bluuebunny/crossref_metadata_2025_split huggingface dataset:
Steam-Foam Pilot Project in Dome-Tumbador, Midway-Sunset Field
Authors: Mohammadi S. S. , Van Slyke D. C. , Ganong B. L. 
Published: December 2007

Summary
This paper describes a steam-foam pilot project in the Potter sand, Midway-Sunset field. The pilot consists of four inverted five-spot patterns with a confined producer covering 5.2 acres [2.1 ha]. Steam foam was generated by continuous injection of steam with NaCl, alpha olefin sodium sulfonate, and nitrogen. Production and subsurface data, obtained from two observation wells, were used as monitoring tools in the pilot. Overall, during the first 2 years of foam injection, 207,000 bbl [32 900 m3] of incremental oil was produced.
A Comprehensive Simulation Study of Steamflooding Light-Oil Reservoirs After Waterflood
Authors: Chu Chieh 
Published: December 2007

Summary
Steamflooding, the most successful among enhanced recovery methods, has been applied mainly to heavy-oil reservoirs. This paper presents a comprehensive simulation study on the use of steamflooding after waterflood in light-oil reservoirs. Some important observations are made on this new application of the process. Guidelines are developed not only for selecting reservoir candidates for steamflooding, but also for designing and operating steamfloods in watered-out reservoirs. Relative importance of key mechanisms to oil recovery is also discussed.

Introduction
The use of steamflooding as a tertiary recovery method for light-oil reservoirs after waterflood has been of interest in recent years. Although steamflooding applied to heavy-oil reservoirs has been a fully proven method, the technology of applying it to light-oil reservoirs, especially those that have been watered out, is still in its infancy. This paper will answer the following questions that remain about steamflooding.Can watered-out light-oil reservoirs perform as well as heavy-oil reservoirs under steamflooding?What kind of reservoirs will be suitable for steamflooding after waterflood?How would one design and operate a steamflood once a reservoir is chosen?What are the main recovery mechanisms in this process?
Several authors have made simulation studies on steamflooding light-oil reservoirs. Aydellote and Ramesh studied steamflooding economics with variations in oil composition, permeability, depth, pattern type, well spacing, and steam injection rate. A uniform fluid saturation was used at the start of the steamflood. Hanzlik improved on this work by preceding the steamflood with a waterflood that generates a nonuniform fluid saturation before steamflood starts. Both waterflood and steamflood were considered to take place in the same 5-acre [2.0-ha] five-spot patterns. He studied the effects of oil composition, reservoir thickness, and steamflood timing on steamflood performance. Hongs studied steamflooding the light-oil reservoir at Buena Vista field, CA, using a uniform fluid saturation at the start.
This work starts with a 40-acre [16.2-ha] waterflood that is later converted to steamfloods with smaller patterns. A three-dimensional multiphase thermal recovery simulator with nine-point finite-difference formulation was used so that the grid orientation effect was greatly reduced in the simulation of steamfloods in five- and nine-spot patterns. A large number of reservoir oil and rock properties and also a large number of steamflood design and operating variables were considered. The following were developed: general observations on the process, guidelines for selecting candidates for steamflooding after waterflood, guidelines for designing and operating steamfloods, and relative importance of the various key mechanisms to oil recovery.
Rock Mechanical Analysis of North Sea Reservoir Formations
Authors: Holt R. M. , Ingsøy P. , Mikkelsen M. 
Published: December 2007

Summary
Core material from a North Sea reservoir has been investigated for strength and elastic properties in triaxial tests. The material behaves nonlinearly elastically, and the rock strength correlates with the static shear modulus in a data range previously little investigated. Dynamic elastic properties obtained by downhole measurements with full-waveform logs are compared with the laboratory-derived strength. Laboratory acoustic measurements show that the sonic velocities are strongly stress dependent, which is closely related to the previously mentioned elastic nonlinearity. Also, dynamic elastic moduli are found to exceed the static moduli considerably, which has to be taken into account when evaluating mechanical properties from logs. Because of the nonhydrostatic stress state downhole or in laboratory triaxial tests, an acoustic anisotropy is induced. On unconfined core materials, the pronounced observed acoustic anisotropy may, to a large extent, be caused by stress relief during and after coring. The possibilities of using this effect in in-situ stress determination are elucidated. Finally, the mechanical-properties logging practice commonly adopted is compared with experimental data, showing that the log interpretation approach must be modified to account for the data.
Postbuildup Drawdown Analysis of Tight Gas Wells in the Rocky Mountains
Authors: Hale B. W. , Firth C. H. , Hansen R. C. , Murphy M. J. , Woodcox S. C. 
Published: December 2007

Summary
Through the use of recently available daily volume data on Northwest Pipeline Corp.'s gathering systems, drawdowns following pressure buildups can be analyzed to predict flush production behavior of tight gas wells that have been shut in, perhaps owing to market restrictions. The "flush" rate as a percentage of the final flowing rate is a function of flowing time after the buildup. The magnitude of the initial flush rate is related to the length of time the well is shut in, to the final flow rate before shut-in, and to the age of the well. The amount of flush production increases as the well downtime increases.
Daily production histories of the wells on the Douglas Creek Arch and the Green River, San Juan, Piceance, and Uinta basins were studied. Wells within each area were grouped by geologic formation, by flow rate, and by similar periods of shut-in time. When plotted on a log-log scale, the ratio of the postbuildup rate to the stable rate shows a straight-line relationship to the drawdown time. Theoretical curves to predict flow rates after a buildup are presented that are based on the superposition of constant-pressure solutions to the flow of a real gas in a porous medium and that show a nearly straight-line rate/time relationship.
In light of the current gas surplus and the evolving spot market, the prediction of accurate short-term performance is useful in scheduling gas sales and gas transportation.
New Applications of the Pressure Derivative in Well-Test Analysis
Authors: Onur M. , Yeh N. , Reynolds A. C. 
Published: December 2007

SummaryThis work presents and illustrates a new general procedure for constructing type curves on the basis of a new pressure-derivative group that involves the dimensionless pressure change divided by its logarithmic derivative. When type curves based on this group are constructed, the vertical scale of the dimensionless derivative group is automatically aligned with the vertical scale of the field-data derivative group. This automatic alignment of the vertical scales simplifies type-curve matching and is advantageous for determining whether field data actually represent the solution assumed by a given type curve. It is also shown that the basic idea used in constructing the type curves can be used to ensure that proper semilog straight lines are chosen when well-test pressure data are analyzed by semilog methods.
The Laminar-Turbulent Transition in Suspension Of Rigid Spheres
Authors: Krieger Irvin M. , Dodge James S. 
Published: December 2007

Abstract
The laminar-turbulent transition was studied for monodisperse rigid polymer latices as functions of particle diameter and concentration at several tube diameters. Breaks in the graph of friction factor vs Reynolds number were used to characterize the transition; rates of shear were sufficiently high so that Newtonian behavior at the high shear limiting viscosity could be assumed. No abnormal behavior was noted at concentrations below 30 volume percent. At higher concentrations, suppress ion of turbulence was observed with critical Reynolds numbers rising to as high as 5,500 at 50 volume percent. No definite effect on the transition was noted due to variation of particle size or tube diameter. The type of surfactant used to stabilize the latex was found to have an important influence on the critical Reynolds number.

INTRODUCTION
For some polymer solutions and solid-in-liquid suspensions, the transition from laminar behavior to turbulence in pipeline flow has been reported to take place at unusually low1-5 and in some cases at higher than normal6,7 critical Reynolds numbers. Extreme values of critical Reynolds numbers (NRe*) have been found to range from 1 to 6,000, as opposed to the values of 2,000 to 3,500 which are obtained for ordinary liquids. Observations have also been reported of drag reduction in fully developed turbulent flow, i.e., a decreased value of the friction factor in the Reynolds number-friction factor plot6,10-14 in colloidal and polymeric fluids. In some cases, turbulence suppression (unusually large values of NRe*) was noted to occur preceding the drag reduction,6 while a normal transition was noted in other cases of drag reduction.14
To relate the occurrence of turbulence suppression and drag reduction to the molecular or particulate structure of the fluid, it is desirable to characterize the structural variables with some precision. For most colloidal dispersions and polymeric fluids, this is very difficult; particle sizes, shapes and stiffnesses may vary over wide ranges in the same sample. Recently, however, a colloidal fluid has become available which consists of rigid spherical particles of highly uniform diameter dispersed in a simple Newtonian liquid. These are monodisperse polymer latices, prepared by carefully controlled emulsion polymerization reactions. The purpose of this research was to study the transition to turbulence in these well-characterized colloidal fluids a s a function of concentration, particle diameter and tube diameter.
Hydrate Dissociation in Sediment
Authors: Sellm M. S. , Sloan E. D. 
Published: December 2007

Summary
An analytical model that describes hydrate dissociation under thermal stimulation in porous media is presented. The model views the dissociation as a process in which gas and water are produced at a moving dissociation boundary. The boundary separates the dissociated zone containing gas and water from the undissociated zone containing the hydrate. A similarity solution to the conservation equations is derived, and results are presented in graphical forms that are useful in numerical computations. In particular, heat fluxes, temperature profiles, and gas pressure distributions are presented for two cases that simulate saturated-steam and hot-water thermal stimulation. A parametric study showed that the dissociation rate is a strong function of the thermal properties of the system and the porosity of the porous medium. The energy efficiency of the dissociation process, defined as the ratio of the heating value of the gas produced relative to the heat input, was also computed. For hydrate thermal stimulation, an energy efficiency value of about nine was found, which appears encouraging for natural gas production from hydrate.
Carbonate Acidizing: Toward a Quantitative Model of the Wormholing Phenomenon
Authors: Daccord G. , Touboul E. , Lenormand R. 
Published: December 2007

Summary
We present the first quantitative study and complete model of the wormholing phenomenon, leading to a means of predicting and optimizing carbonate acidizing treatments. Laboratory experiments on a gypsum model system and computer simulations show that for a given geometry, wormholes can be quantified by a unique parameter, their equivalent hydraulic length. The behavior of this quantifying parameter vs. all the system parameters is studied and allows the quantitative prediction of the efficiency of an acidizing treatment. This study highlights the fractal nature of the phenomenon, which is accounted for in the equations, and the strong effect of the sample geometry. Three types of etching can be obtained: compact, wormhole type, or homogeneous. The optimum conditions for achieving die best skin decrease correspond to the creation of wormholes and can then be defined in terms of fluid reactivity and injection rate.
A Systematic and Consistent Approach to Determine Binary Interaction Coefficients for the Peng-Robinson Equation of State
Authors: Slot-Petersen Carsten 
Published: December 2007

Summary
A new technique to determine binary interaction coefficients for a cubic equation of state (EOS) is introduced. The technique is physically consistent and easy to apply when an EOS is tuned to laboratory-measured PVT data. The method's simplicity provides a rational way of evaluating the sensitivity of binary interaction coefficients to fluid composition and temperature. Laboratory-measured expansion data are demonstrated to be crucial for proper determination of binary interaction coefficients for near-critical fluids.
The ability of the technique has been demonstrated by matching laboratory-measured constant-composition-expansion curves for six fluid compositions, including black-oil, volatile-oil, rich-gas-condensate, and lean-gas-condensate systems. In addition, the near-critical fluid behavior has been evaluated by matching constant-composition-expansion data for a fluid at four temperatures in the near-critical range, two on either side of the critical temperature. The literature reports that the Peng-Robinson EOS (PR-EOS) cannot predict the retrograde phase behavior of the rich-gas-condensate fluids applied in this study. This paper shows that this is because insufficient and/or improper binary interaction coefficients were used in the fluid characterization.
The method enables tuning of near-critical fluid behavior in addition to normal bubblepoint and dewpoint system behavior. Use of the proposed procedure to assign binary interaction coefficients may allow matching of renascent condensation for a near-critical bubble-point system.
Practical Model for Predicting Pressure in Gas-Storage Reservoirs
Authors: Molinard Jean-Eric , Bitoux Philippe Le , Pelcé Veronique , Tek M. R. 
Published: December 2007

SummaryOptimal planning, design, and operation of gas fields in production or storage critically depends on reliable models for predicting pressures that are often based on sophisticated numerical and mathematical concepts. The pressure that prevails at a given time is a direct function of production/injection schedules, past history, and surface equipment as related to reserves and reservoir characteristics. Maintaining the pressure within prescribed limits is particularly important in underground storage to avoid pressures above a maximum for reasons of safety and migration and below a minimum for surface-equipment and contracted-deliverability considerations.This paper presents a new way to calculate the convolution integral on which the pressure variations depend. The classic methods were long and costly to run and seldom used. Our method, which identifies this convolution integral with a finite sum of exponential terms, is much quicker and has been implemented in a program called PREPRE, usable on microcomputers. Based on a production/pressure schedule, the model is capable of forecasting the evolution of pressures in main zones of interest, such as wellbores, gathering systems, and surface equipment. The data required for the model—past production/pressure history—are matched by a special algorithm that automatically calculates the main reservoir parameters used as bases for future projections. The quick and easy-to-run program is now in use at all engineering levels at Gaz de France.
Automatic History Matching With Variable-Metric Methods
Authors: Yang P. -H. , Watson A. T. 
Published: December 2007

Summary
Variable-metric minimization methods are introduced for use with optimal-control theory for automatic reservoir history matching. Variable-metric methods are more efficient and robust than the previously used minimization methods, such as steepest-descent and conjugate-gradient methods. in addition, variable-metric methods can be used effectively with parameter-inequality constraints.
Two variable-metric methods — the Broyden/Fletcher/Goldfarb/Shanno (BFGS) method and a self-scaling variable-metric (SSVM) method — are tested with hypothetical two-phase reservoir history-matching problems. Estimated rock/fluid properties include permeability, porosity, and relative permeabilities. The SSVM method is more efficient than the BFGS method when the number of unknown parameters is large. Both methods perform better than the steepest-descent and Nazareth’s conjugate-gradient methods except when the performance index is nearly quadratic, where the conjugate-gradient methods may be more efficient than the BFGS method. A constrained BFGS algorithm is tested to be successful in problems where the unconstrained algorithms have failed
History Matching With Cumulative Production Data
Authors: Watson Ted A. , Lane Scott H. , Gatens J. Michael 
Published: December 2007

Summary
A measurement-error model is formulated and an appropriate weighted-least-squares (WLS) performance index is developed for history matching with cumulative production data. This performance index provides more accurate estimates of the unknown reservoir properties than the usual ordinary-least-squares (OLS) performance index.

Introduction
The use of numerical reservoir simulators to predict well performance is an important acid well-established process in reservoir engineering. The reliability of these predictions is limited by the accuracy with which the input reservoir properties are determined. The reservoir properties can be estimated by history matching measured pressure or production data, whereby parameters in a numerical reservoir simulator are adjusted so that the resulting calculated quantities m some sense match the measured data. These adjustments can be made with automatic history-matching algorithms.
Most automatic history-matching algorithms determine parameter estimates that minimize an OLS performance index given by the sum of squared differences between the measured data and the corresponding values calculated with the reservoir simulator. Knowledge of the data-measurement process, however, can be used to develop a WLS performance index that may provide more accurate estimates of the reservoir properties.
In this paper, we formulate a measurement-error model and develop a WLS performance index appropriate for history matching with cumulative production data. Residual analysis is introduced as a means for checking the validity of the measurement-error model, and two useful tests are presented for analyzing history-matching residuals.

Background
Two key steps are involved in obtaining accurate estimates of reservoir properties from history matching measured pressure or production data. The first step is to select an appropriate reservoir model for describing the physical process. The reservoir model need not describe the process exactly, but it is desirable that the differences between measured and calculated quantities (for an appropriate set of reservoir parameters) be reasonably described as random error. (The problem of model selection is considered elsewhere I and is not discussed in detail here.) The second step is to estimate unknown parameters (i.e., reservoir rock properties) within the reservoir model by minimizing an appropriate performance index so that the resulting parameter estimates are, statistically, the best estimates for the unknown reservoir properties.
Effect of Nonuniform Core Saturation on Laboratory Determination of the Archie Saturation Exponent
Authors: Lyle W. D. , Mills W. R. 
Published: December 2007

Summary
A simple numerical example is presented to demonstrate that the laboratory-derived Archie saturation exponent, n, will be in error unless the data are taken with the core uniformly saturated. The numerical example is shown by a more rigorous mathematical analysis to be a special case of the general result of this study: even in an ideal case, measurements performed on nonuniformly saturated cores yield erroneous n values. The overall conclusion is that accurate determination of n requires that laboratory procedures be established to ensure that the core is uniformly saturated whenever measurements are made.
Steam Zone Growth During Multiple-Layer Stream Injection
Authors: Closmann P.J. 
Published: December 2007

Abstract
The development of multiple parallel steam zones of equal thickness and uniform separation is described mathematically. At small times, the growth of one of the steam zones is independent of the presence of the orders. At long times, simple relationships are obtained which describe the growth of the steam zones. Generally, it is found desirable to allow steam to penetrate the underground reservoir at a number of vertical positions if sufficient steam-generating capacity is available to maintain comparable injection rates in all the layers. If a limited steam-generating capacity is available, the larger steam zone volume is created in the single-layer system.

Introduction
The use of hot fluid injection as a means of lowering oil viscosity in petroleum reservoirs is becoming increasingly common. Prominent among the thermal techniques being used is steam injection. The basic mechanisms involved when steam flows through oil-containing porous rock have been reported by Willman et al. The growth of the steam zone when steam enters a single layer at constant injection rate has been developed by Marx and Langenheim. Frequently, an underground formation is stratified and presents a number of horizontal paths for the injected fluid to follow. This paper considers the steam zone development when a large number of highly permeable paths of equal thickness, separated by arbitrary but equal distances, are available for flow of injected steam.

THEORY
Consider the system shown in Fig. 1. A number of horizontal zones of equal thickness, hs are separated from each other at distances 1. It is assumed that there are infinitely many layers in the vertical direction. Further, important assumptions of the mathematical model to be employed are as follows.
- Steam enters all the layers at constant and equal rates.
- Steam zone temperature remains constant throughout the steam zone at the value of the input steam temperature.
- The heat capacity of the steam zone may be represented by some average value.
- Heat loss occurs normal to the horizontal boundaries of the steam zones.
- No heat is transported by conduction or convection ahead of the steam front. The formation immediately ahead of the steam zone remains at original reservoir temperature. The shape of the temperature distribution will then be that of a step which moves outward.
The Dispersive Effect of Variable Layer Lengths on Miscible Displacements in Layered Heterogeneous Porous Media
Authors: Kossack Charles A. 
Published: December 2007

Summary
The effect of small- and intermediate-scale heterogeneities on miscible displacements is investigated by Monte Carlo simulations in a two-dimensional (2D) flow field containing random permeabilities and random layering. The effect of the variable layer lengths on the level of dispersion is calculated for various well-to-well distances. It was determined that the variable layer lengths add a significant amount of dispersion compared with constant layer lengths for well-to-well distances on the order of 1,000 ft [305 m] or less.