bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Nonintrusive Flowmetering Method for Two-Phase Intermittent Flow in Horizontal Pipes
Authors: Kouba Gene E. , Shoham Ovadla , Brill James P. 
Published: December 2007

Summary
An experimental and theoretical investigation of horizontal two-phase slug flow was performed to develop a nonintrusive method of measuring the in-situ gas and liquid flow rates. The key measurements were the instantaneous liquid holdups at two positions along the pipe. A new drift model was developed to predict the liquid velocity in the slug from the measured slug translational velocity. Both liquid and gas flow rates were predicted within an accuracy of ±10% of range.
Linear and Radial Flow Targets for Characterizing Downhole Flow in Perforations
Authors: Deo M. , Tarlq S. M. , Halleck P. M. 
Published: December 2007

Summary
Two types of sandstone targets are commonly used to test flow efficiency of shaped-charge jet perforations: "linear" targets, in which flow enters only the unperforated end of the cylindrical sample, and "radial" targets, in which flow enters through the end and sides of the sample. To determine which of these targets best represents downhole conditions, the flow distribution along the length of a perforation has been studied by three-dimensional (3D) finite-element analyses. Linear and radial laboratory targets have been compared with downhole perforations under varying conditions. For ideal perforations, the low-shot-density (LSD) case is adequately represented by the radial target, while the high-shot-density (HSD) case falls between the two targets. With realistic crushed and damaged zones, the HSD case closely matches the linear target, and the LSD case falls between the two targets.
A Study of Horizontal-Wellbore Failure
Authors: Hsiao C. 
Published: December 2007

Summary
A theoretical model of horizontal-wellbore failure has been developed based on maximum-normal-stress theory (for tensile fracturing) and Drucker-Prager failure theory (for compressive failure) under openhole conditions. This model may be used to help determine the permissible borehole operating-pressure range, providing a convenient scheme for selecting borehole pressure to minimize the risk of borehole failure during drilling and production.
Fracturing of a Deviated Well
Authors: Yew C. H. , Li Y. 
Published: December 2007

Summary
The fracturing of a deviated well and the deviation of a hydraulically induced fracture plane were analyzed by applying three-dimensional (3D) elasticity theory. It was demonstrated that, under the influence of the off-plane shear-stress components, the fracture lines on the well surface were inclined at an angle with respect to the direction of the well axis and that the plane initiated from these fracture lines deviates from the plane formed by these initial fracture lines.
Computed Tomography for Rock-Property Determination and Fluid-Flow Visualization
Authors: Withjack E. M. 
Published: December 2007

Summary
This paper discusses the development and application of X-ray computed tomography (CT) for the determination of rock properties and the study of miscible displacements in laboratory cores. Saturation (relative permeability) and porosity measurements by CT scanning are described, and the results are compared to those of conventional methods. Results of corefloods with miscible fluids show the influence of rock heterogeneities (bedding planes) and mobility ratio on volumetric sweepout. The corefloods also illustrate a new display technique that combines a series of two-dimensional (2D) CT slices into three-dimensional (3D) perspective views.
Ultrasonic Saturation Mapping in Porous Media
Authors: Soucémarianadin A. , Bourlion M. , Lenormand R. 
Published: December 2007

Summary
The theory of acoustic propagation in porous media was described by Biot in 1956, but the experimental acoustic technique for measuring two-phase profile saturations along a sample is much more recent. We present an extension of this method for two-dimensional (2D) mapping and comparisons with gamma ray attenuations and visualizations in a transparent cell. The method is based on the difference between the sound velocities in the various liquids saturating the porous medium. The signal is generated by a pulse generator, and the time delay between transmission and reception is measured with a timer/counter. The saturation mappings are obtained by an automated displacement of an array of 32 sensors along the sample followed by computer reconstruction. To check the capabilities of the setup, we performed miscible and immiscible displacements in a three-dimensional planar cell (nonnegligible influence of height). The fluid boundaries are followed simultaneously by visualization and by ultrasonic measurements. We show that this technique not only locates the flood front in the stable case but also reconstructs the exact structure and motion of viscous fingers associated with unfavorable-viscosity-ratio displacements. Unlike X-ray shadowgraphs, quantitative fluid saturation data can also be obtained.
Influence of Electrical Surface Charges on the Wetting Properties of Crude Oils
Authors: Buckley J. S. , Takamura K. , Morrow N. R. 
Published: December 2007

Summary
Reservoir wettability is important to oil recovery by waterflooding and many other oil recovery processes. The difficulties associated with determination of in-situ wettability, together with uncertainties about application of laboratory observations to field conditions, necessitate a more basic understanding of factors that control wettability. We previously reported that the adhesion of crude oil to a solid surface could be related to wettability alteration. In this work, conditions under which oil adheres to a particular solid surface are demonstrated for several crude oils. For a given oil, pH and ionic strength were varied to obtain a mapping of conditions under which adhesion occurs. Results were satisfactorily explained by double-layer calculations in combination with the ionizable surface group model. Lack of adhesion signifies the presence of a stable water film that results from double-layer repulsion between the crude oil and the solid surface.
Relative Permeabilities at Simulated Reservoir Conditions
Authors: Donaldson Erle C. , Clvan Faruk , Alam M. Waqi Ul 
Published: December 2007

Summary
Relative permeability was determined at conditions from ambient to those simulating a depth of 1200 m [3,940 ft] from laboratory displacement data. The data were analyzed with the semianalytical interpretation method of Civan and Donaldson, which includes capillary pressure. The unsteady-state displacement method requires that the data be collected at high flow rates to diminish the influence of capillary end effects. including capillary pressure removes this constraint but results in a more complex mathematical model.
The results show the capillary end effects and the error introduced by not including them in the calculation of relative permeability. When capillary pressure was ignored in our model, it reproduced the literature values. Relative permeability measurements at elevated temperature show the characteristic temperature effect of higher oil relative permeability and lower residual oil saturation (ROS). These effects result from a change of wettability to a more water-wet condition at the higher temperatures.
The equipment used for relative permeability measurement can easily be constructed; in fact, some commercial designs can be used without modification. The results represent data at reservoir conditions; the data are taken on cores that are recompressed, eliminating the adverse influence of microfractures and changes of pore-size distribution frequently present in field cores run at ambient conditions. The displacement data are not restricted to high-flow-rate experimental conditions; removal of this restriction allows the analysis of low-permeability cores when flow rates are necessarily low.
Boundary and Crossfflow Behavior During Displacement in Nodai Systems
Authors: Lambeth Nell , Dawe Richard A. 
Published: December 2007

Summary
Conducting fault boundaries are common features in reservoirs, but realistic modeling of flow through such systems is difficult because the flow is grossly distorted, particularly at the nodes of the permeability contrasts. Standard finite-difference simulators use an uneconomical number of gridblocks and still do not represent the correct physical features. Nevertheless, the realistic simulation of faulted systems is essential for practical waterflood planning and consideration of EOR schemes. This paper presents an extension of a curvilinear grid technique to model the complex crossflow processes that occur in heterogeneous systems where nodes and boundaries are well defined. To test our methods, we performed experiments in a model nodal system and obtained displacement and streamline profiles for unit and nonunit mobility ratios for a permeability contrast of 2.5 and viscosity ratio range of 0.3 to 3.0. Grids were constructed by the numerical solution of a system of generating equations and incorporated into existing simulators. We show that the number of gridblocks required to model the systems effectively may be substantially reduced. This work demonstrates that there is scope for modifying grid generation for current simulators and incorporates more of the physical reality of the displacement processes in heterogeneities with nodes, such as faulted systems.
A General Formulation for Simulating Physical Dispersion and a New Nine-Point Scheme
Authors: Shiralkar Gautam S. , Stephenson Robert E. 
Published: December 2007

Summary
This paper presents a general numerical formulation for simulating physical dispersion that avoids the convergence and grid-orientation problems associated with numerical dispersion. The formulation is applicable to a wide range of problems, including enhanced gasdrives with phase discontinuities. A new nine-point scheme is also presented, along with general rules for any nine-point scheme to obey Darcy's law. Converged solutions are obtained for displacements at adverse mobility ratios of 5, 000 with no grid-orientation effects.
Gas Gravity Drainage in Fractured Reservoirs Through New Dual-Continuum Approach
Authors: Festøy S. , Van Golf-Racht T. D. 
Published: December 2007

Summary
Present theory assumes that a capillary holdup zone of oil remains in all single matrix blocks in fractured reservoirs producing by gas gravity drainage. Model simulations applying a dual-continuum approach in a conventional reservoir simulator showed that, even with a low degree of continuity through the matrix between the blocks, the oil from the capillary holdup zone in each block is produced. The expected oil production rate and recovery is much higher than predicted by the present theory.
Realistic Sand-Production Prediction: Numerical Approach
Authors: Morita N. , Whitfill D. L. , Massie I. , Knudsen T. W. 
Published: December 2007

SummaryThis paper provides an analysis of perforation-tunnel stability through a set of three-dimensional (3D) transient fluid-flow and geomechanical finite-element codes. The results are quantitatively accurate and can be applied to field design completion problems. The paper clarifies the causes of sand problems occurring in a field and suggests techniques to minimize the problems.
Parametric Study of Sand-Production Prediction: Analytical Approach
Authors: Morita N. , Whitfill D. L. , Fedde O. P. , Lovik T. H. 
Published: December 2007

Summary
An unconventional perforation-tunnel stability analysis is conducted in this work by separating the role of two independent factors on sand production: well pressure and local pressure gradient around a cavity. Such a separation clarifies most of the phenomena observed during sand production in oil fields. Simple analytical solutions for poroelastoplastic materials allowed repeated calculations for a parameter sensitivity study. The results obtained should be used qualitatively because of some degree of simplification.
Sensitivity Analysis of Two-Phase Reservoir History Matching
Authors: Watson A. T. 
Published: December 2007

Summary
Reducing the number of unknown reservoir properties (through a method like zonation) is generally recognized to be necessary to obtain accurate estimates from history matching; however, no reliable guidelines exist on how this can best be accomplished. Toward this end, we use a one-dimensional, incompressible, two-phase reservoir model to examine some of the fundamental issues in the estimation of spatially variable permeability and porosity from pressure data. Analytical expressions are developed that relate spatial variations in property values to perturbations in the measured pressure drop. Permeability and porosity are retained as functions so that the developed expressions are functional derivative sensitivity coefficients. Examination of these functions reveals the importance of the saturation distribution in regard to information about reservoir properties represented by pressure data. We determine that the rock properties ahead of the flood front cannot be determined from pressure data. Consequently, having more than a single zone for regions that have not undergone two-phase flow would be unwarranted on the basis of pressure data. Behind the flood front, the sensitivity of the pressure drop to variations in permeability and porosity, for M ≤ 1, declines with time. Consequently, the reliability of forecasts may actually improve with time. Based on measures relating the relative variability of porosity and permeability functions, the contribution of permeability variations to pressure perturbations exceeds that of the porosity by more than a factor of five when M ≤ 1. Thus, the representation of porosity with fewer zones than permeability is appropriate.
Thermal Recovery of Bitumen at Wolf Lake
Authors: Hallam R. J. , Hajdo L. E. , Donnelly J. K. , Baron P. R. 
Published: December 2007

Summary
For more than 20 years, BP Resources Canada Ltd. has faced the technical and economic challenges of oil-sands exploitation in the development of the Cold Lake oil sands of east-central Alberta. In 1985, the Wolf Lake 1 project began commercial bitumen production (7,000 to 8,300 B/D [1100 to 1300 m3/d]), with cyclic steam stimulation used to exploit the Clearwater formation. Construction of a 12,600-B/D [2000-m3/d] expansion started in 1987. Also in 1987, production started from a 22-well satellite that exploits the Lower Grand Rapids formation, a channel sand overlying the Clearwater formation. To develop this and other potentially commercial technology, four experimental projects were conducted: two steamfloods, a cyclic steam and combustion pilot in the Clearwater formation, and a single-well test in the Lower Grand Rapids formation.
Experimentation to develop combustion as a follow-up process to cyclic steam with air lasted from 1979 to 1984 and with oxygen from 1983 to 1988. One of the Wolf Lake 1 satellites will be converted to combustion to obtain further operating experience.
While operating experience has been obtained, numerical models have also been developed and used to improve the cyclic-steam operating strategy. These models, along with the formation properties and project histories, are described. Also, principles of the injection and production operations used in the combustion pilot are covered, and some solutions are offered on how these procedures overcame or avoided problems typically associated with combustion operations.
Study of Continuously Mixed Crosslinked Fracturing Fluids With a Recirculating Flow-Loop Viscometer
Authors: Harris C. Phillip , Harms M. Weldon , Norman Lewis 
Published: December 2007

SummaryContinuously mixed gel fracturing fluids were successfully prepared with polymer slurries of guar, derivatized guar, and derivatized cellulose. The rheological behavior of the continuously mixed fluids was measured on a recirculating flow-loop viscometer over a temperature range of 80 to 300°F [27 to 149°C].Rapid and complete base-gel hydration required proper pH control and high mixing energy. Oil-based polymer slurries allowed rapid hydration rates sufficient to achieve performance from a crosslinked fluid prepared during a completely continuous operation. Water-based polymer slurries required a short holding period for complete hydration.Delayed-crosslink-gel viscosity was influenced by shear rate and the degree of base-gel hydration. Chemical factors influencing viscosity development included base-gel concentration, crosslinking-agent concentration, fluid pH, and ionic strength. Hydration time and pH requirements may differ for specific polymer/crosslinker pairs.
Significance of Regulatory Constraints on the operation of Packerless Waste Injection Wells
Authors: Kamath Krishna I. , Harmon Gary D. , Anzzolin Roger A. 
Published: December 2007

Summary
U.S. federal regulations for groundwater protection require all hazardous-waste disposal wells to be constructed so that casing leaks can be reliably monitored. Wells constructed with static-fluid seals instead of packers are incapable of meeting this requirement and are therefore not in compliance with the regulations.

Introduction
Though fluids (liquids) have been injected into the subsurface to recover minerals and to dispose of oilfield brine in the U.S. for many years, deep-well disposal has been an approved means of industrial waste management for only a few decades. This method now accounts for the subsurface disposal of increasingly large volumes of industrial liquid waste. If not property controlled, the injected waste could threaten the safety of our drinking water supplies.
In the past, subsurface waste disposal was generally regulated by state programs, which varied widely in technical detail. The need for uniform standards for groundwater protection has been obvious for some time. In recognition of this need, the U.S. Congress enacted the Safe Drinking Water Act in 1974 and the Hazardous and Solid Waste Amendments (HSWA) in 1984. The Underground Injection Control (UIC) regulations, which are a part of the HSWA, set minimum standards for the siting, construction, and operation of injection wells in the U.S. The U.S. Environmental Protection Agency (EPA) administers this program directly or through the states to meet the Congressional mandate.
UIC regulations require all injection wells to be constructed with tubing set in packers. This feature allows the well operator to use the tubing/casing annulus for monitoring well casing leaks that could endanger the safety of adjacent underground sources of drinking water (USDW's). As of 1984, only 80% of all hazardous-waste disposal (Class I) wells in the U.S. were completed with packers. The regulations permit the operation of packerless wells only if the operator can demonstrate that the mechanical integrity of these wells can be reliably monitored at a level comparable with that of the well with packer. The most common type of the packerless well currently approved by the EPA features a "static-fluid seal" in the annulus-i.e., annulus filled with a mineral oil, in place of the packer, which totally isolates the annulus from the injected waste.
This paper examines the extent that the packerless well with the static- fluid seal is comparable with a conventional well with packer in providing reliable protection to groundwater. Considerations of theory and available operating-well data from the Great Lakes region facilities suggest that packerless wells do not meet applicable requirements and therefore do not comply with UIC regulations.
Pressure-Buildup Test Analysis— Variable-Rate Case: A New Approach
Authors: Blasingame T. A. , Lee W. J. 
Published: December 2007

Summary
This paper presents a new method of estimating a constant-rate analog for a variable-rate flow period followed by a pressure-buildup test. The time and rate in the analog are used to generate a conventional Horner plot for the buildup test. The approximation is derived rigorously from the Horner buildup and variable-rate superposition equations. The major advantage of this method over other proposals is that it not only forces the production volumes to be equal (material-balance constraint) but also forces the pressures at a particular time to be equal.
Our approximate method has been verified for several variable-rate schemes with a finite-difference numerical simulator. The effect of wellbore storage was studied at both surface and sandface rates. The effects of a short shut-in time and a shut-in time equal to the duration of the production period were also investigated. The results of the new method seldom varied more than 5% from the results obtained with rigorous superposition.
The new method is not intended to replace superposition, but rather to give the best possible constant-rate analog. This method enhances our ability to use the conventional (constant-rate) Horner theory to generate accurate results. Also, our new method requires a single superposition calculation rather than a superposition calculation for each data point, as in the case of the superposition plot.
Novel Approach to Sensitivity Analysis
Authors: Genrich J.F. , Sommer F.S. 
Published: December 2007

Summary
An entropy function is introduced to quantify the uncertainty in reservoir engineering parameters that are represented as random variables and described by probability distributons. When combined with a given algorithm and a Monte Carlo simulation routine, the concept can be used to estimate the degree of certainty required in input variables to yield a given certainty of the output parameters. The method is illustrated with a simplified model for water-alternating gas (WAG) miscible flooding. Two ranking schemes for five input variables are established and compared. The rankings provide an assessment of the overall model response with respect to a base case as related to average value and to degree of certainty of each input variable.

Introduction
Many reservoir engineering studies rely on data that contain some known or unknown error. Measurements are not always available, and key parameters are often estimated by other means. To account for this uncertainty, quantities can be described by probability distributions. Any parameter dud depends on one or more of these quantities has a probability distribution that is a function of the input probability distributions. Uncertainties often accumulate, leading to variances of output parameters that are unacceptably high.
If the overall uncertainty of input variables is reduced, output variances will be lowered. The commitment of manpower and financial resources necessary to achieve this reduction, however, can be substantial. It is important, therefore, to estimate a priori the amount of reduction in uncertainty required for each input parameter to obtain a given increase in output certainty currently used sensitivity analyses do not yield this information.
Combining an entropy function with a Monte Carlo simulation approach yields a new method that provides these estimates.

S Value
The notion of entropy, originally introduced in its differential form as S= /T in thermodynamics, has been successfully applied in other fields as a measure of randomness or disorder. In statistical physics, if quantilies the closeness of a system to equilibrium and plays a central role in describing the thermodynamic properties of ideal gases. In communication theory, it specifies the average amount of information transmitted per symbol. It is used in ergodic theory as a characterization of partitions and measure-preserving transformations. In terms of the underlying measure space, is defined similarly for all three cases.