bluuebunny/crossref_metadata_2025 huggingface dataset:
Distributed Computing for the Technical Professional
Authors: Elliott M. L. , Bassett R. M. , Lamb J. D.
Published: December 2007

Microcomputer technology for working geologists and reservoir engineers is being deployed in the district production offices of Sun Exploration and Production Company. Two workstations have been placed in each of the ten districts, and are linked to the Dallas mainframes and supercomputer via existing communications. These workstations are being used by novice and expert users, and are based around the IBM PS/2 Model 80 microcomputer. Differences in peripherals and software depend upon whether the primary user is a geologist or a reservoir engineer.

The basic strategy is to provide a computing environment for the technical professional "casual" user, with the emphasis on interactive use of "fingertip" computing power to mechanize current operational activities. Wherever possible, interactive rapid on-screen response is provided so that the technical professional can test sensitivities and determine the consequences of actions and changes in parameters. The expected result of this computing environment is a) higher quality professional output, b) improved technical capability, and c) increased productivity. It is stressed throughout that evaluation of the input, and the interpretations and resultant decisions are the responsibility of the technical professional.

The workstation is a modest cost, self-contained computing environment readily available to the technical professional, with mainframe access to data and supercomputer access for computations requiring that capability. The configurations include digitizers, plotters, and storage devices, along with a fully configured CPU.

Commercially available software is provided with each workstation, and it is intended to use "mass market" software in this computing environment to the greatest extent possible. Only a minimum amount of internal software was developed, primarily to integrate the packages and the utilities. All workstations include contouring and volumetrics software. For the Reservoir Engineer's workstation, software for conducting reservoir simulation problems on a supercomputer was also provided.

While the overall program has spanned three years, pilot testing of the workstation and software began in earnest in 1986. As experience was gained, certain hardware and software decisions were made, and field testing was begun in early 1987. The resultant configuration was determined and frozen, and deployment of the workstations in the district offices was begun in November 1987. Before distribution, a one week initial training program on the actual system was held for about 40 engineers and geologists. Response from the technical professionals, including many novice users, has been favorable. The program will be evaluated at year-end and further recommendations will be made.
Successful Application of Microcomputers To Analyze Sucker Rod Pumps
Authors: Svinos J. G.
Published: December 2007

A microcomputer based system for design and diagnostic analysis of sucker rod pumping systems has been developed at Chevron Oil Field Research. The system is currently being applied in 34 field locations that cover over 95% of Chevron's rod pump wells.

System hardware consists of a portable dynamometer for field data collection and an office based microcomputer for data processing. Field dynamometer data are entered with a digitizing tablet, telephone modem or direct RS-232 cable connection.

The system's unique software incorporates state-of-the-art technology in an easy to use package. Since the majority of the users are non-degreed field personnel, the programs provide extensive user help, error trapping and error recovery features. The software perform two main functions: diagnostic analysis and system design. Algorithms used include wave equation modeling, an exact pumping unit kinematic model, and an ability to include inertia effects in pumping unit torque analysis. An in-house developed expert advisor program assists in interpretation and implementation of results. This program consists of a pattern recognition scheme and rules based on company expertise in rod pump system troubleshooting.

Software design was aimed at reducing the time and effort involved in collecting, processing and applying data. As a result, the system has been accepted by field personnel and is used daily as a tool to detect and correct problems. This has resulted is significant revenue increases documented in several field studies.
Enhanced Oil Recovery Model Input Program
Authors: Schroeder A. K. , Kritikos W. P. , Corley M. R.
Published: December 2007

An interactive data input program has been developed in the C language to aid creation of data files for five enhanced oil recovery predictive models. The program is designed to run on an IBM PC or compatible microcomputer with transfer of the files to a mainframe for use. It contains several features to assist the end user and speed up data entry including menus, windowing, context-sensitive help, choice lists for variables, and data validity checks.
How to Solve Lost Circulation Problems
Authors: Vidick B. , Yearwood J. A. , Perthuis H.
Published: December 2007

During drilling or cementing, lost circulation may be encountered due to the presence of highly permeable formations, e.g. high natural permeability in a sandstone, or large natural fractures and vugs as found in limestones. This problem is critical as it increases the drilling costs due to wasted time, plus the possibility of stuck pipe and even losing the well. In most cases, viscous mud pills with lost circulation material, gel, etc, allow to temporarily reduce the losses but do not guarantee a durable plugging of the formation. Cement plugs can be used but their placement and the time necessary to drill through them make their use relatively costly.

The use of an internally activated silicate solution allows to obtain a solid free Newtonian solution with a very low initial viscosity. After a given period of time, which depends on the fluid design and the temperature, the viscosity of the solution increases rapidly to form a gel. This gel is coherent, strong, and does not develop free water as a function of time. The very low initial viscosity of this solid free fluid allows it to be pumped directly through the bottom hole drilling assembly, therefore saving time, and provides deep penetration of the final gel.

A high pressure experimental set up was used to plug various cores of different permeabilities and with different saturation fluids. Results are presented on the extrusion resistance obtained after one hour and after one week. This gel is shown to withstand differential pressures greater than 1500 psi per foot of plugged formation. Some results on the long term stability of this gel to aggressive brines, organic compounds and oil are included.

A case study of a job performed in Europe is also presented.
Application of Production Seismics in Shengli Oil Field
Authors: Xiaomeng Li , Xingli Wang , Fengying Chen , Yigen Yang
Published: December 2007

With the recent development of seismic exploration, prospecting for structure m the exploration stage has evolved into prospecting for lithology in the development stage. Seismic information of large amount, better quality and wider variety will be required. Prospecting for lithology bears a close relationship with other related disciplines. Development seismics has become a comprehensive system approach in petroleum exploration and development.
Single Pulse method of Multiwell Testing with Elimination of Unknown Pressure Trends
Authors: Min Dong Ying , Licheng Ren , Dakuang Han
Published: December 2007

False-testing is an useful technique that has attracted extensive attention in recent years. However, it requires that the wells should be opened and shut-in alternately for several times. A new technique of single pulse-testing is developed in this paper. The advantage of single pulse-testing lies in that only one cycle of openning and shut-in of a well is required so that the tine required for a well testing operation is about 1/3 of that for a multiple pulse-testing, and thus both the loss of oil production and trouble caused by alternately openning and shut-in the well can be reduced greatly.

In the single pulse-testing technique, the unknown pressure trend and other background "noise" from adjacent wells or from the well itself can be eliminated by methods of parallel or arbitrary straight line pairs. The later technique is a generalization of the former and is more flexible in field application.
Factors affecting Residual Oil Saturation and its Distribution in a Water Wetted Tight Reservoir During Waterflooding
Authors: Shengzong Zhang , Chaoyu Wu , Zixian Zhao , Janguo Hu , Maochang Zhang
Published: December 2007

For a low permeability, water-wet reservoir under water flooding development quite a large amount of oil remains in the rocks as residual oil while the oil recovered is only 20-30%. The amount of residual oil is far larger than that in the high permeability reservoirs. Research in this article has identified two major causes of this situation. One is due to the lithology of the reservoir. Such influence on residual oil comes from 1) the content of medium to fine sand and silt 2) the granular sizes; 3) the reservoir pore throat sizes; and 4) the effective fluwable pore volume. The four parameters are interdependent, each reflecting one aspect of their relationship to the residual oil. The other is the capillary "entrapping force" in the low permeability reservoir on the residual oil. It is indicated through theoretical calculation that the residual oil saturation rises up as the permeability goes down.
Study of Reservoir Rock with image Processing Technique and Ellipsoidal Pore Model
Authors: Chaochen Zhang , Fangming Li
Published: December 2007

A ellipsoidal pore model for calculating the true pore size distribution of reservoir rock by use of pore-cast thin-section image analysis is developed in the light of stereology. The equation for calculating the shape function in the ellipsoidal pore model is derived and its numerical solution is realized. Combination of the core-cast thin section image analysis with the ellipsoidal pore model constitutes a quantitative analysis system. The comparative analysis of calculation results shows that the ellipsoidal pore model has more practical application than the spherical pore model. The lithologic parameters such as porosity and specific surface more aproached to practical case can be obtained from the pore size distribution calculated with the ellipsoidal pore model.
Design Study for Optimization of Tubing String Producing Gas with Water from Wells
Authors: Chuandong Yang
Published: December 2007

This paper gives the equations for the calculation of critical volocity. critical flow rate, reduced flow rate and reduced velocity necessary for a continuous lift of bottom hole liquids by gas flow in a gas well under various flow string structures and various down hole flow parameters based on general equations including equation of state of the natural gas and those related to particle mechanics and liquid drop breaking mechanics. It is demonstrated that when the down hole reduced parameter is less than unity, the diameter of the flow string should be optimized again. Mathematical model of the optimization of the flow string size for continuous liquid lifting has been established and is programmed on a microcomputer. Nomograms are developed and prepared. These results are used as a guide to the design of optimization of the tubing structure in the gas production with unloading water, and obvious economic benefits have been obtained.
Well Casing Leaks History and Corrosion Monitoring Study, Wafra Field
Authors: Bazzari J. A.
Published: December 2007

In this paper, the history of well completions, casing leaks occurence and corrosion trends in Wafra Field are reviewed. The main factors that influenced corrosion in the casing strings were identified, mainly the highly corrosive downhole environment, inadequate primary well cementation and the partial application of cathodic protection (CP.). Collectively, these factors initiated and enhanced electrochemical cells on the outer walls of the casings resulting in metal loss and subsequently holes and internal corrosion. Tests made concluded that an integrated CP., system may overcome the electrochemical cells, and mitigate corrosion. At present, one third of the wells drilled in the field have developed casing leaks and if the corrosion problem is not rectified all remaining wells may develop leaks within the next 15 years.
Problems Encountered in Simulating Large Heterogeneous Reservoirs
Authors: Assadoor A. Y. , Fawakhiri A. Y. , Taresh S. H. , Abed A. F. A. R.
Published: December 2007

Simulation of large strongly layered heterogeneous reservoirs requires detailed reservoir description data together with a good understanding of the simulator solution methods and options. This paper presents typical problems that are encountered in simulating such reservoirs together with their solutions, using an established simulation model of a real reservoir.

The majority of the problems are related to the high level of detail that is required in the input data in order to secure a good representation of the heterogeneous nature of the reservoir. These are solved by applying physically sound procedures that maintain data consistency without compromising on detail. Typical areas where problems are encountered cover the design and optimization of the areal and vertical grids, the simulation of multiple fluid contacts and transition zones, and the derivation of the saturation and PVT functions.

The initialization phase problems include the re-production by the simulator of the reservoir description data and the maintenance of a stable equilibration.

The history matching problems include the simultaneous matching of pressure and saturation, the grid block effects on eccentric well locations, and matching the performance of wells that exhibit behind wellbore communication and/or bottomhole cross flow among the completed layers.

The predictions problems are mainly related to the availability of sufficient control levels in the simulator in order to meet the detailed long term development plans and constraints.

The presented problems and their solutions are based on established in-house procedures that are being used successfully in simulating strongly layered heterogeneous reservoirs1.
Design and Field Application of Chemical Gels for Water Control in Oil Wells Producing From Naturally Fractured Carbonated Reservoirs
Authors: Senol N. N. , Gülümser R. , Tekayak N.
Published: December 2007

During primary production life of naturally fractured reservoirs with active bottom water drive, the water-oil ratio may increase rapidly. To overcome this problem which is common in oilfields in southeastern Turkey; a project covering utilization of two different chemical gels (polyacrylamide-chromium gel and silica gel) was performed by Turkish Petroleum Corp. (TPAO) in 1987.

This paper reviews laboratory studies, design and field application of the treatments and the results obtained from ten wells. Although in some of the wells no increase in net oil production was observed, some treatments have resulted in significant additional oil recovery.
SXE/N2 Matrix Acidizing
Authors: Guidry G. S. , Ruiz G. A. , Saxon A.
Published: December 2007

The paper deals with the development and application of a novel technique for matrix acidizing of the soft, low permeability oil bearing Shuaiba Limestone formation encountered in Northern Oman. It describes laboratory development and testing of a new acid system and a well management technique that have provided improved stimulation results from the Shuaiba payzone. Results of several applications are documented.

While the Shuaiba normally responds to matrix acid stimulation, a new technique was required to improve production from these wells. Laboratory investigation indicated that adding Nitrogen to an emulsified acid system resulted in a substantial decrease in the acid-rock reaction rate. Microscopic investigation revealed that the nitrification created a three phase emulsion: when properly introduced, the nitrogen did not dissolve in the oil or acid, but remained as a discrete phase. The continuous oil outer phase surrounded a dual inner phase comprised of both acid droplets and nitrogen bubbles. This combination internal phase creates a situation where nitrogen bubbles compete with acid droplets for release from the emulsion interfaces to make contact with the formation. The higher energy level of the nitrogen bubbles provides them with an advantage in the competition. The result is an improved barrier to acid-rock interaction that allows live acid to penetrate much deeper into the formation.

In combination with this improved acid system, pre-stimulation formation drawdown has also been applied to permit higher than normal injection rates. The matrix treatments have been pumped at rates far above the formation's calculated matrix flow capacity with good evidence that no fracturing has occured.

Results documented in the paper show dramatic improvements in stimulated production that have traditionally been expected only from hydraulic fracturing. Transient analysis results indicate permeability enhancement to depths exceeding 20 feet from the wellbore.
Case History: Application of a Three-Dimensional Carbonate Reservoir Simulation Model
Authors: Dreiman W. T. , Perkins J. L.
Published: December 2007

A three dimensional (3D) ‘Black Oil’ reservoir simulation model was built and history matched to make long term predictions for a multi-zonal carbonate reservoir experiencing strong edge water encroachment and differential pressure depletion. This study examines the importance of integrating reliable and comprehensive field data with sound modelling techniques to prepare a dependable model for predicting results of varying production strategies.

The reservoir being studied was discovered in 1963. After commencing production in 1966, the average reservoir pressure declined rapidly before stabilizing at approximately 90% of the original pressure when aquifer encroachment was strong enough to match reservoir withdrawals. The natural water influx has remained strong to match increased rates of reservoir withdrawals over the 22 years of production history and the reservoir pressure as a result has remained stable for the current production target. However, new producers are drilled periodically to maintain well potential to meet target off-take requirements as productivity declines in producers that start to produce water.

The aggressiveness and the amount of attention spent on the acquisition of reliable field data increased significantly in the late 1970's and early 1980's after some wells started to produce at significant water-cuts and the level of oil production target was increased. The data acquisition program, to develop reservoir management policy, consisted of increased monitoring of existing producers and the acquiring of as much new data as possible from the drilling of new producers and delineation wells. From new RFT* (Repeat Formation Tester) pressure surveys, openhole and production logs, crude samples, production tests and core data that were obtained; a better appreciation and understanding of the fluid properties and water encroachment mechanism into the reservoir has been gained.
Improved Initial Water Saturation Distribution for a Three-Dimensional Model
Authors: Prickett H. D. , Bremer R. E.
Published: December 2007

A new technique was developed for initializing a simulation model to account for areal variation in initial water saturation caused by changes in reservoir quality. The new technique uses permeability and lithology dependent Leverett J-functions with a suite of porosity-permeability transforms to calculate water saturations for finely gridded geologic models of the reservoir. Saturations were then integrated over the larger individual grid-blocks in the 3-D reservoir model.
Laboratory and Simulation Studies of Oil Displacement Behavior Due to Bottomwater Drive
Authors: McCaffery F. G. , Wunderlich R. W. , Cartwright R. P.
Published: December 2007

Laboratory displacement measurements and computer simulations were performed to support field evaluations of residual oil saturation for a high permeability sandstone reservoir exhibiting moderately to weakly water-wet characteristics. Logging and sponge core data had indicated low oil saturations in zones depleted by natural bottom water drive. The laboratory displacement tests were designed to help further verify these results and to provide data most applicable for the prediction of future field performance. Reservoir conditions displacement test data were in reasonable agreement with the field results, but laboratory conditions tests predicted higher residual oil saturations. Water-flood and centrifuge measurements were in agreement under appropriate experimental conditions.

Simple simulations were conducted to evaluate factors affecting the gravity drive process during vertical displacement of oil by water. Particular attention was paid to sensitivity analyses of the effects of the oil relative permeability and viscosity characteristics. The results obtained are useful for reservoir management questions relating to production rates, coning phenomena, and time-lapse monitoring of saturation changes.
Improved Density Log Lithology Identification Using a Borehole-Compensated Photoelectric Factor
Authors: Moake G. L. , Schultz W. E.
Published: December 2007

A photoelectric factor (Pe) measurement is now commonly available with density tools. By aiding in lithology identification, Pe information provides better estimates of matrix densities, thereby improving porosity interpretation from density logs. Pe measurements, however, are adversely affected by borehole rugosity and mudcake. In order to minimize these effects, a borehole compensation method has been developed that yields improved Pe accuracy in non-barite muds.

Prior Pe measurements normally were determined from the density detector farthest from the source (PeL) and were not compensated for borehole effects. However, the Pe obtained from the more tightly collimated short-spaced detector (PeS) is less affected by non-barite mudcake, tool standoff, and borehole diameter than PeL. Thus, unlike the compensation scheme used for density measurements, the primary Pe measurement is obtained from the short-spaced detector.

The densities measured by the short-spaced and long-spaced detectors are both affected by the same borehole factors, although with different sensitivities. It is appropriate, therefore, to derive the density correction term from the difference between the two densities. However, PeL is sensitive to several borehole parameters that do not effect PeS. Thus, a correction based on the difference between PeS and PeL, although partly successful, can lead to inaccuracies. Therefore, a better Pe compensation method was developed.

The primary borehole parameters that affect PeS are the mudcake thickness, mudcake density, and mudcake Pe. (Standoff is included in this analysis by considering the mud between the pad and the formation to be mudcake.) In order to reduce the complexity of the problem, the mudcake Pe is assumed to be small, which means that this model is only appropriate for muds that do not contain barite or hematite. Under this condition, it is shown that the required Pe correction can be determined from the density correction and an estimate of the mud weight.

The correction term is added to PeS to obtain a compensated Pe. A correction term is also obtained for PeL. However, the compensated PeL is less accurate than the compensated PeS, so it is only used in conjunction with PeS to produce a quality curve.

Verification of the Pe compensation is demonstrated with test formation data obtained using various borehole fluids, tool standoffs, and simulated mudcakes. Also, shop calibration procedures and wellsite check tolerances are presented for density and Pe logging. Finally, log examples are presented to illustrate improvements in lithology identification using the compensated Pe.
Applications Using Geochemical Logs
Authors: Colson J. L. , Grau J. A. , Herron M. M. , Herron S. L. , Schweitzer J. S. , Hertzog R. C. , Preeg W. E. , Nurmi R. D. , Johnston J.
Published: December 2007

Elemental logs can be combined with mineral models to provide significant information for geological description and evaluation of downhole formations. Mineral compositions from geochemical logs can be applied to a variety of lithologies, stratigraphie settings, and geological ages including those of the Middle East.

The most abundant element concentrations in the rock-forming minerals are obtained from the Geochemical Logging Tool (GLT*). This tool measures natural, activation, and prompt neutron capture gamma-ray spectra. In addition to the traditional potassium, thorium, and uranium from natural gamma-ray spectrometry, a direct measurement of aluminum concentration is provided. A geochemically-based closure model is used to derive silicon, calcium, iron, sulfur, gadolinium, and titanium concentrations.

The concentration of these elements, expressed in weight percent, significantly improves identification of mineral composition, and allows the estimation of important formation properties -- an excellent basis for a broad range of applications useful to petroleum engineers, geologists, and petrophysicists.
Acoustic Characterization of Permeable Zones From Full Waveform Array Sonic Data
Authors: Poster C. K.
Published: December 2007

Studies of the Stoneley wave in conjunction with log, core and production data have indicated an increase in Stoneley wave slowness and a decrease in amplitude in the vicinity of permeable zones. This case study, in a Middle East carbonate reservoir, compares these Stoneley wave characteristics with open hole Production Logging Tool (spinmeter) measurements which accurately represent variations in the in-situ permeability of formations. The results confirm a qualitative correlation of the Stoneley indicators with both permeable zones and fractures. Examination of the Stoneley waveforms themselves, also indicate events which further suggest the presence of open fractures.

With the Array Sonic Tool* we can carry out routine acquisition and determination of compressional, shear and Stoneley wave slownesses and energies. Stoneley waves are distinguishable in the sonic wavetrain by their large energy, low frequency and late arrival times. The slownesses of all the sonic wave's modes can be estimated from the array's waveforms by a Slowness-Time Coherency (STC) technique.
A Comprehensive Approach To Solve Asphaltene Deposition Problem in Some Deep Wells
Authors: Akbar S. H. , Saleh A. A.
Published: December 2007

Crude oil flowing from deep reservoirs are exhibiting asphalt deposition in the production tubing. In some cases the tubing is getting completely plugged, leading to the loss of production from these wells.

Literature on asphaltene deposition in deep wells with high pressure and high temperature is hardly available. To understand the asphalt precipitation and deposition phenomena and its control, a comprehensive program of work was formulated by the Company as indicated below: 1-Laboratory investigation –asphaltene solubility at various pressures and temperatures–inhibition tests–compositional grading2-Field investigation –effectiveness of plastic coated tubing–down hole chemical injection–effect of PI improvement on deposition behaviour–chemical means of cleaning the tubing–mechanical means of cleaning the tubing

Progress made so far and future continuation of the work is highlighted in this paper.
Field Performance of Submersible Oilwell Pump in Mubarras Field, Offshore Abu Dhabi, U.A.E.
Authors: Miwa M. , Yamamoto Y.
Published: December 2007

Artificial lift with electrical submersible pumps has been applied as a part of oil production in the Mubarras field, offshore Abu Dhabi, U.A.E. since 1975. A trouble analysis is conducted using trouble types experienced in the 13 years to clarify the problems on the electrical submersible pumps. The results show that many problems have been solved by engineering improvements in cable designs, protector systems, etc. Also, transition of pump life time by reservoirs shows that reservoir characteristics are an important factor for the field performances of pumps. The present average pump life time is 774 days and the longest pump life time has reached 1659 days.
Analysis of Pressure Buildup Tests in Naturally Fractured Reservoirs: Field Cases
Authors: Singh B. B.
Published: December 2007

Field cases of pressure build-up tests are presented for two reservoirs which showed existence of fractures on cores. The nature of the pressure build-up data on these tests have shown the importance of preparing various cross-plots to diagnose the existence of fractures in the reservoir. In many cases presented, 2 parallel straight lines with transition in between were noticed on Horner plot. In some cases, the pressure build-up tests conducted in the early life of the well were typical of a homogeneous system with afterflow and skin, although linearity of data points was obvious on Δ p vs square root of shut-in time plot. Subsequent pressure build-up tests of the well, however, showed 2 parallel lines with transition in between on Horner plot. The tests with 2 parallel slopes, showed unique trend on Pollard plot since it yielded two intersecting straight lines after early period, not reported earlier.

The storativity ratios are estimated to be rather high in spite of the large matrix block height estimated, perhaps due to high matrix permeability. These facts underscores the importance of using all available evidences to derive physically consistent parameters for analysis of naturally fractured reservoirs.
Time-Lapse Saturation Monitoring and Its Applications to Time-Lapse Mapping
Authors: Nutt R. L. , Watfa M.
Published: December 2007

Oil production and water injection involve extensive fluid movement through a reservoir. Monitoring of these fluid movements, and in particular water flooding of the hydrocarbon zone, is essential to optimization of reservoir performance. Fluid movements in carbonate reservoirs are complicated by their heterogeneous pore systems, which result in wide variations in permeability and cause uneven sweep and non-uniform depletion. High permeability streaks can promote fingering and channelling within the reservoir. Development of these irregular flow patterns is a function of porosity and permeability distribution, proximity to the original oil/water contact, activity of the underlying aquifer, vertical and lateral distance from injection points, and production and injection rates and distribution. The combined effects of all these parameters cannot be reliably modelled and predicted: their inter-relationship can only be determined by measurement of fluid saturations field-wide throughout the production life of the field.

The normal technique for monitoring water saturation changes behind casing, when water salinity is high, is to survey using neutron decay time logs. These measure the neutron capture cross-section (Σfor) of the formation, which can be interpreted - together with open hole logs - to obtain values for water saturation.

This paper illustrates an application of this technique on a field-wide basis over an extended period. Open and cased hole log data are combined into a data base of long term variations in water saturation. All the interpreted data are represented on maps which show the changes of water saturation with time. Maps of permeability distribution provide additional information which can explain anomalies and irregularities in the saturation maps. Such a field-wide study of reservoir behaviour enhances understanding of fluid movements, identifies high permeability intervals, and indicates zones of undisplaced hydrocarbon. The final objective is to use the derived model and understanding in simulations which will optimize and accurately forecast reservoir performance.
Study of a Complex Carbonate Reservoir Using the Formation MicroScanner (FMS) Tool
Authors: Badr A. R. , Ayoub M. R.
Published: December 2007

The Simsima reservoir is a complex carbonate reservoir exhibiting a high degree of heterogeneity, both vertically and laterally. The reservoir subunit log correlation has always been a difficult task due to its intricate nature, further complicated by high and sometimes erractic levels of radioactive content which affect the GR log response. Hence, correlation of lithology variation within the reservoir has been stressed and has only been possible with the study of cores.

Since it is envisaged not to core this reservoir in each future development well and since core recovery is not always good, the study of these lithology variations and their impact on the reservoir characteristics by use of the Formation MicroScanner (FMS) log, developed recently by Schlumberger, has been applied with encouraging results.
A Field Study and Mapping of Permeability in Gulf of Suez Sandstone Reservoirs
Authors: Khafagi M. R.
Published: December 2007

Permeability is one of the most difficult parameters to determine downhole. The normal procedure is to obtain values of permeability thickness (kh) for a zone from pressure drawdown or buildup tests. Core data for permeability are used extensively for calibrations, and to obtain permeability profiles. Generally, the applications of permeability data can be divided into two categories: To evaluate the performance of zones and sub-zones in each well and predict producibility or injectivity.To map and grid permeability thickness (kh) on a field basis to simulate and optimize field performance.

To obtain a continuous permeability profile as a function of depth, a large number of core analyses are needed over the zones of interest for each well. For economical reasons, however, most of the wells in a field have neither test data nor adequate permeability core analysis. With this limited permeability data for a field, a complete picture cannot be constructed. Thus, additional permeability data is needed. This is achieved by acquiring additional data, or by estimating permeability, using the existing core data as calibration standards.

This paper discusses a statistical technique in which core, test and log data are integrated to estimate permeability values in a Nubia sandstone reservoir. A statistical data-bank of information is constructed from a selected number of key wells where complete data (such as porosity, permeability, and so on) are available. This data-bank is then used to estimate missing permeability values for wells where all the data in the data-bank is available with the exception of permeability. A greater abundance of scattered data is thus obtained, and this allows individual well and field performances to be evaluated. The logic behind using a data-bank is that some of the log parameters, such as porosity, irreducible water saturation (Swirr), Archie Factor (m), etc., are also sensitive to the factors which affect permeability, including pore and grain distribution, and the number of pores and channels. Hence, a multi-dimensional correlation can be established. The results obtained from statistical data-bank analysis were compared with core, production and test data. The results of the correlation gave a reasonable degree of certainty.
Geochemistry and Hydrodynamics of the Partitioned Neutral Zone: Their Impact on Shallow Reservoir Performance
Authors: Ghoniem S. A. , Al-Zenki F. H.
Published: December 2007

This paper presents a hydrodynamic model for the Partitioned-Neutral Zone (PNZ) situated between the State of Kuwait and the Kingdom of Saudi Arabia. Geological and petrophysical data, Potentiometric surface measurements and salinity data were used to split Cretaceous and younger formations of PHZ into nine hydrodynamic layers. Based on these data, it was concluded that 4 layers are hydrodynamically active and at least 3 layers are substatic while the remaining 2 layers do not include enough data to reach conclusion. The geochemistry of the produced water further confirm the hydrodynamic model of PNZ area. The impact of activity of the shallow layers on the respective oil reservoirs is discussed. Results of managing shallow reservoirs in light of the proposed model are presented. Salinities recommended for the estimation of original oil-in-place (OOIP) of the shallow reservoirs are also given in this paper.
Drilling and Completion of Dual Gas Injection Wells in Multilayered Reservoirs
Authors: Farid E. A. , AI Khaffaji N. H. J. , Rayan M. A.
Published: December 2007

In Bab field, one of the major oil fields of the onshore area of Abu Dhabi, U.A.E., there are two limestone saturated oil reservoirs with large gas caps, laying in sequence, called Bab Thamama B and Bab Thamama C reservoirs, which will be referred to as zone B and zone C throughout this paper.

Reservoir studies revealed that the upper zone B which contains the most oil accumulation in Bab structure is divided into two main pseudo reservoirs, B Upper and B Lower. All wells drilled for zone B were completed dually in these two pseudo reservoirs. Consequently, complete separation behind the casing between B Upper and B Lower is mandatory before running the final dual completion. Today, 73 dual oil producers and 90 dual peripheral water injectors were drilled and completed in zone B. It is worth mentioning that zone B was put on production since 1960.

The lower zone C, which is also divided into two main subzones CI and CII, is a saturated oil reservoir with a larger gas cap and an oil rim above the oil water contact. Subzone CI is a short interval with unfavourable reservoir characteristics and is presently not considered for development. Zone C is developed to supply gas for domestic use, and today, 19 gas producers were drilled and completed singly in CII subzone.
3-D Seismic Ihsan/Jameel Area (Oman) Results and Implications
Authors: Gardham R. , Moeshart W. W.
Published: December 2007

During the period July 1983 - August 1985, four wells (Rawnaq-1, Jameel-1 Ihsan-1 and Mawhoob-1) were drilled in the Ihsan and Jameel area of South Oman. Of these four wells, the latter three tested hydrocarbons at commercial rates from the Gharif Formation.

As the seismic coverage over the fields was not sufficient to allow delineation of further appraisal and development wells, a new seismic survey had to be recorded over the area. In view of the obvious migration problems in an area with several small, high relief structures, it was decided to acquire a 3-D seismic survey. This survey was carried out during March and April 1986 and processed in the autumn of that same year.

After intepretation, a new depth map of the top of the Gharif Formation was constructed, which showed significant changes compared to the previous map, based on 2-D seismic data. Subsequent drilling results during 1987 demonstrated the considerable improvement in the accuracy of the 3-D seismic interpretation and also confirmed the presence of a field which was unrecognized on the earlier map. The new information resulted in a four fold increase in Expected Ultimate Recovery for the area.

The acquisition of a 3-D seismic survey in this poor seismic data area has resulted in an early, more accurate estimation of Expected Ultimate Recovery for Field Development Planning which would not have been obtained with a detailed 2-D seismic grid.
Downhole Seismic Array Applications for Reservoir Delineation in Pakistan
Authors: Zaman A. S. H. , Yousaf M. , Ahmed S.
Published: December 2007

The key oil producing formations in northern Pakistan are significantly affected by extensive and complex faulting. The detection of these faults has been an objective of offset Vertical Seismic Profiles (VSPs) for the past several years.

Recently, two land walkaway VSP surveys were undertaken in a cased development well 2750m deep. The objective was to delineate the fault pattern in the Cambrian sandstone and Eocene limestone reservoir formations. A single setting of the eight-receiver Downhole Seismic Array (DSA*) tool enabled the data to be acquired in a single run per line, using two vibrators operating at a regular shot point spacing of 75m, with a maximum offset of 3km from the well. The shot points were located on two orthogonal lines centered at the well. An important factor of the acquisition, affecting the interpretation, was the correct determination of static corrections which were obtained by running refraction spreads. These were then applied to the VSP data prior to velocity filtering.

The final interpretation involved the integration of surface seismic, VSP, walkaway VSP and well logs, including the Formation MicroScanner (FMS*) log. The walkaway VSP results appeared to be superior in resolution when compared to the surface seismic section. In addition, they delineated the fault pattern around the well, thus giving a better understanding of the complex tectonic framework of the area. The major reverse fault crossing the wellbore and causing an abnormal thickness of the Cambrian sandstone was clearly identified on the zero-offset VSP, and its lateral extension away from the well in all the directions was imaged by the walkaway VSPs.
An Experimental Investigation of First and Multiple Contact Miscible Displacement in Arabian Carbonate Cores
Authors: Asar H. K. , Okaygun H. , Arshad A.
Published: December 2007

The application of enhanced oil recovery (BOR) for a Saudi Arabian carbonate reservoir was the subject of this study. Initial process screening revealed that miscible displacement was the only viable EOR process for recovering the relatively heavy oil (28° API). The use of separator gas, separator gas enriched with liquefied petroleum gas (LPG), pure LPG, CO2, and CO2 enriched with LPG as displacing fluids was explored. Some of the experimental results were presented in the 1987 Middle East Oil Technical Conference (see ref. 1). Further results obtained from a continuation of the study are described in this paper.

The minimum miscible pressure of pure CO2 with oil was found to be higher than the reservoir pressure. CO2 enriched with 15 percent LPG gave optimal multiple-contact miscibility conditions. An unconventional apparatus consisting of a slim tube and a core holder joined in series was designed to study multiple-contact displacement. It was found to be very useful for investigating the effectiveness of enriched CO2 as a displacing fluid.

The conclusions of this experimental study for the carbonate cores were: (1)Oil displacement efficiencies by LPG and enriched CO2 were comparable, although the displacement mechanisms were different.(2)The optimal size of LPG and enriched CO2 was 5 and 25 percent, respectively.(3)Water alternating with gas (WAG) gave similar results when used in place of continuous CO2 as driving fluid.(4)CO2 acted as an excellent buffer for separating the displacing fluid from the driving fluid.(5)The amount of oil recovered by the miscible process was twice as much as that recovered by waterflooding.
Performance of a Heavy-Oil Recovery Process by an Immiscible CO2 Application, Bati Raman Field
Authors: Karaoguz D. , Issever K. , Pamir N. , Tirek A.
Published: December 2007

Batl Raman oil field, with its 1.85×109 STB oil in place and poor primary recovery (1.5% of IOIP) was a good target for enhanced oil recovery.

As a result of extensive laboratory, modeling and comparative engineering studies, TPAO has decided that an immiscible type CO2 application would be the most suitable method to enhance the recovery from the field.

Initially planned "huff and puff" has now turned to a successfull CO2 flood.

Around 2×106 STB of incremental oil have been produced, since the project resumed continous operation in late 1986. With daily production increase reaching over 4000 STB, and still having an increasing trend, the project looks promising.
Hydrocarbon Potential of Palaeozoic Pre-Khuff Clastics in Abu Dhabi, U.A.E.
Authors: Ali A. R. , Silwadi S. J.
Published: December 2007

The Palaeozoic pre-Khuff sedimentary section in Abu Dhabi proved to be a new attractive area for hydrocarbon exploration. It is mainly composed of a continental-fluvial/deltaic sandstones, siltstones, shales and subordinate claystones and dolomite of Permo-Carboniferous and Devonian (and older) age. An unconformity surface (at least Haitus) could be defined at 461 to 675 ft. below the top of the pre-Khuff clastics which might mark the latest phase of Hercynian tectonics, separating the Devonian and older rocks from the Permo-Carboniferous clastics.

Depth of the pre-Khuff clastics range between 14730 ft. SS. and 19588 ft. SS. in Abu Dhabi. Maximum sections of pre-Khuff clastics penetrated in wells; Hair Dalmah-3, Shah-16 and Satah-19 were 803, 1464 and 1508 ft. respectively.

Palynological analysis, lithofacies and log response, broadly allow the dividing of the pre-Khuff clastics into two main lithostratigraphic units; pre-unconformity unit (Devonian and/or older – more than 900 ft. thick) and post– unconformity unit (Permo-Carboniferous – 461 to 675 ft. thick). The succession could also be subdivided into four reservoir units; three of them (PK-1, PK-2 and PK-3) are gas bearing in Hair Dalmah-3 and the fourth (PK-4) is highly deteriorated in Satah-19 and Shah-16. The reservoir units PK-1, PK-2 and part of PK-3 in Hair Dalmah are within the post-unconformity lithostratigraphic unit, whereas the rest of PK-3 and PK-4 represent the pre-unconformity lithostratigraphic unit.

The pre-Khuff clastics are generally characterized by poor to fair porosity and low matrix permeability. Porosity types are mainly of primary origin and controlled by original depositional facies, depth of burial and diagenesis. Fractures are rarely defined in the section and have no significant impact on the porosity and permeability.

Production from the Palaeozoic pre-Khuff is mainly free hydrogen sulphide gas. The main gas component is Methane which forms about 69% of the total pre-Khuff gas composition, however, appreciable amounts of Nitrogen (about 23%) and Carbon Dioxide (about 8%) were also encountered.

The source of the hydrocarbon gas in the Palaeozoic pre-Khuff clastics is most probably the Silurian shale which is regionally defined over the Arabian Peninsula and the Arabian Gulf area (not penetrated in any of Abu Dhabi deep wells), however, geochemical analysis of the uppermost pre-Khuff clastics (about 50 ft. of shales and siltstones) in some localities of Abu Dhabi have indicated that this shale is of poor to moderate source potential.