bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas-Lift Valve Performance Testing
Authors: Decker K. L.
Published: December 2007

Gas lift valves are used in many producing wells to increase or maintain production. The spacing of valves in the well, calculation of opening or closing pressures, and selection of port size all play an integral role in the success of unloading and lifting operations. The design procedures that have been developed through the years include many safety factors; however, some of these were based on erroneous assumptions concerning the flow performance of gas lift valves; subsequently, many problems resulted.

Now that recent developments in gas lift valve mechanics have addressed the importance of using gas lift valve performance testing in predicting a valve's true flow performance, considerably more interest is being shown in this topic. One gas lift valve manufacturer has been furnishing gas lift valve performance data and using the data to perform gas lift valve spacing designs since 1962.

This paper will answer the questions of what constitutes performance data, why there is a need for this data and what types of testing techniques must be conducted to obtain a valve's true flow performance when subjected to subsurface conditions. The methods for performing the tests will also be discussed.
Simplified Computer-Aided Analysis of Electrical Current in Motors Used for Beam Pumping Systems
Authors: McCoy J. N. , Podio A. L. , Jennings J. W. , Capps K. S. , West Jerry
Published: December 2007

A substantial cost for operating most oil properties is the monthly electricity charge. Analyzing the motor current in a beam pumping system is a difficult task in that the current is normally changing from consumption to generation during each pump stroke. A gear "slap" will occur during a pump cycle when the motor changes from driving the pumping system to being driven by the counterbalance and the unit's inertial forces. Conventional clamp-on current meters indicate the magnitude of the current flow in the wire but do not indicate whether the motor is consuming or generating electricity.

A new computerized technique for acquiring motor current using a clamp-on probe permits the acquisition of apparent current and the calculation of real ( or active) current. The apparent current is acquired at a one kilohertz rate. These data are processed to obtain real current A plot of the active current ( showing consumption and generation) along with the apparent current is presented to the user. This plot is extremely beneficial for determining electricity costs, pumping unit balance, cost per barrel of oil lifted and other power consumption factors.
Waterflooding of Naturally Fractured Reservoirs: An Efficient Simulation Approach
Authors: Civan Faruk
Published: December 2007

A generalized formulation of the Buckley-Leverett displacement in naturally fractured porous media and an efficient solution by the method of differential quadrature for waterflooding are presented.
An Efficient Semianalytic Reservoir Model for Complex Reservoirs
Authors: Poe B. D. , Dube H. G. , Holditch S. A.
Published: December 2007

This paper presents a summary of the development of a semi-analytic reservoir model for gas reservoirs with various reservoir complexities. The types of reservoir complexities that have been considered in this study include; multiple reservoir layers in which the reservoir layers may be infinite or finite in extent, dual or single porosity systems, and wells that have been fractured. The reservoir model that has been developed and used in this study was constructed with the appropriate Laplace domain pressure and rate-transient solutions that are available in well testing literature.

This reservoir model was developed to provide a more detailed and accurate means of analyzing or predicting the performance of a gas reservoir than is possible with a simple "type Curve" approach, yet would be more computationally efficient than a finite difference reservoir model. The results of the semi-analytic reservoir model have been validated with the reference solutions generated with a commercial finite difference reservoir simulator. The results of the semi-analytic reservoir model are comparable to the results of the finite difference simulator, yet require substantially less computation time and computer memory.
Generalized Inflow Performance Relationships for Three-Phase Flow
Authors: Wiggins M. L.
Published: December 2007

Generalized three-phase inflow performance relationships (IPRs) for the oil and water phases are presented in this paper. These relationships yield adequate estimates of the production-pressure behavior of oil wells producing from homogeneous, bounded reservoirs during boundary-dominated flow. The IPRs are empirical relationships based on linear regression analysis of simulator results and cover a wide range of reservoir fluid and rock properties. Methods to study the effects of changes in flow efficiency and to predict future performance are also presented.
Improved Well Productivity Utilizing a Foamed Borate Crosslinked Fluid
Authors: Pierce A.D. , McNally A.C. , Armstrong R.L.
Published: December 2007

In the past few years, the Boonsville Bend Conglomerate gas field has been fractured utilizing a foamed (70 - 75% nitrogen) organometallic crosslinked fluid. Recent studies illustrate that organometallic crosslinked foamed fluids damage the proppant pack permeability greater than 60% with breaker at 140F. Damage of this extent greatly reduces the outcome of the stimulation treatment. A guar based fluid utilizing a new, organically complexed borate crosslinking system and nitrogen mixed at 60 - 65% was selected. This fluid shows superior rheology properties and excellent clean break characteristics. An independent consortium has confirmed greater than 85% retained permeability with breaker at 140F. Stability of the system is such that increases in sand concentrations from three pounds per gallon up to five pounds per gallon have been incorporated into the designs. This redesign has lowered overall fluid volumes, even thought the quality of the foam is ten to fifteen percent less.

Introduction

Recently, wells fractured with an organometallic crosslinked foam showed low fluid recovery, poor production performance, and post frac sand production in the bend conglomerate formation in the Wise and Jack county areas of North Central Texas. The test wells used in this discussion were all in the Atoka group of the Boonsville field area of North-Central Texas. This group consists of five systems: the Boonsville fluvial-deltaic, the Smithwick pro-delta/basin-fill, the Grant deltaic, the "Pregnant" pro-delta/basin-fill, and the Brazos fluvial-deltaic. The "Conglomerates" of the Boonsville system are the primary reservoir for the field. They consist of fine to coarse grained sandstone and grade more commonly to fine to medium-grained poorly sorted, subrounded conglomerates and occasional thin, widespread limestone. The main constituents of the "conglomerates" are quartz with chert and feldspar, and commonly gluconite, especially in the lower part of the Atoka.

FRACTURE FLUID HISTORY

The use of a nitrogen foamed CMHPG polymer based fluid, utilizing titanium and zirconium as the delayed crosslinker was initiated due to several benefits of the fluid. The main advantages were good thermal stability and reduced tubular friction pressures. However, current research indicates that up to 80% of the proppant pack permeability can be damaged using a transitional metal crosslinker.

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Refracturing: Observations and Theories
Authors: Elbel J. L. , Mack M. G.
Published: December 2007

Treating pressures from refracturing treatments and simulations of horizontal stress changes due to production suggest that the initiation of the refracture plane will be normal to that of the initial treatment. This possibility makes more wells candidates for refracturing.
Encapsulated Breakers in the Red Fork Formation of the Anadarko Basin: A Case History
Authors: Waters G. A. , DeLeon D. D.
Published: December 2007

Since their introduction, encapsulated breakers (EB) for water-based fracturing fluids have gained wide acceptance within the petroleum industry. Their use has improved the retained fracture permeabilities over those previously attained. The net results have been improved production and a greater return on investment for the operator.

While various laboratory experiments have confirmed the need for maximum breaker concentration1-4 a field test was desired to document the effect of the high breaker concentrations attainable with EB. Therefore, a case study of 23 wells, 13 of which contained EB, was undertaken in the Red Fork formation of the West Butler and Strong City fields in the Oklahoma counties of Custer and Roger Mills (Fig. 1). Post-fracture production performances were evaluated to confirm the effectiveness of the EB. These field tests show that increased breaker concentrations do indeed improve well performance.
Reproducibility of Flow Computer-Generated Gas Volumes Using Averaged Flow Parameters
Authors: Haefele R. M.
Published: December 2007

Remote electronic flow computers installed on orifice meters calculate, as part of their audit data trail, averages of the variable flow parameters (Pf - flowing pressure, hw - differential pressure, Tf - flowing temperature) for each time interval defined by the flow computer. Because of the interdependency of the flow parameters within the AGA-3 gas flow equation, the volume produced by applying that equation to the averaged parameters can often be significantly different from the sum of the instantaneous volumes calculated by the flow computer using the same equation. Because of this calculation-induced volume shift, averaged flow parameters should not be used to recalculate the volumes produced by flow computers unless the averages have first been adjusted to reproduce the summated volume for the time interval in question.
A New Model for Production Decline
Authors: Rodriguez Fernando , Cinco-Ley Heber
Published: December 2007

An analytical solution is developed in this paper to forecast the production behavior of two-dimensional closed-boundary reservoirs producing from multiple wells under constant different bottomhole pressures. Wells are represented as line sources arbitrarily located in the domain of the reservoir; damage is considered. Solution is obtained through combination of Laplace transformation and Green's functions Methods.

The production decline of the wells during the boundary dominated flow period is shown to be of a modified-exponential nature: qwDj(tD)=qwDj∞+(qwDj0−qwDj∞)exp(−DtD),j=1,2,  ..nw. When all wells produce at the same bottom-hole pressure, it is shown that qwDj∞=0 and production declines exponentially. It is also shown that the production decline of the reservoir is in all cases exponential: qD(tD)=qD0exp(−DtD), being qD0=∑j=1nwqwDj0.

It is found that the decline coefficient, D, is the same for the reservoir and for each of the wells. D depends on the size and shape of the reservoir as well as on the number of wells, its location and damage. Parameters qwDj0,qwDj∞ and qD0 besides of depending on the same parameters as D, also depend on the bottomhole pressures of the wells. As expected, production under unequal bottomhole pressures or under irregular wells-reservoir patterns, yield uneven well productions. It is also found that stimulation, or damage, of a single well modifies the entire production characteristics of the wells-reservoir system. A simple method of analysis that provides the production decline parameters qwj0,  qwj∞, j=1,2,  …,nw and D, is developed.
Insights Into Good Hot Oiling Practices
Authors: Mansure A. J. , Barker K. M.
Published: December 2007

One of the common oil-field wellbore problems is paraffin deposition. Even though hot oiling is usually the first method tried for removing paraffin, few operators appreciate the limitations of hot oiling and the potential for hot oiling to aggravate well problems and cause formation damage. Several hot oiling jobs were monitored to understand "old pumper's tales" and the dynamics of hot oiling. The field work was supported with laboratory analyses of the oil and calculations of thermal effectiveness. This limited study has shown that the chemical and thermal processes that occur during hot oiling are very complex and that there are significant variations in practices among operators. Key findings of this work include: (1) During a typical hot oiling job, a significant amount of the oil injected into the annulus goes into the formation, and hence, has the potential to damage the formation. (2) Organic particulates in stock tank oil may not completely dissolve/melt as the oil passes through the hot-oiling-truck heat exchanger, hence, these particulates may plug the formation. (3) Hot oiling can vaporize oil in the tubing faster than the pump lifts oil. This interrupts paraffin removal from the well, and thus, since the wax is not removed from the well, the wax is refined into harder deposits, can go deeper into the well, and can stick rods. These insights have been used to determine good hot oiling practices designed to maximize wax removal and minimize formation damage.

Part of this work was performed by Sandia National Laboratories operated for the United States Department of Energy under contract DE-AC04-76DP00789.
Basic Approach to the Application of Field Gas Compressors for Production Engineers
Authors: Shafer J. L.
Published: December 2007

A basic approach to the application of gas compressors is presented to explain the effect of clearance in a reciprocating compressor cylinder. Compression efficiency is not affected by clearance volume, because most of the work required to compress the gas in the clearance volume is recovered when it expands back to suction conditions. Use of clearance enables the operator to maximize the horsepower in a unit by using larger cylinders. Purchase or lease of a well designed unit awards the operator with a broad range of operating conditions. This becomes cost effective. Otherwise, changing out units becomes expensive and time consuming to the producer.
Enzymatic Breaker System for Nondamaging Removal of Cellulose-Based Blocking Gels
Authors: Rickards A. R. , Tjon-Joe-Pin R. M. , Boles J. L.
Published: December 2007

An external breaker system, consisting of a combination of enzymes, has been used to remove polymer damage at low to moderate temperatures. This enzyme mixture produces a stepwise breakdown of cellulose polymers at temperatures ranging from 60 °F to 140°F. The polymer is initially reduced to D-glucose and cellobiose. The complete hydrolysis of the cellobiose is subsequently afforded by the enzyme combination. The entire hydrolysis of the polymer occurs rapidly; therefore, the enzyme complex can be applied as an external breaker after the workover operations have been completed. Post workover injection of the enzyme complex allows blocking gels to retain maximum strength during operations. The enzyme combination is compatible with the brines used to prevent damage from swelling clays. The result is a blocking gel that is reduced to a clean non-viscous fluid that is easily recoverable.
Interpretation of Early- and Late-Time Filtration Phenomena of Crosslinked Polymer Cakes in Front of Long Cores
Authors: Mayerhofer M. J. , Staubmann H. U. , Economides M. J.
Published: December 2007

A potentially important component of the total pressure drop from a fracture into a formation during hydraulic fracture stimulation is that across a polymer invaded zone. Following experimental work with long cores (up to 60 cm-long) and with permeabilities up to 5 md it was determined that the polymer invasion for a zirconate-crosslinked HPG-system has not particular significance and is thus neglegible compared to the very dominant filtercake. The observed early-and late-time filtration phenomena were decribed using a numerical cake layer model and verified by experimental measurements. It is shown that the early-tiine ’’hyperbola" is not a result of polymer invasion but is caused by a changing pressure differential across the filtercake at the beginning of the filtration experiment.
Laying Sand Plugs with Coiled Tubing
Authors: Chambers M. J.
Published: December 2007

A successful technique for placing accurate amounts of sand inside casing was developed for the Western Operating Area (WOA) of the Prudhoe Bay Unit (PBU) on the North Slope of Alaska. Using coiled tubing and a multistage pumping schedule, a sand plug can be laid in one, time-saving operation.

The experience gathered from more than 100 field operations performed in the WOA during 1991 and 1992, in varying downhole conditions, provided for the refinement of the operational steps; allowing the first and each succeeding stage to be adjusted, in situ, for the manner in which the sand plug ‘behaved’ as it was placed.
Inflow Performance of a Horizontal Well Intersecting Natural Fractures
Authors: Guo Genliang , Evans R. D.
Published: December 2007

Analytical single phase and multiphase pseudo-steady state inflow performance equations for a horizontal well intersecting natural fractures are derived. The single phase inflow performance solutions are obtained by combining pseudo-steady state solutions of a horizontal well in a homogenous reservoir block and of a vertical fracture in a sub block. The effects of permeability anisotropy, wellbore eccentricity and fracture characteristics are considered. Multiphase inflow performance equations are derived by incorporating relative permeability and capillary pressure characteristics into the corresponding single phase solutions.

Results are presented using the equations to estimate the optimum number of horizontal wells which should be drilled to drain a given naturally fractured reservoir.
Horizontal Wellbore Collapse in an Anisotropic Formation
Authors: Ong See Hong , Roegiers J-C.
Published: December 2007

This paper discusses an anisotropic model for assessing the mechanical stability of a deep borehole subjected to an internal wellbore pressure and a far-field stress tensor. The model consists of the three-dimensional analysis of stress concentrations around an inclined borehole due to the far-field stress tensor, combined with internal wellbore pressurization, flow and thermally induced stresses to give an approximate non-coupled solution. The model utilizes a generalized three-dimensional anisotropic strength criterion for assessing borehole collapse which is one manifestation of shear failure. Parametric studies indicated that the stability of the wellbore is significantly influenced by high degrees of rock anisotropy, high in-situ stress differentials and excessive wellbore cooling. Pore pressure and porous elastic constant also affect the stability but these effects are less pronounced.
A Second Youth for a Mature Oil Field: Flank Development and Appraisal with Horizontal Wells, Rima Field, South Oman
Authors: van Kossem S. J. , Brouwer G. C. , Lensvelt M. M. A. M.
Published: December 2007

Development of the relatively short undrained oil columns in the flanks of the Rima Field, Oman is an attractive strategy with a view to minimizing water production, increasing productivity and improving sweep efficiency. This paper presents the results of the planning, drilling and initial production phases of four sub-horizontal wells that have been drilled in the flanks of the field to date. Based on the geological and reservoir engineering studies it was clear that flank development with dip-oriented wells is a better strategy than development with strike-oriented wells. The most compelling reason is the flexibility which is retained for future horizontal infill campaigns. The field would not be fenced off as it would be by a ring of strike oriented horizontal wells, and the uncertainties in volumetries are reduced. The initial results show very high oil production rates in the horizontal wells proving the concept of flank development with dip-oriented sub-horizontal wells. Tail- end appraisal proves to be a very important secondary objective for these wells, given the poor quality of seismic data in the Rima Field.
Low-Impairment Mud System for Drilling Horizontal Wells Through Clastic Reservoirs in a South Oman Oil Field
Authors: Glendinning D. R. , Zwolle Simon , Vancura John
Published: December 2007

This paper discusses the development, field experience, cost aspects and the consequences of using a low-impairment drilling fluid system for drilling horizontal wells targeted on clastic reservoirs in a South Oman oil field in the concession area of Petroleum Development Oman [PDO], The first horizontal well was drilled in January 1990 and by October 1992 a total of twenty three wells had been drilled and completed in the field. The first five wells were drilled using conventional water based systems. But once the horizontal well scenario had been proven, subsequent wells were drilled with a fit-for-purpose low-impairment drilling fluid system formulated for specific hole sections. Progressive changes in well and mud design, as well as the optimization of drilling practices, have resulted in significant reductions in drilling times and well costs and increased well productiviities.
Safety Management System
Authors: Carrier H. A.
Published: December 2007

This paper presents a brief history of the development and implementation of ADCO's Safety Management System, provides an overview of each of the system's component parts, and outlines ADCO's plans for the way ahead.

Management concern for the welfare of its employees, coupled with increasing shareholder and public awareness, prompted ADCO in 1991 to review the way in which it managed safety and as a result, to make some significant changes.

Traditionally, ADCO (in line with many other large industrial organisations) measured corporate safety performance using two indicators : accident frequency and accident severity. The review indicated that ADCO's somewhat limited outlook needed to be broadened. In turn, this lead ADCO to reconsider its safety objectives with a new focus on the need for major improvements in safety performance that would be both sustainable and ongoing. The result of this corporate review was ADCO's Safety Management System (SMS) : a system designed to cover a broad band of safety activities and provide positive management control.

The SMS is made up of several component parts, from the various committees and plans to standards, procedures and audits. At its heart are 18 safety elements which, in common with the elements of a quality assurance system, need to be understood and then complied with. SMS implementation plans were devoleped by the company's functions controlling field based activities. In order not to overburden the SMS planners, 9 priority (not the most important) elements were selected for implementation in the first year. An example extract from one of these plans is shown in figure 3.

The hidden, but possibly most important objectives of the SMS are now being realised They are to create a fresh, positive attitude in the minds of ADCO's employees, to change their perceptions from believing that safety is somebody else's responsibility to accepting it themselves, and to modify the patterns of their daily behaviour.

In the latter part of 1992 ADCO's staff worked for 2.5 million consecutive hours without accident. We believe that the SMS made a positive contribution to this ADCO record.
Application of Risk Assessment Techniques for an Additional Loading Line at Jebel Dhanna Terminal
Authors: Saadawi Hisham
Published: December 2007

Jebel Dhanna is the only terminal for storage and export of the onshore oil production of Abu Dhabi Emirate. Crude oil flows from the tanks farm via two 48 inch gravity loading lines to the foreshore area where it is boosted by pumps to the loading berths.

The two gravity lines are needed for export at peak capacity and also for implementing the crude oil re-circulation plan in an emergency. Due to the age of the piping system, a risk assessment study was conducted to evaluate the need for a new gravity line.
Exploration and Petroleum Engineering Computing in the 90's
Authors: Al-Naji A. S. , Gaddourah M. I.
Published: December 2007

This paper shares Saudi ARAMCO's Exploration and Petroleum Engineering Computer Center (ECC) experience in providing the latest in computer technology to service and enhance Saudi ARAMCO's Exploration and Petroleum Engineering efforts. Saudi ARAMCO's data processing requirements have increased dramatically over the past decade. The increase can be mainly attributed to the shift in exploration from 2D to 3D seismic data processing and the growth in the number of cells and complexity of reservoir models. To fulfill these requirements, Saudi ARAMCO has established state-of-the-art computing facilities with supercomputers and highend workstations along with their sophisticated graphical plotting devices all connected through a powerful network. The high-end workstations are utilized for interactive processing and visualization of data both in seismic processing and reservoir simulation. ECC has also expanded the throughput of the network to handle the explosion of data transfer and promote the integration and effective utilization between the user friendly interface of the workstation and the intensive number crunching capability of the supercomputers.
Flexible Gridding Techniques for Coning Studies in Vertical and Horizontal Wells
Authors: Consonni Pietro , Thiele M. R. , Palagi C. L. , Aziz Khalid
Published: December 2007

The numerical study of water coning requires an accurate spatial discretization around the wells which may lead to a large number of grid blocks. Local refinement is therefore desired since it allows for a coarse underlying grid without loosing numerical resolution around the wells. This paper investigates the applicability of flexible gridding to study coning in both vertical and horizontal wells. These techniques can also be used for multiwell, full field coning studies.

A simple sector geometry including a producer and an injector is used. A two step approach is then followed: in the first case, it is assumed that the effects of heterogeneities are negligible and average petrophysical properties are used. In the second part, the heterogeneity of the system is also considered. For both cases, a fine grid simulation on the entire domain is used as the reference response. Various areal hybrid geometries around the producer are then investigated and their response is compared with the reference cases. For the vertical producer, the hybrid geometries are based on a coarse Cartesian grid with either a cylindrical or a Cartesian refinement around the well. For the horizontal producer only an areal Cartesian refinement is considered. In this case though, the hybrid geometry becomes particularly interesting for wells that are not aligned with the overall Cartesian grid. For these cases, the hybrid gridding techniques allow a local Cartesian refinement that is aligned with the well.

For ail cases investigated, the fine grid results can be reproduced by the hybrid geometries provided that an adequate vertical discretization is used. For both vertical and horizontal producers, the various responses suggest that grid refinement is more important than its geometry.
Prediction and Evaluation of Horizontal Well Performance
Authors: Sherrard D. W.
Published: December 2007

Drilling and completing horizontal wells has become almost commonplace in many areas where the petroleum industry operates today. Perhaps the main obstacle to greater utilisation of the technology is confidence in accurately predicting horizontal well performance.

This paper focuses on a relatively early horizontal well program in Alaska, beginning with expectations and analyses prior to drilling, through to extensive efforts to understand well performance once on production. Evaluation of well performance is considered through well testing, production logging, and reservoir simulation. Seven years of field production data are used to compare against pre-drilling forecasts.

The review concludes that accurate reservoir description is critical to successful forecasting; simplistic description can lead to over estimates of productivity. Furthermore modem reservoir characterisation techniques may be necessary to utilise a complex description properly in predictive mode. Production logging is highlighted as a critical diagnostic tool despite the need to run on coiled tubing whereas pressure transient analysis, for which theory is well developed, can be problematic and may require modification to traditional field practices.
A New Arab-D Depositional Model, Ghawar Field, Saudi Arabia
Authors: Meyer F. O. , Price R. C.
Published: December 2007

Bedding characteristics and the vertical distribution of lithofacies divide the Arab-D carbonate reservoir of Ghawar Field into a Lower Arab-D and Upper Arab-D zone. The Lower Arab-D consists of a basal rhythmically interbedded muddy and grainy interval that exhibits TA, TB, TE, and TH classic turbidite divisions, and an overlying massive interval of amalgamated carbonate sand and gravel beds that are graded and hummocky cross stratified. The upper part of this massive interval passes upwards into graded and ungraded skeletal sands and forms a short transition zone into poorly bedded skeletal carbonates of the Upper Arab-D section.

Upper Arab-D passes gradationally upwards from muddy Stromatoporoid framestones, through a Burrowed Skeletal- Peloidal, Cladocoropsis, Foraminiferal, Mixed Skeletal-Peloidal, cross bedded Oolite lithofacies sequence, and into a transitional zone of Mixed Skeletal-Peloidal sands that intercalates with a thick zone composed mainly of nodular anhydrite.

The Arab-D carbonates studied represent part of the fill and subsequent progradation depositional history into separate intrashelf basins situated both North and East of the field. Their stratigraphy and depositional features are consistent with a prograding storm dominated shelf model in which in situ skeletal carbonate production embraces a broad belt of stromatopoids, Cladocoropsis and foraminifers located roughly between fair weather wave base and the lower shoreface. Carbonate transport directed shoreward, mainly by day-to-day processes, includes cross-bedded and hydrodynamically sorted medium to fine skeletal and non-skeletal sands at the top of the Arab-D. Stormgenerated turbidity currents transported carbonates seaward below fair-weather wave base to as suggested by graded and hummocky cross bedded Lower Arab-D strata.

The two different styles of deposition exert significant controls on reservoir performance. Storm sequences (Arab-D, Zone 3) form layered reservoir horizons whose best permeability exists in thin, basal grainy textures of proximal deposits, but thicken as grainy carbonates increases in a more proximal direction. Facies belts in Zone 2 form shingled reservoir zones which climb north- and eastward toward the intrashelf basins. This type of reservoir reconstruction differs significantly from the previous layer-cake model, and should more accurately reflect the geologic architecture needed in reservoir modeling.
Sequence Stratigraphy and Source Rock Potential of Middle Cretaceous (Upper Wasia Group) in West Abu Dhabi
Authors: Azzam I. N. , Taher A. K.
Published: December 2007

The Middle Cretaceous "Upper Wasia Group" in West Abu Dhabi is divided into four Formations: the Shilaif, Mishrif, Tuwayil and Ruwaydha. In this paper, a new stratigraphic subdivisions based on sequence stratigraphy, for the "Upper Wasia Group" is introduced. It consists of three distinct Sequences: I (Mishrif/Shilait), II (Tuwayil) and III (Ruwaydha) that were deposited in the area from Late Albian to Turonian.

Mathematical modeling applied on the Shilaif Formation (Sequence I) study· area, has indicated However,.the volume of hydrocarbon accumulations discovered in the Middle Cretaceous Upper Wasia reservoirs is much less than volumetric calculations of predicted oil-in-place. This demonstrates the generation of adequate volumes of oilfrom the Shilaif, which justifies further exploration activity.
Importance of Sequence Stratigraphic Concepts in Development of Reservoir Architecture in Upper Jurassic Grainstones, Hadriya and Hanifa Reservoirs, Saudi Arabia
Authors: McGuire M. D. , Koepnick R. B. , Markello J. R. , Stockton M. L. , Waite L. E. , Kompanik G. S. , Al-Shammery M. J. , Al-Amoudi M. O.
Published: December 2007

The Upper Jurassic Hadriya and Hanifa carbonate grainstone reservoirs in Berri Field, Saudi Arabia, contain large reserves of Saudi Extra Light crude oil. New geologic models of each reservoir have been built using sequence-stratigraphic principles. These new models have a chronostratigraphic architecture which accommodates the facies transitions observed in cores sampled along the ramp-to-basin profile. Each reservoir contains, from oldest to youngest:(l) a highstand systems tract represented by aggrading and prograding grainstones, capped by a type-2 (subaqueous) sequence boundary; (2) a shelf margin wedge systems tract characteriz.ed by grainstones showing maximum basinward progradation; and (3) a transgressive systems tract typified by a series of backstepping grainstones capped by a surface of relative drowning.These new models clarify the elements controlling fluid movement within the reservoirs.
Development of the Ghawar Scale Squeeze Simulation Model: Using Core Analysis to Evaluate Treatment Chemicals
Authors: Lynn J. D.
Published: December 2007

Calcium Carbonate scaling problems have been detected in three of the Aramco Southern area Helds. As of 6/88, these fields have shown scaling in more then 70 % of the wet producers. The scaling has resulted in loss of production capability and created potential safety hazards throughout the production string, and into the gathering areas. Various methods are being evaluated in order to find a cost effective method of eliminating or controlling the scale problem. The following methods have been evaluated as possible alternatives to solve the problem: Tubing replacementPhysical or chemical removal of the scale (HQ)Down hole chemical injectionScale inhibitor squeeze

The method selected for application to the Arabian fields was the precipitation inhibitor squeeze. Core analysis is playing a major role in the development of the squeeze method, and in defining procedures which will optimize the field treatment.

The final result of the testing was a core based production model which could accurately simulate field behavior of inhibitor treated wells. The data would then be applied to optimization of early field trials. The generated data would then be applied to formulation of a mathematical model for field application. This paper will illustrate the various applications the core testing was used for, and show the relationship of laboratory data to the formation data, and describe the use of the core data in the optimization of the field treatment.
Evaluation of Water and Gas Pattern Flooding Using Horizontal Wells in Tight Carbonate Reservoirs
Authors: Mostafa Ismail
Published: December 2007

ADCD has successfully drilled a number of horizontal wells in its different operating fields, to evaluate its effectiveness in solving certain reservoir problems. Field results confirmed that horizontal drilling is beneficial in enhancing well productivity/injectivity, and alleviating water caning or gas cusping problems. ADCD is currently investigating the feasibility of developing some of its tight carbonate reservoirs, containing large amount of oil reserves, using this new horizontal well technology.

A numerical simulation study was conducted to predict the performance of five-spot pattern development of those poor characteristics multilayered reservoirs using horizontal holes. Horizontal wells were modelled using ECLIPSE-200 enhanced feature of local grid refinement (LGR) where the mesh around the horizontal holes were strongly refined. The model was calibrated successfully against field transient test results of a horizontal well. After model calibration, 100-year prediction runs were performed to evaluate the effectiveness of water and gas pattern flooding with horizontal holes in terms of plateau rate and length, sweep efficiency and ultimate recovery. Previous work was conducted to compare horizontal versus vertical well performance and to study the inpact of different parameters on horizontal well performance.

In this study, emphasis was given to some critical parameters affecting the performance of horizontal pattern in this strongly stratified reservoir mainly; vertical permeability and orientation/positioning of horizontal holes. The effectiveness of different flooding fluids such as water, lean gas or gas followed by water injection was examined in terms of sweep efficiency and ultimate recovery.
Measuring Relative Permeability of High-Permeability Samples From Egypt
Authors: Potter Gary , Lyle G. L.
Published: December 2007

High permeability samples presents problems in handling and in measuring relative permeability. Gulf of Suez core samples frequently have permeabilities in excess of 1 darcy and can be extremely friable. The Gulf of Suez samples are used as examples to illustrate problems with sample stability and practices typically used to handle this type of core.

High permeability samples create problems in getting reliable unsteady-state gas displacing oil relative permeability because of the difficulty in getting the differential pressure high enough to prevent the capillary forces from dominating the flow. When running the test manually, the rate that data can be recorded limits the maximum flow rate and therefore the differential pressure that can be used. An automated unsteady-state gas displacing liquid permeameter was designed and built to improve the reliability of gas displacing oil data by allowing higher flows without problems with data recording.

The minimum differential pressure for unsteady-state relative permeability tests is discussed in terms of the capillary pressure. By using arguments derived from fractional flow equations and saturation profile measurements, the minimum differential pressure should be 10 times the capillary pressure for the saturations expected during the test.
Practical Aspects of Constructing a Large 3D Simulation Model of a Complex Reservoir
Authors: Phelps R. E.
Published: December 2007

This paper presents the practical aspects of building a large simulation model of the Hanifa reservoir, which exhibits complex lithology and fluid movement patterns. It illustrates the important phases of construction and presents several innovative ideas used to analyze the massive amount of geological and engineering data. Some of the major modelling difficulties that were encountered during construction are also discussed.

Some of these techniques include: Team Concept.Use of a coarse grid model of the oil field area in the initial stages of history matching. Results would then be transferred to a finer grid model in the final stages of the history match.Derivation of facies-area specific J-functions from log data.Derivation of facies specific relative permeabilities and reconciliation of laboratory and field data.Use of a six million cell geological model to compute water saturations from J-functions.Developing a 3-D algorithm to model pressure and salinity changes through time.Developing perforation chronology charts to illustrate historic well completion and inflow performance.

In addition, the paper illustrates some of the benefits of the synergistic effort between simulation and reservoir engineers, and geologists that led to a more detailed and reliable simulation of the reservoir.
Gas Penetration into Deeper Strata in Aquifer Storage
Authors: Rzepczynski Walter M. , Katz Donald L.
Published: December 2007

In the development of aquifer storage much has been learned of the behavior and movement of gas when in contact with water under a pressure differential. This paper shows through observation that gas can penetrate deeper into the reservoir than penetrate deeper into the reservoir than anticipated in any one of three ways. First, as a gas wafer early in the gas injection cycle before gravity affects balance pressure effects. Second, vertically into deeper layers through some permeability and lithologic path which permeability and lithologic path which appears to be an easier way to move water through the injection strata itself. Third, downstructure below the expected gas bubble horizon because of higher permeability in that direction and variations permeability in that direction and variations in the reservoir characteristics.

Examples for each type of deeper gas penetration was presented along with penetration was presented along with various illustrations and explanations as to their causes. This behavior of the gas-water system reveals the nature and character of the reservoir stratum. Although this paper only gives a comprehension of the reasons for gas penetrating into deeper layers it recognizes that calculations for various models could be made to give quantitative answers. These calculations would predict the degree of gas penetration into deeper layers when the penetration into deeper layers when the horizontal and vertical permeabilities of the layers are known.

Introduction

One is reluctant to accept the concept that gas goes downhill on occasions but this is what appears to happen in aquifer storage under certain circumstances. Three types of gas penetration deeper into the reservoir than one would expect, will be described for aquifer storage operations. The first is a movement of the gas wafer during the initial injection operation before gravity effects have a chance to balance pressure effects. The second is the penetration of gas into layers deeper than the injection strata through some permeability path which appears to be an easier way to move water than through the injection strata itself. The third is the movement of gas off-structure below the expected storage horizon apparently because of permeability stratification and continued pressurization of water in a given direction.
Simulation of Coning in a Thin Oil Rim in a Fractured Reservoir
Authors: Gallagher John , Prado Luis , Pieters Johan
Published: December 2007

The prediction of coning behaviour is critical to assessing the development potential of thin oil rims and to forecasting performance during the thinning phase of oil rims in general, towards the end of field life. Although coning behaviour has been investigated extensively for homogeneous reservoirs, relatively little has been reported on coning in fractured reservoirs.

A simulation model has been constructed for investigation of gas and water coning in a thin oil rim in a fractured reservoir, undergoing gas/oil gravity drainage in the presence of a strong aquifer. The single well radial model has been used to estimate the watercut and GOR development against gross offtake for varying perforation position and well spacing.

The model is based on a type well from the Ghaba North Shuaiba reservoir, one of several low relief fractured carbonate reservoirs in Central Oman. These reservoirs are potential candidates for development by gas oil gravity drainage, implying the need to produce from oil rims of approximately 30m in thickness. This simulation study has consisted of a first part approximately reproducing typical Ghaba North well performance, followed by a second part with prediction runs which have assisted in estimating the feasibility of gas oil gravity drainage in Ghaba North. The simulation results suggest that a significant amount of extra oil can be recovered by gas injection with an initial production well spacing of 350 m. The wells should be completed in a relatively low position (10-15 m above the original OWC) and produced at relatively low rates (around 50 m3/d). This work may also be useful for forecasting performance of other ongoing gas oil gravity drainage developments in Oman. It is intented to build on this work by considering also horizontal wells and the sensitivity of coning behaviour to basic input data.
Fractured Reservoir Simulation: Case Studies
Authors: Boerrigter P. M. , van de Leemput B. L. E. C. , Pieters Johan , Wit Krijn , Ypma J. G. J.
Published: December 2007

In this paper an overview will be given of some applications of a new modular reservoir simulator MoReS, developed at Shell's E&P Lab (Rijswijk, The Netherlands). Since the completion of a first prototype fractured reservoir simulator in 1989, the simulator has been used for several fractured field studies.

First a survey will be given of important physical mechanisms that are active during production of fractured reservoirs, and their modelling in a reservoir simulator. Subsequently some field applications will be described covering a wide range of recovery mechanisms and associated development options: -the relative effectiveness of gas/oil gravity drainage and water/oil displacement in reservoirs undergoin a prolonged period of depletion, and periods of water and gas injection,-re-infiltration of oil from fracture into matrix upon oil rim reversals in such reservoirs,-water/oil imbibition, either co-current or counter-current, and the scaiing-up from laboratory to simulation-gridblock and field scale,-water production in fractured gas reservoirs,-water and gas coning in fractured reservoirs with thin oil rims.

These applications have been extremely useful for demonstrating the robustness and practical applicability of the fractured simulation capabilities of MoReS, whilst at the same time providing operating companies with early results of the new tool. Applications to non-fractured reservoirs or EOR applications will not be presented here.