bluuebunny/crossref_metadata_2025 huggingface dataset:
Identifying Recompletion Candidates in Stratified Gas Reservoirs
Authors: Hower T. L. , Decker M. K.
Published: December 2007

A performance analysis technique is presented which can be used to identify recompletion candidates in producing gas fields. Through geological description and a field case history, it is demonstrated that p/z versus cumulative production curves can be diagnostic tools in identifying inefficient completions or wellbore damage in a stratified reservoir system. It is also shown that these wells can be recompleted or redrilled to add significant incremental reserves which would have otherwise been abandoned.

Previous theoretical work presented in the literature demonstrated that layered gas reservoirs producing without crossflow display non-linear p/z versus cumulative production curves. This paper presents field data which support that observation and concludes that the absence of this behavior in a stratified reservoir environment may be indicative of a recompletion candidate due to wellbore damage in one or more of the layers. A field case history is presented involving wells producing from the Mesaverde Group in the San Juan Basin of New Mexico. Wells which were originally completed with nitroglycerin were selectively recompleted to yield significant incremental reserves. These wells were identified by their linear p/z behavior in an area where theory and historical performance indicate a non-linear p/z curve should be present. The results of the recompletion program are presented.
Compressed Natural Gas for Vehicles and How We Can Develop and Meet the Market
Authors: Pinkerton W. E.
Published: December 2007

State and federal legislation have mandated the use of clean burning fuels. "Clean fuels" include: compressed natural gas (CN6), ethanol, methanol, liquefied petroleum gas (LPG), electricity, and reformulated gasoline.

The Clean Air Amendments 1990 have created support for the rapid utilization of the compressed natural gas (CNG). Responsively, diverse occupations related to this industry are emerging.1 A coordinated infrastructure is vital to the successful promotion of clean fuels and synchronized endorsement of the law.
Reservoir Characterization of the Bakken Shale from Modeling of Horizontal Well Production Interference Data
Authors: Breit V. S. , Stright D. H. , Dozzo J. A.
Published: December 2007

This paper describes the use of reservoir simulation to refine reservoir descriptions of the Bakken Shale for predictions of single well and multiple well performance. The descriptions were achieved by matching drawdown, buildup, and interference data from horizontal wells in the Buckhorn Field, McKenzie County, North Dakota, Figure 1.

Reservoir descriptions - matrix and fracture storativities, ϕCtH, and matrix and fracture permeability-thickness products, KmH and KfH -- were developed for both single well and multi-well interference data. More than one description could be found to match single well data; however, only one description was found which matched all the data. The best match of long term production interference data was obtained with a dual porosity description that included anisotropic, stress-sensitive permeability.

In the dual porosity model, both microgeneration fractures and enhanced or extension fractures were modeled with a lumped description. The permeability anisotropy for this lumped fracture system was approximately 4 to 1 with the maximum permeability direction in the northern Buckhorn area being east-to-west.

Bakken Shale porosity was determined to be 2 to 3 % with one-tenth of that volume or 0.2% being in microfractures. The ratio of fracture to matrix permeability was 100 to 1 with an effective permeability for the fracture system of 0.6 md at maximum net confining stress. It is believed that silt-stones and dolomites adjacent to the Bakken Shales make a significant contribution to the oil production through the extension fracture system.
An Analysis of Hydraulically Fractured Horizontal Wells
Authors: Brown J. E. , Economides M. J.
Published: December 2007

Horizontal wells with lengths up to 8,000 ft are capturing an ever-increasing share of all wells drilled. However, the performance of many of these wells is significantly less than what is predicted by published well performance models. The factors causing this variance must be understood if horizontal wells are to produce at their potential.

Methods are presented in this paper that demonstrate which reservoirs may benefit from horizontal wells instead of fractured vertical wells. Additionally, an extensive analysis of expected performance shows that many horizontal wells may also benefit from fracture stimulation, and that the vast majority of reservoirs that have traditionally been candidates for vertical well fracturing are obvious candidates for horizontal well fracturing.

There is a need to determine the in-situ stress directions before a horizontal section is drilled, even if hydraulic fracturing is considered unattractive. These contrasting stresses can greatly affect the producing potential of a horizontal well. Analytical approximations are offered which can account for the permeability anisotropγ expected in these cases. Performance comparisons demonstrate that a horizontal well must be drilled in accordance with these stress measurements to maximize production rates.

Case histories are used to demonstrate both successes and failures of hydraulically fractured horizontal wells. Various completion practices are reviewed and their corresponding results are explained.
Drawdown and Buildup Pressure Derivative Analyses for Horizontal Wells
Authors: Issaka M. B. , Ambastha A. K.
Published: December 2007

Horizontal wells are becoming popular for primary and enhanced oil recovery operations because of unique advantages of horizontal wells in comparison to those for vertical wells. However, horizontal well testing is considerably more complex than vertical well testing.

This study uses numerical integration to evaluate an analytical solution for the transient pressure response of a horizontal well located in a closed, box-shaped, anisotropic reservoir. Results from this study show that numerical integration can be used to evaluate the solution with a comparative degree of accuracy, while avoiding the convergence problems associated with the analytical integration. Both drawdown and buildup responses have been studied.

New time criteria, based on the semi-log pressure derivative response, are proposed for well test analysis and design purposes. These time criteria generally suggest shorter flow period durations than those corresponding to the time criteria based on the pressure response. The effects of well radius, well location and reservoir size on the drawdown pressure derivative response are discussed.

Producing time effects on the buildup pressure derivative responses are also investigated. Results show that for a horizontal well in a closed reservoir, the late linear flow period will not occur on the buildup response for any case, even when the late linear flow period is present on the drawdown response. Design equations are presented for the time at which buildup response deviates away from the corresponding drawdown response to establish the applicability and limitations of using drawdown type curves to analyze buildup data obtained from a horizontal well.
Performance of Axial Electric Submersible Pumps in a Gassy Well
Authors: Sachdeva Rajesh , Doty D. R. , Schmidt Zelimir
Published: December 2007

This is a continuation of the earlier work on the I-42B pump presented by Sachdeva1. The dynamic model developed earlier is extended to include axial geometries. Correlations are developed for CD/rb -- the only correlating factor required to complete the model. The performance of radial C-72 and axial K-70 pumps under gassy conditions is studied. Besides the dynamic model, a simple correlation (Model 2) for predicting the pressure rise per stage is also developed for the C-72, K-70 and I-42 pumps.
MEOR—Altamont/Bluebell Field Project
Authors: Streeb L. P. , Brown F. G.
Published: December 2007

This paper presents a field application of microbial treating in the Altamont/Bluebell Field. The project demonstrates the use of microorganisms to treat high wax content crude oil to improve field operations, reduce chemical use, conserve lease fuel, increase production and enhance oil recovery.
The Feasibility of Using CO2 EOR Techniques in the Powder River Basin of Wyoming
Authors: Branting J. K. McDaniel , Whitman D. L.
Published: December 2007

The feasibility of tertiary oil recovery by CO2 injection in fields located in the Powder River Basin of Wyoming was studied. The objectives were 1) to estimate the amount of tertiary oil that could be recovered by CO2 injection in the Powder River Basin of Wyoming; 2) to locate sources of CO2 for this basin; 3) to measure the potential demand for CO2 in this basin; and 4) to find the economic range of feasibility for CO2 utilization in this basin. The work was not intended to be a detailed analysis of the reservoirs in the Powder River Basin and their compatibility with CO2 injection, but rather, an attempt to get a rough estimate of the usefulness of CO2 in the Powder River basin.
Fracture Treatments in a Moderate-Permeability Sandstone: Converse IIA Formation, Lance Creek Field, Wyoming
Authors: Myers V. C. , Arnold L. L.
Published: December 2007

This paper is a study of hydraulic fracturing techniques used in the Converse IIA reservoir in the Lance Creek field, Niobrara County, Wyoming. The Permian Converse formation is composed of interbedded dolomites, anhydrites, shales, and sandstones. In the Lance Creek field, the upper Second Converse section contains an oil-productive sandstone at an average vertical depth of 4600 ft. The pay sand, known as the Converse IIA, is from 15- to 35 ft thick; the average porosity and permeability is 9% and 5 md, respectively. With the depletion of the formerly-prolific Leo and basal Sundance zones below their economic limit, many Lance Creek wells have been recompleted recently in the Converse IIA zone.

To enhance production from this moderate-permeability sandstone, hydraulic fracturing treatments have been performed on most of the Converse IIA wells in the field. A unique situation exists in that fluid and proppant volumes pumped in the treated wells are similar, but fluid and proppant types are varied. In this paper, we evaluate the response of the reservoir to the different treatment materials and techniques that have been used. Conclusions on the relative success of the different treatment options is substantiated by comparing treatment and reservoir data to production and well-history data.
A Numerical Study of Coalbed Dewatering
Authors: Seidle J. P.
Published: December 2007

Unlike conventional reservoirs, the productive capacity of a coalbed is not immediately apparent. New coal wells typically produce at low rates and often exhibit low gas-water ratios. Only after a coalbed has been dewatered does gas rate begin to rise and water rate begin to fall. A numerical study was undertaken to investigate saturation and pressure behavior during the initial dewatering period and to develop methods to predict its duration. These simulations used typical coalbed and well properties encountered in Warrior and San Juan Basin coal wells. Behavior of gas saturation and pressure profiles during dewatering is discussed. It was found that, for engineering purposes, coalbed dewatering can be considered a constant pressure process. Two methods were developed to determine time and cumulative water production required to dewater a new coal well. The first method is based on the classical definition of pseudo-steady state flow, while the second method is based upon the gas-water ratio. Accuracy of both methods is discussed and a recommendations made for application to actual coal wells. Effective coalbed porosity is difficult to measure, but is necessary for reservoir engineering calculations and numerical simulations of coal well performance. Once a coal well has been dewatered, the gas-water ratio method developed here can be used to determine effective porosity. An example calculation is presented.
Coalbed Methane Well Production Forecasting
Authors: Soot P. M.
Published: December 2007

A method (NWFuel Method) has been developed to predict the cumulative production from coalbed methane (CBM) wells. This Method has been developed from actual production data from over 1,500 wells in the Black Warrior and San Juan Basins. The technique involves ranking of individual wells against a series of generic production curves. These generic curves are based on computer simulations representative of the respective basins. The assigned "Rank" provides an indication of the amount of production anticipated from a given well over its lifetime. Both water and gas production are predicted by this Method. Although the Method is not precise for individual wells, it should be statistically significant for groups of CBM wells.

The technique involves ranking individual wells against a series of cumulative production curves. These generic curves are based on computer modeling of wells in the respective basin. It has been observed that most wells proceed along a given cumulative production curve, providing the basis for projecting future production.

Applying the Method in the Black Warrior Basin indicates that the average CBM well in that Basin will produce about 200 MMCF (5.7 million m3) in ten years. This is the result based on an evaluation of 641 wells which were on line before 1990. The San Juan Basin typically has a considerably higher production potential per well. An average for the entire Basin is not meaningful. The best and worst wells in that Basin vary in their reserves by two orders of magnitude.

The results from the NWFuel Method can be mapped. This allows one to associate production results with geological parameters. The subsequent result can enhance the exploration for new wells in a basin.
Modeling Coalbed Methane Production With Binary Gas Sorption
Authors: Arri L. E. , Yee Dan , Morgan W. D. , Jeansonne M. W.
Published: December 2007

A description of binary gas sorption on coal is developed and incorporated into a reservoir simulator for use in predicting primary and enhanced recovery of coalbed methane.

The sorption of methane-nitrogen and methane-carbon dioxide mixtures was measured at 115°F and total pressures of 500, 1,000, and 1,500 psia. A moist Fruit-land coal sample from the San Juan Basin of Colorado was used. The results showed that each gas did not sorb independently, instead both gases were competing for the same sorption sites. An extended Langmuir isotherm provided a reasonable correlation of the data.

A compositional reservoir simulator was modified using the extended Langmuir isotherm as the basis for the equilibrium relationship between the free and sorbed gas. The resulting formulation is functionally equivalent to a compositional representation using K-values expressed as a function of total pressure and the concentration of one component. The modified simulator was successfully tested for the cases of primary recovery of a single sorbing component and the enhanced recovery by nitrogen injection.
Laboratory Study of the Effects of Miscible WAG Process on Tertiary Oil Recovery
Authors: Zekri A. Y. , Natuh A. A.
Published: December 2007

Misciblc gas flooding using carbon dioxide and natural hydrocarbon gases is currently being investigated as possible EOR process in a number of Libyan reservoirs. The major reason for selecting miscible gas flooding as an EOR process was because of the adaptability and possible gas availability at reasonable cost. C02 and hydrocarbon gases could achieve miscibility with a number of reservoir oils at current conditions [pressure] through a multi-contact miscibility process.

The main disadvantages of miscible gas flooding is the high mobility ratio so that the gases have the tendency to channel through the oil which results in by-passing much of the oil in the reservoir and low sweep efficiency. To solve this problem, a technique was tested consisting of alternately injecting small solvent [hydrocarbon gas or CO2] and water slugs. The slug of water reduces the speed of the solvent which results in reducing the chance of solvent fingering and improving the mobility of the system.

The main objective of this study is to investigate the effect of WAO RATIO on overall reovery of tertiary miscible flooding. Laboratory tests were conducted on three stacks of composite cores arranged in permeability descending order. The effects of lithology on overall performance was also tested.. The system studied in this work was an oil wet system. Tests were conducted in 3 ft. oil wet sandstone and carbonate rock cores. Cores utilized in this projcct were obtained from two Libyan reservoirs and arranged in desending order to form three composite stacks. Water and solvent were iinjected separately.
Operational Aspects of Drilling and Completing Horizontal Wells Offshore Abu Dhabi
Authors: Bowen J.F. , Hassan M.M.
Published: December 2007

Since June 1989, Zakum Development Company (ZADCO) has drilled and completed eight horizontal producing wells in Upper Zakum Field and one well in Umm Al Dalkh Field.

With numerous development drilling locations remaining in Upper Zakum Field, the potential for increased usage of horizontal techniques is significant. Most of the required production platforms are in place and most of the remaining slots are dedicated for medium and high departure wells. One high departure horizontal well with a horizontal section extending more than 9000 lateral feet from the platform has been successfully drilled and completed.

In addition, the potential to sidetrack numerous existing low/medium/high departure wells for horizontal drilling is significant. In fact, five of the nine horizontal wells drilled to date were reentry sidetracks and four were drilled from the surface.

The purpose of this paper is to present an operational overview of ZADCO's experience with horizontal wells. Topics of special interest include:the unusual horizontal well trajectories required offshore (i.e. high-departure wells),efforts to minimize top-hole doglegs to minimize torque and drag and reduce casing wear,a technical and economic comparison between sidetracking and drilling new wells,a discussion of current and future completion techniques, andstimulation techniques.

Introduction

Discovered in 1963, Zakum Field is the fourth largest field, and the largest offshore field, in the Middle East. Early development efforts focused on Lower Zakum Field. Development of Upper Zakum Field began in 1977.

Thus far, a total of 310 wells have been drilled and completed in the 465 square mile Upper Zakum Field, most of which are deviated wells with dual completions. More than one hundred infill wells remain to be drilled.

There are three distinct groups of limestone reservoirs in Upper Zakum Field, the Thamama I, II, and III. Well spacing ranges from 2500 to 5000 feet. Water injection was initiated in 1984 to maintain reservoir pressure and maximize profitability.

ZADCO first studied horizontal drilling in 1988 as a potential means to optimize the development of Upper Zakum Field. Operating on behalf of Abu Dhabi National Oil Company and in conjunction with Abu Dhabi Marine Operating Company, ZADCO drilled the first horizontal well in the Arabian Gulf in 1989, in Upper Zakum Field.1

The advent of horizontal drilling technology has provided ZADCO with a unique opportunity to develop Upper Zakum Field using state-of-the-art technology. Initial results of the horizontal trial program have been excellent from both operational and reservoir management viewpoints. Present plans include increased usage of horizontal techniques, including dual horizontal producing wells and horizontal injection wells.
Application Of Horizontal Drilling To Alleviate Water Slumping
Authors: Kader S. A. , Hafez H. H.
Published: December 2007

Within ADCO, horizontal drilling has been used successfully to enhance well productivity, injectivity, and to reduce water coning in some production wells. This paper presents a case history of how horizontal drilling has been used to reduce the effects of water slumping between psuedo-reservoirs, resulting in reduced water cut and increased productivity; and reservoir simulation efforts to match and predict well performance.

A short radius horizontal hole of 850 ft length was drilled in the dry Thamama B Lower pseudoreservoir in an existing well in the Asab field, and succeeded in reducing water slumping from the wet upper pseudo-reservoir. This resulted in a reduction in the water cut from 20% to less than 1% with a five fold increase in the well productivity. A simulation model of a reservoir element was constructed with local grid refinement to represent the horizontal well. Past performance of the well was matched and the model was used to predict future well performance.
Logging and Stimulating Horizontal Wells Offshore Abu Dhabi
Authors: El Sebai H. D. , Ghneim G. J.
Published: December 2007

_

This paper was a repeat presentation at the SPE Middle East Oil Technical Conference and Exhibition held in Bahrain, 3-6 April, 1993.

During 1991 ADMA-OPCO planned to drill two horizontal producers. It was also planned to measure the petrophysical properties of the horizontal sections by Logging While Drilling (LWD) and by conveying conventional open hole logs on drill-pipe under Tough Logging Conditions (TLC). Each well was suggested to be logged by different LWD contractor.

Bullheading the acid into the formation is very inefficient and not expected to stimulate more than a few feet of the horizontal section as the acid tends to spend near the top when it contacts the limestone formation. Thus, to allow uniform distribution of the acid in the horizontal sections, the coiled tubing was used to pump the acid into the formation while pulling ft out.

Batches of foam diverters were pumped at regular intervals to ensure proper diversion of the acid. During the pumping sequence, a diesel oil was pumped down the coiled tubing X production tubing annulus to prevent the injected fluids from travelling up the hole by creating a back pressure on the upper sections.

Part one of this paper reviewed the logging operations and compared the results of the two LWDs with the open hole logs and with the core analysis results.

Part two discussed the operational and efficiency aspects of stimulating an offshore horizontal well.
Well Testing of A Fractured Well in a Multilayered Bounded Square
Authors: El-Sayed Osman Mohamed
Published: December 2007

This study presented the pressure behaviour of a well located in multilayered bounded square and crossed by a vertical fracture (uniform flux or infinite conductivity). It was found that pressure function and its derivative and fractional flow from different layers are mainly controlled by the fracture extension into the formation. The effects of transmissibility and storativity on fractural flow and pressure derivatives are significant. Such effect on pressure functions are insignificant. Therefore, type curves of pressure functions can not be used in evaluation reservoir characteristics while those of pressure derivative can be used for this purpose. The nature of the fracture was found to have minor effects on different parameters included in this study. It was found that type curves of buildup pressure function can be used only for very small values of fracture extension and production time.
Environmental Planning through Risk Assessment
Authors: Cayias J. L. , Gordon R. D.
Published: December 2007

The risk assessment process can be used as a strategic planning tool to manage environmental risks in the oil industry. Risk assessment allows for evaluation of clean up levels at contaminated sites based on reducing human health risk to acceptable levels while selecting the most cost effective remedial approach. The use of this approach gives consistency to the management of environmental risks and allows the risk manager to allocate resources so that they will have the greatest impact on reducing risk to human health. This paper discusses the risk assessment process and uses two examples to show how it can be applied to solve environmental problems in the oil field.
New Method for Better Control of Cement Performance in High-Temperature Wells
Authors: Nelson E. B. , Casabonne J. M.
Published: December 2007

Deep, hot wells present special cement-system design challenges. Among them is the simultaneous achievement of adequate slurry-placement time and acceptably short waiting-on-cement (WOO time. This paper describes a new slurry-design method and a novel retarder that address this problem. To reduce the potential of job failure and to save rig time, the new design method relies more upon the static temperatures at the top (ST @ TOC) and bottom (BHST) of the cemented interval. Traditionally the bottomhole circulating temperature (BHCT), which is often not accurately known, is the most important design criterion. The new technology allows uncommonly long thickening times, providing an increased safety margin, without sacrificing rapid compressive strength development.
Treatment of Production Tank Bottom Sludge by Composting
Authors: Nordrum S. B. , Fyock Leroy , Findlay Margaret
Published: December 2007

Treatment of oily waste by composting was demonstrated at a Chevron facility. The full-scale operation involved mixing sludge with bulking agent and fertilizer, and aerating the mixture using a tractor-mounted auger. Ninety-seven percent of the petroleum hydrocarbons were destroyed in 41 days, based on quantitation of major constituents by gas Chromatograph.
A Laboratory Study of Cement and Resin Plugs Placed With Thru-Tubing Dump Bailers
Authors: White W. S. , Calvert D. G. , Barker J. M. , Bour D. L.
Published: December 2007

Laboratory experiments were conducted to study the factors that influence the successful placement of cement and resin plugs using thru-tubing dump bailers. The five-phase study included: (1) cement slurry design, (2) full-scale visual tests, (3) full-scale cured plug tests, (4) shear bond tests, and (5) gravel pack penetration tests.

This paper presents results from the test program and provides data on commonly used dump bailer practices and equipment. Recommendations are made for placing cement and resin plugs utilizing dump bailers. This information should be useful to operators in planning and completing successful thru-tubing plugbacks.
Conversion of Drilling Fluids to Cements With Blast Furnace Slag: Performance Properties and Applications for Well Cementing
Authors: Cowan K. M. , Hale A. H. , Nahm J. J.
Published: December 2007

A new method of obtaining unproved zonal isolation using drilling fluid solidification technology has been developed. A water-base drilling fluid is converted into a cement using a hydraulic blast furnace slag. Hydraulic blast furnace slag is a unique material which has low impact on rheological and fluid loss properties of drilling fluids, can be activated to set in drilling fluids which are difficult to convert to cements with other solidification technologies, is a more uniform and consistent quality product than Portland well cements, and is available in large quantity from multiple sources.

Because of its low impact on drilling fluid properties, blast furnace slag may be added to a drilling fluid at low concentrations during drilling operations. The Alter cake and drilling fluid in washed out sections thereby contain a hydraulic material. After reaching casing point, a mixture of drilling fluid containing chemical activators and higher concentrations of slag may be used to cement the casing string. Chemical activators from this mixture cause the slag in the filter cake and any bypassed drilling fluid to set. The result is a more complete seal for the annulus.

Fluid and hardened solid properties of blast furnace slag and drilling fluid mixtures used for cementing operations are comparable to properties of conventional Portland cement compositions. The design, testing and field application for this technology are similar to conventional cementing methods. Fluids with densities between about 1198 kg/m3 (10 lb/gal) and 2397 kg/m3 (20 lb/gal) may be prepared. The mixtures have been applied in wells where temperatures range from about 4°C (40°F) to 315°C (600°F).

This new solidification method provides the proper combination of fluid and solid properties, simplicity of design and application, improved zonal isolation, and broad applicability to bring drilling fluid solidification technology into widespread use.
Quantifying Common Drilling Problems With Mechanical Specific Energy and a Bit-Specific Coefficient of Sliding Friction
Authors: Pessier R. C. , Fear M. J.
Published: December 2007

The conventional way to assess drilling performance in the oil field is to compare actual performance to statistical standards derived from offset records. By their nature, these standards are subjective and variable. While they are ideal to monitor short-range performance and trends in well- known, older fields, they lack the power of physical models to establish absolute, technical performance standards. Several authors have proposed models in which the drilling process is treated as a mechanical, energy-balanced system. Mechanical specific energy input, drilling efficiency, and a minimum specific energy equal to the rock strength are the three key elements of these systems.

Full-scale simulator tests were conducted under controlled laboratory conditions to develop and validate an energy- balanced model for drilling under hydrostatic pressure. In these tests, wide variations in drilling efficiency from a few percent to three and four times were observed in the spectrum of common drilling practices. They provided new insights into the drilling process and the nature of common drilling problems.

Analysis of field data revealed good correlation between simulator and field results. Using mechanical efficiency, specific energy input, and a bit-specific coefficient of sliding friction as key indexes of drilling performance makes bit selection and the diagnosis of failures and drilling practices more accurate and less ambiguous.
Effect of Wear and Bending on Casing Collapse Strength
Authors: Kuriyama Yukihisa , Tsukano Yasushi , Mimaki Toshitaro , Yonezawa Tetsuo
Published: December 2007

In high-angle and horizontal wells, casing is subjected to severe wear and bending. Effect of wear and bending on the collapse strength was investigated by experiments and was evaluated using analytical approach as well as FEM. Empirical formulas allowing imperfections based on elastic collapse and yield onset pressure are derived.
Operational Advances from Field Application of Short-Radius Horizontal Drilling in the Yates Field Unit
Authors: Odorisio V. G. , Curtis S. C.
Published: December 2007

Operational advances in short radius horizontal drilling have been achieved in conjunction with the placement of 23 drainholes in the Yates Field Unit, Pecos County, Texas. These advances include improvements in drilling of the curve section, application of gel squeezing technology to isolate the curve section, and drilling of the lateral section which are discussed for horizontal recompletions from existing vertical wellbores with 7 inch and 5-1/2 inch casing. In addition, the cost savings and performance enhancements realized from these operational advances are reviewed.

The most significant improvements have been realized through implementation of a short radius articulated mud motor system to replace rotary tool assemblies. The motor system has been optimized through refinement of motor and steering assembly specifications, and bit selection. The refined system has provided as much as a five-fold increase in penetration rates, a three-fold increase in lateral length, and a substantial improvement in directional control. The enhancements have also resulted in a reduction of over 60% in the cost per foot of drainhole length drilled.
Guidance for Designing Offshore Modules Evolving from Gas Explosion Research
Authors: Bakke J. R. , van Wingerden Kees
Published: December 2007

Recent accidents in the North Sea1,2 have confirmed that gas explosions constitute a major hazard for gas and oil production on offshore facilities.

Research on gas explosions at CMI has for more than 10 years focused on experimental research into flame propagation in complex geometries as well as the development of a gasdynamic code (FLACS) capable of predicting gas explosion propagation in industrial environments.

The FLACS code calculates the turbulence generated by the interaction of the gas explosion with confinement and equipment and the positive feedback of this turbulence into the gas explosion. The code predicts pressure and drag forces due to gas explosions for specified module layouts and for different fuels and ignition locations.

The paper gives a brief introduction to the nature of gas explosions and an overview of previous research at CM, followed by a presentation of results from the present research on the subject. As an example the effect of water deluge on explosion propagation will be discussed.

Finally an overview is given of lessons that have been learned by using the FLACS code, which is used by operators to design offshore modules. The effect of vent area location, types of vent area covers, module shape, equipment location and platform layout is discussed.
Cyclic Steam Injection with Additives: Laboratory and Field Test Results of Steam/Foam and Steam/Solvent Processes
Authors: Mendez Zuleyka , Alvarez J. M. , Escobar Elena , Colonomos Peter , Campos Enrique
Published: December 2007

Cyclic steam injection is the most commonly used method to produce the heavy oil reservoirs in the Bolívar Coast in Western Venezuela. The efficiency of this method in this field, as measured by the oil to steam ratio, is remarkably high, mainly due to compaction drive. Nevertheless, later cycles show a natural decline in the efficiency of the process.

In order to improve the efficiency, and to extend the application of cyclic steam injection in the field, different types of additives are being tested. Laboratory study, and field tests were conducted in order to study the possible merits of the addition of small amounts of solvent as part of the injection process. On the other hand, due to the massive sand bodies, and shale intercalations that exist in the heavy oil reservoirs of the Bolívar Coast, foam was used in order to improve the vertical sweep efficiency of steam injection during huff’n puff.

After the conduction of laboratory experiments with steam/foam, a set of 16 wells were selected in order to test the injection of two commercial foaming agents (LTS and BBS). In this work, the field results of these pilot test of foam injection are analyzed, and correlated with several variables.

Four wells were stimulated with steam injection with solvent. The solvent used was an industrial diesel. As in the previous case, field results were analyzed. The merits of the process are obtained by comparing the response of the wells, with neighboring wells with similar characteristics. Prior to the field tests, laboratory experiments were carried out, in order to obtain the operating conditions.
Optimum Water Alternate Gas Injection Schemes for Stratified Reservoirs
Authors: Surguchev L. M. , Korbfll Ragnhild , Krakstad O. S.
Published: December 2007

Water alternate gas (WAG) injection technology is a method which may improve oil recovery efficiency by combining effects from two traditional technologies - water and gas flooding. Both microscopic oil displacement and sweep efficiency can be improved by WAG implementation. This paper describes a method of designing an effective water/gas flooding in stratified reservoirs.

The analytical approach taking into account effects of three phase flow, gravity and viscous forces in anisotropic media, allows the determination of optimum parameters of water/gas injection. A three-phase extended black oil simulator with relative permeability and capillary pressure hysteresis, was used to validate the optimum WAG injection parameters obtained by the analytical method. In this work, the efficiency of different injection schemes was compared. Simulation results which demonstrate the influence of WAG injection parameters, as water-gas ratio, injection rates and cycle periods, on the recovery process, are discussed.
A Case Study of Reservoir Characterization From DST and Seismic Data
Authors: Klimentos Theodoras , Steyn Andries , Stallbom Kevin
Published: December 2007

Resevoir heterogeneity can be created by complex sedimentary and diagenetic processess and modified by a sequence of tectonic changes. Integrated information from geophysical, petrophysical, geological and reservoir engineering studies could enhance reservoir characterization even at the discovery-appraisal stage which is vital for oil company sound development and economic planning.

This paper presents a dynamic characterization of a gas-condensate reservoir from well-test interpretation in conjunction with the static description obtained from reflection seismics, well-logging, core and other studies.
Interpretation of a Heavy Mineralogy Formation, North Slope of Alaska, Using Logging-While-Drilling 2 MHz Resistivity: Laboratory Measurements, Modeling, and Wireline Comparisons
Authors: Murphy W. F. , Auzerais F. M. , Lüling M. G. , Anderson B. I. , Tomanic J. , Bonner S. D. , Sakura Shinichi , Wolcott D. S.
Published: December 2007

In order to understand better the effects of lithology, an anomalous log from a 2-MHz Logging While Drilling propagation resistivity tool is compared to a log from a wireline dual induction – SFL* Spherically Focussed Tool. The C-sand in the Kuparuk River Field contains the minerals siderite and glauconite which exhibit atypical dielectric properties. For several wells in the Kuparuk River Field where both the 2-MHz and wireline logs were obtained, the agreement is good after dielectric processing. However in this well, the 2-MHz tool reads differently from the wireline induction tool. In this well, the 2-MHz tool had been run during a washdown trip rather than while drilling. A combination of laboratory core characterization and forward modeling is used to reconcile the differences between the two logs. The 2-MHz and induction tool responses were modeled based on the laboratory results. The remaining differences between the 2-MHz and induction resistivity were caused by invasion effects in the washdown mode.
Transient Pressure Response of a Well With Partial Completion in a Two-Layer Crossflowing Reservoir
Authors: Shah P. C. , Thambynayagam R. K. M.
Published: December 2007

Although the technical literature contains several transient pressure response models for reservoirs producing multiple crossflowing layers, none of these models is adequate for the applications where they are most needed. None of these models accounts for partial completion. Further, all but one of these models approximate the crossflow through a steady-state assumption and ignore the variation of the pressure within each layer in the vertical direction. Layered models with crossflow are often used to interpret tests in thick carbonate reservoirs or in wells with bot-tomwater drive or gas caps. Partial completion, often in the extreme form, is invariably employed in such systems. Ignoring it in test interpretation may lead to incorrect estimation of some key parameters and unidentifiability of others.

An analytic model is presented for the transient pressure response of such systems. This model rigorously accounts for both partial completion and the dynamics of vertical flow. The Laplace domain solution includes a different skin factor in each layer and can account for the effects of wellbore storage and dual porosities. The solution is obtained by applying the finite Hankel transforms and employing the pressure averaging technique. Computer-based symbolic manipulation was necessary to render the solution into a form suitable for practical evaluation.

The new model enables improved interpretation of well tests in several types of reservoirs to yield parameters that cannot be estimated with the existing models (e.g., the vertical permeabilities in two communicating layers, and. the horizontal mobility in the gas cap or in the water zone communicating with an oil reservoir). This model can also be used for interpretation of the single well vertical interference test.
Models for Meandering and Braided Fluvial Reservoirs With Examples From the Travis Peak Formation, East Texas.
Authors: Davies D. K. , Williams B. P. J. , Vessell R. K.
Published: December 2007

Meandering and braided rivers produce reservoir sand bodies of different size and heterogeneity. The heterogeneity and size of channel reservoirs can be predicted at an early stage in field development. Reservoir models derived through geological analysis of meandering and braided channel sands in the Travis Peak Formation are similar to those developed independently by reservoir simulation studies.
Pressure Transient Behavior of a Finite-Conductivity Fractured Well with Spatially Varying Fracture Properties
Authors: Poe B. D. , Shah P. C. , Elbel J. L.
Published: December 2007

The pressure transient behavior of a finite-conductivity vertically fractured weil is important in reservoir engineering because it provides valuable information concerning the well completion, and provides estimates of the in-situ reservoir properties and the propped fracture dimensions and conductivity. The pressure transient behavior of finite-conductivity fractured wells has typically been analyzed using mathematical models that assume relatively simple fracture properties. Most of these models assume uniform fracture height, width, and proppant permeability distributions with respect to space, and many of these models also assume that fracture storage effects are negligible.

This paper presents the pressure transient solution of a well intersected by a finite-conductivity vertical fracture with a lengthwise variation in the fracture geometric and material properties. The general solution of the fracture fluid-flow problem, and an approximate solution of the problem in which the effect of fracture storage has been assumed to be negligible, are presented. Comparisons of the pressure transient behavior predicted with the two finite-conductivity fracture solutions are given. The effects of spatially varying fracture height, width, and material properties are investigated with these pressure transient solutions. The new solutions provide more realistic pressure transient analysis models which may be used to better design, implement, and evaluate hydraulic fracture treatments. They will also provide better agreement between the prediction of the fracture geometry and its post-treatment evaluation.
Integration of Seismic Monitoring and Reservoir Simulation Results for a Steamflood at South Casper Creek Oil Field, Wyoming
Authors: Johnston P. F. , Andersen G. R. , Wachi Noboru , Lee D. S. , Martens F. G. , Han D. H.
Published: December 2007

Repeat 3-D and cross-well seismic surveys were acquired to monitor inter-well temperature distribution during a steamflood at South Casper Creek Oil Field, Wyoming. Baseline surveys were acquired before steam injection started in an inverted pilot 5-spot pattern. Monitor surveys were acquired after 7 and 12 months of steam injection. Laboratory ultrasonic velocity measurements were made on 1" plug samples of reservoir rock, over a range of temperatures, to quantify a velocity-temperature relationship. A numerical reservoir simulation predicted reservoir temperature and saturation distributions vs. time for the 5-spot being studied. The velocity-temperature relationship and these simulation distribution predictions were used to compute expected seismic velocity changes and seismic travel-time changes after 7 and 12 months of steam injection. Simulation derived velocity and travel-time changes were compared to measured travel-time changes, and the agreement was found to be good.
Use of Flowmetering Technique for Improved Drillstem Test Interpretation
Authors: Brown P. A. , Ehlig-Economides C. A.
Published: December 2007

Fluid flow rate and density at the sandface measured during drawdown in a drillstem test (DST) are key measurements that are normally unavailable using conventional techniques. Production logging flowmeters cannot be used in most cases, and the presence of wireline in the test string when the well is flowing is sometimes an undesirable complication. Furthermore, intrusive devices such as spinners have proven especially vunerable to damage by cuttings and produced sand.

This paper presents field data recorded using a prototype downhole multiphase flowmeter sensor that is particularly well-adapted to DST. This fullbore tool can be positioned below the test valve and provides continuous mass flow rate, density, pressure and temperature measurements.

Drawdown data were interpreted to yield permeability, skin and reservoir limits which were comparable to the values determined from a conventional buildup interpretation. In addition, it was possible to monitor any changes in skin while flowing the well during the cleanup period.
Interpretation of Gas Condensate Well Tests With Field Examples
Authors: Saleh A. M. , Stewart George
Published: December 2007

The total apparent skin factor in a gas condensate system contains contributions from mechanical damage and perforation, liquid drop-out and non-Darcy flow. A comprehensive theory of the skin factor in two-phase flow based on pseudo-pressure is developed. Field data from three gas condensate reservoirs have been analysed using the pseudo-pressure function. The effect of compressibility variation was accounted for by the use of pseudotime extended to two-phase conditions. The method requires knowledge of relative permeability relations and a review of these for gas condensate system is given. The determination of relative permeability from well tests is shown to be nearly impossible in practice. Conditions where the reservoir pressure is above or below the dew-point are examined. In the former case the test can be analysed in a dry gas with a composite skin. In the latter a two-phase pseudo-pressure must be used. Permeability relation are utilised in the interpretation of gas condensate well tests.
Transient Test Analysis: Solution-Gas-Drive Reservoir Examples
Authors: Chu Wei-Chun , Little T. M. , Robinson J. C.
Published: December 2007

Considerable research has been devoted to the analysis of pressure-transient data obtained from solution-gas-drive reservoirs. Several techniques from the literature are demonstrated on data acquired from two wells in the Sand Dunes Field. Comparison and discussion of the resulting analyses are provided to aid the practicing engineer in selecting the appropriate evaluation method. Techniques evaluated for determination of flow capacity include pseudopressure, pressure-squared, modified MDH, direct calculation from derivative data, and type-curve analysis. Recent developments that enhance the quality of pressure-transient analysis, including the integral pressure, normalized integral pressure and changing wellbore-storage model, are also applied. Additionally, determination of drainage area from pressure-derivative data is demonstrated.