bluuebunny/crossref_metadata_2025 huggingface dataset:
North Sea Reservoir Simulation: Practical Considerations
Authors: Johnson H. A.
Published: December 2007

Digital numerical simulation has played an increasing role in planning, developing, and depleting oil and gas reservoirs in the past 25 years. Through simulation, alternative development options can be evaluated to optimize development decisions (ref 1).

Since all of the North Sea fields have been developed since the advent of numerical simulators, numerous North Sea examples of applying numerical simulation to select reservoir development options exist in the literature. Virtually every field has had some simulation studies leading to its development.

The technology advances in both high speed computers and simulation software allow today's petroleum engineer to construct models with an ever increasing degrees of definition and complexity. The proper consideration of the need for a simulation study, the complexity required and the ultimate use all must be considered before a cost effective study can be undertaken. It is all to easy to design a model which is more complex than is required (ref 2). However, the limitations of a simulation model must be considered. A full field model is only as reliable as the data quality which is input. The most efficient use of simulation requires careful consideration of the ultimate use of the model, which frequently is dependent on the stage of field development.
Approaches to Full Field Simulation
Authors: Barnes A. L.
Published: December 2007

This paper discusses the objectives of full field simulation and the important considerations in full field model development. Major ARCO fieldwide models are described to illustrate these considerations and show how the use of full field simulation has developed. It is concluded that the reservoir management plans and investment decisions are made around full field modeling. Also, reservoir simulation has become more routine as computer costs have dropped. The trend of faster and larger computers should continue, increasing their use in reservoir engineering in the future.
Finite Element Representation of Two-Phase Fluid Flow Through a Naturally Fractured Reservoir
Authors: Bhatia K. S. , Advani S. H. , Lee J. K.
Published: December 2007

Two phase fluid flow through a naturally-fractured reservoir is investigated. The naturally-fracturedreservoir is characterized by two superimposed continua, with the fluid flow coupled via a fluid exchange term. The Galerkin-Newton method is used to discretize and solve the coupled differential equations. Problems associated with the representation of wellbore and induced fractures are initially evaluated. Steady state as well as time-dependent fluid flow around a wellbore is examined. It is demonstrated that curved isoparametric elements in the vicinity of the well with rectangular elements in the remainder of the reservoir can be used to obtain accurate solutions. Eight noded elements yield improved accuracy over four noded elements for single phase fluid flow through a porous medium. These elements also realistically model the flow field near induced fractures, for both single and two phase fluid flow cases. Langmuir's theory is used to model the sorption phenomenon in naturally fractured reservoirs. A onedimensional model is used to demonstrate the proposed procedure for dual permeability representation of naturally fractured reservoirs. The rapid convergence of solutions reveal the effectiveness of the finite element method in reservoir simulations. However, additional research on the presented methodologies is necessary.
Application of Reservoir Simulation Models to a New Parallel Computing System
Authors: Mayer D. F.
Published: December 2007

The Connection Machine, which uses over 65,000 processors in parallel, is a SIMD (Single Instruction Multiple Data) computer capable of computing large reservoir simulation models efficiently. Features of this computing system are ideally suited to finite-difference solutions where equivalent operations are performed on different data in the grid blocks. The Connection Machine hardware and software are described, the application to reservoir simulation discussed, the code for a simple example problem provided, and timing results for this problem tabulated.
Enhanced Drilling Softwares and Integrated Advisor Expert Systems
Authors: Fenoul R. G.
Published: December 2007

This paper describes the evolution of scientific softwares applied to ELF AQUITAINE's drilling operations.

Starting from an historically scattered situation, it points out how strategic decisions taken by the company have led to the development of a framework.

This framework, called CALPIN, set up to receive and integrate scientific programs, is now operational. It contains numerous softwares, including expert systems which are useful for drilling planning on operational bases and also help decision-making, directly on the rigsite.

The development guidelines as well as the solutions adopted are described in detail. The modular structure of the development allows for easy maintenance of the system and favours its evolution. In particular, it is easy to integrate a new software in the framework. Open to the outside, CALPIN enables the user to be connected with nearby data bases and to process his own data files by means of independent data-processing tools.
Control Aspects of Drilling High Pressure Wells
Authors: Prieur J. M.
Published: December 2007

Shell Expro ("Shell U.K. Exploration & Production", operators in the U.K. North Sea on behalf of Shell and Esso) have recently reviewed equipment requirements for the control of kicks incurred while drilling high pressure wells. Based on a "worst case" of a well bore full of gas, deriving from a reservoir pressure of some 14,000 psi [97 MPa], analysis of existing well control equipment standards has indicated a requirement for enhancements. New equipment standards have been developed and implemented, which will in all circumstances permit the well to be controlled, and the influx to be safely circulated out. These new standards principally apply to equipment which was already installed, though this equipment has been modified where necessary. These new standards mainly affect the BOP's elastomers, the choke manifold and the casing design. In some instances, control procedures have also been modified to take into account those equipment limitations that cannot readily be overcome. The main procedure change is the establishment of a maximum allowable kill rate which is governed by the capacity of the gas handling equipment on surface. These revised equipment standards and procedures will enable to control a well kick without danger to personnel or to the installation and should engender the confidence of the rig personnel.
Common Carriage and the Gas Act
Authors: McKinnon J.
Published: December 2007

In terms of the Oil and Gas (Enterprise) Act it has been possible since 1982 for competitive activity in the gas supply business. By the time the Gas Act 1986 had come into force there had been no successful development in the market. By the end of 1987, fifteen months after the privatisation of the British Gas Corporation nothing had occurred in terms of competition to its successor British Gas plc. What had happened however was that by that time the Gas Consumers Council and a number of individual customers of British Gas (BG) had complained to the Office of Fair Trading not only about the prices being charged for gas but also that British Gas had been acting unfairly in this regard. At that point no mention was being made about the lack of competition to British Gas.

The Director General of the Office of Fair Trading took the view based on the material presented to him that British Gas had a case to answer and referred the matter to the Monopolies and Mergers Commission. At the time of this reference media commentators emphasised the points on pricing but ignored or failed to realise the significance of the words combined in the OFT reference which indicated that the question of competition should also be considered by MMC. Perhaps this was because no commentator believed that there was ever going to be gas to gas competition.

In December 1987 OFGAS published a Report which examined the area of gas to gas competition. The Report suggested reasons as to why there had been no competition to date and made proposals about the steps needed if there were ever to be competition to British Gas. There were those who expressed surprise that OFGAS should have become involved in this area. After all OFGAS was supposed to have been brought into existence to look after the interests of the 17 million or so tariff customers of British Gas. Consequently it was stated that OFGAS had no reason to become involved in this the most vital area of the industrial and commercial segments of the gas supply market.
Performance of Manual Eddy Current Inspection of Welds in Offshore Steel Structures.
Authors: Cumming R.
Published: December 2007

The inspection of protected welded steel structures for fatigue cracks during their service life creates a set of problems which can be minimised by the efficient use of eddy current NDT techniques.

The oil industry has been cautious to adopt the techniques until the reliability of the equipment, the profiency of the personnel and the validity of the procedures have been demonstrated.

During the last five years SSNDT has provided a total package of support, by training and certifying technicians, by measuring the performance of equipment, and by devising and checking procedures in conjunction with industrial partners, details of which will be presented.

Over the last 18 months an industrial sponsored project has measured the limits of performance of eddy current equipment. The project work has specialised in the application of manual eddy current equipment ou fatigued and coated welds where the performance of the technician is a major contributing factor to overall reliability.

A method has been devised to provide a framework for the comparison of alternative manufacturers equipment and the validity of the basic measurements.

The latest results of the project will be described and include the limit of attainable performance of the inspections and the procedures which have become industrial standards.
Factors Affecting Gravel Placement in Long Deviated Intervals
Authors: Gurley D. G. , Hudson T. E.
Published: December 2007

Properly designed and installed gravel pack completions have proven to be the most effective method of controlling sand production. The advent of slurry pack techniques, clean fluids and NODAL* analysis have been responsible for improving gravel packed well productivity. Further improvement in gravel placement is needed in long deviated completions.

Although quantitative evaluations of perforation packing cannot be precisely measured, there is good field and laboratory model evidence that the effectiveness declines rapidly in intervals longer than about 10 ft -- even in vertical wells. Both field treatment reports and laboratory data indicates that bridging may occur in the screen/casing annulus before there is adequate leakoff into the formation to pack the perforations. Premature bridging is not always obvious in vertical wells because the bridge usually collapses after the differential pressure across the bridge dissipates. However, in wells deviated more than about ≈ 55° the gravel does not settle after collapse of the bridge. The result is a void in the annulus pack.

Full-scale model studies of screen/casing annulus and perforation packing by numerous researchers have made important contributions in understanding the packing process1-12.Development of a mathematical model by Wahlmeier provided a method to scientifically apply the knowledge provided by these researchers to real wells.13 Factors studied by these researchers and described mathematically by Wahlmeier are: 1) gravel transport, 2) friction pressure and its influence on slurry flow in the screen/casing annulus, and 3) carrier fluid leakoff and its influence on perforation packing.

This paper discusses rheological properties of particulate slurries and geometrical conditions encountered that affect these factors. Simple, but relevant mathematical relationships are used to demonstrate the importance of particle settling, slurry flow velocity, shear rate in the screen/casing annulus, shear rate entering the formation and downhole placement pressures.
The Effect of Temperature on the Size Stability of Conventional and Ceramic Gravel Packs
Authors: Alcocer C. F. , Toups M. M. , Hayatdavoudi A. , Ghalambor A. , Okoye C.
Published: December 2007

Laboratory research was performed to study materials used in gravel packs. There were conventional quartz sand and ceramic pellets. The main objective of this research was to determine the effects of elevated temperatures on the size and shape of subject materials, specifically as related to the generation of fines within the gravel pack itself. Also, the feasibility of using ceramic pellets versus conventional quartz gravel as pack sand material was investigated. These objectives were achieved by examining 20/40 and 40/60 mesh samples of subject materials for the influence of various temperatures (room temperature -up to 550° F) on particle size distribution, grain surface degradation, mechanical strength, permeability and conductivity stability, and fracture limits. SEM photograhs of 40/60 mesh gravel indicated an increased amount of pits caused by temperature. Also, the formation of striations and/or flaking were present on the 40/60 mesh gravel. The crush test performed at 10,000 psi on the 40/60 mesh gravel produced fines in excess of 25% by weight. The 20/40 and 40/60 mesh ceramics and 20/40 mesh gravel displayed a decrease in permeability with increasing temperature. A linear regression analysis was performed. Based on this study, the ceramics appear to be best suited for gravel pack material at elevated temperature. Even though both gravel and ceramics produced fines, the ceramic grains are able to withstand much higher pressures and stresses coupled with higher temperature.
Investigation of Gravel Pack Damage Due to HF Acidizing
Authors: Yeager V. J.
Published: December 2007

Reaction of hydrofluoric acid on 20/40 Ottawa sand used for gravel packing was simulated in a large-scale model under realistic conditions. Changes in (1) silica content of the effluent, and (2) sieve size distribution of the proppant pack indicate that changes are occurring, but that they are relatively small. Formation sand and fines are also affected, however, overall API specifications for gravel pack proppants were maintained even in the presence of substantial volumes of hydrofluoric acid.
Use of CT Scanning in the Investigation of Damage to Unconsolidated Cores
Authors: Gilliland R. E. , Coles M. E.
Published: December 2007

The use of Computed Tomography (CT) scanners has proven to be a valuable tool in the evaluation of damage to unconsolidated cores. When examining sleeved cores to determine slabbing angle, undamaged sites for future plug and whole core analysis, sample heterogeneity and depositional features, CT scanning proves invaluable by providing nondestructive internal inspection capability.

The core material recovered from these unconsolidated friable formations typically undergoes, a series of damaging alterations between in situ conditions and the laboratory. Studies have shown that improper handling techniques in the lab can often do as much damage to the core as the coring, wellsite handling and transportation phases. In the process of investigating the fragility of these sands and evaluating which processes are generally responsible for their damage, CT scans aid in greatly reducing such damage in subsequent cores by revealing not only the magnitude of the damage but also the implied cause in many cases. Examples are provided to demonstrate the effect of several types of core damage from both unavoidable sources such as pressure and temperature changes associated with bringing the core to the surface to the more catastrophic events resulting from physical shock. Invasion profiles and other useful drilling information can also be gleaned from this technique,
The Occurrence and Control of Acid-Induced Asphaltene Sludge
Authors: Houchin L. R. , Dunlap D. D. , Arnold B. D. , Domke K. M.
Published: December 2007

Successful acid stimulation programs are achieved when more near well-bore damage is removed than is induced by the acid treating fluid. Acid induced asphaltene sludging is becoming an increasing cause of oil well stimulation treatment failure. Laboratory tests on 231 crude oils from 17 formations in the U.S. and Canada, have been tested for sludge sensitivity.

Numerous chemical processes involved in an acid system contribute to the effect of acid on sludge potential. Surface tension has been used in the past as a guideline for predicting the sludge potential of a chemical system. However, surface tension, in and of itself, is not a factor in acid induced sludge. In addition, this data indicates that as oilfields mature and are placed on secondary and tertiary recovery, sludge sensitivity increases. As a result of this data, a crude oil classification system is presented based on API gravity and asphaltene content. By classifying the crude oil, conclusions can be reached regarding sludging potential.

This study addresses many such chemical options which include acid strength, acid type, solvent preflush, iron control and additive compatibility. The oxidation potential of iron contaminated acid is also clarified.
Shock Wave Boundary Effects on Jet Perforator Penetration in Stressed Berea Targets
Authors: Henderson S. W. , Navarette M.
Published: December 2007

Tests in annular stressed Berea targets demonstrate that shock wave reflections can have either positive or negative influences on shaped charge perforator penetration. These results imply that boundary effects which alter shaped charge performance are inherent in the current API RP 43 Section II target. Data and results begin to identify a target which more realistically models downhole conditions.
Evaluation and Treatment of Organic and Inorganic Damage in an Unconsolidated Asphaltic Crude Reservoir
Authors: Efthim F. P. , Garner J. J. , Bilden D. M. , Kovacevich S. T. , Pence T. C.
Published: December 2007

Formation damage results primarily through three types of mechanisms: particulate plugging, organic deposition and chemical incompatibilities. Each of these damage mechanisms can be very detrimental to production performance. Complex damage caused by a combination of formation fines migration, calcium carbonate scale and asphaltene precipitation can result in severe reduction in productivity. When this type of complex damage exists, a specialized stimulation treatment design is required to effectively remove the damage.

The production history of an unconsolidated, asphaltic crude reservoir indicated that a damage mechanism existed and was responsible for abnormally low production rates. Quantitative and qualitative studies were performed in order to analyze this damage and generate an operationally feasible and cost effective treatment. The conclusions generated from this investigation resulted in the design of a unique treatment and placement technique. This technique was applied using a specialized solvent and acid system in a stimulation program that resulted in significant, stabilized improvement in well productivity.

Treatment descriptions and production results are presented from the 18 wells that were included in this ongoing stimulation program. Candidate selection criteria and corresponding stimulation performance are also discussed.
Petroleum Investments in the Asia-Pacific Region
Authors: Partowidagdo W. , Cockcroft P. J.
Published: December 2007

The earnings from oil and gas sales are a very important source of income, both directly and indirectly, for many countries in the Asia-Pacific region. During the past few years, exploration and development has been low, and the future activity level is not expected to be significantly higher. Thus new incentives are needed to entice investors to allot funds for petroleum activities in this region.

A comparison of different fiscal regimes in the Asia-Pacific region is presented, including exploration and development risk and potential, political risk and fiscal risk.
PDC-Bit Evaluation by Cutter Instrumentation and Computer Simulation
Authors: Homstvedt G. , Rødland A.
Published: December 2007

A new tool for monitoring cutter performance is developed for selecting best PDC drilling conditions.

The drilling efficiency of different PDC-bits can show great variations due to different drilling conditions and formations being drilled. Field tests are often unreliable for evaluation purpose because of limited data quality. Theoretical calculations and laboratory experiments have also limited significance often due to unrealistic conditions.

An instrumentation and evaluation system is developed for PDC-bit evaluation purposes. Temperature sensors, mounted in different cutters 1 mm behind the cutting edge, give an 80 % response in 2 seconds. A data monitoring unit is also part of the instrumentation setup situated in a hollow version of a drill collar behind the bit. Cutter-temperatures together with other drilling parameters are monitored for later readout and analysis. Analysis and simulation programs are developed to predict the PDC-wearflat temperatures of each cutter at the bit. The influence of drilling through different formations has thus been evaluated. The influence of actual drilling conditions like pumping rate, weight on bit, rotation speed has also accurately been monitored and analyzed.

By this tool it is possible to make innovative evaluations of bit design and recommended drilling strategies for different formations.
A Petrophysical Model for Shaly Sands
Authors: Stenson J. D. , Sharma M. M.
Published: December 2007

Equations for the electrical conductivity, the electrochemical potential, and the streaming potential of a clay-lined, brine-filled capillary tube have been developed from fundamental principles of irreversible thermodynamics and electrochemistry following the work of Gross and Osterle. Use of the equations gives insight into the role of clay in determining the electrical conductivity as well as the electrochemical and streaming potentials in shaly sand reservoir rocks. The variation in these electrical properties with the magnitude of the electrical potential of the pore lining clay, the radius of the capillary, and the concentration and composition of the saturating brine is investigated. A constant value of surface potential is shown to yield plots which exhibit good qualitative agreement with the experimental shaly sand data of Waxman and Smits and Hill and Milburn. By contrast, a constant value of surface charge density is shown to yield plots of brine saturated capillary conductivity versus brine conductivity which exhibit good qualitative correlation to the experimental shaly sand data of Schon and Borner. The electrochemical potential is shown to vary smoothly form the diffusion potential to the theoretical limit of the Nernst potential as either the surface charge or the capillary radius is changed. The streaming potential of a clay-lined capillary tube is directly proportional to the surface potential of the tube at sufficiently large values of tube radius and brine concentration. This is consistent with Smoluchowski's equation.

Incorporation of the clay-lined capillary tube model into a 3-dimensional network model allows for study of the variation of resistivity index with water saturation in water-wet shaly sand formations. The effects of brine concentration, ion radii, and clay distribution on the magnitude of the Archie saturation exponent, n, are investigated. Relative changes in n are shown to be consistent with experimental results of Waxman and Thomas. The distribution of clays in the rock is shown to significantly alter the resistivity index-saturation plots.
Thin-Bed Reservoir Analysis from Borehole Electrical Images
Authors: Trouiller J-C. , Delhomme J-P. , Carlin S. , Anxionnaz H.
Published: December 2007

In very thinly bedded sand-shale sequences, sand counts and sand/total ratios can be determined from high resolution electrical images of the borehole wall. This technique is illustrated here by a case study in turbidites with sand laminae down to 1 cm in thickness. The numerical modeling of the tool response and a comparison with fullbore core data help assess the accuracy of bed thicknesses derived from electrical images for this type of formations.
Correction for Oil-Based Mud Effects on Neutron and Density Tools
Authors: Lau M. N. , Luquette M. B. , Bassiouni Z.
Published: December 2007

Oil-base drilling fluid density changes considerably with temperature and pressure. Significant density changes prevailing in oil-base drilling fluids can seriously affect the neutron and density sonde readings. The effects of oil-base muds on these logs are discussed, and a technique to account for such effects is proposed. A new approach for true porosity determination in gas-bearing formations is also presented for cases where the gas is miscible with the invading fluid. Two well examples representing different lithologies, fluid types, and miscibility conditions are presented. These examples confirm the need for the proposed corrections and their drastic impact on the qualitative and quantitative interpretation of neutron and density logs.
International Variations in Professionalism
Authors: Ikoku C. U.
Published: December 2007

The engineering profession in the West African sub-region is not much different from what it is in developed countries all over the world. The relatively under-developed environment has hampered the maximum utilization of the indigenous engineers, The engineering profession in this region has developed from the free-for-all era of the 1960s to a stage in which it is now regally regulated.

There is now an accepted code of conduct for all professional engineers. The professional engineering societies ensure that high standards of professional practice and ethics are maintained, and that the engineering profession meets the needs of the West African region. The era when non-registered engineers held posts which discharge and purport to discharge functions which are properly those of registered engineers is rapidly being phased out.
Gas Economics and Regulation in the 1990’s
Authors: Carson M. M.
Published: December 2007

The dynamics of the natural gas industry are changing dramatically due to major federal regulatory policy shifts, and growth of the gas transport and spot gas markets. Gas industry sales and transport activities had traditionally been regulated from wellhead to burnertip, but competition is growing due to: ∘growth in 3rd party transport volumes∘growth in non-regulated gas marketing∘pipeline gas supply portfolios being reformed∘negotiation of new gas supply contract terms∘take-or-pay problems being worked down∘deregulation of the traditional pipeline's roles to allow marketing of new services∘swings in spot market gas prices vs. volumes moved∘number of new pipeline projects proposed∘storage trends

The above 9 trends will be analyzed in the paper for their impacts on the future of the gas industry.

The seven years of the American Revolution era characterized the struggle by which the colonies that were to become the United States won independence from British regulation of colonial commerce.

We could say that the 7 years from 1985 to 1992 is the American pipeline revolution era, characterized by the struggle to free interstate pipelines from their overly restrictive regulation of the past.

Let's turn back the pages of history and look first at some recent history:
Measurements and Correlations of Three-Phase Relative Permeability at Elevated Temperatures and Pressures
Authors: Maini B. B. , Kokal S. , Jha K.
Published: December 2007

Three-phase relative permeabilities have an important role in numerical simulation of oil recovery processes. Thermal methods for heavy oil recovery, such as steam injection and in situ combustion, involve simultaneous flow of oil, water and gas at high temperatures. A knowledge of three-phase relative permeabilities at elevated temperatures is required to predict performance of these processes by reservoir simulation studies. Measurements of three-phase relative permeabilities for heavy oil systems at elevated temperatures have been unavailable due to experimental difficulties.

The objectives of this work were to develop an experimental apparatus for measuring three-phase relative permeabilities at elevated temperatures and pressures and to carry out such measurements in a model system. The rock-fluid system used in these measurements comprised Ottawa sand - refined mineral oil - distilled water - nitrogen gas. A high viscosity mineral oil (405 mPa.s at 23°C) was selected to simulate heavy oil behaviour. The measurements were carried out at 100°C temperature and 3.5 MPa pressure. Two-and three-phase relative permeability measurements were obtained using the steady-state technique. A large number of steady-state tests were carried out to completely define the three-phase relative permeability characteristics in two types of saturation histories; (1) water and gas saturations increasing and oil saturation decreasing, (2) water and gas saturation decreasing, oil saturation increasing.

The three-phase water relative permeability was found to be a function of water saturation only and did not change with the direction of saturation change. The gas relative permeability was also a function of its own saturation only. It was lower in the direction of decreasing gas saturation. The oil relative permeability was found to vary with saturations of the other fluids. Oil isoperms were concave towards the oil apex.
Two-Phase Flow in Heterogeneous Porous Media: The Method of Large-Scale Averaging Applied to Laboratory Experiments in a Stratified System
Authors: Quintard M. , Bertin H. , Whitaker S.
Published: December 2007

The theoretical study of the flow of two fluids in a porous medium begins at the pore level with the Stokes equations. The method of local volume averaging is used to derive the well known extension of Darcy's law. For a heterogeneous porous medium, the method of large-scale averaging is used to average the Darcy-scale equations over a region that is large compared to the length scale of the heterogeneities. The closure problem developed with this method is used to compute the large-scale coefficients, such as the permeability, associated with the heterogeneous porous medium. The closure problem is simplified for the quasi-static (capillary dominant) case, and results are presented for two-dimensional, periodic, heterogeneous media, and stratified media.

The experimental study consisted of the waterflooding of a stratified porous medium made up of Berea sandstone and Aerolith-10, a sintered artificial porous medium. During the waterflooding experiments the saturation field was measured by gamma-ray absorption. The large-scale capillary pressure and permeabilities were computed from the independent characterization of the two layers by solving the large-scale closure problem assuming that the quasi-static condition was valid. The numerical results consisting of averaged volume fractions over a section of the stratified medium, and these are compared satisfactorily with the experimental data.
Evaluation of Two-Phase Steam Flow Through an Orifice
Authors: Griston S. , Cire F. L.
Published: December 2007

Proper management of steamflood projects requires accurate information about heat input to the petroleum reservoir. The first logical step toward obtaining this information is to meter the steam flow rate and quality directly at the injection wellhead. However, this is not an easy task. The need for reliable, cost effective wellhead steam metering methods has existed for many years.

Recently, methods using an orifice or nozzle in series with a second device, such as a critical flow choke or densitometer, have been introduced for metering wellhead steam quality and flow rate. Although orifices are commonly used to monitor superheated or high quality saturated steam exiting an oil or gas-fired boiler, little is known about the reliability and accuracy of using orifice meters over the wide range of pressures, flow rates, and qualities that exist at injection wells. Of primary concern is whether or not there is a strong correlation between the pressure drop across the orifice and changes in steam quality and/or mass flow rate. The effects of two-phase flow regime on pressure drop are also important and must be considered.

This paper presents results of field testing and evaluation of two-phase steam flow through an orifice over an extended range of flow rates, qualities, and pressures. Overall accuracy and reliability of orifice meter data are discussed and compared to published studies. An overview of the fundamental aspects of steam flow through an orifice is given and reasons for the variation in existing empirical correlations are discussed. Finally, the problems encountered when using an orifice or nozzle in conjunction with other metering devices to determine wellhead steam quality and flow rate are examined.
On Fracture Design of Deviated Wells
Authors: Yew C. H. , Schmidt J. H. , Li Yi
Published: December 2007

This paper presents technical concepts and procedures for the design of hydraulic fracture treatments for deviated wells. These Include: the width and location of well surface tensile zones,the length and angle of deviation of initial fracture intersections with the well surface,the orientation of fracture plane propagation relative to the wellbore,the maximum distance between perforations permitted for multiple fracture linkup in open holes,and the effect of casing on perforation orientation and density for cased wells.

Previously derived equations were modified and expanded for use in this analysis. Results of plastic model experimental studies are presented which verify these calculations and agree qualitatively with theoretical predictions. Finally, an example is presented which demonstrates the use of the above procedures.
Design and Performance Properties of Oilfield Fiberglass Tubulars
Authors: Huntoon G. G. , Alkire J. D.
Published: December 2007

Fiberglass reinforced pipe (FRP) has numerous advantages over steel pipe in oil field applications. Dominant among the advantages is resistance to corrosion and ease of handling. Historically, most FRP has been used for low-pressure beam pump well flowlines. Low-pressure applications usually demand only minimal pipe performance to be successful. In recent years FRP has been thrust into more demanding applications, such as high-pressure flowlines and downhole tubing strings. Field experience made it clear that the majority of methods used for design of these earlier applications were not adequate in high-pressure services. A rating method for high-pressure line pipe and tubing has been developed by API task groups. The rating method is based on test data that measures the long-term performance of FRP tubulars. Amoco has initiated an in-house program to develop this test data on commercially available FRP products. Results of this program to date have been most enlightening in regard to FRP behavior especially in relation to performance claims by manufacturers. In one case, slight changes in pipe design by the manufacturer more than doubled the long-term strength. Temperature effects have been measured and for some products are very dramatic, producing as much as 50% decrease in strength. Tests have shown that changing the type of connection can drastically affect system performance. The development of specifications can greatly influence the successful application of fiberglass tubulars.
The Asphaltic Properties of an Apparently Ordinary Crude Oil May Lead to Re-Thinking of Field Exploitation
Authors: Garland E.
Published: December 2007

The discovery of a light but abnormally asphaltic oil field held some surprises for producers who are not used to handling such oils. The crude in question has its asphaltenes which destabilize during their raising in the tubing.

This caused a difficult problem of sampling. Moreover, within a few weeks, most of the surface equipment were plugged with asphaltenes deposits. It was consequently necessary to re-design the production chain for processing and transporting the crude, and to account for the inevitable floculation and deposit of these asphaltenes.

The intensive laboratory studies which supported this work, are presented herein, as well as the tests on an 500 meters loop that we realized to study the risk of plugging the pipeline at low points, after a shut down.

All these lead to a production project, implemented on site, which is evaluated after eighteen months of operation.
Oilfield Fluid Rheology: The Use of a Controlled Stress-Measuring System to Determine Oilfield Fluid Properties
Authors: Clark P. E.
Published: December 2007

Historically, controlled shear rate instruments have been used to determine the rheology of fluids used in the oil field. Construction of controlled shear instruments is easier, and the electronics to control the instruments are readily available. In the last few years, technological advances in electric motor design have made it possible to build a controlled stress instrument which is both accurate and easy to use.

Particle settling is one example of a stress controlled process that is found in the oil field. Measurements made with controlled shear rate instruments have not been particularly successful in predicting particle settling behavior. Controlled stress measurements have been shown to be a better measure of fluid properties for the prediction of particle settling. Yield stress measurements are another area where controlled shear rate instruments are difficult to use. In a controlled stress instrument, a stress is placed on the fluid and the resulting displacement is measured. Small stresses can be applied in a stepwise fashion resulting in accurate determinations of yield points.

This paper covers the aspects of controlled stress rheological measurements and gives several examples of the use of these measurements in the evaluation of oil field fluids. Applications to polymer solutions and fracturing fluids will be discussed.
A Field Evaluation of a Gravel-Diverted Acid Stimulation Prior to Gravel Packing
Authors: Matherne B. B. , Hall B. E.
Published: December 2007

Chevron USA Inc. has successfully applied a completion technique that is an enhancement to the conventional circulating gravel pack. The technique requires acidizing prior to gravel packing utilizing a gravel slurry to divert the acid stages and to pre-pack the perforations. Gravel placement and diverter effectiveness are indicated by using radioactive tracers and the spectral gamma ray logging tool. Calculated gravel placement by the two completion methods is compared. This enhancement to the circulating gravel pack has resulted in more efficient and greater well productivity.
Confirmation of Thermodynamic Modeling of Reservoir Fluid-Rock Systems with Subsurface Data
Authors: Riese W. C. , Riese A. C.
Published: December 2007

Thermodynamic modeling of reservoir fluid-rock systems can accurately predict the tendency for scale to form in a formation during completion, stimulation, and production, and can be useful in identifying well bore fluids which exacerbate this tendency if they are employed during any of these procedures. The calculations which we employ in modeling these reservoir systems account for activity coefficients via the extended Debye-Huckel relationship and for elevated temperatures with van’t Hoff or Kirchoff equations. The description of reservoir environments that can be obtained using these thermodynamic relationships is more accurate than any obtained using Stiff-Davis or similar approaches. Concurrent consideration of all potential precipitation phases is also only possible with this type of analysis.

Characterization of the Oligocene age Vicksburg Formation reservoirs in the Tabasco field in Hidalgo County, Texas began after a well failed to come on line as predicted: fluids introduced to the wellbore and formation during testing and completion procedures were suspected to have caused formation damage in spite of the fact that these same fluids had been used successfully in other wells in the same field without causing apparent damage.

Our modeling of the fluid-rock reservoir systems demonstrated that these CaBr2-bassd fluids were in fact the probable causes of damage to the formation and thus accounted for the poor reservoir performance. Our modeling also indicated that KCl-based fluids would have induced scale precipitation had they been used as alternatives.

Subsequent frac stimulation of another well in the field allowed us to confirm these predictions. During frac cleanup, some of the proppant used was flowed back and found to be coated with a foreign substance. This coating proved to be composed of aragonite, a finding consistent with the results of our modeling and our prediction that introduction of KCI-based fluids to the formation would result in carbonate and other scale precipitation.
A Three-Dimensional Hydraulic Propagation Theory Coupled With Two-Dimensional Proppant Transport
Authors: Lee W. S. , Jantz E. L.
Published: December 2007

A three dimensional hydraulic fracture propagation theory, coupled with two dimensional proppant transport, has been developed. Principal features of the theory are listed below. Initial fracture is assumed to be initiated from a line source with length equal to the perforated interval, and the fracture will, propagate as an ellipsoid if the formation is homogeneous with no stress variation.Fracture shape deviates from the perfect ellipsoid as soon as the fracture reaches a layer having stress change.Pressure drops from the center of the fracture in the perforated interval to fracture tips in all directions are equal. Thus the width profile in every flow line varies according to the stress variation in that direction.Proppant is assumed to move with equal velocity as fluid along the flow line but has an additional vertical settling velocity which allows proppant pumped at earlier stages to mix with proppant pumped in latter stages. Settled proppant will continue to fall to a place where fracture is too narrow to allow further drop.Fluid losses are considered for both the pay zone and non-pay zones. With state-of-the-art improvement in microfracturing processes, fluid losses in non-pay zones are measurable and should be measured.

The new theory can handle the special case of a fracture that is confined to a constant gross height either from above or below.

Deficiencies of two dimensional models are removed by the new theory: Assumption that constant height is achieved instantly.Assumption that the width at any vertical plane is either constant (Christianovich and Zheltov)1 or with a fixed shape (Perkins and Kern).2 Subject paper presents development of theory and an example of selecting proppant-laden fluids for optimum proppant transport.
Nurturing the Geology-Reservoir Engineering Team: Vital for Efficient Oil and Gas Recovery
Authors: Sessions K. P. , Lehman D. H.
Published: December 2007

Of an estimated 482 billion barrels (76.6 Gm3) of in-place oil discovered in the U.S., 158 billion (25.1 Gm3) can be recovered with existing technology and economic conditions.1 The cost-effective recovery through infill drilling and EOR methods to recover any portion of the remaining 323 billion barrels (51.4 Gm3) will require a thorough understanding of reservoirs and the close cooperation of production geologists and reservoir engineers.

This paper presents the concept of increased interaction between geologists and reservoir engineers through multi-functional teams and cross-training between the disciplines. A discussion of several factors supporting this concept is covered, including educational background, technical manpower trends, employee development, and job satisfaction. There are several ways from an organizational standpoint to achieve this cross-training, with or without a formal change in job assignment. This paper outlines three approaches, including case histories where each of the approaches has been implemented and the resulting benefits described.
Applicability of Fractals to the Description of Viscous Fingering
Authors: Fanchi J. R. , Christiansen R. L.
Published: December 2007

The applicability of fractals to the description of fluid flow in porous media is evaluated. Special attention is paid to determining the feasibility of using fractals to predict the performance of unfavorable mobility displacement processes. The state-of-the-art of viscous fingering research is established before the fractal concept is explained. The application of fractals to fluid flow problems is then considered.

Laboratory measured fractals are shown to have potential usefulness as predictors of such field-scale information as sweep efficiencies and breakthrough times if the fractal dimension of a displacement process is scale independent. Calculations using data from the literature and laboratory experiments with a radial Hele-Shaw cell indicate that viscous fingers do not have scale independent fractal dimension except in regions of fluid flow which are free of steep pressure gradients. Steep gradients are usually present near sources (injectors) and sinks (producers). Thus, fluid displacement in regions near wells does not appear to be fractal.
Pressure Transient Behavior of Naturally Fractured Reservoirs Considering the Effect of High-Velocity Flow
Authors: Villalobos-L. H. , Rodriguez F. , Samaniego-V. F.
Published: December 2007

The influence of high-velocity flow of a liquid of constant compresibility on the transient pressure behavior of a naturally fractured well is studied in this paper. The study is based on a numerical solution to the radial liquid flow problem as described by Warren and Root but considering high-velocity flow through Forchheimer equation. An expression for the rate-dependent pseudo-skin term is derived. It is demonstrated through an integration of the Forchhaimer equation and the simulation of drawdown tests that consider no skin damage that this pseudo-skin in essentially equal to the product Dqw, where D is the turbulent term coefficient defined as βρk/2πrwhμ. It was also found that the correlation of Ramey et al. for the end of the wellbore storage period in homogeneous systems, can be extended for conditions of high-velocity flow in naturally fractured reservoirs provided that the apparent skin s’ is used instead of the skin factor s. This study also considers the influence of high-velocity flow on pressure buildup tests. The effects of a finite formation skin and wellbore storage are also included in this work. One main conclusion of this work is that after the high-velocity flow region is stabilized, the slope of the semilog straight line for matrix dominated flow is equal to the conventional value of liquid flow of 1.151. Results of this study show that pressure derivative analysis with Bourdet et al.'s type curves are to be taken with caution when high-velocity flow affects the test.
Detecting Compartmentalization in Gas Reservoirs Through Production Performance
Authors: Hower T. L. , Collins R. E.
Published: December 2007

Diagnostic techniques are presented for detecting and quantifying poorly drained compartments in volumetric gas reservoirs. It is shown that p/z versus Gp data can be used to assess unrecovered gas reserves and assist in targeting infield development.