bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Development Planning For The Semangkok Field Offshore Pen Insular Malaysia
Authors: Khandwala S.M. , Rani Abd Malek Abd , Rahman Mohd Nasir Abdul
Published: December 2007

In the Semangkok field the hydrocarbon-bearing formations are two sandstones which contain rim type oil accumulations. The paper discusses the seismic and exploration drilling carried out for field delineation and other studies conducted to determine an optimum reservoir development strategy. The discussion includes the geology, preliminary development assumptions, and use of symmetrical element numerical models to determine the number of wells, well locations and initial completions, and the recommended reservoir depletion plan. Selection of the optimum development plan included geologic uncertainty, facilities options and interrelations plan included geologic uncertainty, facilities options and interrelations of the two oil sandstones.

Introduction

The Semangkok field is located in the South China Sea, 35 kilometers off the east coast of Peninsular Malaysia in a water depth of 64 meters (Figure 1). Esso Production Malaysia Inc. (EPMI) has explored the field and is developing it as a contractor to Petroleum Nasional Berhad (PETRONAS), the Malaysian national oil company. The field is scheduled to go on production in 1984.

The structure that contains the field is an east-west trending anticline that is cut by faults at both ends. The field is located in the downthrown western fault block of the Semangkok anticline. The hydrocarbon-bearing reservoirs are Late Miocene group E sandstones that contain rim-type oil accumulations with associated gas caps. Commercial quantities of oil are found in two of the sandstone units in this field. These two primary reservoirs, E-6/16 and E-34/36 sandstones, are interpreted to be delta plain bar and channel deposits. Group E strata consist of sandstone, plain bar and channel deposits. Group E strata consist of sandstone, siltstone, shale, and coal sequences of marginal marine environments.

Two detailed reservoir simulation studies using symmetrical element models have been carried out to optimize the proposed field development plan. These major modelling efforts have enabled selection of optimum well location and spacing, initial completion, and reservoir drive mechanism. The reservoir models were also used to quantify the effects of reservoir heterogeneity, aquifer strength and benefits of gas injection and recovery efficiency for the field.

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Measurement Uncertainty in the Determination of Weight and Centre of Gravity of Large (Offshore) Modules, Using Strain Gauge Load Cells
Authors: Tegelaar P
Published: December 2007

When measuring the mass and the co-ordinates of the centre of gravity of a large structure, reliability, reproducibility and measurement accuracy are increasingly important. The various items that affect the measurement accuracy will be discussed. A method is given for the determination of an overall uncertainty, starting from errors that cannot be eliminated by proper corrections, in combination with the statistical uncertainty of the measurements.

A standardized weighing procedure is described, underlining stable and reproducible loading conditions to get good statistical reliability.

The state of the art in the best attainable measurement uncertainty is given.
A Worldwide Survey of Floating Production Facilities, Applications, and Future Possibilities
Authors: Hammond G. R.
Published: December 2007

In June 1975 Hamilton Brothers started production in their Argyll Field in the North Sea. Besides being the first offshore production in the U.K. sector, the project ushered in a new trend – the floating production system. Since that time the interest in the cost, schedule and flexibility of floating production systems has increased dramatically.

This paper will look at the advantages of a floating system over a fixed platform concept, and survey where installations have been made. Comparisons will be made between the various types of installations, and concepts for the future will be reviewed.
Associated Gas Utilisation in Sabah, Malaysia
Authors: Kia Tan Ek , Sikchi K G
Published: December 2007

Based on extensive studies and planning, the State Government of Sabah are now investing the equivalent of 1 billion US Dollars in a gas utilisation project which will stop the venting of associated gas produced offshore Sabah and broaden the state's economy base.

The project involves the installation of new platform facilities adjacent to existing oil production platforms in the Samarang and Erb West fields for collection, processing and transmission of up to 90 mmscfd of gas to the island of Labuan where gas will be utilised by a 47MW combined cycle power plant, a 2000 ton/day hot briquetted iron plant and a 2000 ton/day methanol plant presently under construction.

The project is targetted to come on stream second quarter of 1984.
A New Technique in Sand Control Using Liner Vibration with Gravel Packing
Authors: Solum J. R.
Published: December 2007

Vibration of the liner in shop tests and field gravel completions illustrates the substantial difference achieved in compaction of the gravel. The standard gravel pack results in cubic packing' of the gravel whereas the liner vibration technique results in hexagonal packing. This achieves a denser more stable pack with an average 15% to 25% more gravel in the same volume. Vibration eliminates the fluid placement to the formation to achieve compaction with viscous aqueous polymer completion fluids. Also, this method of vibration has eliminated liner washing which stops the comingling of the formation with the gravel. Liner vibration is now being used extensively in development wells and also for completions in injection, steam and gas storage wells.
Steam Condensate: Formation Damage and Chemical Treatments for Injectivity Improvement
Authors: Amaefule J. O. , Padilla P. C. , McCaffery F. G. , Teal S. L.
Published: December 2007

This paper discusses the results of laboratory studies conducted to determine the potential for formation damage from alkaline condensates during steam injection in a reservoir in the San Joaquin Valley, California. The paper also reviews various remedial treatment options and recommends some optimal treatment injection sequences to sustain steam injectivity.

Laboratory flow tests conducted in field core plugs with condensates at different steam qualities reveal the tendency of the condensates to dissolve the rock, destabilize the clays, and hence reduce the permeability. The alkaline condensates from once-through steam generators were also found to be incompatible with the formation water, and thus had the potential to form calcium carbonate precipitates and scales.

Pretreament of boiler feeds and/or concurrent treatment of boiler effluents with either a low concentration (<0 .1 % wt.%) phosphoric acid in 2 % potassium/ammonium chloride solution or 2 % ammonium dihydrogen phosphate reduced silica dissolution, stabilized the clays and rendered the condensates more compatible with the formation water.
Determination of Rock Properties by Quantitative Processing of Geophysical Borehole Logs
Authors: Peveraro R. C. A. , Cable H. W.
Published: December 2007

Geophysical well logs can be used to determine subsurface lithological units. Currently available methods generally provide only qualitative descriptions based on crossplots of two well logs. Comprehensive error analysis within this method is not possible, so some information can be misinterpreted. Other investigators have proposed specifying the well logs as a linear system responding to the proportion of each lithology component. Signal processing and information theory techniques can then be employed to quantitatively determine these components and their associated errors. The general form for this system is L = CV, where L is the geophysical log response vector, C is the response coefficient matrix, and V is the lithological component proportions vector. Solutions are obtained for all combinations using under-determined, determined, and over-determined systems. The error computation allows the initial model to be modified and the results further improved.

This technique can be generalised to include the computation of bulk volume estimates viewing the well logs as a linear system responding to variation in all geophysical parameters. It should, therefore, be possible to estimate from the solution of the general system not only the proportions of the lithological elements but also the proportion of the fluids filling the pore space. Known non-linear responses can be eliminated by prior processing or by appropriate linearisation models of. log responses. This is particularly required for resistivity and acoustic measurements.
Phase Behavior and Dense Phase Design Concepts for Application to the Supercritical Fluid Pipeline System
Authors: Hankinson Risdon W. , Schmidt Thomas W.
Published: December 2007

This paper presents a summary of the work performed and the results obtained to determine the feasibility, from phase-behavior considerations, of operating a supercritical, single-phase pipeline to transport NGL rich gas through the Norwegian North Sea. The experimental and computational objectives of the study were:

To provide experimental benchmark points to validate the computational models for dew points, cricondentherm, and vapor densities. To test the ability of both the Peng-Robinson and the Phillip-Soave equations of state to model rich gas behavior in the retrograde regions. To provide visual demonstrations of the retrograde phenomena and the formation and disappearance of liquids with isothermal changes in pressure.
Effects of Supercritical Carbon Dioxide on Well Cements
Authors: Onan D. D.
Published: December 2007

Due to the widespread manifestation of large scale miscible CO2 enhanced recovery projects, particularly in West Texas and Gulf Coast regions, considerable concern has developed regarding the performance and/or durability of hydrated cement located across producing and injection intervals in CO2 related wells.

It is known that carbonation affects the micro-structure of cement affecting both porosity and compressive strength. The CO2 reactivity of a cement is characterized not only by its chemical composition, but also by the properties of the CO2 medium itself, that is, partial pressure, temperature and relative humidity. However, a clear understanding of this phenomenon and its effects on portland cement is still not completely substantiated, giving rise to contradictory opinions in this particular area of research.

This led to the need and development of a laboratory program for examining the effects of supercritical CO2 on preset cement, as well as the influence of carbonation on the early stages of the cement hydration process. This article presents the findings of a comprehensive study which show that after prolonged exposure to CO2 under supercritical conditions, the hydration products formed in the hydration of common portland cement undergo decomposition into calcium carbonate and a siliceous residue. Cement samples exposed to the lower extremes (temperature and pressure) of a supercritical CO2 environment exhibited greater reactivity under dynamic conditions as compared to static conditions, while increasing CO2 pressure increased the degree of reaction regardless of the carbonation conditions employed.
Injectivity Improvement in the Grayburg Formation at a Waterflood in Lea County, NM
Authors: Martin F. D.
Published: December 2007

The purpose of this project was to improve water injectivity into the Grayburg formation at MORANCO's Rice-Hardin Waterflood in Lea County, NM. The project was a cooperative effort between the Petroleum Recovery Research Center, the New Mexico Petroleum Recovery Research Center, the New Mexico Energy and Minerals Department, the New Mexico Energy Research and Development Institute, and MORANCO of Hobbs, NM.

Laboratory tests with reservoir cores were conducted at the Petroleum Center. These tests indicated that certain chemical treatments had the ability to increase water permeability about 30%. The treatments were designed to reduce the oil saturation in a region about 8 to 10 feet out from the injection wellbore, and to improve injectivity by increasing the relative permeability to water.

Two of the most promising treatments were selected for the field trial. Rice No. I injection well was treated with a surfactant solution, and Hardin No. 3 was treated with an aromatic solvent followed by a surfactant solution. Costs of chemicals were approximately $3,000 per well. As a result of these treatments, slightly more water could be injected at pressures 400 psi less than the before-treatment levels. Since improvement in flow efficiency, observed from the injection rate and pressure data, is on the order of 50 to 60%, the field treatments apparently worked somewhat better than indicated by the laboratory tests.

Based on the encouraging results obtained from the trial, these concepts should have applicability in other waterflood projects and may also have potential in certain enhanced recovery projects where low injectivity is a problem. projects where low injectivity is a problem.
Liner Rotation and Proper Planning Improve Primary Cementing Success
Authors: Hyatt C. R. , Partin M. H.
Published: December 2007

Throughout the industry's history, successful liner cementing is one of the most difficult operations associated with drilling and completing of oil and gas wells. When utilizing liner rotation while cementing with proper displacement mechanics, it is possible to obtain an optimum liner cement job. Employing recent tool development and cementing techniques with proper displacement mechanics will result in more successful primary liner cement jobs. This paper presents an improved liner cementing technique. State of the art equipment, its historic development, design, and recommended procedures are discussed. Theory, test results, and field experience of displacement mechanics are combined to illustrate the relative importance of proper planning to displace drilling mud from the annulus.
Pressure Transient Analysis in an Elongated Linear Flow System
Authors: Ehlig-Economides C. A. , Economides M. J.
Published: December 2007

The prominent examples of linear flow behavior in the well test literature relate to linear flow within or to a fracture penetrated by a producing well. The resulting pressure transients generally are exhibited in the early portion of a well test and are followed by infinite-acting radial flow behavior and/or boundary effects.

In this paper, the linear flow occurs in the formation, which has a predominantly linear shape. Analysis of interference, drawdown, and build up tests is described in theory and illustrated by practical examples. The necessary equations for the analysis are provided for testing gas, geothermal steam, and oil wells.

In elongated linear flow systems, the pressure transient behavior associated with linear flow occurs late in the drawdown or build up test. The type curves provided in this work show that this pressure behavior is readily distinguishable from conventional well tests, particularly in interference tests.
The Effect of Stratification, Fractures, and Dip on Steam Sweep Efficiency and Heat Requirements of Steamflood Operations
Authors: Abad B. P. , Hensley C. A.
Published: December 2007

A one-phase, thermal simulator has been utilized to study the applicability of steamflooding in different reservoir geometries.

Two and three-dimensional numerical models of homogeneous dipping (0°, 15°, 30°, 45°, and 60°), heterogeneous dipping (0°, 30°, and 45°), and fractured dipping (0°, 30°, and 45°) reservoirs have been developed. The parameters investigated were heat utilization, steam vertical and areal sweep efficiency. The simulator was also utilized to generate temperature profiles for different reservoir types at different injection times. Results of this study show that dip and/or fractures should not be considered detrimental when screening reservoirs for steamflooding. Heat utilization and vertical sweep efficiency are not significantly affected by dip. Formation heterogeneities tend to control steam displacement in a reservoir more-so than dip does. Natural or induced fractures improved the steam sweep efficiency but at the expense of heat utilization. Averaged (over the upper, middle, and lower section of the reservoir) steam areal sweep efficiency improves with dip and/or fractures, and for extended injection periods the observed differences become less significant.
Mine-Assisted Heavy Oil Recovery Technology
Authors: Harding T. G. , Farouq Ali S. M.
Published: December 2007

A summary is made of technical considerations in underground mine assisted production of oil sand as well as a review of field experience in Canada and the U.S.S.R.

An assessment is made of future prospects for the application of such technology. It is concluded that although the technology exists to construct underground shafts and tunnels, and that mine assisted methods are well suited to certain oil reservoirs, these reservoirs may not be developed in the short term in preference to other more economically attractive projects. It is also concluded that, because of large lead times required for technology development, research and development activities, and in particular piloting work, should continue in the near term in order to establish methods and experience for certain large deposits.
Heavy Oil Mining Technical and Economic Analysis
Authors: Lyman T. J. , Piper E. M. , Riddell A. W.
Published: December 2007

U.S. Department of Energy studies have indicated that the United States has produced only about one-third of its estimated reserves of heavy oil, primarily because this oil is unrecoverable by conventional production methods. One technology that shows promise for recovering these reserves is oil raining. Of three fundamental mining methods, surface extractive mining, underground extractive mining and underground mining for access, the surface extractive mining and underground mining for access methods appear to be technically feasible for oil recovery.

Two heavy oil reservoirs are used as the basis for an economic evaluation of the two technically feasible mining methods. These two reservoirs were selected from an extensive list of heavy oil reservoirs in the United States based on a favorable combination of physical characteristics including depth, net pay thickness, oil saturation in barrels per acre, reservoir area, and total estimated reserves. The Kern River Field, Kern County, California was used as the basis for an economic evaluation of oil production using surface extractive mining methods. The McKittrick Field, Kern County, California was used as the basis for an economic evaluation of oil production using underground mining for access methods.

The economic evaluation of surface extractive mining was based on a mine plan capable of producing approximately 38,000 barrels of oil per day for a 20 year project life. The economic evaluation indicated that surface extractive mining would require an oil selling price of $27.26 per barrel to produce a 20 percent return on investment. This evaluation included capital and operating costs for mining, processing, and disposal of the processed oil sand ore.

The economic evaluation of underground mining for access was based on a mine plan capable of producing between 10,000 and 20,000 barrels of oil per day for a nine year project life. The mining for access method was determined not to be economical without thermal assistance because capital and operating expenses were not fully recovered over the project life due to low oil mobility. The economic evaluation indicated that mining for access with thermal assistance would require an oil selling price of $43.25 per barrel to produce a 20 percent return on investment. This analysis indicates that lighter oils with higher mobility offer better potential for successful economic demonstration of mining for access technology.
Offshore Drilling with Preformed Stable Foam
Authors: Hall D. L. , Roberts R. D.
Published: December 2007

Preformed stable foam has proven successful in drilling many onshore underpressured or fluid-sensitive formations, however, its use in offshore applications to date has been limited. Recently two redrills were completed offshore in the Santa Barbara Channel with stable foam. Because the operation was performed offshore, it offered new challenges.

The use of foam in conjunction with a downhole mud motor in directional drilling was a concern, as no data was available. Since foam is not recirculated, its disposal, particularly given the limited platform space and environmental considerations, was a major challenge to overcome.

Two wells were redrilled where lost circulation had occurred in past conventional redrill programs. A preformed stable foam program was designed to meet the offshore lost circulation, well deviation and directional needs.
The Planning and Control of Offshore Hook-up and Commissioning
Authors: Claridge John
Published: December 2007

Hook-up and commissioning is a critical phase in the successful development of an offshore oil production platform, and one where the particular problems of carrying out major works at a remote offshore location make good planning and control very difficult to achieve. This paper describes a general approach to planning and control which is aimed at overcoming these problems. How best to set up the organisation and management is considered, a planning method is outlined, and the major factors which influence the control of cost and schedule are discussed.
Auk Lower Zechstein—Drainage Mechanism Model
Authors: Tosdevin Michael A.
Published: December 2007

By modelling a fractured carbonate reservoir as being composed of a highly permeable fracture zone and a greatly less permeable section representing the matrix it has been possible to match the historical water cut performance exhibited by wells completed in the Lower Zechstein formation of the áuk field. The model was developed as a cross-section to match the water cut of a single well and subsequently extended to three dimensions to obtain a history match of water cut in the seven wells drilled in the area to date.

Once a satisfactory history natch had been obtained the model was run until 1988 to predict future water cut behaviour and to estimate field ultimate recovery.
Applicability of Tailored Pulse Loading for Gas Well Stimulation
Authors: Keough D. D. , Curran D. R. , McHugh S. L.
Published: December 2007

Tailored-pulse loading is a gas well stimulation technique that is promising for particular situations. The key factor in determining the probability of success is the interaction of the loading history with the material properties and in situ stresses of the geologic formation. On the basis of theoretical and experimental studies, tailored-pulse loading is expected to be successful if (a) the rock is fairly competent, (b) the yield stress is greater than about 100 MPa, (c) the overburden pressure is less than about 100 MPa, (d) the natural fracture or joint spacing is less than several meters.
Multiple Fracture Stimulation Using Controlled Pulse Pressurization
Authors: Hanson J. M. , Schmidt R. A. , Cooley C. H. , Schatz J. F.
Published: December 2007

Tight oil and gas reservoirs often require stimulation in order to make economic exploitation possible. Tailored pulse loading, usually by downhole use of propellants or explosives, has been studied as a means of improving production in these reservoirs. This paper presents an overview of the first year's effort on a three-year combined theoretical-experimental research program to develop a systematic understanding of the tailored pulse loading/fracturing phenomena. The project is designed to address the sensitivity of multiple fracture initiation and propagation to rock and fluid properties and pressurization history. The results will ultimately contribute to the design procedures for field applications.
Cavity Stress Relief Method To Stimulate Demethanation Boreholes
Authors: Alain A. K. , Denes G. M.
Published: December 2007

Most demethanation programs which use boreholes from the surface to access the coal, incorporate a stimulation program to enhance the well production. In most cases, the stimulation selected is a frac using nitrogen foam or other fluids. Novacorp has determined that fracing the coal may not be the best technique to apply to a well.

Novacorp, whose experience includes over eighteen (18) fracs on demethanation wells, has developed and patented an alternative stimulation method, called the Cavity Stress Relief (CSR) technique, which it believes is more effective than the frac, in most cases.

Through a review of the basic parameters which affect the desorbtion of gas from coal, a comparison is made between the frac and CSR stimulation techniques. A description of the conditions and results of two field tests of CSR are given. Also, the areas which need further development will be discussed. Although still not totally proven, the CSR stimulation technique promises to be a very effective method of stimulating most demethanation wells.
Estimating Formation Permeability From Single-Point Flow Data
Authors: Lee W. J. , Kuo T. B. , Holditch S. A. , McVay D. A.
Published: December 2007

Many operators do not routinely run pre-stimulation pressure buildup tests in low permeability gas reservoirs. Frequently, all that is available is a single-rate flow test. To obtain permeability estimates for FERC filings and to evaluate the reservoir, a new method has been developed for analyzing typical pre-fracture production data.

Permeability estimates obtained from this method have been used as a major source of data in numerous successful tight gas determinations, including the Cotton Valley, Wilcox Lobo, and Canyon formations in Texas.

The paper shows that this simple method can be quite reliable. This conclusion is based on a comparison of permeabilities estimated with this technique and with more rigorous determinations from pressure buildup tests.
An Ultrasonic Borehole Flowmeter for Production Characterization of Eastern Shale Gas Reservoir
Authors: Semmens M. G. , Tausch H. J. , Ondrik M. A.
Published: December 2007

A gas borehole flowmeter providing high resolution flow measurement is being developed to support natural gas production enhancement research within the United States Eastern Devonian Shale. The flowmeter utilizes ultrasonic technology which will provide excellent resolution and measurement accuracy. Early developmental test data indicate that the tool will be able to measure very low flow rates produced by borehole gas entry before fracture, i.e., .009 dm3/s (0.02 cfm). The use of time-of-flight dual transceivers will provide accurate gas velocity and flow measurements previously unavailable.
Liquid Permeability of Coal as a Function of Net Stress
Authors: Rose R. E. , Foh S. E.
Published: December 2007

Coalbed methane production is initiated by the removal of formation water in quantities sufficient to accomplish a large reduction of fluid pressure in the cleat system. Pressure reduction causes gas to be desorbed from the coal; the cleat system channels this gas to the wellbore. The rate and quantity of water removal is limited by permeability of the cleat system which is usually stimulated to facilitate dewatering and gas production.

Experiments were performed at IGT under in-situ conditions on coal from five U.S. basins. Results showed that water permeability of a given sample decreased by as much as two orders of magnitude over pressure ranges that simulated normal dewatering and production cycles.

Knowledge of the behavior of permeability as a function of net stress allows a better understanding of the following realities of coalbed stimulation: 1) a horizontal drill hole of a given length is much more productive than a propped fracture of the same length; 2) in general, fractures induced in coalbeds are much shorter and wider than designed; and, 3) frac pressures in coalbeds are abnormally high — significantly above overburden in many cases.

Other consequences of a permeability-net stress functionality include: 1) skin factor determinations from injection tests are necessarily more optimistic than those based on drawdown data; 2) overbalanced drilling increases the invasion radius of drilling fluid filtrate, thereby creating the potential for more extensive formation damage than in conventional reservoirs; and, 3) leakoff during fracturing operations is significantly higher than for "conventional" sandstone or limestone beds having identical pre-injection permeabilities.
Use of a Computer Model To Design Optimal Wellfields for Dewatering Coal Seams for Methane Production
Authors: Bumb A. C. , McKee C. R.
Published: December 2007

A model is presented for optimizing the number and locations of wells for various hydrologie and reservoir conditions. It can handle confined or unconfined aquifers, leaky or non-leaky aquifers, isotropic or anisotropic permeabilities, existing wells at fixed or model-determined optimal flow rates, complex boundaries, and specified regions to be excluded from possible well location sites for environmental or other reasons.

Examples demonstrate that optimum wellfield design differs significantly from the patterns widely used in the gas industry. Optimum patterns depend heavily on the reservoir and hydrologie characteristics of the target, the shape of the project site, existing wells, the total number of wells, and water pressure drop in the coal seam required to commence gas flow.
Practical Methods for Detecting Production Mechanisms in Tight Gas Reservoirs
Authors: Ammer J. R. , Sawyer W. K. , Drophin M. J.
Published: December 2007

A recent study has been conducted on the "Clinton" sandstone of Ohio by the U.S. Department of Energy. The purpose of the study was to identify production mechanisms as related to the geometry of the "Clinton" sandstone. The theory behind the study was that a log-log plot of cumulative production versus time is indicative of the flow behavior in the reservoir. A 0.50 slope would indicate linear flow exists while a slope of about 0.90 would indicate radial flow exists.

Data from 284 producing "Clinton" gas wells from six counties in eastern Ohio were used in this study. Log-log plots of cumulative production versus time were generated and then the slope values were contoured so that a comparison could be made with regional geological parameters. The results of the study showed that the production mechanisms in the four regions are causing a linear to "intermediate" (between linear and radial) flow. Radial flow was exhibited in wells where the "Red Clinton" was better defined on the gamma ray log, suggesting an offshore bar or shoal. Linear flow was exhibited in wells where the "White Clinton" was more well developed suggesting channel or distributary bars.

The intent of this paper is to make available to industry a practical approach to analyze the performance of past production. This knowledge can be used to gain insight to the factors affecting recovery so that an approach to improvements can be made.
Enhanced Production From a Slightly Geopressured Water-Drive Gas Condensate Field
Authors: Anderson L. L. , Peterson K. P. , Parisi W. A.
Published: December 2007

The production history of a Texas Gulf Coast Frio water drive gas field is presented, including performance data from a well which was recently restored to commercial production after having been abandoned six years. Areas of additional study which would help forecast future performance are discussed.
Negative Decline Curves of Coalbed Degasification Wells
Authors: Harrison G. C. , Gordon R. B.
Published: December 2007

Production data from coalbed degasification wells characteristically exhibit a negative decline curve. The dynamics of this methane production are complex and interrelated. As production begins, water and free gas are often first recovered. Continued production lowers pressure and increases permeability to gas, allowing adsorbed gas to flow. This pressure drop within the formation causes sublimation whereby gas, which is absorbed within the coal, forms on the walls of the micropores. Finally, the desorption through production disturbs the chemical and physical equilibrium of the coal, thus enabling the coal to resume generation of methane.
Evaluation of the Influence of In-Situ Reservoir Conditions on the Geometry of Hydraulic Fractures Using a 3-D Simulator: Part 2—Case Studies
Authors: Abou-Sayed A. S. , Clifton R. J. , Dougherty R. L. , Morales R. H.
Published: December 2007

The development of the basic theory and numerical implementation of a three-dimensional hydraulic fracturing simulator has been completed. The description of the model is being presented in two companion papers. The first paper (Part 1) discusses the analytical elements of the theory, while this paper considers the practical applications. The simulator can predict fracture geometry in a layered rock media under a wide range of in situ and fluid treatment conditions.

A total of 15 cases are discussed. The effects of fracture pressure gradient, stress contrast, reservoir layer stiffness, fluid viscosity and initial fracture geometry are evaluated. Resultant fracture shapes are presented and their implications on fracture design are discussed. Fracture containment is shown to be strongly dependent on the elastic modulus of the formation, magnitude of stress barriers, and fluid viscosity.
New BallaSet Diamond Bit Proves Effective for Drilling Twincreek Limestone and Nugget Sandstones in the Overthrust Belt
Authors: Ivie C. R. , Wood J. E.
Published: December 2007

Early in 1984 a new type of synthetic diamond drill bit war, introduced. The bits, know as ballaset diamond bits, are designed for and work well in medium to hard, moderately abrasive formations such as limestones, dolomites, hard brittle shales, and sandstones. Two years of field tests, many in the overthrust belt, have proven that ballaset diamond bits offer faster rates of penetration, longer life on bottom and overall improved performance when compared to types 3, 4, 5, and 7; tungsten carbide insert bits in mediun to hard formations like the Twincreek limestone and Nugget sandstones of the Overthrust Belt.

The ballaset cutting elements are polycrystalline, synthetic diamond. They differ from other polycrystalline synthetic diamonds (diamond compact) such as General Electric's Stratapax, in that they are thermally stable up to 1200°C. Other synthetic diamonds are thermally stable up to 800°C. Recognizing that frictional wear is a major factor limiting the hardness and abrasiveness of diamond compact drillable formations, thermally stable ballaset diamond bits can now drill these formations.

The Rocky Mountain Overthrust Belt, particularly the areas around Evanston, Wyoming and Duchesne, Utah, offer a wide variety of medium to hard moderately abrasive formations such as the Twincreek limestone, Tensleep sandstone/anyhdrite, Nugget sandstone, Madison dolomite and Gannet sandstones. Case histories illustrating runs in these formations are included.

Several runs with ballaset diamond bits have been made. Many runs were economical, and some formations tested were too abrasive and some were too soft. Therefore, application selection is important in the successful economic use of ballaset diamond bits. TwincreekCase HistoriesSizeStyleWOBRPMFeetHoursROP6 1/4″S248545073181.59.08 1/2″S24815400466528.88 1/2″S2483Motor7071007.1Nugget6 1/4″S2481040024128.58.56 1/4″S2481640021232.56.5

The successful runs of ballaset diamond bits in the Rocky Mountain Overthrust Belt, particularly in Twincreek limestones and Nugget sandstones have demonstrated economical advantages. Increased performance and cost reductions in other areas will be possible by careful application of these bits.
The Effect of Filtrate Invasion and Formation Wettability on Repeat Formation Tester Measurements
Authors: Phelps G. D. , Stewart G. , Peden J. M.
Published: December 2007

This study addresses some of the problems (conceptual and practical) associated with the Repeat Formation Tester (RFT)* tool. It is shown that although the RFT detects the filtrate phase pressure at the sandface, this may differ from the oil phase pressure in the undisturbed formation as a result of capillary interface effects, formation wettability effects and supercharging (the pressure superimposed on theinitial formation pressure as a result of the viscous flow of filtrate).

It is shown that whilst capillary driven flow may be significant in high permeability formations, the effect of capillary gradients in low permeability formations may be neglected and the Buckley-Leverett immiscible displacement equation used to model the invasion process.From this basis a modified theory of supercharging is developed. The theory recognises that supercharging can be a two phase problem and that the difference between the invaded and uninvaded zone mobilities should be taken into account. It is found that depending on the stability of the displacement, supercharging in a hydrocarbon zone can be enhanced or reduced by the presence of mud filtrate.

A field example is analysed in an attempt to validate the proposed theory, as well as to demonstrate how an estimate of the downhole static filtration rate may be determined from RFT measurements.

Consideration of formation wettability characteristics leads to the conclusion that most formations possess some degree of mixed wettability and that consequently the free water level (FWL) should lie above the oil-water contact (OWC). It is suggested that if such a reservoir were analysed on the assumption that it was water wet, then the reversal of the FWL and OWC from the water wet case would probably notbe observed. In addition the estimated formation pressure would be too high and the estimated FWL to low.
Some Well Test Analysis Results For A North Sea Oil Well
Authors: Wilson Mike R.
Published: December 2007

With modern computing capabilities, well test interpretation has evolved from simple straight-line techniques to a methodical interpretaion process making use of a variety of analysis procedures and complex well models. These analysis procedures range from engineering methodology to computer automation. Regardless of which procedure is used, however, there is a fundamental limit to the amount of information that can be extracted from a given well-test. This limit can only be overcome by using information obtained from other sources.

This paper uses a general buildup analysis procedure suggested by A.C. Gringarten as a framework to present an argument as to why there is a limit. The analysis procedure is based on three steps making a diagnostic plot of the data to select a well model, fitting the model to the data, and checking the fit for consistency with all the pressure data. The central point in the argument is if a well model matches a buildup and yields a correct pressure at infinite shut-in time, the model will be found to be consistent with all the pressure data. This results in two limitations which state when all consistency checks are not necessary and when well models cannot be distinguished from one another.

The results from the analysis of a North Sea oil well are presented to illustrate these limitations to well test interpretation. This analysis shows a comparison of results for two diferent bounded reservoir well models and a double-porosity model. Two of the models yield equally good matches of the buildup and drawdown data. Only by using other information about the well and reservoir could a choice be made between the two.
Completion of the Claymore Gas-Lift Optimisation Project
Authors: McAllan J. L.
Published: December 2007

This is a case history of an innovative process, thatof a gas lift optimisation supervisory system, currently in operation on Occidental's Claymore Platform.

It describes the initial arrangement on Claymore, showing why and how the system came into being, what it consists of by way of hardware, and how the offshore operation has benefited as a result of the project.
Weight Control: A Growing Awareness
Authors: Elleston F. G.
Published: December 2007

Since the mid-1970's the subject of weight control has, increasingly, become accepted as a necessary part of offshore projects. Gradually, weight control systems have been developed and improved, and awareness of the subject is definitely growing.

Little by little, design and fabrication contractors, client companies, and finally, government agencies, are learning the trade.

The first published article on the subject was in October 1978 (1), but, since that time numerous articles have followed, and a number of international seminars have been convened (2).
An Integrated Computerised Maintenance System for Offshore operations
Authors: Logan W. A. , Hasell B. H. , Trussell P.
Published: December 2007

This paper reviews the evolution of a mainly manually operated maintenance, warehouse and purchasing system for the Mobil North Sea Limited ('Mobil') operated Beryl field inthe U.K. North Sea and gives the strategy of a transition toward an on-line computerised systemcalled MIMICS (Mobil Integrated Maintenance and Control System).
A New Concept in Floating Production Systems
Authors: Patel M. H. , Montgomery J. I. , Worley M. S.
Published: December 2007

This paper describes a tandem hull floating production platform which combines the large deck space and high payload carrying advantages of a monohull vessel with some of the low wave induced motion characteristics that are typical of semisubmersible vessels. The basic features of the tandem hull platform are presented and comparisons made with the motion characteristics of various other hullforms. The model tests and computer simulation programs used in the design of the tandem hull platform are described and the results presented. Assessments are made of the capital and operating costs of a tandem hull production system and comparisons made with those of other floating production systems that are based on alternative hull forms.
The First Purpose-Built Stimulation Vessel for North Sea Application
Authors: Cooper R. E. , Marshall L. B.
Published: December 2007

A purpose-built, well-stimulation vessel has just been put into service in the North Sea. Previous limitations of existing converted supply-boats need no longer inhibit North Sea stimulation technology. Described is the evolution of this vessel, the design criteria selected for its marine and stimulation capabilities, and details of en-visaged future typical well-stimulation treatments.
Cavity and Gravel-Pack Logging in Groningen Gas Wells A Progress Report
Authors: Strobl W. , Plackett W. G.
Published: December 2007

Various logging tools have been tested in the Groningen gas field to: .Determine thepresence, size andshape of cavities behind perforated production casings caused by formation sand production..Evaluate the success and quality of gravel packing operations.

Cavities can be detected, but extensionfrom the borehole cannot be quantified.

In gravel packs, gravel tops, pack density, failures, etc. can be evaluated qualitatively.
The Role of Taxation in Optimising the Exploitation of the U.K. Continental Shelf
Authors: Underdown D. J.
Published: December 2007

The UK Government has already shown itself responsive to the need to adapt the structure of taxes on offshore oil to meet the changing economics and patterns of activity which can be expected as the UKCS matures.

A gradual modification and relaxation of the UKCS tax regime should be seen as a vital ingredient in policies to ensure that the full hydrocarbon potential of the UK offshore is realised.
GEODYN: A Geological Formation/Drillstring Dynamics Computer Program
Authors: Baird J. A. , Caskey B. C. , Tinianow M. A. , Stone C. M.
Published: December 2007

This paper describes the initial development phase of a finite element computer program, GEODYN, capable of simulating the three-dimensional transient dynamic response of a polycrystalline diamond compact (PDC) bit interacting with a non-uniform formation. The ability of GEODYN to simulate response variations attributable to hole size, hole bottom surface shapes, and formation material non-uniformities is demonstrated. Planned developmental phases will address the detailed response of a bottom-hole assembly (BHA), a drill ahead (rock penetration and removal) simulation, and ultimately, the response of the entire string.
Onset of Drillstring Precession in a Directional Borehole
Authors: Dunayevsky V. A. , Judzis A. , Mills W. H.
Published: December 2007

This paper presents a mathematical procedure for the determination of drillstring precession in a directional borehole and stability of drillstring rotation constrained by borehole geometry.

The conditions are found when the energy of axial vibrations is transformed into energy of transverse vibrations. Under these conditions the drillstring rotation around its axis becomes unstable and the transition to the rotation around borehole axis, i.e. pre-cessional motion, takes place. The conditions are formulated in terms of rotary speeds, amplitude of weight-on-bit vibrations, damping and geometry. A finite element procedure reduces the partial differential equation describing drillstring dynamics to a set of Mathew-Hill ordinary differential equations. The boundaries of parametric resonances for these equations determines the onset of precessional motion of the drillstring.

The results can be used to predict stable performance of drillstrings during directional drilling operations.
Propagation of Polymer Slugs Through Porous Media
Authors: Lecourtier J. , Chauveteau G.
Published: December 2007

This paper describes an experimental and theoretical study of the mechanisms governing polymer slug propagation through porous media. An analytical model taking into account the macro-molecule exclusion from pore walls is proposed to predict rodlike polymer velocity in porous media and thus the spreading out of polydispersed polymer slugs. Under conditions where this wall exclusion is maximum, i.e. at low shear rates and polymer concentrations, the experiments show that xanthan propagation is effectively predicted by this model. At higher flow rates and polymer concentrations, the effects of hydrodynamic dispersion and viscous fingering are analyzed; A new fractionation method for determining molecular weight distribution of polymers used in EOR is proposed.