bluuebunny/crossref_metadata_2025 huggingface dataset:
Transient Pressure Behavior for Horizontal Wells in Naturally Fractured Reservoir
Authors: de Carvalho R. S. , Rosa A. J.
Published: December 2007

This paper presents a mathematical model to describe the pressure behavior for infinite conductivity horizontal wells in naturally fractured formations. A double-porosity medium with pseudo-steady state interporosity flow is considered.

The general method of extending solutions for homogeneous reservoirs to double-porosity models is used. Wellbore storage and skin effects are included by applying the Laplace transformation to the superposition equation. This is also a general and simple method.

Methods of well testing analysis are examined, such as conventional and type-curve matching techniques.
A Reservoir Engineering Study of the Margham Field, Dubai, U.A.E.
Authors: Ernster G. A. , Boiling J. D. , Goecke C. R. , Seader R. A.
Published: December 2007

A reservoir study of the Margham field in Dubai, United Arab Emirates was performed. The main objectives of the study were to combine and evaluate all current production and geologic data to better understand historic reservoir performance and develop reservoir management plans for future field depletion and development. To realize this objective a number of simulation tools were developed to help better understand the condensate recovery mechanisms occurring at Margham. This paper concentrates on the development and application of a full-field computer model of the Margham reservoir.

Due to the complexity of the Margham reservoir special procedures were required to describe the reservoir geology, represent the field's structure, and model gas condensate phase behavior. A successful match of two and one half years of pressure and production data was achieved using a single porosity simulator. Preliminary results from a strip model indicated the dual porosity mechanism to be inappropriate. However specific areas with extensive, sometimes unmapped faults appear to behave in a manner similar to a dual porosity system. These small areas were adequately modeled with the single porosity model by implementing pore volume reductions to represent areas of low sweep efficiency. An aquifer was included in the reservoir description in order to match the field pressure history. Predictions of future field performance emphasized increasing condensate recovery by optimizing current field operations, understanding the benefits of continued gas cycling versus immediate full or partial release of produced gas, and the need for additional infill wells. This paper includes a comparison of actual performance versus the model predicted response during the year following the completion of the study.
Improved Volumetrics with the Computer: Hugoton Gas Field, Kansas
Authors: Swanson Donald C. , Giovinco Sam
Published: December 2007

Mesa Limited Partnership (Mesa) recently completed volumetric analyses of its Hugoton Field gas reservoirs. Assistance was provided by Swanson Geological Services, consultants, who used computer technology to determine total hydrocarbon pore volume.

The Hugoton Field has for years produced gas from multiple heterogeneous carbonate reservoirs. Present spacing does not drain the field. Volumetrics, properly calculated, should result in a more accurate and realistic determination of not only the amount of gas in place but also its original spatial distribution. Computer technology was used to eliminate errors often encountered with volumetric methods.

When reservoirs are superimposed, operators often add up the data for all units at each well, and the sums are contoured. This leads to errors. Stacked reservoirs should have their thicknesses individually distributed. Similar treatment is desirable for all contributing parameters to volumetrics.

Hydrocarbon pore volume is a product of thickness, porosity, and saturation. These parameters should be individually contoured, after which the percent hydrocarabon pore feet and total hydrocarbon pore feet can be determined by cross-contouring or computer methods. Hydrocarbon pore feet should not be calculated at wells and then contoured.

Mesa's Permian Chase Group reservoirs consist of seven separate units: Herrington, Krider, Winfield, Towanda, Florence, Fort Riley, and Wreford. Typical thicknesses vary between 15 and 35 feet and porosities and water saturation from 6 to 25 percent and 10 to 90 percent, respectively.

Mesa analyzed over 4 00 wells that had density or sonic logs. These were used for distribution of porosity and hydrocarbon saturation. About twelve hundred wells were used for thickness data.

Radian CPS software and two Compaq Deskpro 286 PC's were used for the volumetric study. Individual section polygons had been digitized and were used with the total hydrocarbon pore feet grid to calculate section by section volumes. These were then used to determine reserves.

Using accurate volumetric procedures will not necessarily result in reserve increases; however, in the case of the Mesa project, a significant gas volume increase resulted over that previously determined by well performance.
Putting Geology into Reservoir Simulations: A Three-Dimensional Modeling Approach
Authors: Johnson C. R. , Jones T. A.
Published: December 2007

Eighteen years ago Exxon initiated the development of a three-dimensional geological modeling program to automate the generation of geologic maps and cross sections from exploration data. This program is also well suited for providing a highly complex reservoir description for reservoir simulation and has become a standard operating procedure for many of Exxon's simulation projects.

Because these models are directly interfaced to the reservoir simulator, the reservoir engineer can easily utilize the complex reservoir description provided by the geologist for field development planning. In addition, the reservoir engineer can routinely and readily update his model with new data or interpretations and quickly provide consistent maps and sections for assessing results of development drilling.
Evaluation of Oil Recovery From a Thin Oil Column by a Horizontal Well in the Oseberg Gamma North Reservoir
Authors: Fantoft S. , Krogh P. K. , Pollen S.
Published: December 2007

In the Gamma North Structure a thin oil zone is sandwiched between a gas cap and an aquifer, and the oil production rates are limited by the gas and water coning. Compared to vertical wells, horizontal wells will reduce the coning tendencies and may lead to a substantial increase in the oil recovery. The orientation of the horizontal well is important forthe recovery in a structure like Gamma North, with dipping layers and high permeability anisotropy.
Field Experience with a Novel Calcium-Tolerant Fluid-Loss Additive for Drilling Muds
Authors: Plank J. P. , Hamberger J. V.
Published: December 2007

A novel sulfonated polymer used as a fluid loss additive in water base drilling fluids is introduced. Major features of this 100% synthetic polymer are temperature stability up to 400°F (200°C), salt tolerance up to saturation, hardness tolerance to 75,000 ppm calcium ions and complete neutral effect on viscosity. A remarkable thermal stabilizing effect on polysaccharide fluid loss reducers like e.g. starch, CMC, PAC, HEC, CMHEC is found. The mode of action of the novel polymer is investigated by means of SEM photos from drilling mud filter cakes.

Field experience with the novel polymer includes such fluid systems as fresh water, sea water, salt saturated, KCl/polymer, dispersed muds and solids free brines. Field data from over 20 wells in Europe and North America both on and offshore are presented and analyzed.

Field examples for the thermal stabilization effect of the novel polymer on starch are given. The novel polymer extends the thermal stability of starch from 245°F (120°C) to 295°F (145°C). More than a dozen German Zechstein. wells have been drilled with this system to depths up to 15,750 ft (4800m), BHST to 280°F (137°C) and calcium contamination up to 42,000 ppm.

Cellulose type polymers such as CMC, PAC, HEC and CMHEC were thermally stabilized by the novel polymer. A North German gas well using CMC for filtration control added the novel polymer, reduced the HPHT filtrate from 22 ml to 12 ml and cut the daily maintainance rate of CMC by half. Offshore Norway a KCl clay-free fluid with CMHEC was extended to over 320°F (160°C) by addition of the novel polymer.

The novel polymer significantly reduces the HPHT filtrates of dispersed systems. On an offshore Gulf of Mexico well the HPHT filtrate was reduced from 45 mls to 5.3 mls in a lignosulfonate sea water mud with 5.25 ppb of the novel polymer being added. A Central Texas well with a lignite fresh water mud required lime treatment to combat a heavy CO2 influx resulting in calcium contamination. The novel polymer lowered the HPHT filtrate from 35-40 to below 20 mls.

In a highly deviated Mobile Bay (USA) well a combination of the novel polymer and a lignite-phenolic resin yielded temperature stability over 500°F (260°C) and reduced the HPHT by 80%.
A Systematic Approach: The Key to Successful Core Analysis
Authors: Heaviside J. , Salt H. J.
Published: December 2007

The application of core analysis to provide data for reservoir evaluation is not a new science but has seen continued research activity over a long period. Core analysis is complex containing many stages between the reservoir and the final measurements and interpretation. To ensure the data produced is valid every step along this route must be handled with equal attention. This paper describes an integrated set of procedures for the generation of valid data for prediction of field waterflood performance.

Core samples chosen must be representative of the reservoir in all respects: lithology, petrography, permeability and porosity. Sample preparation must ensure that fluid saturations and distributions (initial water saturation, S.) and wettability are equivalent to their native state. Finally the measurements themselves must be made such that displacement is representative of the reservoir scale and is not distorted by any core scale artefacts.

The particular study described was conducted in support of reservoir engineering studies of waterflood performance in the Welton reservoir, an onshore field in thé UK. It is located in the basal Silesian sandstone of the East Midlands. The reservoir unit is an amalgam of river channel deposits with intervening shales. The work was carried out as part of an overall objective to improve the definition of reservoir properties and hence enable more accurate prediction of reservoir behaviour.

The systematic approach is described, beginning with sample selection using X-ray CT and petrography to ensure representative lithology.

This is followed by an investigation to establish representative wettability for the Welton fieldand to identify a suitable preparation method. This was then used in generation of capillary pressure data using the centrifuge technique and in waterflood experiments at realistic flow rates. Finally a numerical method is used to interpret the corefloods and obtain representative rock relative permeability data.
The Petroleum Industry and the Environment
Authors: Bloemendal J. W.
Published: December 2007

During the last few decades the Petroleum Industry has made ever increasing efforts to prevent damage to the environment in the course of all its operations. In consultation with the public, governments and other authorities, the international oil industry studies the impact of wastes on the environment and presents well balanced proposals for international legislation.

The paper reviews quantatively the various sources of pollution, and the degree of damage caused by actual con-centrations.

Referring to numerous studies the paper evaluates measured effects to distinguish between actual and apparent damage, the rate of decomposition and the differences between stagnant and flowing waters.

The preventive measures to reduce or eliminate pollution, as well as methods to remove harmful agents from effluents are listed. The effectiveness and relative economy of the various methods are discussed as a balance must be struck between protection obtained and the costs involved.

Existing and forthcoming legislation is given, with due attention to the trend for international standardization. Although the main focus is on offshore drilling and production, the onshore operations and the relative importance of pollution in exploration, transport, refining and distribution are mentioned.

The report has been written from the actual situation in The Netherlands, but where different approaches are practiced in other North Sea operations they are mentioned.
Effects Of CO2 Attack on Cement in High-Temperature Applications
Authors: Shen J. C. , Pye D. S.
Published: December 2007

Well cement carbonation by CO2 containing gas or brine can happen to CO2 flooded oil fields, gas fields and geothermal fields. Due to the Unocal's interests in these applications, especially in the high temperature geothermal wells, a field and laboratory testing program was conducted to examine the effects of CO2 gas on high temperature cement.

Wellhead cement samples from geothermal wells in the Brawley and Geysers fields were collected and analyzed for carbonation. The degree of cement carbonation was found to be dependent on factors such as, temperature, CO2 content in the fluid and location. Both the carbonated and the uncarbonated cement have developed extensive fractures and fine fissures in the matrix due to thermal cycles. The carbonated cement has an acceptable level of compressive strength, but its permeability is normally higher than desired.

Preliminary results from laboratory cement carbonation tests under simulated downhole high temperature, high pressure conditions are presented. A new analytical technique was used to measure the depth of carbonation. The CO2 diffusion coefficient in the cement solid matrix was estimated with this technique.

By comparing field, lab and published data, the carbonation mechanism in high temperature cement is found to be a function of several parameters, i.e., temperature, CO2 content in the fluid and cement additives.
A New Approach to the Prediction of Gas Flow After Cementing
Authors: Rae P. , Wilkins D. , Free D.
Published: December 2007

Gas migration after cementing is a well-known and costly problem and one which is extremely difficult to prevent. Its causes are fairly well understood and several commercial techniques are offered today to prevent it, with varying degrees of success. Despite this understanding of the phenomenon, few attempts has been made to examine the parameters which may be relevant to it and, thereby, try to predict the probability of gas migration for a given well. Evaluating this risk, on a well-by-well basis, would allow the engineer to match his job design to this risk level.

In this paper, we describe a new approach to the prediction of post-placement gas flow. Our method is based on the identification of four key factors which are considered fundamental to the occurrence of gas migration. By using these four factors, we attempt to quantify the contributions made by the formation and annular configuration, the fluid hydrostatics, mud removal, and slurry performance, respec-tively. The factors consider such well parameters as reservoir productive capacity, annular geometry, pore pressure, hydrostatic head, mud removal efficiency, cement hydration kinetics and fluid loss.

Analysis of field data from a wide variety of gas wells in the United States, Canada, Latin America, Europe, Africa, Middle East, and Far East, has allowed the calculation of semi-empirical relationships between the four factors. The wide range of field conditions, through which this method has been established permits its use in most real cases. Field examples are provided.
Investigation of Natural Gas Hydrates in Various Drilling Fluids
Authors: Lai D. T. , Dzialowski A. K.
Published: December 2007

This paper presents laboratory-derived equilibrium temperature and pressure data for gas hydrates in drilling fluids. Data are included for lime, sea-water gyp, polymer and dispersed muds with varying salt concentrations, as well as several experimental fluids. Equilibrium curves to determine salt requirements in deep-water drilling muds also are included.
Land Drilling Contractor: Can We Afford To Survive?
Authors: Loy S. E. , Johnson G. P.
Published: December 2007

The U.S. land drilling contractor is in a serious financial condition. A continuous surplus of rigs and services over the past 8 years has threatened his economical survival. Capital replacements, particularly drill strings, must somehow be financed. The capital needs and a method of financing is discussed.

The economic dilemma of the drilling contractor has caused an attrition of experienced personnel. As a result, the drilling contractor must seize the opportunity to move his organization from one that is industry-based to one that is information-based to provide quality services and minimize both labor and G&A requirements.
Economics of the U.S. Onshore Contract Drilling Industry
Authors: Holm D. W.
Published: December 2007

The principle purpose of this paper is to evaluate the pricing procedures of the onshore contract drilling industry and the resulting effect on contractor practices.

This evaluation includes an example, with discussion, of the cost factors included in the rates used by drilling contractors who desire to exercise prudent operating and management practices.

The paper discusses the areas of prudent operating practices that are currently being neglected, as well as management deficiencies which are prevalent, and how these factors are contributing to the drilling industry's problems.

Probable reasons for these actions by drilling contractor management and/or their financial supporters are reviewed to provide additional insight.

The paper concludes with the potential outcome of the current industry situation and general recommended strategies for drilling industry management, financial supporters, and operators.
An Economic View of the Drilling Industry
Authors: Strong R. E.
Published: December 2007

During the past few years there has been some confusion, outside the industry, concerning contractor profitability. A survey was undertaken during early 1988 to evaluate rig operating cost and contractor profit potential. Sufficient information was obtained from six contractors who operate over 130 rigs to develop a representative average daily bid base and operating cost. Data is presented which will show the average contractor is operating at least 20% below the break-even point at 70% utilization. Investment and utilization sensitivities are shown and how they affect the contractor's cash flow.
Semisubmersible Rig Modifications for Subsea Field Development
Authors: Hoppingarner J. B. , Bates T. R.
Published: December 2007

Subsea development is becoming commonplace in the UK sector of the North Sea. Over 50% of all fields to be developed in the next ten years on the UK Continental Shelf will be developed subsea and tied back to existing facilities or floating production facilities. In order to facilitate the development of these subsea fields a number of semisubmersibles have been converted from exploration to development mode. These rig modifications have included top drive installation, improved solids control equipment and oil base mud handling facilities, special subsea tree handling equipment, semi-permanent production test facilities and addition of saturation diving equipment.

These modifications have enhanced project economics by accelerating the drilling and completion of subsea wells. Each modification is discussed in detail.
Amendment to Louisiana Statewide Order 29-B Suggested Modifications for Barium Criteria
Authors: Deuel L. E. , Freeman B. D.
Published: December 2007

This study was conducted to address the problem of inconsistent barium (Ba) analyses and the need to de-fine an acceptable criteria level. The study provides both mechanistic and comparative data in support of suggested changes in the Amendment to Statewide Order 29-B.

Initial non-hazardous oilfield waste (NOW) studies, which served as the basis for Ba criteria, used 1979 ERA protocol for estimating total metal contents. Three published revisions have since been made by EPA concerning Test Methods for Evaluating Solid Wastes (SW-846, 1982; SW-846, 1984; and SW-846, 1986), Sample size was the principal difference reflected in the revised protocols; sample size decreasedover time.

Experiments were designed and conducted to provide a method for determining "true" total Ba for comparison to SW-846 protocol. Regression analyses comparing SW-846 Ba as the dependent variable and corresponding total Ba as the independent variable showed the data best fit a polynomial (Y = -3.29 x 10 b(X)Z + 0.43 (X) + 376) with a r2 = 86%. Multiple linear regression analyses showed SW-846 Ba levels a function of the matrix pH, salinity, oil & grease, and "true" total Ba content.

A metals fractionation by sequential chemical extrac-tion technique demonstrated that Ba remains in a solid phase (barite form), evenafter being circulated down hole and subjected to extreme heat and strongly alka-line reactions. Chemical distributions varied signi-ficantly in response to mixing NOW solids with native soil and subjecting mixtures to reducing (diminished oxygen tension) conditions. Total Ba and oxygen ten-sion (redox potential) were found to have the greatest affect on Ba activity.
Integrity and Trends in Current Drilling Contracts: Risk vs. Reward
Authors: Williams D. W. , Schaffner W. R.
Published: December 2007

The document which precedes the performance of work and governs the operator/contractor relationship from the outset is the drilling contract. It is desirable that the contract be structured in a manner commensurate with the respective role of the operator and the contractor and in a manner where the combined parties have parallel goals. Often too little emphasis is placed on the construction of a fair, equitable and comprehensive contract which will promote a positive working relationship. In many instances, work is undertaken with the operator and contractor in an adversarial mode resulting from a lack of communication during the contract negotiation. The trend in today's contracts seems to be toward the shifting of risks and away from the quality and value of the service provided.
Offshore Operators Committee Gulf of Mexico Spotting Fluid Survey
Authors: Ayers R. C. , O'Reilly J. E. , Henry L. R.
Published: December 2007

In the fall of 1986, the Offshore Operators Committee conducted a survey on spotting fluid use by member companies operating in the Gulf of Mexico. The purpose of the survey was to compare diesel and mineral oil spotting fluids for effectiveness in freeing stuck drillpipe. The survey covered the years, 1983 - 1986. Operators were asked to specify the number of wells drilled with water base mud for each year covered by the survey (1983 - 1986) and to supply certain information on each stuck pipe event where an oil base spotting fluid was used. The results showed that the success rate for freeing stuck pipe with diesel pills was 51%, while the success rate with mineral oil pills was 33%.
Rig Performance Monitoring and Measurement: Can It Again Be Useful?
Authors: Cochrane J. E.
Published: December 2007

During peak activity in onshore Arabian fields (1981-1983) workover rig performance was monitored and measured against performance targets. The results were used to significantly improve rig productivity and, when activity dramatically dropped, to aid in rig lay-down decisions.

The lessons learned during this period were valuable both to the operator and the contractors; they should again be applicable when rig activity reaches moderate levels.
Running and Handling of a Premium Connection on a Rig
Authors: Raney J. B. , Lamb J. F.
Published: December 2007

Adequate control of field running procedures for premium connections has been a dilemma for users and thread manufacturers alike. Extensive studies were undertaken to develop improved field running procedures and to investigate factors considered to be major sources of field damage. The results of this work have led Mobil to develop a unique statistical approach using shoulder torque values to control field running procedures for premium connections.

Through the utilization of statistical control charts and a torque monitoring system, Mobil, as an operator, has been able to establish a high level of confidence in the performance of a premium shouldered connection (PSC) run into the well. The power of this statistical approach is that it provides a real time decision making tool on the rig during field make-up and a method for adjusting the qualification criteria due to changes in the rig environment.

A torque monitoring system is the rig site device used to qualify connection make-ups. Other factors affecting the connection make-up are minimized by properly utilizing accessory equipment (i.e. stabbing guides, alignment yokes, single joint weight compensator and calibrated make-up tongs) and by implementing controlled make-up procedures (i.e. proper cleaning and drying of the connection, doping practices and controlled make-up speed).
What Is the Condition of Your Downhole Tools and How Are They Being Repaired?
Authors: Brinegar D. W.
Published: December 2007

Economic considerations have required many contractors and rental companies to repair and reuse downhole equipment that would have been discarded much sooner in previous years.

While the practice of striving to obtain the maximum life cycle for each piece of equipment should be encouraged, increased attention must be given to inspection and repair methods.

API Specifications detail mechanical properties and dimensions for the manufacture of new products. But the vast scope of repair of used equipment cannot always be covered by exacting procedures or specifications. Consequently, the repair and maintenance of used equipment is often left to the imagination and ingenuity of the user and/or the repair shop foreman. Successful repair may require the interpretation and blending of several specifications by competent machine shop personnel.

One of the objectives of this paper will be to review repair methods that are being used to increase the life of downhole tools. Particular attention will be paid to welding procedures.
New Developments in Short-, Medium-, and Long-Radius Lateral Drilling
Authors: Karlsson H. , Cobbley R. , Jaques G. E.
Published: December 2007

While traditional definitions classify short-, medium- and long-radius lateral wells by angle build rates, the technology now employed to achieve those build rates suggests an industry definition which characterizes lateral wells not only in terms of wellbore geometry, but in engineering terms as well.

In proposing such a definition, this paper examines new developments in downhole technology, focusing on short- and medium-radius systems to show how choice of drilling hardware can determine the type of curve drilled, as well as how it is planned and completed.

New horizontal well-planning techniques developed in light of recent hardware improvements are also discussed, while technicaf innovations still in development are noted.

Field results of recent lateral wells present examples of problem-solving, since a detailed discussion of lateral applications exceeds the scope of this paper. Concluding remarks suggest areas for further development to improve economics and performance in lateral drilling.
Enchova Blowout: Record Relief Time
Authors: Maduro W. P. , Reynolds Jim
Published: December 2007

On April 24 during workover operations on the Enchova Platform in the Campos Basin, one of the platform's 21 wells blew out and eventually ignited. Relying on state-of-the-art technology, Petrobras drilled two relief wells in 30 days time and successfully controlled the blowout.

The organization for this operation encompassed three project subteams: one on each of the two offshore semi-submersible platforms and one at the land-based control center. Each was equipped with directional software designed to facilitate rapid data analysis and determine required changes in key drilling parameters.

A steerable system incorporating measurement-while-drilling (MWD) with a slow-speed, high torque downhole motor was used throughout the entire course of both relief wells. A rate gyro and a downhole casing detection tool complemented this package. Using this combination, both relief wells safely passed through a network of 21 existing wellbores.

This article outlines the primary considerations used in organizing and managing this successful relief effort Factors in well programming are discussed in detail along with the attendent problem areas.
State-of-the-Art of In-Situ Combustion Modeling and Operations
Authors: Islam M. R. , Chakma A. , Farouq Ali S. M.
Published: December 2007

In situ combustion continue to be an important oil recovery process. The applicability of in situ combustion to wide range of reservoirs, and the recent advances, show that this process has unique advantages (as well as disadvantages). This report analyzes existing numerical models developed in recent years. Also reviewed is the state-of-the-art of in situ combustion from the point of experimental modeling and some field operations.

A comparative evaluation of existing in situ combustion numerical models helped identifying shortcomings of each model and detect missing links. This helped in developing new ideals and draw attention to the areas which have been ignored largely in numerical simulation studies. A complete in situ combustion model description is presented and difficulties in implementing such a model are pointed out.

This paper discusses in detail various mechanisms involved in in situ combustion operations and points out shortcomings of present experimental techniques. Guidelines are provided for experiments to be conducted in order to provide data for an ideal in situ combustion simulator.
Miscible Displacement of Heavy West Sak Crude by Solvents in Slim Tube
Authors: Sharma A. K. , Patil S. L. , Kamath V. A. , Sharma G. D.
Published: December 2007

In enriched gas drives, for correct interpretation of slim tube displacement (STD) tests and for determination of minimum miscibility pressure (MMP) or minimum enrichment (ME) required to achieve dynamic miscibility, it is extremely important to identify the correct mechanism of misciblity development. Traditional, pseudo-ternary diagram construction and limiting tie-line method or the criteria of very high (90-95% plus) ultimate oil recoveries or the criteria of breakover point in ultimate oil recovery versus pressure diagram in STD tests, used to determine MMP or ME are not always valid and can lead to solvents designed either too rich or too lean.

In this study, STD tests supported by equation-of-state (EOS) predictions were used to evaluate the ability of various solvents such as CO2, n-butane and various mixtures of Prudhoe Bay natural gas (PBG) and natural gas liquids (NGL), to miscibly displace heavy, asphaltic West Sak crude. Results indicate that for enriched gas drives, the development of dynamic miscibility occurs via simultaneous vaporizing and condensing mechanisms. The solvent minimum enrichments for this dual mechanism were obtained from the solvent-oil, pressure-composition isotherms, compositional path in multicontact test (MCT) calculations and the methane spike disappearance phenomena in STD tests and were compared to those determined by condensing type, pseudo-ternary diagram construction method.

STD test results indicate that the ultimate oil recoveries, even for first contact miscible (FCM) solvent were considerably lower due to asphaltene precipitation. Asphaltene tests were conducted for various solvent-West Sak crude mixtures to determine the amount of precipitation and it's effect on oil composition.

STD results and EOS predictions indicate that CO2 was unable to develop dynamic miscibility with West Sak crude at reservoir pressure and temperature conditions and the process mechanism for CO2 drive is simultaneous vaporizing-condensing drive.
A Review of Gas Injection Projects in California
Authors: Babson E. C.
Published: December 2007

This paper summarizes reservoir and recovery data for 12 of the more important gas injection pressure maintenance projects in California. These projects were initiated during the period from 1940 to 1960 and the reservoirs are now approaching depletion.

A brief description of each project is included.
Thermal EOR in Salt Dome Structures of the Gulf Coast, Saratoga Field, Hardin County, Texas
Authors: Pebdani F. N. , Kleb M. S. , Johnson G. P.
Published: December 2007

Field tests of various thermal enhanced oil recovery processes in the thin reservoirs of the Saratoga field in southeast Texas are in progress. The primary objective is to evaluate recovery and economics for each of: dry in-situ air combustion, wet in-situ air combustion, and steamflooding, to determine the optimal process.

The Saratoga field is one of many piercement type saltdomes located along the U.S. Gulf Coast. The field contains numerous Miocene sandstone stringers, averaging 20 feet in thickness and ranging in depth from 150 to 1900 feet, from which approximately 17% of the original oil-in-place has been produced by primary methods. The reservoirs contain low to medium gravity (14-22 °API) crude, with moderate to high viscosity (100-1000 cp), which make secondary recovery by a process such as waterflooding highly unfavorable. Thermal recovery processes were initiated in this field in the early 1970's; eight fireflood projects have been completed, while four wet in-situ air combustion projects and one steamflood project are ongoing.

Evaluation of these projects will provide a basis for the application of the appropriate thermal recovery process in thin, shallow reservoirs, typical of the Gulf Coast.
Role of Foam, Non-Newtonian Flow, and Thermal Upgrading in Steam Injection
Authors: Kasraie M. , Farouq Ali S. M.
Published: December 2007

Foam formation and flow, non-Newtonian behaviour, and thermal upgrading phenomena play a role in steam injection processes, which is still not clearly understood. This investigation addresses these effects in the context of steamflooding. The results are based upon a steam injection simulator, which was modified to account for foam, non-Newtonian oil viscosity, and thermal upgrading.

Steam-foam flow was represented by means of a shear-dependent mobility, which was also a function of pressure, temperature, foam quality, and flow velocity. The relative permeability to gas was also a function of surfactant concentration. Non-Newtonian flow behaviour was implemented in the conventional manner, making the apparent viscosity of oil a function of local shear rate. Thermal upgrading was represented as a permanent decrease in oil viscosity depending on the residence time and temperature. These effects were incorporated into a three-phase, three-dimensional, fully implicit steam simulator.

It was found that a steam foam led to an increase in oil production rate, compared to steam alone. However, the increase was small, since the foam acted to increase steam viscosity, although the blocking effect was present to a small extent. The oil production behaviour in the case of a non-Newtonian oil was superior to that for a Newtonian oil, because the apparent viscosity of oil decreased in the cold part of the reservoir. Thermal upgrading, on the other hand, was less effective in increasing oil recovery, because the oil viscosity decrease due to cracking, over and above that due to temperature, was small.
The Design of a Modern Steamflood in a Thick, Dipping, Heavy Oil Reservoir
Authors: Atkinson D. S. , Clayton C. A. , Baldwin J. O. , Smith R. C.
Published: December 2007

Mobil has completed the design phase of a steamflood project in a thick, moderately dipping, unconsolidated heavy oil reservoir. The design takes advantage of the gravity drainage recovery mechanism in the thick reservoir, allowing vertical steam zone expansion with minimal steam breakthrough. This steamflood project is economic in the late 1980's period of low oil prices. The design was completed with an interdisciplinary teamwork approach using concurrent studies for expediency.

BACKGROUND

During 1987, Mobil undertook a scoping study of its U.S. heavy oil producing properties, looking for areas of high potential for the 1990's. Several successful cyclic steam operations were identified as having potential that could be exploited using modern steamflood technology. The scoping study showed that the subject project had a reserve potential on the order of tens of millions of barrels of oil. The study documented here was undertaken to better determine the potential of this project.
The Use of Insulated Tubulars in Thermal Projects
Authors: Kutzak A. R. , Gunn D. W.
Published: December 2007

Many enhanced oil recovery steam projects are underway in Canadian heavy oil properties. Various well completion designs are employed to optimize the recovery and overall economic performance of these projects. This paper discusses both economic and design considerations regarding the selection of insulated tubulars as well as operational experience in some Canadian heavy oil recovery operations.
Study of the Cyclical Performance of Berm Pump Motors
Authors: Lea J. F. , Durham M. O.
Published: December 2007

Cyclic loads, such as eccentric pumping units, cause a varying torque on the driver. Determination of the most effective induction motor for the load is addressed. Ultra high slip motors as well as NEMA design motors are evaluated. Comparison of operating costs for the same load are presented.
Elimination of Liquid Loading in Low-Productivity Gas Wells
Authors: Neves T. R. , Brimhall R. M.
Published: December 2007

Liquid buildup in the wellbore has long been recognized as being detrimental to flow from gas wells. This paper will discuss a programmed approach for analyzing liquid loading problems and for selecting the optimal artificial lift method to be used once a liquid loading problem occurs.

This paper discusses factors affecting methods to alleviate liquid loading problems and guidelines for selecting in advance the optimum method to be used when liquid loading occurs.
Foam Recompletion of High-Angle, Low-Pressure Dry Gas Wells, Offshore Louisiana
Authors: Pardo C. W. , Andrus T. S. , Bibb B. E. , Bibb S. E.
Published: December 2007

Planning and executing recompletions in low pressure reservoirs (less than 4 lbm/gal equivalent) present operators with several challenging conditions. These include the necessity to protect against formation damage and fluid loss when using low density brines and well control when using foam as the completion fluid.

Low density brines can be effectively used for workover operations in wells to be recompleted in a low pressure reservoir. However, because of the overbalanced condition that exists during workover operations, fluid loss must be controlled by spotting lost circulation pills. These pills can contribute to formation damage and can also affect the gravel placement unless they are effectively removed during the workover operation. In contrast, the formation can be more effectively protected by taking advantage of the low fluid leak-off characteristics and near-balanced pressure when a foam system of the required quality is used as the workover fluid.

A workover program using foam as the workover fluid on wells completed in a low pressure, dry gas reservoir (3.5 lbm/gal equivalent) was conducted offshore Louisiana. This program included cleaning sand from the tubing and/or casing below the packer, reperforating and gravel packing. A conventional foam system was used for cleaning the sand, and a stable foam system was used for well control. The gravel placement was accomplished with a Xanthan polymer system.

This paper will summarize the operational aspects related to the use of foam, the gravel packing operations and the production results after recompletion.
Onsite Design, Analysis, and Automation Maximizes Efficiency of Fracturing Operations
Authors: Van Domelen M. L. , Jantz E. L. , Murphy K. S.
Published: December 2007

Recent advances in onsite data acquisition and automation of field equipment have led to the development of a new fracturing treatment control center. This mobile control center combines design, monitoring, and analysis capabilities with the ability to automatically and remotely control, from within the same unit, all of the fracturing equipment on location.

By using a computer system with increased processing power, and a sophisticated data communications network, many new capabilities are provided:

All fracturing equipment on location can be monitored and/or controlled from inside the control center using a variety of operator interface screens. Set points are sent from the control center to each piece of equipment through a single communications line. More than 1200 measured and/or calculated job parameters, ranging from blender suction pressure to fracture geometry predictions, can be displayed on color monitors during the job. All data are stored internally and can be accessed at any time. Commonly used mainframe computer programs have been downloaded into the control center and can be executed in a background environment. This provides for analysis, design and, if necessary, redesign capabilities while the job is in progress.

This paper describes the system and presents field case histories to illustrate the practical use of the increased computing power and automatic and remote controls now available to help improve the efficiency of the fracturing treatment.
Pressure Buildup Behavior of Partially Completed Wells in Layered Reservoirs
Authors: Olarewaju J. , Lee W. J.
Published: December 2007

This paper presents a study of pressure buildup behavior of partially completed wells intercepting layered reservoirs. We present correlations for estimating skin due to partial penetration for homogeneous and layered systems with contrasting layer permeabilities. We demonstrate the correct procedure for analyzing buildup tests from partially completed wells using conventional type curve analysis methods.

Using an automatic history matching approach, we present a field example application of the analytical model and the developed correlations.
Granular Diverting Agents Selection, Design, and Performance
Authors: Nitters G. , Davies D. R.
Published: December 2007

One of the main problems in chemical treatments concerns the proper placement of the treatment fluids. Specifically, a very distorted inflow pattern may result after stimulation by matrix acidising treatments carried out without a means to distribute the injected fluids over the entire zone to be produced.

A theoretical and experimental study is reported aimed at developing a better understanding of the diversion process. This has resulted in practical guidelines for the application of chemical diverters in general and, in particular, for the use of benzoic acid and its derivatives.

The results of the current study also indicated some areas of uncertainties requiring further investigation.

It is concluded that benzoic acid can successfully be applied in matrix acid treatments in water injectors and gas wells.
Relating Water Quality and Formation Permeability to Loss of Injectivity
Authors: Pautz J. F. , Crocker M. E. , Walton C. G.
Published: December 2007

Water quality is an important consideration in the design of a cost-effective reservoir maintenance or secondary oil recovery project. Proper filtration equipment selection often is not based on scientific facts since knowledge of the formation may be unavailable. Rules-of-thumb that relate size of particulate in injection water to potential permeability reduction have been developed and are used for selection of proper filtration equipment. However, laboratory procedures have not been rigorously applied to the 1/3 and 1/7 rules-of-thumb currently being used to specify water filtration equipment design.

This evaluation of the 1/3 and 1/7 rules-of-thumb used three different core types: Berea sandstone, Cottage Grove sandstone, and a synthetic core. The results showed that rules-of-thumb based on permeability and contaminant particle size are useful in selecting filtration equipment. Results indicated that loss of permeability (core damage) during coreflooding was more severe than expected when the 1/3 rule-of-thumb was used, but not severe enough to consider application of the more stringent 1/7 rule-of-thumb. These two competing rules appear to bracket a reasonable range for water quality.

A model used to relate the amount of oil production to loss of injectivity confirmed these results by indicating reasonable oil production using the 1/3 rule-of-thumb with slightly improved production using the 1/7 rule-of-thumb.
An Investigation Into Practical Removal of Downhole Paraffin by Thermal Methods and Chemical Solvents
Authors: Straub T. J. , Autry S. W. , King G. E.
Published: December 2007

One of the most recurrent problem in the oilfield is the removal of paraffin deposited on downhole equipment and near-wellbore. Several field experiments were conducted to evaluate the effect of hot oiling for either the removal or redeposition of paraffin downhole. Laboratory work is presented that suggests the use of hot solvents has the greatest potential benefit. Means of conventional field application are limited, and nonconventional means are discussed.
Prediction of Downhole Temperatures Can Be Key for Optimal Wellbore Design
Authors: Mitchell R. F. , Wedelich III H. F.
Published: December 2007

This paper describes an advanced method to predict downhole temperatures during operations. Examples are presented that represent actual field cases and demonstrate the advantages of using the advanced method compared to conventional methods of estimating downhole temperatures.

Two specific field cases are investigated in detail: Tubing movement during stimulation and well deliverability. In the stimulation case, comparison of the conventional and advanced methods indicates that 35% fewer packer seals are needed in the specific well studied, and the thermal loads magnify the casing stresses by 25-35%. The well deliverability predictions show that a smaller tubing size increases gas production for a constant surface pressure.

The paper also presents the key engineering and computing features needed to aid engineers in evaluating and interpreting results predicted with the advanced method. Key variables are identified for the different applications. With the model, variables can be controlled to optimize performance of well components and well operations.
The Valuation of Oil Reserves
Authors: Adelman M. A. , Koehn M. F. , de Silva H.
Published: December 2007

The decision to make investments in oil or gas reserves is determined by the relationship between the value of a barrel in-ground and the cost of creating a new one. Wide disparities between these two values will result in investment or disinvestment until the in ground value is equal to the cost of replacement.

Over the past few years there have been several mergers and acquisitions in the domestic oil and gas industry. Some of these mergers have include the purchase of large quantities of proven reserves at prices that were deemed to be low in relation to the development cost of the reserves. This is evidenced in the oft-repeated saying that "it is cheaper to buy oil on Wall Street than by drilling". If so, the price of the asset oil in the ground is much less than its cost. It is difficult to see why sellers insist on giving away assets, year after year. The implication is that the capital market is inefficient, a proposition worth testing. In this paper we examine the market value of reserves to test this proposition.