bluuebunny/crossref_metadata_2025 huggingface dataset:
Miscible Displacements in a Heterogeneous Rock: Detailed Measurements and Accurate Predictive Simulation
Authors: Davies G. W. , Muggeridge A. H. , Jones A. D. W.
Published: December 2007

This paper describes comparisons between the prediction of high resolution simulation and the results of detailed laboratory measurements of miscible flow in a heterogeneous rock slab. The permeability distribution was characterised using minipermeametry and an X-ray radiography technique was developed to obtain quantitative concentration maps. Displacement experiments were conducted at four mobility ratios. Both stable and unstable flows were investigated, enabling the effects of physical dispersion and viscous fingering to be quantified. Excellent agreement was obtained between simulation and experiment without the use of history matching. The simulations predicted the development of individual viscous fingers as well as the correct effluent and recovery profiles. This work has validated characterization techniques and demonstrated our ability to simulate single phase flow in a heterogeneous rock. The experimental results also provide a set of data for use in bench-marking other simulation packages.
Impact of Recent Federal Tax and R&D Initiatives on Enhanced Oil Recovery
Authors: Brashear J. P. , Biglarbigi K. , Ray M. R.
Published: December 2007

The National Energy Strategy contains two major elements designed to increase oil production from known reservoirs in the contiguous United States: 1) a tax credit for specific investment and injectant costs for qualified enhanced oil recovery (EOR) projects; and 2) a highly focused, public-private cooperative R&D program. Both are currently being implemented by the Department of the Treasury and the Department of Energy, respectively. The present study estimates the potential reserve additions and impacts on public treasuries at oil prices between $22 and $34/Bbl. The new Federal tax credit, alone, could double current proved EOR reserves at oil prices in the $22/Bbl range and increase them by about one-third at prices in the $30/Bbl range. The effect of technology advances alone could also about double EOR reserves at these prices. The combination of technology advances and the tax incentive synergistically amplifies the effects on potential EOR reserves. The benefits of the tax credit come at some cost to the Federal treasury, but increase state revenues. Increased EOR activities due to the tax credit and technology advances could also increase economic activity and gross domestic product (GDP) and contribute to reductions in oil imports and the U.S. trade deficit.
Conditions for Generating Foam in Porous Media
Authors: Chou S. I.
Published: December 2007

The generation of foam in porous media remains a controversial issue. It has been reported that foam is formed only above a minimum flow rate (or capillary number), above a minimum pressure gradient, or below a critical capillary pressure. In this paper we investigated experimentally how these and other parameters affect the formation of N2 and CO2 foams in Berea sandstones.

We found that foam was readily formed by co-injecting gas and surfactant solution whenever the core was presaturated with surfactant, regardless of flow rate or pressure gradient In general, foam generation can be initiated by first creating regions of high surfactant saturation in situ and then draining those regions; the onset of foam generation coincided with the onset of drainage. Somewhat surprisingly, it was easier to generate a stronger foam than a weaker foam, and fewer pore volumes of injection were needed to form foam in a longer core than in a shorter core.

A consistent mechanism that emerges from these observations is that foam is formed by raising capillary pressure in a surfactant-saturated region. As gas enters such regions, individual lamellae are formed by snap-off in certain pores. These lamellae must be sufficiently stable to allow the local capillary pressure to increase in time, forcing gas to enter increasingly smaller pores and generate more lamellae. Presaturating the porous medium with surfactant ensures that stable lamellae are formed whenever snap-off occurs. In contrast, if continuous gas channels exist over sample-spanning distances, the injected gas preferentially flows through such channels, capillary pressure cannot rise significantly, and foam generation is delayed. Practical implications of these findings on applications of foam are discussed.
Numerical Simulation of Peace River Recovery Processes
Authors: Glandt C. A. , Malcolm J. D.
Published: December 2007

This paper reports on a new model which upgrades earlier history matches of Shell’s Peace River in-situ bitumen sands recovery process. The new model uses a four component oil phase description which includes high and low molecular weight components, carbon dioxide and methane. A mild thermal cracking reaction based on laboratory tests reduces bitumen viscosity to match produced fluid viscosity. A water-rock reaction which generates carbon dioxide is also used in the model.

Two Cartesian and one radial simulation prototypes of the reservoir are described. A 1/12th element of symmetry model of inner and outer wells of seven 7-spot patterns uses 59 ft [18 m] grid blocks and is adequate for modeling the steam drive. Another 1/6th element of symmetry model of a single 7-spot pattern using 29 ft [8.8 m] grid blocks is adequate for modeling soak processes. Both models require connection to a pseudo-aquifer beyond the patterns to represent historical performance. Details of the models and history match results are presented.

A radial model history matched to the extensive field data gathered from a high rate injectivity/productivity single well test and subsequent multiple soak cycles formed the initial basis for all models. Subsequent matching of average performance of seven 7-spot patterns (PRISP) with the 1/12th element of symmetry model indicated that reduced bitumen mobility was required. By adjusting Kv/Kh and the activation energy of the mild thermal cracking a good match with PRISP field data was obtained, while yielding and overall reasonable but a poor oil production match to the single well test.

History matching of the early production response of the Peace River Expansion Project (PREP) on a cluster by cluster basis has resulted in an improved understanding of significant process mechanisms at work during the soak cycles and subsequent pressure cycle steam drive. The numerical model was used to evaluate current operations at PREP. This evaluation showed that a low pressure continuous steamdrive was a viable alternative to the pressure cycling process. As a consequence of this work and additional operational benefits recognized, the project was converted to a continuous steam drive in October, 1990 after the completion of the first pressure cycle.
Performance Prediction for Finite-Conductivity Vertical Fractures
Authors: Azari M. , Soliman M. Y. , Wooden W. O. , Hunt J. L.
Published: December 2007

An analytic solution for finite-conductivity, vertically fractured wells is developed for both the constant-pressure and the constant-rate cases1,2. This solution includes linear skin on the fracture, wellbore and fracture storages, wellbore phase redistribution, and fracture-to-formation height ratio. The Laplace-space solution is direct, and no convolution is performed to include the skin, storage, and phase segregation effects.

This paper presents type curves and corresponding analysis techniques for constant-pressure declining rate cases. A unique asymptotic approach to pseudoradial flow is used to produce the solutions for the unbounded reservoirs. The type curves provide all possible flow regimes encountered in pressure transient testing of finite-conductivity, vertically fractured wells. Tabulated comparison between this analytic solution and the ones obtained with finite-difference simulator for both bounded and unbounded formations are also provided.
A Practical Approach for Analysis of a Pressure Transient Test from a Horizontal Well in a Gas Storage Reservoir
Authors: Zuber M. D. , Holditch S. A. , Deters J. C. , Lee W. J.
Published: December 2007

A pressure transient test (injection/falloff test) was conducted on a horizontal well in a gas storage reservoir to obtain a reservoir description for injection and production analysis. In our analysis of the test data, we used currently available analytical solutions for a horizontal well in a closed, rectangular reservoir. We found that it was difficult to reach a high level of confidence in the reservoir description obtained from analysis of the test data using only analytical solutions because of uncertainties associated with identification of the various flow regimes. Therefore, we used a reservoir simulator to validate and improve the accuracy of the reservoir description derived from the analytical solutions. The improved reservoir description led to an accurate forecast of the horizontal well’s injectivity and productivity, further verifying the utility of this approach to test analysis and of the inherent value of the idealized analytical solutions.
The Role of SPE in International Oil
Authors: Chatas A.T.
Published: December 2007

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Although the oil industry was born and reared in the U.S.A., its centroid of activity has shifted to an international base. As a consequence, an effective program by the SPE is required in foreign countries for foreign-based engineers. The planning and implementation of such a program should consider certain apparent differences between foreign and domestic oil operations and also the problems facing the expatriated engineer. Several specific objectives are recommended for incorporation in this program.

Introduction

Historically speaking, the "story of petroleum" stretches back into the limbo of pre-civilized man. Surface oil seeps had been known in ancient times, and the Zante field of Greece is still often referred to as the world's oldest oilfield. In the Far East, wells were used in Burma to recover oil by Mining methods as far back as the Thirteenth Century. Official archives record petroleum production in Roumania in 1857. production in Roumania in 1857. Nevertheless, the fact remains that the "oil industry", as we now know it, was born in the U.S.A. It was born with the completion of Drake's well at Titusville Pennsylvania on 27 August 1859. This was the first well ever drilled with success deliberately to search for oil. Subsequently, the oil industry grew and matured in this country, and for almost a century America predominated virtually every phase of petroleum activity. As recently as the era of the Second World War, the U.S.A. led the rest of the world in every significant category. American petroleum reserves were abundant, we out produced all other countries combined, and we were the world's principal petroleum consumer.
Two-Phase Transient Testing of Water Injection Wells in Layered Reservoirs
Authors: Abbaszadeh M. D.
Published: December 2007

This paper presents analytical solutions and interpretation methods for transient testing of water injection wells in a commingled multilayer oil reservoir without crossflow in the formation. The solutions account for saturation distributions that are established in the layers due to relative permeability effects. These solutions show that pressure falloff data usually provide averaged waterflooding parameters for a layered reservoir, and that the properties of individual layers may not be obtained uniquely from such data. An alternate testing and interpretation technique based on simultaneous acquisition of transient downhole layer flowrates and bottomhole pressure is presented. The sensitivity of the interpretation method to errors in flowrate measurements is discussed.
A New Technique for Linear Boundary Detection with Wellbore Storage and Wellbore Skin
Authors: Chu L. , Grader A. S.
Published: December 2007

This paper presents an analytical solution for a finite radius well with wellbore storage and skin in a two-composite reservoir separated by a linear boundary. The constant-pressure and impermeable linear boundary are limiting forms of the composite case. The solution technique, which employs the Laplace transformation and the addition theorem for Bessel functions, is new and is different from past works. This solution is a subset of a generalized multi-well composite-reservoir solution.1

An analysis technique, both predictive and interpretive, for detecting an impermeable linear boundary using pressure transient data from a well with storage and skin is presented. A new set of pressure and pressure-derivative type curves are advanced along with a new correlating parameter, CD es / LD. This parameter correlates all the responses when CD / LD2 ≥ 0.1, where combined effects of wellbore storage and the boundary interfere with the formation of the first infinite-acting, semi-log straight line. The interpretation technique yields estimates of the distance to the linear boundary, reservoir transmissivity and wellbore storage. The effects of a constant-pressure linear boundary on a constant-rate well with storage and skin are discussed. Also, the parametric behavior of true composite reservoirs separated by a linear boundary is presented.
Development and Applications of an Improved Cubic Equation of State
Authors: Haynes B. , Silberberg I. H.
Published: December 2007

Compositional reservoir simulators require volumetric and compositional predictions of reservoir fluids from an Equation of State (EOS). This paper presents a method to optimize the parameters of a General Cubic EOS. The generalized cubic has four parameters that are related to the compositions of mixtures through pure component critical properties and binary interaction parameters.

The method to improve density predictions is a two-step process. First, the EOS parameters ξc, b, and γ are optimized from a nonlinear least squares regression of pure component volumetric data. This step insures that the critical constraints and the fugacity criterion are met. The second step extends the predictions to binary mixtures by introducing quadratic mixing rules to the parameters a, b, α, and β, including binary interaction parameters kij. Two iterative techniques were developed to establish values for the kij.

The average density predictions of three single-phase multicomponent hydrocarbon systems and 26 pure components were within 1% and 0.5% of their respective experimental values. The commonly used Peng-Robinson EOS (PR) predicted densities of these multicomponent hydrocarbon mixtures and pure components within 4% and 3%, respectively. Although emphasis was placed on improving density predictions, phase composition predictions of seven multicomponent hydrocarbon systems were also compared to the predictions from the PR EOS.
Futurizing the Continuing Education Program For SPE Members
Authors: Sarem A.M. Sam
Published: December 2007

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

The SPE was one of the first technical societies to formally initiate a continuing education and refresher course program on the national level. Although this program was enthusiastically supported at the start, a decrease of enthusiasm has recently been observed. It is hoped that a review of the program at this time will help to renew program at this time will help to renew enthusiasm among the membership. In this paper the author, who recently taught the paper the author, who recently taught the SPE Advanced Reservoir Engineering course for the LA Basin Section (last course organized by the late Floyd Schoonover), discusses some of the problems that are arising and offers some possible solutions to them. possible solutions to them. The suggestions detailed below are concerned with type of material and technical content of the courses (whether they should be practical or theoretical), fields covered, types of presentation (short course, study group, forum, etc.), duration of each course, spacing of various courses, desired varieties, and requirements of small sections versus large sections.

Included in the Paper are suggestions offered by students who have taken some of the SPE courses.

Introduction

The inability of a professional man to keep abreast of the new technical developments in his field and to retain the knowledge he gained through his formal schooling is termed technical obsolescence. The problem is not new; it is as old as civilization itself. However, because of its increasing intensity in recent years, we have now become more aware of the problem. We now live in an age where technical development in any given decade is equal to, if not greater than, all prior technical development.

The traditional means of warding off technical obsolescence has been continuing education. For the reason noted above, this is more important today than it has ever been. Today, as a consequence of the ever-increasing production of new knowledge, the conventional production of new knowledge, the conventional methods and tools used by the professional man to solve his technical problems are no longer sufficient. They must continually be augmented by up-to-date information.

Almost all technical societies have met this challenge squarely by providing continuing education programs for their members.
Influence of Multiphase Flow in Well Test Analysis of Nonflowing Wells
Authors: Kato E. T. , Serra K. V.
Published: December 2007

This work considers the influence of multiphase flow (oil and gas) in well testing analysis of non-flowing wells: For example, Drill Stem Test (DST) and Slug Test. The problem is solved by a two-dimensional (r-z), variable bubble-point, black oil simulator that incorporates the typical DST inner boundary condition. Initially, the oil in the reservoir is in equilibrium condition at the initial reservoir pressure which is considered greater or equal to the initial oil bubble-point pressure. A sequence of flow and/or buildup periods can be imposed at the reservoir sandface to simulate a non-flowing well test condition. Inertial, friction, and multiphase flow effects in the wellbore are neglected. Comparisons with analytical methods (developed for single phase flow of a fluid of small and constant compressibility) traditionally used to obtaining reservoir parameters (eg., transmissibility) are made to determine how good or bad these methods are in the presence of more than one phase flowing in the porous medium. During flow periods significant discrepancies are obtained, whereas in buildup flow periods these discrepancies are less significative. Explanation to these multiphase flow effects on the determination of reservoir parameters are given in detail, and justify why, usually, reservoir parameters obtained from flow tests do not match results obtained from build up periods in well test analysis.
Pressure Transient Behavior of Slanted Wells in Single- and Multiple-Layered Systems
Authors: Khattab H. A. , Yeh N-S. , Agarwal R. G.
Published: December 2007

In recent years, a need has been recognized to develop pressure transient technology for slanted wells in single and multiple layered systems. To date, none of the published results pertains to the pressure transient response of a slanted well in a layered system. Moreover, the published pressure transient response of a slanted wellbore for single layered systems is based on a uniform flux assumption along the wellbore surface. Therefore, a 3-D finite element numerical model utilizing the infinite conductivity wellbore assumption was developed to study the pressure transient behavior of slanted wells in both single and multiple layered systems.

The purpose of this paper is to present pressure transient responses for a variety of cases using the finite element and the analytical solutions. The slanted wellbore cases include the effect of partial penetration, wellbore storage, and reservoir heterogeneity for single layered systems, and typical pressure transient responses for multiple layered systems. The important parameters which influence the pressure behavior of slanted wells in a layered reservoir, with and without interlayer cross-flow, will be presented. In addition, the response of a slanted well in a naturally fractured (dual porosity) system will be discussed. Finally, the pressure transient analysis of the data using field examples will be shown to demonstrate the usage of the developed model.

The present study of the pressure transient responses of slanted wells in both single and multiple layered systems should enhance our understanding and add to our capability to design and analyze well tests.
An Advanced and Integrated Approach to Coal Formation Evaluation
Authors: Ahmed U. , Johnston D. , Colson L.
Published: December 2007

The new surge in drilling for coalbed methane gas brought on by the attractive tax credits has increased the need for quantitative evaluation of coal formations. The potential resource base in the U.S. alone is on the order of 422 Tcf. Currently available petrophysical and fluid flow mechanistic models for gas reservoir analysis in traditional clastic or carbonate environments are notably inadequate for coal formation evaluation and well productivity assessment. Existing coal formation evaluation techniques rely on core measurements and certain basic log measurements such as "bulk" density, The evaluation program as such, is typically site specific and devoid of critical answers like recoverable reserves and well productivity assessment. Additions and improvements to the existing technology are needed to efficiently exploit the production of methane gas from coalbeds.

In this paper we present a methodology that integrates the existing technology with new measurements and techniques. Such a procedure can allow one to evaluate the coal formation specifically for identification, resource definition (thickness), gas content (reserves), recoverable reserves (permeability, porosity and reservoir pressure) and to plan for the de-watering process (reservoir performance). The methodology provides evaluation alternatives depending on the coal seam thickness and the type and concentration of the fracture system. The thin laminated coal seams found in basins like the Black Warrior and the Appalachian require a different evaluation suite of logs compared to those required for the relatively thick (greater than 2 ft) coal seams found in the San Juan and Piceance Basin. Also, the type and concentration of fractures within the cleat system dictate the capillary pressure pattern and thus may require specific transient pressure tests. The majority of coal basins found in the U.S., Canada, U.K., Central Europe and Australia can be broadly categorized within the above aspects of seam thickness and fracture system distribution.
Improved Models for Interpreting the Pressure Response of Formation Testers
Authors: Waid M. C. , Proett M. A. , Chen C. C. , Ford W. T.
Published: December 2007

New finite element models are presented in this paper which describe the pressure response of formation testers. The influences of formation anisotropy, bed thickness, and horizontal and dipping bed boundaries are investigated. The simulator utilizes techniques for grid optimization already used in improving the quality of finite element solutions for stress analysis of elastic solids and structures. Examples are given comparing interpretation results using the simulator against results obtained using prior standard models.

Near-wellbore simulation (NEWS©) permits the investigator to introduce factors into the model in a manner consistent with basic principles of physics. A new analytic model is presented which incorporates some of the new observations from the finite element models, maintains space-dimensional consistency, and decouples the formation anisotropy and fluid compressibility relationship assumed in the development of the classical spherical flow model by Moran and Finklea.1

Observation points placed at strategic locations in the formation and around the wellbore allow investigation of the pressure response of formation testers with multiple-sensor capability.

New techniques are presented for interpreting the pressure response of formation testers. NEWS© is a powerful tool for understanding and predicting the near-wellbore production dynamics of a well. It is anticipated that the simulations will lead to verification of new or existing models and will aid in developing improved tools and interpretation techniques.
The Combined Use of Sedimentary Process Modeling and Statistical Simulation in Reservoir Characterization
Authors: Tetzlaff D. M.
Published: December 2007

The results of a sedimentary process model are used to provide lithologie variability information to a stochastic conditional simulation model. The scenarios thus produced incorporate constraints imposed by geologic processes, yet honor hard data. The method appears to have advantages over other methods when data are sparse.
A New Economical Method of Subsea Completion for Jackup Depth Waters
Authors: Brown R. , Pierce J. W.
Published: December 2007

This paper describes a new economical concept in subsea drilling and completion that has allowed the justification and recent installation of a diver-assist wet subsea tree in the Gulf of Mexico from a jack-up rig. This concept reduces costs on subsea completions and now makes profitable the production of innumerable small reservoirs, either looked at and counted uneconomical by previous parameters, or yet to be discovered small reservoirs in the marine environment. The simplicity of this concept greatly reduces costs and allows the operator to use the concept on every exploratory well drilled from a jack-up rig.
Optical Methods for Monitoring Treating Chemicals in Oilfield Water Systems
Authors: Brost D. F. , Rexach F. M. , Winslow G. A.
Published: December 2007

Spectroscopic methods of analysis have been developed for the determination of treating chemicals in oilfield water systems.

Part 1 describes a xenon flash photometer (XFP) that was designed for on-line measurements under harsh, oilfield conditions. The instrumentation is capable of absorption and fluorescence measurements in the ultraviolet and visible spectral ranges. Chemicals are determined by virtue of their ability to absorb or emit light at characteristic wavelengths. Light signals are carried between a central photometric console and remote analysis sites by fiber optic cables, eliminating the need for troublesome flow-through cells. Aspects of instrumental design, drift compensation, and calibration methodology are discussed. Laboratory and field data are presented.

Part 2 describes the potential of short-wave ultraviolet spectroscopy for the simultaneous determination of multiple treating chemicals in supply water. Absorption measurements at wavelengths between 190 and 250 nm are shown to yield part-permillion sensitivity for a wide range of chemical products. The severe spectral overlap, which has previously limited the analytical utility of this portion of the spectrum, is overcome by multivariate calibration. Using this technique, a scale and corrosion inhibitor were simultaneously determined from a single spectrum with approximately 2% relative error.
Walking Beam Pumping Unit System Efficiency Measurements
Authors: Kilgore J. J. , Tripp H. A. , Hunt C. L.
Published: December 2007

The cost of electricity used by walking beam pumping units is a major expense in producing crude oil. However, only very limited information is available on the efficiency of beam pumping systems and less is known about the efficiency of the various components of the pumping unit.

This paper presents and discusses measurements that have been made on wells at several Shell locations and on a specially designed walking beam pump test stand at Lufkin Industries. These measurements were made in order to determine the overall system efficiency and efficiency of individual components.

The results of this work show that the overall beam pumping system efficiency is normally between 48 and 58 percent. This is primarily dependent on the motor size, motor type, gearbox size, system’s age, production, pump size, tubing size, and rod sizes. Typically the surface unit efficiency (including the motor) is between 60 and 75 percent and the subsurface equipment efficiency is between 70 and 85 percent for well designed systems.
Alternate Path Gravel Packing
Authors: Jones L. G. , Yeh C. S. , Yates T. J. , Bryant D. W. , Doolittle M. W. , Healy J. C.
Published: December 2007

A new and superior gravel packing method called ALLPAK™, for alternate path gravel packing, is reported here. It has been found that gravel packing problems associated with formation of sand bridges in the annulus outside the screen can be eliminated by adding alternate flow paths for slurry flow. The alternate paths are provided by perforated shunts or secondary piping placed in the annulus, usually by attaching the tubes to the screen. Laboratory gravel pack simulator tests indicate that essentially complete annulus packs can always be obtained, even in cases where current methods provide very poor pack efficiencies. This paper describes the laboratory experiments and field tests which verify the advantages from this new concept.
Measurement of Additional Skin Resulting From Perforation Damage
Authors: Behrmann L. A. , Pucknell J. K. , Bishop S. R. , Hsia T.-Y.
Published: December 2007

Single shot laboratory flow tests were performed on perforated Berea and Gold sandstone cores to determine the additional skin caused by the presence of a perforation damage zone. A variety of underbalances, stresses and wellbore volumes were used.

Whole core diametral and axial permeabilities were measured for each core tested. Cores were then perforated under simulated downhole conditions, and radial flow tests were conducted to determine the skin due to the perforation damage zone. Because these measurements gave no information on the distribution of permeability damage, further experiments were carried out using a radial flow permeameter to directly measure the permeability distribution.

The radial flow permeameter confirmed the presence of a low permeability region around, but not always adjacent to, the perforation tunnel. Permeability damage at the outside of the cores due to the coring process was also determined.

Although one set of experiments shot under identical conditions, at a low underbalance, showed a degree of randomness in the results, the following observations could be made: 1) For the conditions tested, there is no apparent stress effect on the perforation damage skin, 2) The size of accumulator attached to the wellbore affected the resulting skins, and 3) Results of single shot experiments should be used with extreme care.
Mathematical Simulation of Nonequilibrium Separation in Gas Production Equipment
Authors: Sinaisky A. G. , Zaitsev Y. V. , Shevelev D. I.
Published: December 2007

New methods for predicting non-equilibrium phase behavior of natural multicomponent gas/gas-condensate dispersed systems in regions with sharp change of pressure, temperature and geometric parameters with application to main processes of gas preparation for transport such as separation, absorption and dewatering are developed. Mathematical simulation includes processes of mass-transfer flow with sedimentation and deposition, breakage and coagulation of droplets in gas flow.

Using these methods efficiency of gas production equipment with change of pressure, temperature, physico-chemical properties of gas/gas-condensate mixture and constructive design parameters of equipment may be determined without carrying out experiments.

As a result application programs for computing phase separation parameters are created. Appropriate software structure is described. Some examples of determining efficiency of different separators (gravitational, centrifugal, with droplet capture sections), co- and counter- current absorbers for extracting higher hydrocarbons and water from natural gas and whole technological plant for gas and gas-condensate preparation are presented. Received results are in good agreement with experimental ones.
System Design for the Measurement of Downhole Dynamic Rheology for Foam Fracturing Fluids
Authors: Spörker H. F. , Trepess P. , Valkó P. , Economides M. J.
Published: December 2007

To investigate the rheology of multi-phase fluids and especially foams under realistic field conditions a downhole flow loop has been constructed and tested. The interactions between gravitational, frictional and other (e.g. gas solubility) factors have been investigated and isolated in a series of experiments. Here the system design of the multi-phase fluid flow loop and the special considerations of the design and their justification are described. To evaluate the data a new two-phase flow equation and a methodology of interpretation are outlined. Applications of the methodology in the treatment of sample data are also presented. The choice of a vertical instead of a horizontal apparatus is justified from the fundamental treatment in this work. It shows that the presence of the gravitational effects magnifies the frictional effects, allowing their more accurate estimation.
Using a Simulated Bidirectional Associative Neural Network Memory with Incomplete Prototype Memories to Identify Facies from Intermittent Logging Data Acquired in a Siliciclastic Depositional Sequence: A Case Study
Authors: Baldwin J. L.
Published: December 2007

This case study compares core photographs, core analysis, a geologist’s facies analysis, sequence stratigraphie analysis, and a description of cores to facies identified by a Simulated Neural Network (SNN). The SNN operates by mimicking human-like reasoning-under-uncertainty from incomplete and partial inputs. The facies identified by the neural network matched those in the geologist’s facies description. The well from which these data were taken penetrates intertidal, lower shoreface, and shelf-to-lower shoreface sequences containing sandstones, siltstones, shales, mudstones, coal, and minor sandy-dolomite beds. Siltstones and mudstones are at times highly interbedded, burrowed, calcareous, and contain organic matter. The log database’s 1/4-foot depth increment currently limits the neural network’s resolution. However, the network’s resolution will be enhanced if dipmeter data is also input. In this case study, the network rapidly and accurately identified 11 lithofacies in the test interval.

Operation of this neural network does not require knowledge of geology or experience as a geologist, although assigning a name to the facies identified does require knowledge of the local geology. For this case study, a petrophysicist unskilled in geology performed all parameter selections.

Log analysts routinely adjust their log correlations and descriptions to incorporate the fact that log data are sometimes missing. In this study, acoustic shear waves could not be measured in facies composed of very soft rock. The neural network’s method of operation automatically accounted for the fact that shear data are missing across some intervals.

The SNN program used for this case study, as implemented on an affordable, highly accessible PC platform (but not restricted thereto), is suitable for depositional environment studies, facies identification, sedimentation studies, and well-to-well facies correlation. Additional applications include identification of productive intervals, and fracture identification.
Modeling and Laboratory Investigation of Microbial Transport Phenomena in Porous Media
Authors: Chang M-M. , Chung F. T-H. , Bryant R. S. , Gao H. W. , Burchfield T. E.
Published: December 2007

Simulation and experimental results on the transport of microbes and nutrients in one-dimensional coreflooding experiments are presented, and the development of a three-dimensional, three-phase, multiple-component numerical model to describe the microbial transport phenomena in porous media is described. The governing equations in the mathematical model include net flux of microbes by convection and dispersion, decay and growth rates of microbes, Chemotaxis and nutrient consumption, and deposition of microbes on rock grain surfaces. Porosity and permeability reductions due to cell clogging have been considered and the production of gas by microbial metabolism has been incorporated. Governing equations for microbial and nutrient transport are coupled with continuity and flow equations under conditions appropriate for a black oil reservoir.

The computer simulator has been used to determine the effects of various transport parameters on microbial transport phenomena. The model can accurately describe the observed transport of microbes, nutrients, and metabolites in coreflooding experiments. Input parameters are determined by matching laboratory experimental results. The model can be used to predict the propagation of microbes and nutrients in a model reservoir and to optimize injection strategies. Optimization of injection strategy results in increased oil recovery due to improvements in sweep efficiency.
An Improved Model of Mud Acid/Sandstone Chemistry
Authors: Bryant S. L.
Published: December 2007

The chemical reactions between mud acid (HF/HCl mixtures) and sandstone minerals are numerous and complex. To obtain tractable models of mud acid treatments it is common practice to approximate the chemistry as the dissolution of two "lumped" minerals. Examination of coreflood data shows that this approximation does not consistently account for HF consumption. In particular, this approach cannot account correctly for the effect of flow velocity. Consequently this model cannot reliably extrapolate laboratory data to different operating conditions. Neither can it be used with confidence in the simulation of well treatments, since local flow velocity decreases with distance from a well.

This paper presents an improved chemistry model that includes a secondary dissolution/precipitation reaction recently established in the literature. The improved model provides a consistent prediction of acid consumption. Thus this model provides a more reliable basis for extrapolating laboratory data and for simulating matrix acid treatments. The improved model also accounts for porosity changes more reliably, thereby providing a stronger basis for calculating productivity changes using permeability/porosity correlations.
Identification of a Desaturated Zone and Its Effect on Steamflood Performance/Development at Lost Hills, California
Authors: Kerns J. R. , Kirst T. L.
Published: December 2007

The Etchegoin B sand contains significant thermal recovery potential, but core data at Mobil’s Lost Hills 2 lease indicated unusually low oil saturations in the upper third of the reservoir. The geology of the B sand and its affect on fluid saturations is discussed. A pilot was designed and implemented to test steamflooding the B sand, and 16 months of performance data are presented.
Measurement of "Rock Properties" in Coal for Coalbed Methane Production
Authors: Gash B. W.
Published: December 2007

Standard laboratory techniques for measurement of rock properties (porosity, permeability and gas-water relative permeability) must be modified when applied to coal for use in coalbed methane reservoir engineering studies. Coal is unlike most conventional reservoir rock in that fluid flow occurs in a network of naturally occurring microfractures or cleats. Drying coal alters the cleat structure. Therefore, a miscible displacement technique, in which coal cores are not dried, was used to determine an upper limit for cleat porosities of around 2% for cores from coalbed methane wells. There is no significant difference between the cleat porosity measured with the miscible displacement technique and the mobile water porosity for a coal core, indicating there is little or no irreducible water saturation in the cleat network. (The mobile water porosity is the volume of water which is driven out of a water-saturated core by helium injection divided by the bulk volume of the core.) Absolute permeability to water in coal cores can decrease with continued flow by an order of magnitude, probably due to fines migration. Unsteady-state gas-water relative permeability techniques can be modified to handle both the small volumes of water produced from cores with less than 2% porosity and the decreasing absolute permeability. Representative unsteady-state gas-water relative permeability curves for San Juan and Warrior Basin cores which have been used in coalbed methane reservoir engineering studies are presented. In steady-state gas-water relative permeability measurements using sodium iodide as a tracer, sodium iodide adsorption on the coal surfaces will result in systematic error in saturation values. However, within the experimental error with which saturations in the cleat networks can be determined, unsteady-state and steady-state with sodium iodide gas-water relative permeability measurements yield the same results.
Simulation of a Gas Naturally Fractured Reservoir: A Case History
Authors: Au A. D. , Franks L. N. , Aguilera R.
Published: December 2007

This case history discusses the Palm Valley gas field in Central Australia. Production is obtained from a naturally fractured sandstone characterized by a very low matrix permeability (km <0.1 md).

An integrated study including detailed geology, core and log analyses, well testing and numerical simulation led to a good history match of a 33 hour interference test and over 7 years of production.

The conclusion was reached that 98% of the gas was stored in a very tight matrix and that the prolific production was only possible via a network of natural fractures.

The methodology used to reach a history match in this case history is presented in detail together with discussions of critical parameters such as fracture spacing, fracture porosity, and fracture permeability.
Quantifying Horizontal Well Logs in Naturally Fractured Reservoirs—II
Authors: Svor T. R. , Meehan D. N.
Published: December 2007

Naturally fractured reservoirs are the most significant target for horizontal wells in the U. S. While most of the horizontal wells drilled to exploit naturally fractured reservoirs are not logged, substantial useful information can be obtained by logging such wells. A previous paper1 contrasted various logging technologies including acoustic televiewers, sonic logs, and oriented microresistivity devices. Union Pacific Resources (UPRC) has logged 42 of the 120 horizontal wells drilled to date; 38 of these wells have been logged with Schlumberger’s Formation MicroScanner (FMS), an oriented microresistivity device. Extensive analysis of these logs on UNIX-based workstations and correlation with horizontal well performance has resulted in a correlation between the horizontal well fracture index (RFI) and horizontal well fluid Productivity Index (PI). Attempts to correlate RFI with ultimate oil or oil and gas recoveries have been unsuccessful; however, a correlation with ultimate fluid (oil+water) recoveries has been developed. These correlations have been used to integrate FMS information with artificial lift, stimulation, isolation, and repair decisions as well. Example cases are used to illustrate these decisions. Further, the quantified data have been used in making development, exploitation, and spacing decisions. Geostatistical techniques used in reservoir characterization efforts have also incorporated the spatial distribution and correlation of RFI density.
The Assessment of Geological Uncertainties in Development Project Planning
Authors: Bléhaut J-F.
Published: December 2007

This paper describes some of the results obtained in a large operating company after the implementation of new procedures for reserves calculations in development projects. A number of inconsistencies in historical trends of hydrocarbon-inplace volumes, together with an evolving business environment, justified the introduction of a new methodology where a more realistic assessment of geological uncertainties is emphasised. The experience gained so far indicates that, although the new approach is more manpower intensive, the benefits justify the extra effort. In particular, expectation reserves figures are positively affected, and the general quality of geological interpretations is enhanced. The economics of a few projects appear not to have taken sufficient account of geological risk. Finally, a worthwhile compromise between theory and practical use can be achieved without resorting to excessively sophisticated techniques.
An Improved Wireline Formation Fluid Sampler and Tester
Authors: Crocker H.
Published: December 2007

Research has been undertaken in the development of an improved wireline formation fluid sampler and tester. Formation fluids are pumped from the formation to the well bore at surface controlled rates. The formation fluid characteristics are measured and surface monitored. When the mud filtrate has been removed a sample may be taken. The resistivity, conductivity and temperature are measured and hence the formation water salinity may be determined.

Flowing fluid density is measured and thus oil, gas and condensate may be distinguished and the API gravity estimated. There is almost no theoretical limit to the number of samples that may be taken and therefore the entire well may be tested and the salinity and pressure profiles recorded. The use of controlled flowrates to match the reservoir deliverability and the surface recording of flow pressures allows multi-rate testing, the determination of permeability and formation damage. Since the reservoir pressure may be measured after repeated small fluid volumes are taken, the problem of supercharging or depletion, that often invalidate present wireline measured pressure profiles in low permeability formations, may be avoided. An isolation valve is used to trap a known volume of hydrocarbons, taken under minimum drawdown, which is then expanded to determine the compressibility and bubble-point. These tests may be repeated to ensure accuracy.
Formation Damage in Heavy-Oil Formation During Steamflooding
Authors: Okoye C. U. , Onuba N. L. , Ghalambor A. , Hayatdavoudi A.
Published: December 2007

An experimental study was undertaken to examine formation damage due to plugging caused by precipitates and scales generated from the dissolution of silicate compounds and associated minerals. The experimental tests include: roller oven tests, petrographic, SEM and EDEX studies. The tests were carried out at various temperatures (200°F to 500°F) and steam alkalinity in order to ascertain the factors and conditions that lead to formation damage and wellbore erosion during steam injection.

The results from this investigation indicate that elevated temperatures (above 200°F) as a factor can cause irreversible formation damage because of hydrothermal effects. Also high PH causes irreversible formation damage mostly due to hardness precipitation from divalent ion exchange processes. The combined effect of temperature and alkalinity increases the degree of formation damage at low temperatures (below 200°F). However, at high temperatures, the more severe formation damage caused by increased alkalinity can be reduced by thermal effects. Formation crystals and precipitates seems to be hindered at temperatures above 300°F. SEM, X-Ray, EDEX and petrographic analyses show pseudo-hexagonal stacks of mineral overgrowth which blocked pore throats. The SEM micrographs show the dissolution of certain minerals such as kaolonite and the precipitation of aluminosilicate compounds such as zeolite.