bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stochastic Formulation for Uncertainty Analysis of Two-Phase Flow in Heterogeneous Reservoirs
Authors: Zhang Dongxiao , Li Liyong , Tchelepi H. A. 
Published: December 2007

Summary
In this article we use a direct approach to quantify the uncertainty in flow performance predictions due to uncertainty in the reservoir description. We solve moment equations derived from a stochastic mathematical statement of immiscible nonlinear two-phase flow in heterogeneous reservoirs. Our stochastic approach is different from the Monte Carlo approach. In the Monte Carlo approach, the prediction uncertainty is obtained through a statistical postprocessing of flow simulations, one for each of a large number of equiprobable realizations of the reservoir description.
We treat permeability as a random space function. In turn, saturation and flow velocity are random fields. We operate in a Lagrangian framework to deal with the transport problem. That is, we transform to a coordinate system attached to streamlines (time, travel time, and transverse displacements). We retain the normal Eulerian (space and time) framework for the total velocity, which we take to be dominated by the heterogeneity of the reservoir. We derive and solve expressions for the first (mean) and second (variance) moments of the quantities of interest.
We demonstrate the applicability of our approach to complex flow geometry. Closed outer boundaries and converging/diverging flows due to the presence of sources/sinks require special mathematical and numerical treatments. General expressions for the moments of total velocity, travel time, transverse displacement, water saturation, production rate, and cumulative recovery are presented and analyzed. A detailed comparison of the moment solution approach with high-resolution Monte Carlo simulations for a variety of two-dimensional problems is presented. We also discuss the advantages and limits of the applicability of the moment equation approach relative to the Monte Carlo approach.
A Simple Spinning-Drop Interfacial Tensiometer
Authors: Gash Bruce , Parrish D.R. 
Published: December 2007

This article describes the design and use of a simple, relatively inexpensive device for measuring interfacial tension by the spinning-drop technique. The benefit of low interfacial tension between crude oil and a displacing phase (such as a micellar fluid) in tertiary oil recovery is well documented in the literature. Cayias et al. at the U. of Texas perfected the spinning-drop technique for measuring interfacial tension and created a great deal of interest in the use of this technique for formulating suitable micellar fluids. They designed, fabricated, and offered spinning-drop interfacial tensiometers for sale. Because of its capability of operating over a wide range of rotational speeds, the instrument is rather expensive. Use of spinning-drop interfacial-tension measurements for screening, designing, and evaluating micellar fluid systems requires several instruments because a single instrument can be used to make only about four measurements per day, depending on equilibration time. Thus, there is a real need for inexpensive spinning-drop instruments that permit interfacial-tension measurements for formulating micellar fluids on a "mass production" basis. We have found that for interfacial-tension measurements in the millidyne/centimeter region the capillary containing the fluids can be rotated conveniently at 3,600 rpm. A simple and comparatively inexpensive fixedspeed spinning-drop tensiometer can be made easily by using an aluminum collar to fasten a capillary tube to the end of the shaft of a hysteresis synchronous motor driven at 3,600 rpm by the line frequency (Fig. 1). Good quality motors of this type are smooth running and well balanced.
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Detection and Location of Two Parallel Sealing Faults Around a Well
Authors: Djebbar Tiab , Anil Kumar 
Published: December 2007

A new technique is presented for detecting the existence of and distance to two parallel sealing boundaries surrounding a producing oil or gas well. A log-log plot of time rate of change of well pressure vs. time provides a unique behavior to detect such a condition and allows the use of type-curve matching techniques to determine the khproduct.

Introduction
The idea of detecting and locating a reservoir boundary from transient pressure-time data first appeared in 1951. In that year Horner1 presented the transient pressure behavior of a constant-rate well located near a linear sealing fault. He also presented a method to calculate the distance to the fault from buidup pressure data. Dolan et al.2 applied the technique to drillstem tests. Davis and Hawkins3 gave an equation to determine the distance to the fault from drawdown pressure data. Gray4 reviewed these methods and discussed their limitations.
Bixel et al.5considered a more general problem: a well located close to a linear discontinuity across which hydraulic diffusivity changes. They showed a procedure to determine the distance to such a discontinuity.
Evrenos and Rejda6 employed superposition techniques to simulate various combinations of linear boundaries of interest in gas storage systems and showed how a match between the actual test data with various hypothesized model conditions can be used to arrive at a probable configuration of boundary conditions.
Overpeck and Holden7 considered the effect of reservoir anisotropy on fault detection and showed that the distance calculated could differ by as much as 20% with those obtained by assuming isotropic medium. They gave a procedure for imaging when the principal permeability axes are at some angle other than 0 or 90° to the fault boundary.
Rodgers and McArthur8 employed a minimum in standard deviation between observed pressures and a least-squares straight-line fit to determine boundary configuration. Prasad9presented a procedure to compute transient pressures for a well between two sealing faults intersecting at any angle.
Jones10 in 1961 drew attention to the possible use of rate change of well pressure with time in detecting reservoir boundaries. Van Poollen11 presented graphs of time rate of change of well pressure during drawdown for various well locations between faults intersecting at 90 and 36°. Although this approach yields interpretable drawdown behavior, it has not been used widely in the petroleum literature.
Witherspoon et al.12 considered the effect of a linear no-flow or flow boundary and presented the dimensionless pressure behavior caused by a constant-rate producing well at an observation well some distance away. They discussed techniques to analyze drawdown test data.
The Contrast in Initial and Present Application of the Term, "Connate Water"
Authors: Case L.C. 
Published: December 2007

For several years it has been noted that the use of the adjective "connate" as applied to buried waters has become increasingly confusing. Recently published articles and discussions on core analyses have made no progress toward clarification of the terminology of pore water. Rather, it would appear that the situation has deteriorated to the extent that very few engineers have a clear idea concerning the conditions implied by "connate" in description of the water of oil formations.
The existing varied usage is best illustrated by the opinions received from a number of engineers. These men are all reservoir or petroleum engineers, excepting one who is a mechanical engineering graduate serving as field area engineer. The following definitions of "connate" water were obtained orally, no time being allowed for reference or discussion.Irreducible minimum water, by any method of obtaining restored state.Interstitial water in the formation, with oil, before wells are drilled.Interstitial water in pores of formation. normally immovable.Interstitial water - will not move.Irreducible water of saturation, sometimes producible.Interstitial water in formation, not necessarily with oil.Water in formations which is immobile.Original water in place.Water which fills finer pores, with oil and above oil-water contact.The per cent of water saturation in an oil reservoir which exists before wells are drilled.Water remaining in the rocks after partial displacement by oil or gas.Water existing in formations before wells are drilled. Some is mobile, some is not.
The absence of agreement in the above definitions is remarkable. Let us now examine briefly the original conception of the term "connate water" and the vicissitudes to which it has been subjected in the last two decades of its 50-year history.
The word "connate" is of Latin origin and antedated considerably its application to subsurface waters. The initial use of "connate water," occurring in 1906 and being firmly established in succeeding publications prior to 1930, caused it to appear in dictionaries long before engineers became aware of core analyses and their interpretation. Webster's New International Dictionary still carries the unchanged definition: "Connate water. Geol. Sea water held in the interstices of sedimentary deposits and sealed in by the deposition of overlying beds."
Conditioning Stochastic Reservoir Models to Well-Test Data
Authors: He Nanqun , Oliver Dean S. , Reynolds Albert C. 
Published: December 2007

SummaryGenerating realizations of reservoir permeability and porosity fields that are conditional to static and dynamic data are difficult. The constraints imposed by dynamic data are typically nonlinear and the relationship between the observed data and the petrophysical parameters is given by a flow simulator which is expensive to run. In addition, spatial organization of real rock properties is quite complex. Thus, most attempts at conditioning reservoir properties to dynamic data have either approximated the relationship between data and parameters so that complex geologic models could be used, or have used simplified spatial models with actual production data.In this paper, we describe a multistep procedure for efficiently generating realizations of reservoir properties that honor dynamic data from complex stochastic models. First, we generate a realization of the rock properties that is conditioned to static data, but not to the pressure data. Second, we generate a realization of the production data (i.e., add random errors to the production data). Third, we find the property field that is as close as possible to the uncalibrated realization and also honors the realization of the production data. The ensemble of realizations generated by this procedure often provides a good empirical approximation to the posteriori probability density function for reservoir models and can be used for Monte Carlo inference.We apply the above procedure to the problem of conditioning a three-dimensional stochastic model to data from two well tests. The real-field example contains two facies. Permeabilities within each facies were generated using a "cloud transform" that honored the observed scatter in the crossplot of permeability and porosity. We cut a volume, containing both test wells, from the full-field model, then scaled it up to about 9,000 cells before calibrating to pressure data. Although the well-test data were of poor quality, the data provided information to modify the permeabilities within the regions of investigations and on the overall permeability average.
Drag Forces on an Accelerated Cylinder
Authors: Laird A.D.K. , Johnson C.A. 
Published: December 2007

Abstract
Drag coefficients for a cylinder being towed through water at constant velocity and also at constant linear acceleration were measured. Drag coefficients for constant velocity towing showed reasonable agreement with previous results. The drag coefficients found for constant acceleration showed little correlation with either the magnitude of the acceleration or the value of the modulus and tended to be slightly lower than those for constant velocity.

Introduction
For the design of offshore structures, wave forces acting on immersed cylinders are of importance. Several investigations have been made of these forces and of how they can be predicted from wave theories. A paper by Crooke summarizes much of the work already done. More recent research by the Wave Research Laboratory at the University of California, Berkeley, has added much to the body of data collected under ocean wave conditions, but has not found a reliable method of force prediction from basic theories of wave motion. The present investigation is part of a long-range program to collect data with which to test current and future theories and correlations. The immediate objective was to measure drag forces on a circular cylinder subjected to linear accelerations over a range of Reynolds numbers where the drag coefficient was a constant for constant velocities. In particular, the effect of constant acceleration from rest and from uniform motion was to be investigated.
Determination of Oil/Water Saturation Functions of Chalk Core Plugs From Two-Phase Flow Experiments
Authors: Bech Niels , Olsen Dan , Nielsen C. M. 
Published: December 2007

SummaryA new procedure for obtaining oil/water saturation functions, i.e., capillary pressure and relative permeability, of tight core samples uses the pronounced end effect present in flooding experiments on such material. In core material with high capillary pressure, the end effect may allow determination of the saturation functions for a broad saturation interval. A complex coreflooding scheme provides the fluid distributions and production data from which the saturation functions are computed for both drainage and imbibition by a least-squares technique. A chemical shift NMR technique is used for fluid distribution determination. An undesirable interdependency of the saturation functions is avoided by their calculation from different data sets. Killough's method is employed to account for the scanning effect in hysteresis situations for both capillary pressure and relative permeability. The procedure is demonstrated on chalk samples from the North Sea. The experimental time is intermediate between the centrifuge and porous plate methods.
Thermodynamic Micellization Model for Asphaltene Precipitation From Reservoir Crudes at High Pressures and Temperatures
Authors: Pan Huanquan , Firoozabadi Abbas 
Published: December 2007

Summary
Asphaltene precipitation from reservoir crudes has been modeled using liquid-liquid equilibrium; the precipitated heavy phase is assumed to be in the liquid state and to consist of only asphaltene and resin. The light liquid phase is assumed to consist of the monomers of all the components and the micelles. A thermody-namic micellization model and the Peng-Robinson equation of state (EOS) description of all monomers fully describe the ther-modynamic equilibrium state. From the direct minimization of the Gibbs free energy of the liquid-liquid system, the composition and the amount of each of the phases are calculated.
The above model is used to calculate precipitation from three different reservoir crudes. Once vapor-liquid equilibrium parameters are obtained, there is no further adjustment of the parameters of the EOS for precipitation calculations. The predictions from the thermodynamic micellization model are in good agreement with the data. The effect of pressure, temperature, and composition on precipitation is properly predicted by the model.
Designing Effective Sandstone Acidizing Treatments Through Geochemical Modeling
Authors: Quinn M. A. , Lake L. W. , Schechter R. S. 
Published: December 2007

SummaryThis work reports on the application of a complex kinetic geochemical model to explore key issues in sandstone acidizing.1 The issues include the importance of the minerals initially present, the consequences of mineral precipitation, and the effect of acid formulation and injection rate. The model's capabilities exceed those of its predecessors that have greatly simplified the reaction chemistry or have ignored kinetics altogether. No assumptions were made as to the nature of precipitation that could ensue; all potential precipitates were considered.An important advance is the use of a new permeability prediction model taken from the work of Panda and Lake.2 This model relates the permeability of a permeable medium to the porosity, grain size distribution and the amounts and identities of all detrital minerals present. Coupled with the reaction chemistry, this model allows predictions that are relevant for specific treatments. The use of this model also gives quite realistic productivity improvement predictions.We study three cases of generic mineral assemblages: high quartz, high clay, and high feldspar. Model results indicate that the precipitation of reaction products is both inevitable and substantial. Hence, the optimal matrix stimulation is a compromise between maximizing the dissolution of the damaging minerals and minimizing secondary precipitation. Given such competitive effects, our results indicate that high rate stimulations tend to give the largest productivity improvements even though these usually do not cause the largest removal of damaging minerals.
Injectivity Decline in Water-Injection Wells: An Offshore Gulf of Mexico Case Study
Authors: Sharma Mukul M. , Pang Shutong , Wennberg K. E. , Morgenthaler L. N. 
Published: December 2007

SummaryA decline in injectivity in water injection wells can have a large impact on the economic feasibility of offshore water disposal operations. A case study is presented for an offshore Gulf of Mexico water injection project. Data are presented for five typical offshore wells for which a rapid decline in injectivity was observed due to water injection. The wells were successfully acidized every few months over a period of 2 years. An analysis of the data indicates that in injection wells that are not fractured, such declines in in-jectivity may be expected even for relatively clean injection water. A comparison of the different completion types indicates that both open hole and perforated completions would have yielded similar results. Cleaner water would have improved the situation but at a substantial cost. Fracturing the injection wells appears to be the only plausible way of substantially increasing the half life of such injectors. In cases where reservoir conditions dictate that the wells not be fractured, the economics of periodic stimulation vs. the cost of installing surface facilities for cleaning up the water should be evaluated using models for injectivity decline. "What if" simulations conducted to study the impact of different process parameters such as injected particle size and concentration, injection rate and reservoir properties were found to be a useful tool in specifying water quality requirements.
Quantitative Formation Permeability Evaluation from Stoneley Waves
Authors: Brie A. , Endo T. , Johnson D. L. , Pampuri F. 
Published: December 2007

Summary
The borehole Stoneley wave has been shown to be sensitive to fluid mobility, the ratio of permeability, and viscosity. The phenomenon is well described using the Biot theory and the effect of the mudcake was modeled as an elastic membrane. An inversion technique, which uses both slowness and attenuation of the Stoneley wave over a range of frequency to evaluate mobility, was proposed.
This paper describes the implementation of an interpretation methodology based on this technique. The error analysis shows that an accurate determination of the fluid mobility requires that some critical parameters, such as the mud slowness, mud attenuation, and the pore-fluid modulus, be precisely determined. An interpretation procedure is proposed to determine these parameters with good accuracy. The fluid mobility can then be determined without the need for external calibration with another measurement.
The intrinsic permeability of the rock can then be derived, knowing the various fluid components, their relative permeabilities, and their respective viscosity.
When using the proposed methodology within the applicable limits, the Stoneley wave can provide a continuous estimation of the formation permeability along the well. Core measurements are not required for calibration although they can be used for verification. This technique will find applications in reservoir engineering optimization of well production through better placement of the perforated intervals.
Laminar Flow of Non-Newtonian Fluids in Concentric Annuli
Authors: Vaughn Robert D. 
Published: December 2007

The limiting cases of non-Newtonian fluids flowing inside a concentric annular duct are developed without using a model of the fluid behavior. The solutions provide limits with which to test the various models of fluid behavior such as the power law and Bingham plastic models. The results of previous theoretical work are discussed in terms of limiting cases. This limiting case study also shows that experimental work on flow of non-Newtonian fluids in annular ducts should be confined to ducts for which the ratio of the radius of the inner wall to that of the outer wall is less than 0.3 and preferably less than 0.2.

Introduction
During the last 10 years the problem of laminar flow of non-Newtonian fluids in concentric annuli has received much attention largely because of its application to the hydrodynamics of the wellbore. Recently solutions utilizing the power law and Bingham plastic models have been published.In this paper the method of limiting cases, which has been successfully applied to laminar-flow heat transfer will be applied to the problem of flow of non-time dependent, non-Newtonian fluids through annuli. This method permits solutions for the limiting cases to be made without using a model of unknown validity. The solutions, therefore, provide limits with which to test the various models which have been or will be proposed. A pertinent conclusion concerning the region of experimental work is also provided.

DEVELOPMENT OF LIMITING CASES
The limiting cases for the axial flow of fluids in concentric annuli may be defined with reference to Fig. L It is possible to define two limiting cases which pertain to the physical dimensions of the annulus. First, the annulus must degenerate to a circular pipe as the radius of the inner wall decreases or, as K = (KR/R) - 0. Second, the annulus must approach the limit of parallel plates of infinite extent as the spacing between the inner and outer tubes becomes small in comparison with the radius R of the annulus, or as K - 1. It is also possible to ascertain three limbing cases which pertain to fluid behavior.
With reference to Fig. 2, as a fluid becomes progressively more pseudoplastic, the shear stress- shear rate relationship progressively approaches the indicated horizontal line more closely. At this limit the shear stress becomes independent of the shear rate. At the other extreme of increasingly dilatant behavior, the vertical asymptote is approached. Intermediate between these two limiting cases lies the case of the Newtonian fluid. Fluids which exhibit a yield shear stress also approach the limbing case of "infinite" pseudoplastic behavior.
SPEJ
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