bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk Assessment in Project Financing
Authors: Campbell J. M. , Hubbard R. A.
Published: December 2007

Project financing has grown in popularity and monetary volume over the last five years, partly because of the budget cut backs in major oil companies, and partly because of the attractive terms offered by the, lending institutions. Many companies mistakenly view project financing as a lower cost source of funds, making previously marginal prospects justifiable using standard evaluation procedures. The costs and risks to the borrower are illustrated in this paper, and shown to be much larger than typically incorporated into most evaluations. A methodology is developed and illustrated to incorporate cost/risk consequences into the project financing decision.
Performance Analysis and Field Testing of a Compact Dual-Piston, Hydraulic Sucker Rod Pumping Unit
Authors: Evans R. D. , Weaver P.
Published: December 2007

An analysis and evaluation of a new conpact dual acting piston hydraulic sucker rod pumping unit is presented. The hydraulic unit offers some unique advantages over that of a conventional rotary beam unit. In particular stroke length and speed are readily changed by simple adjustments made to the hydraulics. For deep wells larger hydraulic piston cylinders are interchangable without having to replace the entire unit in order to meet pumping requirements. Performance data is presented which compares the hydraulic unit against selected conventional rotary beam pumping units. The performance analysis is based upon an optimum sucker rod design for a beam unit as a function of producing depth.

Comparison of the hydraulic unit against conventional beam pumping units are made for the following cases; (1) a 72 inch stroke hydraulic unit operating at a constant pumping speed versus API 80 and API 114 beam units, (b) a 96 inch stroke hydraulic unit operating at constant pumping speed versus API 114 and API 160 beam units, (c) a 144 inch stroke hydraulic unit operating at a constant pumping speed versus API 228 and API 320 beam units. In each of these cases the beam pumping units were assumed to be operating at optimum pumping speeds for a given pump setting depth.

To asist in the performance evaluation of the hydraulic unit versus that of a conventional beam pumping unit a 72 inch stroke hydraulic unit was installed in a well of depth 3800 feet located in Payne County, Oklahoma and operated for a period of 14 months. During this time numerous accoustical well sounding and dynamometer tests were performed on this unit as a means of monitoring its performance. Simultaneously, an offset well with identical downhole lifting equipment producing from the same depth and equipped with an API 114 beam pumping unit was monitored with the same test equipment. Field dynagraph cards and their analysis are presented which provided a quantative comparison of the hydraulic unit versus the beam unit.

From the performance analysis and the actual field tests of the dynamometer and acoustical well sounding information the results obtained verify that the hydraulic unit is superior to that of a conventional beam pumping unit over a wide range of operating conditions. In particular, the hydraulic unit will normally operates at lower rod stresses and at the same-time move more fluid since the pumping efficiency of the hydraulic unit exceeds that of the beam pumping unit. This fact is verified by the near ideal dynagraph obtained for the hydraulic unit.

Other advantages of the hydraulic unit including economic considerations are discussed as well as potential applications where the hydraulic unit will offer distinct advantages over its beam counterpart.
Log-Derived Evaluation of Gas-Bearing Cherokee, Red Fork, and Morrow Formations, Custer County, OK
Authors: Busch E. A. , Sobkowich K. N. , Neill B. E. , Sinha A. K. , Fertl W. H.
Published: December 2007

Medium to low porosity and rather tight Cherokee, Red Fork and Morrow sands, located in Oklahoma, contain significant hydrocarbon resources.

To evaluate the commercial importance of wells drilled in Custer County, Oklahoma, an innovative digital shaly sand analysis approach (CLASS® – Epilog®) has been applied, which provides information on total and effective reservoir porosity, total and effective fluid distribution based on the Waxman-Smits equation, shaliness, clay typing, and reservoir productivity.

Several field case examples are presented and discussed based on (1) open hole logging suite, consisting of induction, compensated density/neutron and SpectralogSM, (2) CLASS® analysis, (3) well completion and stimulation data, and (4) the resulting production test results.
Use of Capillary Pressure Curves for Analysis of Production Well Formation Damage
Authors: Donaldson E. C.
Published: December 2007

Capillary pressure phenomena in the vicinity of the wellbore govern the rates of production of oil and water because the relative fluid saturations are functions of the capillary pressure existing between the fluid phases. Assuming that water is the wetting phase in contact with the porous system, which is generally true of fields that have been waterflooded, the imbibition capillary pressure curve applies since the water saturation at the well is gradually increasing. With water wetting the solid, the capillary pressure of the aqueous phase must be continuous within the porous system and into the well. Capillary pressure does not exist (is zero) at the exit face with the rock (the wellbore), therefore water cannot flow into the well until a condition of zero capillary pressure is obtained within the formation in the vicinity of the well. Hence, a newly drilled well initially produces only oil until the capillary pressure reduces to zero. Water is then produced in greater and greater quantities as the water saturation moves from the point of zero capillary pressure toward a residual oil saturation by imbibition. When imbibition ceases the imbibition capillary pressure curve becomes negative requiring input of greater energy for simultaneous production of oil and water, until finally the imbibition curve approaches a negatively infinite value and all production of oil stops as the residual oil saturation is attained.

The pore size distribution of the rock governs the capillary pressure behavior. A decrease of the pore size distribution produces a higher residual oil saturation and results in a decrease of the oil production rate that may be as much as 2–5 times less.

Factors adversely changing the pore size distribution, and hence the capillary pressure, at the production well are migration of fines, precipitation of crude oil components (paraffins and asphaltenes), and campaction of the sand due to pressure draw-down.

These aspects of adverse capillary phenomena at the wellbore are analyzed by capillary pressure measurements of cores having large and small pore sizes and by comparison to results with cores which are partially plugged with fines, bacteria, etc. The pore size distributions and capillary pressure are measured before and after plugging.
Liquid Extraction From Produced Gas on Small Oil Leases
Authors: Skinner D. R.
Published: December 2007

"Micro" gas plants, small, refrigerated, liquid extraction plants that are capable of removing hydrocarbon liquids from small gas production streams normally associated with oil production operations are described and the processes involved are discussed. Operation and maintenance of these small units are described. Two examples are presented to illustrate application of the small units. Although not all lease operations can benefit from these units, small liquid extraction units can recover substantial volumes of propane, butane, and natural gasoline (often called liquifiable natural gases or LNG) from produced gas streams on many small oil leases.
Reservoir Geology of Some Tight Clinton Sandstones, Eastern Ohio
Authors: Knutson C. F. , Ammer J. R. , Yost A. B.
Published: December 2007

In an effort to better understand the geologic and engineering factors that explain the production performance of the tight Clinton sandstone of Eastern Ohio, logs, completion data, and production performance records were evaluated for a number of Clinton sandstone wells in east central Ohio.

The wells were divided into low slope (linear) and high slope (radial) groups based on plots of log cumulative production versus log time. The distributions of expected recoveries from these two groups of wells were compared using the chi square and Pearson's P-M correlations, and were found to be significantly different. The linear wells had a median expected ultimate production of less than 20 MMcf (5.7 × 105 m3) while the radial group had a median of more than 50 MMcf (1.4 × 106 m3). Some of the wells tended to be located in contiguous trend areas. The distance to the drainage boundary was also calculated for the linear and radial wells. The median length for the linear wells is about 500 feet (150 m) while the median radius for the radial wells is about 2,000 feet (600 m).

The intent of this paper is to provide industry with a methodology that can be used to calculate reservoir parameters, such as size and geometry, which are important in designing stimulations and in estimating reserves.
Fracturing Without Proppant
Authors: Harper T. R. , Hagan J. T. , Martins J. P.
Published: December 2007

The results of fracture stimulation treatments implemented with and without propping agents in two reservoirs in England are compared. The effect upon the conductivity of proppant-free fractures of a minor departure of the wellbore axis from a principal stress plane is assessed.
Pressure Decline Analysis With the Christianovich and Zheltov and Penny-Shaped Geometry Model of Fracturing
Authors: Lee W. S.
Published: December 2007

In 1979, Nolte1 pioneered an analysis of pressure decline after fracturing to gain information on fluid loss characteristics, fracture dimensions, fluid efficiency and fracture closure time. Since then, this method has received ever increasing attention in the petroleum industry. In the Nolte method, a fracturing job of short duration is performed on a formation, and pressure decline data are collected after shut-in before attempting a large-scale treatment. The information gained from the pressure decline analysis is utilized to design large-scale treatments to help achievebetter performance. This treatment of short duration is conventionally called a 'MINI-FRAC' job. This analysis by Nolte was initially limited to the Perkins and Kern model for fracture geometry. In Nolte's original work, two type curves were developed for analysis, one being used for treatments in which fluid efficiencies are low and the other for treatments in which fluid efficiencies are high.

In the present paper, Nolte's analysis has been extended to two other standard models, i.e. Christianovich-Zheltov and the Penny or radial model. An additional type curve has been developed which can be used for all three models. This type curve should replace one of the Nolte type curves used for high fluid efficiency.

The results of this analysis indicate that for minifrac treatments of short duration, it is advisable to first run a penny model analysis and compare results obtained from the Christianovich-Zheltov model and Perkins and Kern model because at earlier stages of growth the fracture may be penny-shaped. This model also indicates that Christianovich-Zheltov model is less sensitive to the estimate of gross fracture height than the Perkins and Kern model. The estimate of gross fracture height is rather difficult.
Single-Stage, Multiple-Zone Stimulation: An Effective Method of Stimulating the Niobrara Formation
Authors: Eason C. R.
Published: December 2007

Recently developed fluid technology incorporated with a limited entry perforation design has proved to be an effective alternative in stimulating low-yield secondary reservoirs. Three benches within the Niobrara Formation have been identified as a secondary source of hydrocarbons in existing wells. Through a comprehensive study on core extracted from the Niobrara Formation, a precisely engineered technique of simultaneously stimulating the complete three zones or a combination of these three zones has been successfully implemented.

Further extrapolations from original design work include stimulation of the complete Niobrara and Codell Formations. Early evidence has suggested a design success. Evaluation of this most recent treatment is still in a data-acquiring mode. If proved valid, implications are suggesting a greater reduction in costs of stimulating these secondary reservoirs.

Presented within the following paper are associated problems of fluids and formation characteristics of the Niobrara Formation. Also included are production data for before and after the treatment. A representative job-design discussion of Niobrara and Niobrara-Codell Formations is outlined.
Prediction of Vertical Hydraulic Fracture Migration Using Compressional and Shear Wave Slowness
Authors: Newberry B. M. , Nelson R. F. , Ahmed U.
Published: December 2007

Documented field results of vertical hydraulic fracturing suggest that quite often the created fracture migrates vertically away from the formation of interest (the hydrocarbon-bearing zone), thereby producing undesirable results. The single set of information needed to help answer questions concerning fracture migration consists primarily of in-situ stress, tensile strength, and elastic constants of the rock material in and around the formation of interest.

This paper describes the use of full waveform data from a sonic wireline tool to determine the relative stress distribution and the resultant induced hydraulic fracture height. Compressional and shear wave slowness, derived from the sonic waveforms, are used to calculate the dynamic elastic rock properties. A transversely isotropic model is used to compute the in-situ stress from the elastic properties. Advantages of the use of wireline measured data are discussed, as are the limitations of the technique. Final evaluation of the technique is shown through the comparison of predicted and poststimulation measured vertical fracture height. Two field cases are presented to illustrate the technique.
Perforation Stability in Low-Permeability Gas Reservoirs
Authors: Chenevert M. E. , Thompson T. W.
Published: December 2007

A perforation into the side of a borehole sets up a very high stress environment which may lead to rock collapse around the perforations. This study shows that a formation which has a low permeability, and is abnormally pressured, should be permeability, and is abnormally pressured, should be produced with a very limited drawdown so as to prevent produced with a very limited drawdown so as to prevent perforation collapse. perforation collapse.
Proppant Settling in Non-Newtonian Fracturing Fluids
Authors: Roodhart L. P.
Published: December 2007

Experimental results of the settling of spherical particles in flowing non-Newtonian fracturing fluids show that Stokes Law based on 'Power Law' viscosities is insufficient to predict particle fall rates in both flowing and quiescent fluids.

In a stagnant fluid the experimental settling velocities are more than an order of magnitude higher than those calculated, while in a flowing fluid, settling is lower than that calculated. These phenomena can be explained by extending the 'Power Law' model with a zero shear viscosity and by assuming an anisotropic viscosity in a flowing fluid.

Anisotropy in the viscosity only becomes important above shear rates of, say, 25 s-1, and so will not play a role in the majority of fracturing treatments where average shear rates in the fracture will be below this value.
Modern Maintenance Management in Mobil Producing Nigeria
Authors: Ogunlade O. A. , Peters Klaus E.
Published: December 2007

This paper describes the process of reorganizing the maintenance function in a remote offshore oil producing operation from a breakdown repair system to a planned, structured system based on Planned Maintenance. Highlighted are the creation and operation of a maintenance planning department and the role of warehouse operation in a remote area. The function of data processing is discussed and an outlook towards future industry trends in respect to personal computers is given.
Appraisal of Steamflood Models
Authors: Abou-Kassem J. H. , Farouq Ali S. M.
Published: December 2007

Eleven numerical steamflood models, developed by various investigators over 1969-1982, are analyzed for this evaluation. These models are sometimes similar in certain aspects and different in others. A comparative evaluation of existing numerical steamflood models contributes greatly to the state of the art, and helps in developing new ideals and detecting missing links that may not be realized otherwise.

This paper presents a general steamflood model. The assumptions and derivation of equations of various steamflood models are presented. Similarities and differences between models in the areas of mathematical models, treatment of nonlinearities, formulation methods, and methods of solution used are presented and discussed in detail.
The use of Reservoir Engineering in the Development of the Magnus Oil Reservoir
Authors: Atkinson J P
Published: December 2007

The Magnus Field was discovered in 1974. Data sets from thirteen wells were used in extensive reservoir engineering studies to delineate the reservoir and formulate a development plan. Close examination of data from pressure build up tests, wireline logs, formation pressure sampling tools, and analyses of sampled fluids revealed variations in rock and fluid properties which could have indicated the presence of reservoir discontinuities and hence introduced uncertainty in the production forecasts. The fluids in the Magnus reservoir were initially at a much higher pressure than would be calculated due to hydrostatic gradient. This indicated that the oil accumulation could be isolated from surrounding aquifers and that water injection would be essential during production in order to maintain reservoir pressure and to sustain oil production rates. Test results on wells 211/12-2 and 211/12a-9 indicated that the permeability in the aquifer zone underlying the Magnus oil was an order of magnitude lower than that in the oil zone. Following examination of core material it was decided that direct injection of water into the aquifer zone was not practicable and that injection into the oil and residual oil zones would be necessary.

Seven of the Magnus wells, drilled from semi-submersibles, were suspended and subsequently tied back to the platform to give early oil production before production wells, drilled from the platform, became available.

This paper outlines the field data available prior to the start of production, and shows how reservoir engineering studies have used the early production history data to resolve uncertainties in the conceptual reservoir model and to optimise the future development well locations in order to maximise data acquisition, oil recovery and oil production potential.
Probabilistic Hydrocarbon Reserves Estimation: A Novel Monte Carlo Approach
Authors: Behrenbruch P , Turner G J , Backhouse A R
Published: December 2007

Probabilistic reserves estimating using a generalised Monte Carlo approach has many advantages over simpler deterministic or other probabilistic methods. The particular method described deals more thoroughly with geologic structural dependency and at the same time allows for a high degree of accuracy. Data preparation is kept to a minimum, allowing seismic and other basic data to be used directly in calculations without the need of preparing time consuming area-depth graphs used in more conventional methods. A further advantage is the elimination of certain arbitrary decisions related to extreme structural scenarios based on geological mapping of a very limited number of possible situations. Sensitivities related to uncertainties and errors are handled in an easy m anner.

The approach related to gross rock volume calculations is different from more conventional probabilistic reserves simulations in that it involves the direct manipulation of all surfaces bounding the most likely rock volume. Such uncertainty, described by statistical distributions (e.g. seismic velocity error) and functional relationships, involves geological horizons bounding individual sands (reservoirs), structural surfaces such as unconformities and faults, and fluid contacts.
Drill Vessels Float in Aerated Water
Authors: Hammett D S
Published: December 2007

Model tests, calculations, and case studies prove that a floating vessel will not sink due to gas reducing the water density in or adjacent to a subsea blowout. Several floating drill vessels have been lost as a result of subsea blowouts. Reports have circulated that the rig sank into something similar to a hole in the ocean caused by gas bubbles suspended in the water reducing its specific gravity. These erroneous reports, believed as truth by many people, have resulted in the modification of operations resulting in decreased safety.

Several subsea well control operations have caused accidents and losses because the riser was not disconnected. This action was taken in fear of sinking in aerated water. The losses occurred because the vessel winched itself off the drill site to get away from the subsea well before disconnecting. Due to the high riser/BOP angle, the riser could not be disconnected and well control was later lost and the gas/oil flowed directly to the rig floor where massive fire/explosion damage occurred.

If there had been a better understanding of water density, the rig personnel could have closed all hatches, shut-down all engines, disconnected the riser and released mooring lines at one end of the rig, and safely removed the rig out of the aerated water.

This paper presents some of the technical data and references available which prove that a floating vessel will not sink due to loss of water density.

Also presented in this paper is a concept which intentionally subjects a floating vessel to aerated water, to divert and control subsea blowouts. Several blowouts have occurred which have resulted in oil and/or gas flowing from a subsea well or BOP. When oil flows to the surface pollution occurs and it is impossible to control or collect pollution on the ocean surface. The concept reported in this paper diverts the subsea well pollutant flow to a collection vessel before the flow reaches the surface. A funnel with riser suspended from a barge is positioned over the subsea well. The well flow, which contains gas, lightens the fluid column inside the riser and the well fluids flow up through the riser to the collection barge. Once the well flow is diverted, a method of entering and stopping the well flow from the well bore is available via the funnel and riser. This complete system, the model tests, the field application, and the future use of the diverting and controlling procedures are reported in this paper.
Reliability Analysis of Alternative Gas Well Safety Valve Completions
Authors: Wilson P M , Okeke S O
Published: December 2007

Using conventional reliability analysis techniques, a gas well completion was examined to determine the best subsurface safety valve installation for maximum well safety. Consideration was given to a well's production, wireline and workover activity, and use was made of reliability data based upon 3600 gaswell years of experience in the Netherlands and a worldwide survey of offshore blowouts.

A deep set (packer depth), surface controlled subsurface safety valve completion was found to be the most reliable completion, whilst wireline activity posed the dominant risk in well safety.
Development of a Deepset Electric Solenoid Subsurface Safety Valve System
Authors: Gresham J S , Turcich T A
Published: December 2007

This paper reviews the project to develop a wireline retrievable, surface controlled, subsurface safety valve system capable of being set at great depth.

Following alternative system reviews, four valves were selected for further evaluation and possible development. Only one of them, the electric solenoid safety valve system, has been fully developed and field proven.

In addition to the development of the electric solenoid safety valve and its respective nipple, the special cable that was developed for the system, the high pressure wellhead pack-off arrangement for cable passage through the wellhead and the electric safety valve control system are discussed.

The field experience with this safety valve, in two gas well completions, the wider application in Shell's operations and possible future developments are described.
Development of Downhole Equipment for Beatrice Electrical Submersible Pump (ESP) Wells 1981 – 1985
Authors: Brown J K , Bills D
Published: December 2007

SYNOPSIS

The Beatrice Field in the North Sea relies exclusively for production on artificial lift, using electrical submersible pumps (ESP's).

Beatrice came on stream during September, 1981 from 3 wells on the ‘A’ platform. ‘B' and ‘C' platforms were completed during 1984/1985 and there are now 22 production wells, each with an ESP and 12 water injection wells for pressure maintenance.

The ESP installation performance on Beatrice has progressively improved in the pumping of mono-phasic fluids. Average pump life (excluding non-start failures, which are counted at completion installation failures) over the operating period has steadily increased and for the last year has been running at approximately 10 months. Average installation and retrieval times for equipment have steadily decreased. Both improvements can be largely attributed to equipment developments that have taken place in the UK. The principal developments described in this paper are:- –Electrical developments for downhole power trasmission systems–Connectorless packer penetrations–Metal cable protectors–wireline adaptors
High Pressure Flexible Pipes for Marginal Oilfield Development
Authors: Griffiths A. D.
Published: December 2007

The major fields in the North Sea are currently in production and the average size of prospective development fields will decrease with time. The smaller or ‘marginal’ field development technology will represent a major factor in the future of oil and gas development in the North West European Continental Shelf area. Worldwide the number of exploitable marginal discoveries to date is believed to exceed 800. In the North West European Continental Shelf it is forecast by Hoare Govett that more than 45 marginal developments will be underway before 1990 in this area. These will be chosen from a known potential of 200 discoveries.
Formation Evaluation Using EWR Logs
Authors: Coope D. F. , Yearsley E. N.
Published: December 2007

In the first few years of using logs measured while drilling (MWD), experience has revealed unexpected benefits for reservoir evaluation. MWD formation logs can deliver high quality measurements, often made before significant invasion or before the borehole has enlarged. The MWD induction resistivity log, the EWR*, is used to define reservoirs and accurately determine true formation resistivity. In fact, these measurements are often more accurate than conventional open hole wireline logs, as is proven with field examples. MWD users are combining "while drilling" logs with "after drilling" logs to observe hydrocarbon movement, or non-movement.

We discuss briefly the operating principles and characteristics of the EWR. Examples are shown which demonstrate the salient features of the logs. In particular, its thin bed resolution and good depth of investigation are obvious when compared with the conventional Deep Induction log. Field data will demonstrate the application of MWD logs for complementing or supplementing wireline logs, water saturation calculations, thin bed evaluation, and indication of hydrocarbon movement.
Improve Drilling Results Using a Real-Time Data Center
Authors: Guidry T. F. , Scego J. F.
Published: December 2007

An operator has expanded the capacity and capability of an existing real time drilling data center to produce a drilling information system that provides a variety of services to all domestic affiliates. This system serves to unite field, enigneering, management, and technical support personnel into a drilling team by integrating real-time data and applications programs on a dedicated system to which all parties have continuous access.

The system provides for well surveillance, well management information, and engineering application programs.

A drilling team can choose to use one or all of the services including engineering application programs, morning reporting and/or real-time drilling data on terminals located in the field or office, or on portable dial-up terminals. A brief discussion of data center operations, including field data input, communications, data processing and surveillance, is presented.

Several examples of actual field applications demonstrate various aspects of the system's utility.

A brief dicussion of future developments is offered for completeness.
Marine Safety on Mobile Offshore Drilling Units
Authors: Cole M. W. , Marucci T. F. , Taft D. G.
Published: December 2007

Several years ago, Exxon instituted a survey of contracted mobile offshore drilling units to evaluate structural integrity and readiness to properly respond to marine emergencies that might arise offshore. Results showed structural integrity and marine readiness varied from rig to rig and prompted Exxon to implement an ongoing and more rigorous Marine Safety program throughout its offshore operations.

This paper will briefly describe results of Exxon rig inspections and Exxon's on-going Marine Safety program. Work in progress by the American Petroleum Institute (API) and the International Association of Drilling Contractors (IADC) to promote industry-wide upgrading of the mobile drilling fleet will also be highlighted.
Computer-Aided Well Test Analysis
Authors: Gringarten A. C.
Published: December 2007

The paper discusses the use of computers for the analysis of well tests. A survey of available technical and commercial publications indicates that computer usage to-date has generally been limited to reproducing manual interpretation processes or to performing parameter estimation based on some fit of observed data with a preselected interpretation model. In other words, computers have mainly been used to solve the easiest part of the interpretation process. The most difficult parts, namely, the identification of the applicable interpretation model and the validation of the analysis, have received little attention. As a result, computers still do not help the practicing engineer to do better interpretations; they only help him to do his usual interpretations faster.

Theoretically, identification of the interpretation model applicable to the test data is an artificial intelligence problem, requiring an expert system which is not available to-date. Yet, as discussed in the paper, it is possible to combine a systematic methodology with the use of interactive graphics to enhance considerably the interpretation capability of an average interpreter.
Use of Crosslinked Xanthan Gels in Actual Profile Modification Field Projects
Authors: Avery M. R. , Burkholder L. A. , Gruenenfelder M. A.
Published: December 2007

Most fields around the world suffer from formation heterogeneities that significantly reduce the sweep efficiency of waterfloods. For over five years xanthan gum/trivalent chrome gels have been used successfully in North American oil fields to improve injection well flow profiles. The process involves selectively placing the complexed biopolymer into water thief zones which, after it has developed gel strength, diverts subsequent water flow to underswept oil bearing zones. This paper discusses the general theories behind this technology, the features and benefits of the xanthan /Cr(III) gels, and actual field results.
Hydrocarbon Solvents: An Alternative to Acid for Removing Some Formation Damage
Authors: King G. E. , Holman G. B.
Published: December 2007

Hydrocarbon solvents such as xylene, toluene, and alcohols are being used with acid and sometimes instead of acid to treat some types of formation damage. In addition to the familiar roles of removing paraffin and tar, the solvents can be used successfully to remove oil-based mud damage, sludges, oil wetting problems and many emulsions. The solvents may also be used as preflushes for acids or mixed in with acids to enhance acid reaction. The success of solvent use depends upon the selection of the correct solvent and the best conditions for its application. The advantages of solvent usage are reduction or elimination of the acid and its accompanying corrosion and precipitation problems.

This paper deals with selection of the type and amount of solvent and the method of application. The actions of the solvents with various emulsions and sludges are discussed and suggestions are given for optimum reaction times. The guidelines were developed in the laboratory and have been field tested with excellent results. Laboratory and field results are given.
Economic Evaluation of Cooperation Projects in the Offshore Petroleum Exploration and Development
Authors: Shi Hongxi
Published: December 2007

Abundant petroleum resources are predicted to be present in the Chinese offshore continental shelf. Since 1979 when the policy of "Opening toward outside world and stimulating domestic economy" was adopted by the Chinese government, in order to speed up the pace of the four modernization, over one million km2 on the offshore continental shelf covering Bohai, South Yellow Sea, Pearl River Mouth, Beibu Gulf and Yinggehai of South China Sea were offered for bidding to cooperate with foreign contractors in the cooperative exploration and development. The practice of recent years proves that such an undertaking has played a positive role in speeding up the development of our offshore petroleum resources and in the introduction of foreign advanced technology and managerial expertise. Remarkable success has been achieved.

In the light of the precondition of safeguarding the state's sovereignty, the following considerations were given and implemented in dealing with the cooperation: first, to consider whether our country's four modernizations can benefit technically and economically through such cooperation, secondly, whether the state can maximize its economical rent from it because the petroleum resources are owned by the state; and thirdly, whether foreign contractors can obtain their reasonable profits through such cooperation and whether it is attractive to foreign investments, because foreign contractors have put in a great deal of risk money, manpower as well as material resources. This is also a basic principle which we are following with in the cooperative exploration and development of offshore petroleum resources.

We all understand that the offshore petroleum exploration and development cover the stages of geophysical surveying, drilling (including wildcat and appraisal drilling), field development (including platform design and fabrication, installation of production facilities, storage and transportation facilities, drilling of production wells as well as injection wells, and onshore facilities), and oil/gas production, etc. When a decision is to be made before commencing any activities of these stages, evaluations are needed for decision making. Thus, we consider that evaluation would certainly be carried out without interruptions in every stage, for the purpose of decision making during each stage. As for offshore petroleum exploration and development projects, the evaluations usually include resource evaluation, development evalution, engineering evaluation and finally economic evaluation. Therefore, economic evaluations are carried throughout the whole process of projects with their contents and accuracy changing with the advancement of activities. The so-called successive evaluation is the fact that, along with intensification of the work and updating of the knowledge, the requirements for evaluation are also upgraded.
Determination of Fracture Conductivity in Moderate-Permeability Reservoirs Using Bilinear Flow Concepts
Authors: Britt L. K. , Bennett C. O.
Published: December 2007

The creation of highly conductive fractures has been shown to be important to the successful stimulation of wells in moderate permeability reservoirs. Therefore, the ability to determine fracture conductivity through pressure tests can be extremely beneficial to the proper design and ultimately to the success of future fracture stimulations.

Previous studies have shown techniques which can be used to determine fracture conductivity from pressure transient data. These techniques have been successfully applied to hydraulically fractured tight gas wells. This paper will illustrate the application of these techniques to wells in moderate permeability reservoirs.
Recent Development in Oil Well Cementing
Authors: Thompson Joe L. , Callison Jimmy D.
Published: December 2007

The success of oil field cementing operations, whether for completion or remedial purposes, is a vital factor in determining the well's future productive life and the eventual return on the well owner's investment.

With the advent of deeper and deeper wells, requiring specialized cement formulations with critical solid-to-water ratios, slurry density must be closely controlled. If the cement job is to be successful and the set cement is to have optimum strength and sealing characteristics, proper slurry density is important to insure proper initial viscosity, pump ability time, and strength after a predetermined waiting-on-cement time.

The problems of the control of cement density, cement water-loss, and cement retardation have been solved by the use of such additives as Diacel"D", Diacel "LWL" and Diacel "A". Another fairly recent development is a cementing service called "Cealment" (R) employing a specialized mixture of latex and Portland cement designed to improve the properties of the Portland cement.
Rock Breakage Mechanisms With a PDC Cutter
Authors: Zeuch D. H. , Finger J. T.
Published: December 2007

Some aspects of chip generation by a polycrystalline diamond compact (PDC) cutter moving through a rock can be understood by examining the shapes of the chips and the fracture patterns in the remaining rock. Data from laboratory experiments have led to general conclusions about the uniformity of chip generation mechanisms in different kinds of rock and about crack nucleation position relative to the cutter tip.
Optimization of PDC Bit Hydraulics by Fluid Simulation
Authors: Crouse R. , Chia R.
Published: December 2007

Fluid flow across complex PDC bit geometry is difficult to optimize by drilling tests in the laboratory. Insight into this flow field has been developed within a computer program which simulates the fluid flow at the bit. The development aspects of the computer code which allow for the three-dimensional flow visualization are reviewed. Graphical representation of the velocity vectors and pressure fields for six bit geometries are given to show the effects of nozzle location, orientation, baffles and flow channels. This in turn serves as data for a bottom hole cleanup, cooling rate and body erosion analysis. Dull bit observations are discussed and compared to the computer-derived hydraulic conditions.
New Optimization Drilling Fluid Programs for Reactive Shale Formations
Authors: Ritter A. J. , Geraut R.
Published: December 2007

To solve the drilling problems with reactive shales, it is necessary to know the reactive clay contents of the shales exactly. This reactivity proceeds from the crystalline clays and the amorphous minerals. Association of several methods of analysis allows to measure crystalline clays and amorphous reactive minerals. Choice of adequate muds is runned with an motorized penetrometer which test reactions between clays and recommended muds. Efficacious polymeric additives and concentrations are choosen by zeta potential techniques.
Horizontal Pumps: A New Approach to Water Injection Pressure Boosting
Authors: Johnson C. L. , Vandevier J. E.
Published: December 2007

Secondary recovery operations utilizing waterflood technology require the maintenance of reservoir pressure via water injection wells. To maintain adequate injection pressure, it is common to utilize large pressure boost pumps. Typically, these systems have made use of positive displacement or large diameter centrifugal pumps. Economic advantages can be obtained by the application of small diameter multi-stage submersible centrifugal pumps applied horizontally at the surface. These systems have repeatedly demonstrated benefit with regard to total operating costs, serviceability, and minimized downtime.
A Generalized Correlation for Characterizing the Hydrocarbon Heavy Fractions
Authors: Ahmed T. H. , Cady G. V. , Story A. L.
Published: December 2007

In the absence of detailed analytical data for the heptanes-plus fractions in a hydrocarbon system, major problems arise in predicting the thermodynamic behavior of the system by equations of state. These problems result because of the difficulty in characterizing the heavy-plus fractions. However, they can be reduced by splitting the plus fractions into pseudocomponents.

This paper presents a concise and accurate method for extending the molar distributions of the heavy fractions of naturally occurring hydrocarbon systems. This method originated from studying the molar behavior of thirty four hydrocarbon systems with a detailed Laboratory compositional analyses of the heavy fractions.

The proposed correlation will enhance the predictive capabilities of equations of state when applied to naturally occurring hydrocarbon systems.

A FORTRAN subroutine to perform the computations of the proposed method is included.
A Correlation To Predict Maximum Condensation for Retrograde Condensation Fluids and Its Use in Pressure-Depletion Calculations
Authors: Cho S. J. , Civan F. , Starling K. E.
Published: December 2007

A correlation which is a function of the reservoir temperature and the heptanes plus mole fraction has been developed to predict the maximum condensation during pressure depletion of retrograde condensate fluid reservoirs.

A generalized equation of state has been used in phase behavior calculations. The phase behavior of a condensate fluid for which the compositional analysis of the heavy components is known was accurately predicted using eleven pseudocomponents. Then under the guideline of the maximum condensation criterion, the phase behavior of the fluid also was predicted by using only three pseudocomponents, thus providing a recipe for using as few as three pseudocomponents in equations of state for depletion calculations.

A principal use of the method would be for estimation purposes in the initial period after discovery of a condensate reservoir, where the compositional analysis of the reservoir fluid may be only approximate and the dew point if not known, is assumed to be the reservoir temperature and pressure.
Reservoir Rock Descriptions Using Computed Tomography (CT)
Authors: Honarpour M. M. , Cromwell V. , Hatton D. , Satchwell R.
Published: December 2007

The petroleum industry is increasingly interested in accurate descriptions of reservoir rocks for better performance prediction of EOR processes. Detailed reservoir heterogeneity study methods are essential for generation of reliable statistical data input for predictive discrete numerical simulation methods.

In this study, reservoir rock descriptions are developed using X-ray computed tomography (CT) for formation mineral and rock property evaluation. An investigation of the mineral X-ray attenuation characteristics is documented. Rock fabric heterogeneities such as directional flow permeabilities, macroscopic permeability barriers, and fracture system orientations are demonstrated using North Sea Danian chalk and Wyoming Phosphoria formation, full-diameter cores. These results are verified using directional permeability tests, thin-section analysis, gamma ray responses, pore throat size distribution measurements, and visual inspection. The minerological data are presented as tabulated Houndsfield Unit (H.U.) attenuation densities and are cross plotted using g/cc-H.U. diagrams. The core images are displayed for comparison with the verification test results.
The Alteration of Rock Properties Due to Interactions With Drilling Fluid Components
Authors: Sharma M. M. , Wunderlich R. W.
Published: December 2007

The effects of water-based drilling fluid components on wettability and permeability have been evaluated. Most of the components tested are generally considered to be acceptable for a bland drilling mud, that is, a mud which will not alter rock properties. However, we have found that almost all of the components do alter wettability, and that some components reduce permeability significantly.

Both capillary pressure behavior and contact angle measurements were used to evaluate the effects of drilling fluid components on wettability. The capillary pressure tests were performed on strongly water-wet Berea sandstone samples and on Berea samples which had been treated to be oil-wet. Contact angles were measured on quartz and calcite crystals and on asphaltene films. The bland components tested included bentonite, carboxymethylcellulose (CMC), dextrid, drispac (a polyanionic cellulose polymer), hydroxyethylcellulose (HEC), pregelatinized starch, and xanthan gum. Two components excluded from bland muds were also tested: Coat 415 (a filming amine) and lignosulfonate.

All of the components considered to be bland, with the exception of bentonite filtrate, made oil-wet samples significantly less oil-wet. None of the bland components apparently affected the wettability of the water-wet samples. Coat 415 reversed the wettability of the water-wet samples, and lignosulfonate made the oil-wet samples less strongly oil-wet. CMC, starch and dextrid were found to reduce permeability significantly. This work demonstrates that additives generally considered to be bland can, in fact, alter reservoir rock properties.
Optimized Oilwell Fracturing of Moderate-Permeability Reservoirs
Authors: Britt L. K.
Published: December 2007

This paper presents results from an analysis of the effect of fracturing on moderate permeability oil reservoirs under primary depletion and secondary recovery processes. This analysis indicated that the optimum fracture half length in wells having a reservoir permeability of 1–10 md is relatively short and highly conductive. Both simulated and field production data are used to support this conclusion.
Vertical Fracture Growth Considerations in the Mission Canyon/Ratcliffe Formations of the North Alexander Area
Authors: Begnaud W. J. , Claiborne E. B.
Published: December 2007

The North Alexander Field located in the NW area of Mackenzie County, North Dakota consists of two productive horizons within the Madison group (Figure 1). These productive intervals, the Mission Canyon (Nesson) and Ratcliffe formations, are separated by a questionable barrier, the Midale, and an equally questionable lower Mission Canyon barrier below. This paper discusses several testing techniques used in the determination that a lack of vertical fracture containment within the pay zone is achieved during both Mission Canyon and Ratcliffe fracture treatments. Several methods of determining horizontal stress differences between pay zones and boundaries including insitu measurements (using acid treatments, mini-frac, and pump-in/flowbacks), differential strain curve analyses, conventional core analyses, and log-spaced sonic logs are also discussed.

A comparison between the data produced from the above techniques is reviewed. Sensing strings were used in conjunction with Nolte net pressure curves, from which interpretations concerning fracture behavior were made. Fracture height predictions using the Simonson equation are plotted and analyzed for varying degrees of stress differences and net pressure changes. As a result of the lack of stress differences seen between the barriers and pay zones, various completion modifications are discussed and several conclusions drawn.