experienced insafety and the environment, drilling, production, reservoirsimulation and reservoir management. Team membersleverage their diverse areas of expertise to add value whenanalyzing volumes of reservoir data using advancedcomputer applications.

Geophysicists and geologists use seismic and geologicaldata to develop structural and stratigraphic interpretations.They integrate their insights to create rigorous andenhanced geological models. These models are used to

predict geobodies, locate areas of high and low porosityand permeability, and focus in on high quality reservoirzones. The geological models are also important forwellbore planning and geosteering.

Reservoir simulation models that use dynamic data topredict reservoir performance provide another piece of thedevelopment plan puzzle. Engineers use dynamic data tocondition geological models to actual reservoir parameters.The conditioned geological model makes it easier for thesimulation model to match past production and it improvesthe accuracy of the history match. The benefit is increasedaccuracy of the simulation model in prediction mode whenthe team analyzes various production scenarios.

An asset team then integrates the optimum productionscenario into the final development plan. An IT specialistfacilitates the efforts of engineers and geoscientists whocollaborated in a visualization center. Team membersanalyze reservoir and geological variables in a virtual modelof the reservoir and evaluate numerous wellbore type andplacement options.

A montage of Shaybah field shows the accomplishment of developing a large oil operation in the Empty Quarter. The 500,000 BPD Arab Extra Light incrementcost billions of dollars to commission. The giant fields of Saudi Arabia add a noteworthy dimension to the importance of continuous learning and innovation.Remote locations and a harsh environment combine to produce development commitments of labor and capital seldom found elsewhere. Saudi Aramco uses state-of-the-art technologies to develop and reliably produce energy in an efficient, safe and environmentally responsible manner.


DEVELOPMENT STAGE

The development stage begins when company managementapproves field development plans. The stage continuesthrough commissioning and ends with early production.The end of early production corresponds to 25 percentdepletion of reserves. The goal is to deplete hydrocarbonsfrom the bottom of the reservoir to the top. Asset teamsexamine development plans continuously because learningamidst rapid technological change fosters creative ideas andinnovation.

DEVELOPMENT AND OPTIMIZATION

A significant change is occurring in the field developmentstage due to the influence of a competitive energymarketplace and emerging technologies. These forces aredriving reservoir management to adopt a learning modelthat carefully manages new trends and selects emergingtechnologies that optimize the development of a field(Saleri, N. G., Learning Reservoirs). Oil and gas prices inthe 1990s were low and volatile. The rapid drop in oilprices that accompanied the Asian economic crisis in 1998typified the industry’s experience.

Inflation-adjusted oil prices in 1998 were lower thanbefore the 1973 price increase. At the same time, 3Dseismic, horizontal well and information technologies weremaking a business impact on the energy industry. Operatorsembraced emerging technologies as a way to increaseupstream efficiency during a period of low and uncertainprices. Oil prices stabilized at higher levels by 1999, but thepush for increased efficiency continued and gainedmomentum when a recession two years later reduced oildemand in the world’s major economies.

The giant fields of Saudi Arabia add another dimensionto the importance of continuous learning and innovation.Remote locations and a harsh desert environment combineto produce development commitments of both labor andcapital seldom seen elsewhere in the world. Shaybah fieldprovides a powerful example of field development using acontinually self-improving process and it is the fieldexample for the development stage.

SHAYBAH FIELD DEVELOPMENT

Saudi Aramco’s exploration geoscientists discoveredShaybah field in the Empty Quarter in 1968. The field islocated 495 miles (800 km) from Dhahran. Saudi Aramcocommissioned the field in 1998 to meet supply commitmentsand field development has continued. Shaybah field is acase study for the business impact of horizontal wells.

Horizontal wells gained attraction in the energy industryin the early 1990s. A few years later, when Saudi Aramcoinitiated Shaybah field development, horizontal welltechnology had evolved to where incorporating thetechnology into the Shaybah field development plan madebusiness sense. Vertical wells played an importantsurveillance role in the development plan.

VERTICAL WELLS

Vertical wells delineated Shaybah field. The vertical wellsprovided critical reservoir information for the fieldappraisal and development stages. To appreciate thissurveillance role, it is necessary to know the topography of


Russia drilled horizontal wells in the 1930s. The energy industry drilledrelatively few horizontal wells over the subsequent 50 years. Technologyrapidly progressed after 1985 with the successful exploitation of the AustinChalk trend in Texas using horizontal wells. A recommendation to drill ahorizontal well once required intense discussion before approval. Theparadigm shift is so complete that a horizontal well, rather than a verticalwell, is now the standard completion.

the vast, harsh and remote Rub‘ al-Khali desert underwhich Shaybah field lies.

Shaybah field lies under sand dunes that rise 175 meters(574 ft) above the desert floor. Interspersed between the tallsand dunes are flat sabkhahs. A drilling rig would set up ona sabkhah and drill a vertical producer with the objective ofgathering reservoir information. Vertical wells areoperationally easier and less expensive to log and corecompared to horizontal wells. Once the geologists andengineers characterized the reservoir beneath a sabkhah,they drilled horizontal producers off the sabkhah pad underthe sand dunes, much like an offshore operation. The initialplan included drilling and coring 17 verticaldelineation/production/monitoring wells. The team useddata from these wells to design and drill more than 100horizontal production startup wells.

Geoscientists used vertical wells to calibrate 3D seismicdata by running vertical seismic profiles (VSPs) from totaldepth to the surface. VSP calibration was important inShaybah field where the mixed terrain of high sand dunesand flat sabkhahs contributed to a low signal-to-noise ratiofrom source to receivers. Shaybah field is approximately 40miles (64 km) long and 8 miles (13 km) wide. Due to thelarge field size and inter-well spacing, geophysical data willcontribute to reservoir characterization throughout the lifeof the field.

HORIZONTAL WELLS

The producing wells in Shaybah field are horizontal.Objectives for drilling them horizontally includedimproving sweep and recovery by limiting water and gasconing, increasing productivity in low permeability andnon-fractured facies, and reducing development costs.

The Shu’aiba formation is the principal hydrocarbon-bearing formation in Shaybah field. The Shu’aibahydrocarbon accumulation is a gently folded anticline. Agas cap overlays, and an aquifer lies underneath, the oil inthe Shu’aiba reservoir. Faults seen on 3D seismic imagesand confirmed by image logs suggest the reservoir is proneto gas and water coning. Reducing pressure drawdown tolimit unwanted water or gas movement under producingconditions is an objective of the horizontal well.

Theoretically, horizontal wells deliver productivitiesseveral times higher than offset vertical wells. The realizedproductivity gain depends on reservoir characteristics andtotal contact with the reservoir. Fewer horizontal wells arethus required to meet a desired production rate and, as aresult, the cost of developing a field is reduced, as was thecase in Shaybah field.

EVALUATING HORIZONTAL WELLS

Logging horizontal wells involves challenges andopportunities different from those in logging vertical wells.Challenges arise because coil tubing (or drill pipe) isrequired to run logging tools through a horizontal section.This specialized operation consumes rig time and is costly.Opportunities relate to the large footprint a horizontal wellmakes in a reservoir compared to a vertical well. Thefootprint of a horizontal well enables image logs tointersect vertical heterogeneities not detectable in verticalwells. The team uses this petrophysical information to

The Shaybah team innovates with horizontal well technology to producevarious Shu’aiba reservoir rock types. To address the challenge of producinglow permeability and non-fractured rock types, reservoir contact lengths wereincreased. Compare a 1998 1 km well to a 12 km MRC (Maximum ReservoirContact) well drilled in 2002. Asset teams match MRC well design to reservoirmanagement objectives at specific locations.

Well testing provides 1. initial reservoir pressure – a primary parameter ofreservoir management and 2. permeability – a key attribute for the reservoirsimulation model. Among the various formation evaluation options, welltesting is unique in that it samples the reservoir out to distances of hundredsor even thousands of feet from the wellbore via pressure transient analysis.Interpreting this response is the fundamental objective of well testing andprovides insight into reservoir dynamics.


model fractures and facies distribution in the reservoir. Logresults from horizontal wells complement vertical wellresults and together improve reservoir characterization.Effective use of horizontal well technology requires a robustunderstanding of fracture type, fracture orientation andfacies distribution.

TESTING HORIZONTAL WELLS

The asset team instituted a rate test program concurrentlywith the drilling program to confirm if deliverabilitiesmatched development plan assumptions. Four horizontalwells, tested for two weeks, yielded a choked rate of 12,000BPD per well. These tests included a production loggingtool and oriented four arm calipers for hole stabilityevaluation. The rate tests were consistent with predictedproduction rates, increasing the team’s confidence tocontinue with field development as planned.

CONTINUOUS INNOVATION

The Shaybah team continuously introduces newtechnologies into the development plan. One example is theutilization of satellite communication technologies togeosteer horizontal wells through the reservoir in real time.Optimized well trajectories maximize well productivity andlong term performance.

Another example is the Shaybah team’s use of horizontalwell technology to achieve specific reservoir managementobjectives. In 1998 the longest reservoir contact for anywell in Shaybah field was one km. Horizontal welltechnology evolved so that by 2002 the Shaybah team

could match a specific reservoir management objective to aspecific completion design. Field development is atechnology-led process guided by continuously innovativereservoir management teams.

MAXIMUM RESERVOIR CONTACT

A maximum reservoir contact (MRC) well has longreservoir contact through a single or multilateral wellboredesign. It is an example of an innovative technology withpotential to improve how Saudi Aramco produces lowpermeability and non-fractured facies in the future. Thefirst MRC well in Saudi Arabia was drilled in Shaybah fieldin 2002 having reservoir exposure of 27,880 feet (8,500 m).A well with a reservoir contact of 12 km (7 miles) followeda few months later.

The initial assessment of MRC wells indicates a 30percent cost reduction when compared to offset three kmsingle lateral wells, based on a sustainable well productionrate ($/BBL/day). A permanent downhole monitoringsystem installed in the 8.5 km (5.3 miles) MRC well willprovide long term testing and monitoring capabilities. Theteam will compare test results from offset horizontal wellsof varying reservoir contact lengths. The business impact ofMRC wells is to increase well productivity and improvehydrocarbon recovery in low permeability and non-fractured facies.

RESERVOIR CHARACTERIZATION

Reservoir characterization is a very important part of thereservoir management process. Reservoir characterization

The Shu’aiba reservoir consists of several textural rock types. Muddy rocks in the lagoon and open marine environments have high porosity but low permeability.Rocks in the back and fore barrier are grain-rich with high porosity and moderate permeability. The rudist barrier consists of coarse grained rocks having the lowestporosity and highest permeability. The asset team used detailed reservoir geocellular models to determine optimum locations for horizontal wells.



describes a reservoir using geological and engineering dataobtained in numerous ways. Cores provide petrophysicaldata essential to reservoir engineering. Openhole logsprovide in-situ information about the rock and fluids in theimmediate vicinity of the wellbore. Well testing investigatesdeep into the reservoir, far beyond the wellbore, providinglarge scale reservoir characterization. Horizontal andmultilateral wells with their large footprints also aidreservoir characterization.

Data from the above sources, and others, contribute toa descriptive matrix of reservoir information. Thissupports an understanding of the depositionalenvironment, lateral and vertical rock heterogeneities, andproductivity characteristics of the reservoir. The asset teamintegrates new reservoir characterization and engineeringinsights into the full-field simulation model. Updatedreservoir simulation predictions serve as the basis for fine-tuning the depletion strategies.

NEW TECHNOLOGIES REDUCEDEVELOPMENT COSTS

Shaybah field provides a powerful demonstration of thebusiness impact of two key technologies. First, drilling costswould have been six times higher on a ($/BBL/day) ofinitial crude production basis had Shaybah field beendeveloped with vertical rather than horizontal wells.Horizontal well technology dramatically reduced Shaybahfield development costs. Second, as the result of significantcomputational advances between 1996 and 2001, thePOWERS full-field simulation model indicated a 2.5-foldreduction in overall run time in spite of an almost five-foldincrease in model size.

REAL TIME GEOSTEERING

Real time geosteering technology enables an asset team tosteer a drill bit in real time while drilling a wellbore a mileor more underground (Smith, R. G., Real TimeGeosteering). Saudi Aramco utilizes real time reservoirnavigation systems on its drilling rig operations andworkover re-drills. Satellite technology sends drilling andLWD (logging while drilling) data directly from the drill bitto desktops and visualization centers in Dhahran. A team ofexperts in EXPEC analyzes the data as it comes in andnavigates the wellbore trajectory through the reservoir toachieve reservoir management objectives.

Real time geosteering technology applied in lowpermeability reservoirs significantly improves wellproductivity, increases the drainage area of a well, andimproves hydrocarbon recovery because of reduced

drawdown pressure. The Shaybah team uses geosteeringtechnology to achieve these important objectives.

GAS DEVELOPMENT

In 1975, the government of Saudi Arabia requested SaudiAramco to design, construct and operate a system tocollect, process and utilize the Kingdom’s associated gasreserves. Saudi Aramco commissioned the system, called theMaster Gas System (MGS), in 1980. Associated gas, as thename suggests, is gas associated with oil production. Oilwells flow to a GOSP where the produced fluid is separatedinto oil, gas and salt water. The gas then flows, or iscompressed and piped, to a MGS plant that processes thegas into natural gas liquids or sales gas.

In recent years, Saudi Aramco embarked on an ambitiousprogram to develop non-associated gas as a swing source offeed gas to the MGS. Non-associated gas is independent ofoil production. Saudi Aramco enlarged the MGS to gatherand process high pressure non-associated gas from the deepKhuff reservoir, as well as the pre-Khuff, Jauf and ‘Unayzahreservoirs. Non-associated gas is a valuable resource tomeet national power generation demand and to fuel theKingdom’s petrochemical industry. Non-associated gasreserves in the Kingdom are typically in deep, high pressureand temperature and heterogeneous reservoirs.

GAS CONDENSATE RESERVOIRS

Detailed phase behavior of the hydrocarbon system isimportant in order to assess the potential of gas condensatereservoirs. Conventional black oil models cannot capture allaspects of the phase behavior of these systems. Instead, theevaluation and prediction of reservoir performance require


compositional simulators based on equation of statetechnology. The Khuff and Jauf non-associated gasreservoirs exhibit significant spatial compositionalvariations. Extensive field sampling of reservoir fluids, withlaboratory studies to determine their composition, wasrequired to develop equation of state models.

PRODUCTIVITY ENHANCEMENT

Enhancing the deliverability of gas wells is a top priority.Productivity enhancement options include acid fracturing,matrix acidizing, proppant fracturing and horizontal wells.The gas asset team based its evaluation on reservoir flowcharacteristics, formation heterogeneity, net pay thicknessand reservoir continuity.

In the southern areas of Ghawar field, Hawiyah andHaradh, the quality of the Khuff-C reservoir deterioratesand productivity enhancement becomes the main challenge.The type of porosity development changes areally from thinand continuous intervals to thick and broken intervals. Thestrategy is to utilize a horizontal well in the Type-A areas ofthin and continuous porosity development (wherehorizontal wells are more effective), and rely upon acid

fracturing of a vertical well in the Type-B areas of thick andlayered porosity.

PRODUCTION STAGE

The production stage includes advanced and matureproduction and corresponds from 25 percent depletion ofreserves to the start of enhanced oil recovery. An asset teamsupports early life cycle strategies with field scaleparameters that carry considerable uncertainty. Certaintyincreases with the acquisition of additional data from eachnew well. The reservoir characterization effort duringadvanced and mature production harnesses enormousvolumes of data and turns unstructured data into mission-critical reservoir information. The energy industry andSaudi Aramco rely heavily on computers. One reason is therequirement to store and analyze the vast amounts ofreservoir data acquired during advanced and matureproduction.

The objectives of the production stage are the same asthe previous two stages, but plans reflect a maturing asset.New maintain/potential and evaluation/observation wellsare drilled in yet undeveloped areas of the reservoir to meetsupply commitments. Existing wells are worked over to

Real T ime and High Resolut ion Datafor Better Wel ls


maintain desired productivity/injectivity rates. Facilities aremodified to handle production of expected fluid volumesand increase efficiency.

MIGHTY GHAWAR FIELD

Ghawar field is the largest oil field in the world and is thefield example for the production stage. The field hasproduced for half a century and has many decades ofproduction remaining.

Ghawar field was discovered in 1948 with ‘Ain Dar No.1. The field is about 174 miles (280 km) long and 16 miles(26 km) wide. Additional discoveries followed in five moreproducing areas: Haradh in 1949, ‘Uthmaniyah in 1951,Shedgum in 1952, Hawiyah in 1953 and Fazran in 1957.Ghawar field contains several oil and gas reservoirs.

Commercial production from Ghawar field began in1951 from ‘Ain Dar and peripheral water injection inGhawar field started in 1965. Treated seawater from theArabian Gulf is pumped across the desert through two 56inch (142 cm) trunklines and one 60 in (152 cm) trunklineto distribution points within the field. Seawater injection isenvironmentally preferred because it avoids the use ofWasia aquifer or Biyadh aquifer waters.

The primary reservoir in Ghawar field is the prolificArab D reservoir that optimally combines the elementsrequired for high productivity: high porosity and highpermeability. Oils were derived from thermally matured,Jurassic age and organic rich carbonate source rocks. Thenthe oils migrated into highly porous and permeablecarbonate reservoirs in large structural traps. The Arab Dreservoir consists of 76 meters (250 ft) of reservoir qualitylimestone and dolomite.

RESERVOIR MONITORING

Saudi Aramco’s oil and gas reserves are its most valuableassets. Surveillance of those reserves is the primary objectiveof reservoir monitoring. Monitoring takes on a data-intensive nature as the number of wells in a field increases.

Production, injection and observation wells are windowsthrough which asset team members investigate a reservoir.Pressure, temperature and flow rate data, along withproduction log results, are some of the importantengineering variables used by an asset team to monitor anentire reservoir system. Digital technologies have expandedthe capabilities of previous analog-only SCADA systems,making real time reservoir monitoring a reality. Intelligentwells combine real time monitoring and remote downholeintervention to provide robust flexibility to a team.

Remote downhole intervention is an emergingtechnology that enables an asset team to manage eachlateral in a multilateral well. With this technology, the assetteam manages multilateral wells based on productionprofiles for each lateral generated from real time rateinformation. Intelligent wells provide the capability to makeand implement decisions in real time to avoid downholeproblems and optimize well and reservoir productivity. Thehigh flow rate of a typical Saudi Aramco multilateral wellnecessitates a competence to manage and control lateralsseparately, so an impaired lateral does not disrupt

Saudi Aramco commissioned the Hawiyah Gas Plant on January 1, 2002. Theplant has a capacity of 1.6 billion cubic feet of gas per day.

Reservoir compartmentalization of the Jauf reservoir along the east flank ofHawiyah field is based on 3D seismic mapping of faults that are integratedinto a multilayer geocellular model. The model shows the truncation of theJauf reservoir by a major north-south fault (blue slab) and the successiveerosion of the layers by a major period of erosion, following deposition andstructural tilting of the Jauf reservoir sandstone. Reservoir characterization isessential for optimum well placement and is the basis for simulation studiesthat assess the impact of faults on fluid flow in the reservoir. The asset teamupdates its reservoir depletion strategies based on this assessment.

productive laterals. Intelligent well technology is climbingthe learning curve as installed systems around the worlddemonstrate its promise. The following pages touch onSaudi Aramco’s participation in real time monitoring andintelligent wells.

REAL TIME MONITORING

A real time monitoring system developed by a servicecompany was installed recently in an ‘Uthmaniyah well.The tool continuously monitors the movement of salinity-calibrated water injected into the reservoir. Monitoringoccurs by measuring downhole deep resistivity up to 15meters (50 ft) away from the wellbore with dynamic andstatic openhole logs. The system also monitors pressure,temperature and flow rate in real time. The team analyzesall of the data to better understand residual oil saturationafter waterflooding, recovery factor and relativepermeabilities to oil and water. Better insights into thesekey reservoir management parameters in turn are used tofine-tune Ghawar field depletion strategies.

Another application of real time reservoir monitoring isin Haradh, in south Ghawar field. Downhole gaugesmonitor reservoir pressure in real time. This provides thereservoir management team the information needed toproduce low transmissibility wells within the optimumpressure range above the bubble point.

INTELLIGENT WELLS

Intelligent well technology is an innovation that enables areservoir management team to monitor a reservoir in realtime, analyze the data and remotely initiate downholeintervention. Enough installations exist around the world toconsider the technology proved, and experience has greatlyincreased the technology’s reliability. The tradeoff is highercapital expenditures up front for faster production,improved recovery and lower operating expenses later.

Recent internal studies highlighted the benefits of usingintelligent completions. The vision is to integrate intelligentwell technology with the demonstrated effectiveness ofhorizontal, multilateral and MRC wells to accelerateproduction while enhancing sweep efficiency and delayingwater breakthrough. When water enters a lateral, intelligentcompletions create value by providing the capability tointervene from the surface and shut off the wet lateral,allowing the remaining laterals to produce undisturbed. Thecost of intelligent wells will decrease as the industry climbsthe learning curve. Saudi Aramco is participating in thislearning effort.

The heterogeneous nature of the Khuff and Jauf non-associated gas reservoirsand the wide well spacing make 3D seismic a prerequisite in selecting goodwell locations. Seismic results improve the probability of connecting with thebest porosity development.


METRICS

An accurate view of reservoir performance is required tomake long range decisions in a timely manner.

Reservoir management metrics provide a highly effectivesolution to measuring and improving performance bytracking a variety of key performance indices. Metricsprovide a scorecard for every field on how and when assetteams achieve their goals. Key indices measuring reservoirperformance include:

• Recovery factor• Mobile oil recovery efficiency• Rate of depletion as a percentage of remaining reserves• Reservoir injection to production ratio• Producing water cut• Reserves depletion state• Mobile oil depletion state• Dead well statistics• Strategic studies• Annual production

When water enters a lateral, intelligent completions create value by providing downhole intervention capability to shut off the wet lateral from the surface, leavingthe remaining laterals to produce undisturbed. The tradeoff is capital expenditures up front for faster production, improved hydrocarbon recovery and loweroperating expenses.


Members of the Ghawar team finalize reservoir monitoring priorities for the field.

• Annual decline rates• Unit development costsRegular reviews of these and other key indices provide

an accurate and timely critique of performance by field.Performance metrics ensure stringent and uniformevaluation of all active Saudi Aramco reservoirs and theresults guide strategic decisions. A performance metric-guided process is consistent with the company’s vision to bea leader in the application of best-in-class reservoirmanagement practices.

RESERVOIR DEPLETION

At the field level, as opposed to the well level, a time lapseflood front map monitors reservoir depletion. The maptakes into account wireline log data and water productionmeasurements and documents water entry over time. Asexpected, the general trend is for water to initially appearon the periphery and subsequently envelop up structurewells. A cross check for sweep efficiency is made bycomparing the volume of cumulative produced oil to thevolume of original oil in place.

PRODUCTION STRATEGY

Production must take into account reservoir heterogeneitiessuch as strataform high permeability intervals, faults and

fractures. Heterogeneities may lead to premature waterbreakthrough, and barriers lead to bypassed oil or lack ofpressure support.

The reservoir management strategy is to balance oilproduction with water injection. A proactive dataacquisition program monitors reservoir pressure andproduced fluids to determine the conformance of verticaland areal sweep of hydrocarbons.

THE CHALLENGE OF TAR

Uniform reservoir sweep contributes to improvedhydrocarbon recovery. The lack of reservoir rock qualityand conductive flow paths, as well as tar that acts as abarrier to fluid flow, are obstacles to an efficient sweep. Tar,when found, usually occurs at or near the interface of theoil and water columns. It is possible to identify taroccurrence with reservoir monitoring programs and carefulmeasurement of rock and fluid samples.

Tar on the eastern flank of ‘Uthmaniyah has nothampered historical sweep, but wells to the west of the tarhave shown an increasing lack of pressure support, andconsequently a reduction in production potential. Aninnovative approach to the challenge is to “tunnel” throughthe tar barrier with a horizontal well as shown in theadjoining figure. A planned tunnel well will bridge the

Monitoring Reservoir Sweep: Injection water in the Ghawar Arab D reservoirefficiently displaces oil from the flanks of the reservoir to the crest and from thebottom of the reservoir to the top. Data acquisition results incorporated into3D visualization models monitor the effectiveness of depletion strategies.Seismic and image log data have confirmed the existence of fractures and faultsin the Arab D reservoir that until relatively recently were not mapped. Thecontinuous learning process utilizes technology to fulfill reservoir managementobjectives, and reservoir metrics monitor the results for business impact.


The typical distance between wells is one kilometer. The wide spacing between wells is a reason why geophysical data is an important tool toreservoir management.


PROSPERITY WELL

The effort to find oil in Saudi Arabia began in 1933 when the concession wassigned under the wise leadership of King ‘Abd al-‘Aziz ibn ‘Abd al-Rahman AlSa‘ud. His Majesty is shown on a rig tour with Floyd Ohliger, resident manager ofthe venture. The first commercial discovery occurred in Dammam Well No. 7 onMarch 4, 1938 in the Arab D reservoir. Initial production from Dammam Well No.7 averaged 1,585 BPD and increased to 3,810 BPD. The well produced 32 millionbarrels of oil by 1982, when production ceased due to economic reasons. MaxSteineke, also shown (seated), was the geologist who never wavered in the vision tofind oil in Saudi Arabia. He was knowledgeable, optimistic, intuitive, and hadperseverance – valuable traits of energy finders.


peripheral injectors to the central producers, thus providingthe necessary pressure support to produce the oil.

EXCELLENCE AND STEWARDSHIP

The reservoir management process sets goals and objectives,creates a plan to achieve them, monitors theirimplementation and analyzes the results. Emergingtechnological trends energize this process. Success dependson professionals who are committed to excellence and whohave a sense of stewardship, as seen in the Shaybah fielddevelopment and the Hawiyah Gas Plant projects.

CREATIVITY AND INNOVATION

The extrapolation of current and emerging trends inreservoir management points to a process that isincreasingly multidisciplinary, integrated, technologybased, information loaded and real time. None of thesetrends by themselves, however, guarantees profitability orsuccess in the future. The right path for the reservoirmanagement process to take suggests a learning model thatensures that change is a positive force necessary to achieveresults and succeed.

Innovation harnesses opportunities from among theoptions technology offers. Technology is a tool to achieve

Saudi Aramco and the energy industry have come a long way since 1938, when Dammam Well No. 7 was discovered. Future technologies will allow a reservoirmanagement team to work virtually inside the reservoir. Improved reservoir management processes using future technologies will lower risk and improvehydrocarbon recovery.

The Challenge of Tar: Uniform reservoir sweep contributes to improvedhyrdocarbon recovery. The lack of reservoir rock quality and conductive flowpaths, as well as tar that acts as a barrier to fluid flow, are obstacles to anefficient sweep. Tar, when found, usually occurs at or near the interface of theoil and water columns. It is possible to identify tar occurrence with reservoirmonitoring programs and careful measurement of rock and fluid samples.

Tar on the eastern flank of ‘Uthmaniyah has not hampered historicalsweep, but wells to the west of the tar have shown an increasing lack ofpressure support, and consequently a reduction in production potential. Aninnovative approach to the challenge is to “tunnel” through the tar barrierwith a horizontal well. A planned tunnel well will bridge the peripheralinjectors to the central producers, thus providing the necessary pressuresupport to produce the oil.



goals and then stretch them. Successful results accelerate themomentum of asset teams. Members share experienceswithin web-enabled communities in the company and in theprofessional societies of the global energy industry,improving what works and discarding what does not. Assetteams manage and implement creative ideas and reservoirmetrics benchmark results for its business impact.

FUTURE TECHNOLOGIES

Technologies with an expected business impact in the futureinclude diagnostics, information and knowledgemanagement, as well as enhanced production.

• Diagnostic technologies span the spectrum of reservoirimaging and/or characterization tools. Teams will useseismic data from 3D, 4D and seismic while drilling asthe input to dynamic simulation models. Reservoirmanagement will use high resolution 4D seismicmodeling to view field characteristics, analyze well dataand predict production potential.

• Information and knowledge management technologiesinclude advanced communication systems (e.g.satellites), real time visualization platforms and web-enabled data pools.

• Enhanced production technologies include intelligentdownhole completions and novel production or drillingtechnologies.

Real time technologies and improved proactive processeswill influence how asset teams manage reservoirs in thefuture. The vision remains the same whatever the futurebrings. Dedicated professionals will manage Saudi Aramco’sreservoirs using best-in-class reservoir managementpractices to meet supply commitments, improvehydrocarbon recovery and increase upstream efficiency.

ACKNOWLEDGEMENTS

Special thanks go to S. A. Al-Fassam, S. A. Turaiki and N. G. Saleri. Contributors to this article included A. S. Al-Muhaish, I. M. Buhidma, S. P. Salamy, D. H. Jonesand R. J. Heil.

REFERENCES

Collins, J., “Good to Great,” HarperCollins Publishers Inc.,New York, New York, 2001.

Saleri, N. G., “Disruptive Technologies and Real TimeReservoir Management Issues”, Sixth InternationalForum on Reservoir Simulation, Salzburg, Austria, 3-7September 2001.

Saleri, N. G., “Learning Reservoirs: Adapting to DisruptiveTechnologies,” Distinguished Author Series, Journal ofPetroleum Technology, Vol. 54, Number 3, pp. 57-60,March 2002.

Saudi Aramco E&P, “Saudi Aramco Reservoir ManagementGuidelines and Standards Manual,” Dhahran, SaudiArabia, March 1997.

Smith, R. G., and Maitland, G. C, “The Road Ahead toReal Time Oil and Gas Reservoir Management,”Transactions of the Institution of Chemical Engineers:Chemical Engineering and Design, Vol. 76A, pp. 539-552, 1998.

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