bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calibration Measurements of Dielectric Properties of Porous Media
Authors: Nguyen Buu-Long , Geels A. M. , Bruining Johannes , Slob E. C. 
Published: December 2007

SummaryWe present a specially designed experimental setup for accurate measurements of the frequency-dependent relative complex dielectric permittivity (RCDP) in porous media. The setup operates on the principles of steady-state flooding and time-domain reflectometry (TDR). The steady-state flooding technique allows for a well-controlled uniform saturation distribution in the sample. The TDR technique enables on-line measurement of the dielectric response. We derive the equations for the propagation and reflection of an electromagnetic (EM) signal along a coaxial transmission line consisting of a standard coaxial cable, a transition unit, and the sample holder. The RCDP at different oil saturations are calculated by means of frequency analysis of the scattered signal.We present the RCDP obtained from experiments in sand samples at different saturations. We compare the obtained results with those calculated with a number of existing mixing models, including the complex refractive index (CRI) model and the classical Rayleigh formula.The experimental method has proved to be suitable for on-line measurement of dielectric properties of porous media with varying fluid saturation. It turns out that a small saturation difference can be discerned in the measurements. We have found that the RCDP calculated with the CRI model (refractive index exponent α = 0.75) show the best agreement with those obtained from the experiments.
Foam Propagation on Semi-Reservoir Scale
Authors: Vassenden Frode , Holt Torleif , Ghaderi Amir , Solheim Arild 
Published: December 2007

SummaryFoam propagation in co-injection of gas and surfactant solution has been studied in a 10-m-long flow apparatus, equipped with pressure ports and fluid sampling valves for every 1 m. The data have been compared to the results of a core scale foam flooding experiment with the same porous medium.The propagation experiments on the 10 m scale revealed that the foam front propagated significantly slower than the injected fluid front. It appeared that foam propagation was not limited by surfactant transport, but was delayed due to the presence of oil in the porous medium. The experiments have been interpreted with the aid of a numerical foam simulator.
Prediction of Waterflood Behavior in a Stratified System
Authors: Warren J.E. 
Published: December 2007

Abstract
A general model which approximates the effect of cross-flow has been developed to give a practical method for predicting the water flood behavior of a stratified reservoir. The model is based on a modification of Dietz's theory and allows for variations in both the permeability and hydrocarbon pore volume.in the particular cases considered, it is assumed that the permeability can be characterized by a log- normal distribution and the hydrocarbon pore volume by a normal distribution. A simple graphical method which enables the practicing engineer to predict the behavior of a stratified system is presented The results obtained by the proposed method are compared with those obtained by the Dykstra-Parsons method As a result of this study the following conclusions have been drawn:
- The effect of cross-flow in a stratified system can be appreciable, particularly at very favorable or very unfavorable mobility ratios;
- Under normal conditions, the effect of variations in the hydrocarbon pore volume can be neglected; and
- The failure to use all of the available permeability data can lead to large errors in the prediction of the behavior of a stratified reservoir.

Introduction
Various methods have been proposed to characterize and to predict the waterflood behavior of a stratified reservoir. Most of the methods assume that the reservoir is composed of discrete homogeneous continuous layers. With this model, the degree of stratification can be measured by several parameters based on core-analysis data. Among these are the Lorenz coefficient and the variation of a log-normal permeability distribution. The behavior of stratified systems is usually predicted by the Stiles, Dykstra-Parsons method or some modification of these. In both of these methods the reservoir is divided into discrete homogeneous layers with no cross-flow between layers. In the Stiles method the mobility ratio is assumed to be equal to unity while in the Dykstra-Parsons method it is allowed to take on any value. Other predictive methods have been proposed; Hiatt's method allows for cross-flow between the beds and a method by Schmalz and Rahme correlates the recovery directly with the Lorenz coefficient. In this new approach, which is essentially a continuous analog of Hiatt's method, the effects of both mobility ratio and cross-flow between the beds have been included. It is assumed that the permeability can be represented by a log-normal distribution and the hydrocarbon pore volume or porosity by a normal distribution. These types of distributions have been observed by several authors, and most field data seem to confirm their observations; e.g., if these distributions are assumed and there is a 1:1 correspondence between porosity and permeability samples, the commonly encountered linear relationship between porosity and the log of permeability is obtained.
The Use of Air-Mist for Well Cleanout and Deepening
Authors: Holder Louis E. 
Published: December 2007

Abstract
A method of cleaning out and deepening using air-mist as the circulating fluid and with specially rigged portable rotary drilling tools has been found to be ideally suited for use in fields having low reservoir pressure. Three typical examples from the West Texas-New Mexico Permian Basin are cited. One is the Permian Sand fields of Ward and Winkler County, Texas, and Lea County, New Mexico. Another is the San Andres dolomite fields of Ector, Andrews, Hockley and Terry Countries, Texas, and the third is the Spraberry area trend of Midland, Upton and Reagan Countries, Texas.

The Use of Air-Mist For Well Cleanout and Deepening
As production rates begin to decline in fields which have been producing for a number of years, engineers and management begin searching for ways to restore the productive capacity, either through workover operations or by means of pressure maintenance or secondary recovery projects. Several factors should be considered in deciding the best method to be employed in work-over and/or reconditioning operations. First, an operation which should give the desired result must be selected, with care being exercised to assure no damage to the reservoir could result from the method to be used. Second, the cost of this operation, considering not only the initial outlay, but also loss of revenue during the workover period and the resulting payout, must justify authorizing the work. The use of air-mist as a circulating medium for cleanout and deepening operations has been found to be most satisfactory, having a number of advantages over the conventional reverse circulation, or cable tools for this type work.

Equipment and Processes Used
The equipment for air-mist clean-out and deepening is specialized. To reduce the moving costs to a minimum, a trailer mounted rig is used. For deeper work a conventional rotary table is required; however, for shallow cleanout and deepening, a Guiberson rotating head permits the use of a working platform. This further reduces the moving time and cost by eliminating the need for a substructure. These two types of rigs are shown in Figs. 1 through 4.
A rotating blowout preventer in addition to a conventional double gate type is required for air-mist circulation as shown in Fig. 5, and a discharge or "blooie" line, preferably of at least 7 in. diameter, fitted with quick break type connections is used to handle the return samples and spent air. If the cleanout or deepening operation is being performed in an area where surface damage would result from an unrestricted blowing of the returned fluid and air, a mist arrester can be attached to the end of the "blooie" line to kill any spray before discharging the returns into a pit. This mist arrester is shown in Fig. 6.Air compressor equipment capable of delivering from 1.5 to 2.5 MMcf/D at pressures ranging from 1,200 to 1,500 psi are required.
Streamline Approach for History Matching Production Data
Authors: Wang Y. , Kovscek A. R. 
Published: December 2007

SummaryIn this study, we propose and develop a streamline approach for inferring field-scale effective permeability distributions based on dynamic production data including producer water-cut curve, well pressures, and rates. The streamline-based inverse approach simplifies the history-matching process significantly. The basic idea is to relate the water-cut curve at a producer to the water breakthrough of individual streamlines. By adjusting the effective permeability along streamlines, the breakthrough time of each streamline that reproduces the reference producer fractional-flow curve is found. Then the permeability modification along each streamline is mapped onto cells of the simulation grid. Modifying effective permeability at the streamline level greatly reduces the size of the inverse problem compared to modifications at the grid block level. The approach outlined here is relatively direct and rapid. Limitations include that the forward flow problem must be solvable with streamlines, streamline locations do not evolve radically during displacement, no new wells are included, and relatively noise-free production data are available. It works well for reservoirs where heterogeneity determines flow patterns. Example cases illustrate computational efficiency, generality, and robustness of the proposed procedure. Advantages and limitations of this work, and the scope of future study, are also discussed.
High Volume Pumping in the Rangely Weber Sand Unit
Authors: Allen D.D. 
Published: December 2007

Abstract
A review of high volume pumping operations in the Rangely Weber Sand Unit is presented in this paper. The pumping problems encountered and methods used to combat them are discussed. High volume pumping is utilized on both oil producing and water source wells. Pumping problems resulted from free gas interference and pounding, plus corrosive and scale forming well fluids. Submersible as well as large capacity rod pumps are operating at depths of 6,500 ft. High volume pumping is economically successful.

Introduction
High volume pumping in the Rangely Weber Sand Unit consists of electrically driven submersible pumps and rod pumping units with a stroke length of 100 in. or greater. High volume pumping is utilized in oil producing wells and water source wells. At the end of 1962 there were 73 long-stroke rod pumping units and nine electrically driven submersible pumps in operation in oil producing wells. The water source wells included 10 electrically driven submersible pumps and one shaft driven submersible pump. The Weber wells flowed on initial completion. As the reservoir pressure declined, conventional 64-in. stroke rod pumping units were installed. The wells were pumped through the tubing and flowed on the casing-tubing annulus. When the wells would no longer flow on the annulus they still contained much more potential than could be produced with the conventional units. At this time installation of the 100- to 120-in. units began. Subsequent water flooding increased well potentials, and the 192-in. rod pumping units and electrically driven submersible pumps were installed.

Field History
The Rangely Weber reservoir was discovered in March, 1933, by the California Oil Co. Development of the field was not started until Oct., 1943, and continued through May, 1949.The reservoir structure is an asymmetrical anticline. The field is approximately 12 miles long and 5 miles wide. The Weber sand contains interbedded shale that increases with depth. The Weber is 1,200 ft thick. Only the upper 700 ft is considered oil productive. There was a small original gas cap. The top of the Weber at the crest is –205 ft subsea. The original gas-oil contract was at –330 ft subsea and the water-oil contact at –1150 ft subsea. Surface elevations range from 5,200 ft to 5,700 ft which result in pumping depths to 6,700 ft. The wells have 7-in. casing set to the top of the Weber or gas-oil contact, and then have an open hole completion to the oil-water contact, or to 700 ft of Weber penetration. Approximately one-half of the wells have been shot. Nearly all the wells have been sand-oil fractured. There is a gas injection program that dates back to Nov., 1950. Gas injection has been dispersed over the field rather than all into the gas cap. The field was unitized on Oct. 1, 1957, with the California Oil Co. its operator. A waterflooding program was initiated in Jan., 1958, utilizing water from the Navajo and Entrada formations.
Asphaltene Deposition During CO2 Flooding
Authors: Srivastava R. K. , Huang S. S. , Dong Mingzhe 
Published: December 2007

SummaryIn this article we present results of dynamic and static precipitation tests to investigate the likelihood of asphaltene deposition problems in southeast Saskatchewan's Weyburn reservoir. Tests were conducted at the reservoir temperature and pressure conditions. The effect on asphaltene flocculation/precipitation of the operating pressure, CO2 concentration, gas contaminants in CO2, and presence of formation brine was investigated for three different oil samples using static pressure/volume/temperature (PVT) tests. The extent of asphaltene deposition was also assessed through coreflood experiments and through an x-ray computer- aided tomograph (CAT)-scanning visualization experiment.Static tests indicated the most important factor on which the asphaltene precipitation depended was the CO2 concentration. For oils belonging to the same pool, the increase in asphaltene precipitation with solvent concentration was proportional to the initial asphaltene contents of the oil. Coreflood experiments showed a considerable increase in asphaltene deposition in the core matrix following CO2 injection. Pore topography of the core matrix played an important role in the extent of CO2-induced asphaltene deposition. X-ray CAT-scanning tests depicted localized areas of asphaltene deposition along the length ofthe core, with significant deposition suspected to be occurring near the inlet of the core.
Post-Frac Analyses Indicating Multiple Fractures Created in a Volcanic Formation
Authors: Sato Kozo , Wright C. A. , Ichikawa Makoto 
Published: December 2007

Summary
The technology of hydraulic fracturing is faced with a conceptual transition from a classical single-planar fracture to a tortuous fracture network and simultaneously propagated multiple hydraulic fractures. This new concept is applied to analyses of two propped fracture treatments conducted in a volcanic formation. In both cases, the productivity was doubled, but the treatments themselves were unsuccessful, experiencing extremely high net fracturing pressures and very premature screenouts.
The classical concept of a single-planar fracture could not explain either the fracturing-pressure behavior or the post-frac production rate/pressure. Adopting a multiple-fracture geometry resolves this problem. The fracturing pressures are successfully simulated, and the resultant fracture geometries are consistent with both the premature screenouts and the post-frac production performances. Combined analyses of fracturing pressure and subsequent production performances confirm the creation of multiple fractures in a volcanic formation.
A Semianalytical Approach for Productivity Evaluation of Complex Wells in Multilayered Reservoirs
Authors: Basquet Rémy , Caltagirone J. P. , Alabert F. G. , Batsalle J. C. 
Published: December 2007

Summary
We present a new approach to solve the problem of complex wells located in layered reservoirs with crossflow. First, the well path is discretized into a carefully chosen series of source points. Second, pressure solution for each source point is obtained in the Laplace domain anywhere in a rectangular reservoir, where crossflow is permitted between layers and with possibly mixed boundary conditions (no-flow or constant pressure). We used the Fourier transforms in the space variables after removing the time variable by the Laplace transformation. The problem is reduced to a matrix product to solve in the transformed domain.
The above method is validated through comparisons with known line source solutions and numerical simulations. It can be used to compute the pressure distribution within a well with complex geometry in a stratified bounded reservoir under the assumption of infinite well conductivity. The well can be located anywhere in the reservoir. Boundaries can be no-flow or constant pressure. Last, variable skins along the well path can be imposed.
An application on a field located in the deep offshore of the Gulf of Guinea demonstrates the great value for well design optimization in the context of complex heterogeneous reservoirs where classical analytical approaches are typically inappropriate.
Stochastic Analysis of Immiscible Two-Phase Flow in Heterogeneous Media
Authors: Zhang Dongxiao , Tchelepi Hamdi 
Published: December 2007

Summary
We present a stochastic analysis of immiscible two-phase flow (Buckley–Leverett displacement) in heterogeneous reservoirs. Since the detailed spatial variabilities of reservoir properties such as permeability and porosity cannot be described deterministically, both permeability and porosity, or either, are treated as random space functions. In turn, water saturation and oil production rate are also random variables. The main purpose of this study is to estimate the saturation field (by its expected value) and the associated uncertainty (by its standard deviation) for Buckley-Leverett displacement in such random media. The expected value and standard deviation may be used to construct confidence intervals for the saturation field in a reservoir and to evaluate the risk associated with a project caused by the incomplete knowledge of reservoir properties. Through transforming to coordinates attached to streamlines, the evaluation of saturation statistical moments is simplified to that of travel time and transverse displacement probability density functions. The latter do not vary with the two-phase composition but entirely depend on the total velocity under some conditions. Through some one- and two-dimensional examples, we found that the well-known discontinuities existing in saturation profiles and oil production curves for homogeneous media disappear in the case of heterogeneous media. This is due to heterogeneity fingering, or the so-called "heterogeneity induced dispersion." The effect of heterogeneity on oil production is the earlier water breakthrough and later oil arrival. The oil production is expected to take longer in heterogeneous media than in homogeneous media.
Polymer-Free Fluid for Fracturing Applications
Authors: Samuel M. M. , Card R. J. , Nelson E. B. , Brown J. E. , Vinod P. S. , Temple H. L. , Qu Qi , Fu D. K. 
Published: December 2007

Summary
Polymer residues that stay in the fracture after fracturing can limit the treatment effectiveness. A new and easy-to-prepare, surfactant-based polymer-free fluid, ClearFRAC™, that consists of a quaternary ammonium salt derived from a long-chain fatty acid is described. In brine, it builds fluid viscosity and viscoelasticity due to the formation of highly entangled worm-like micelles. The micelles have a gross structure similar to a polymer chain. Since the viscosity of the fluid depends on the nature of micelles, the fluid can be broken by changing this micellar structure. The breaking occurs when the fluid is exposed to hydrocarbons or diluted with formation water. Therefore, conventional breakers are not required, and the produced oil or gas can act as breakers for this fluid system.
The structural characteristics of this viscoelastic surfactant-based fluid to its chemical and physical properties are correlated in this article. Structure, rheology, fluid loss, and conductivity of this surfactant fluid together with its case histories are presented.
Evaluating Reservoir Architecture in the Northern Gulf of Mexico With Oil and Gas Chemistry
Authors: Westrich Joseph T. , Fuex Anthony M. , O'Neal Patricia M. , Halpern Henry I. 
Published: December 2007

Summary
A post-development study was carried out at Bullwinkle Field in the Gulf of Mexico to develop and test geochemical methods for evaluating reservoir architecture, establish confidence in reservoir geochemistry technology, and provide a framework for surveillance work at Bullwinkle. In line with previous work, this study shows how fluid composition data can be used to obtain improved reservoir architecture interpretations. Geochemistry is a low-cost direct approach for determining reservoir architecture. When data are integrated with results from other tools and techniques, the final result is to improve decision making and production efficiency for both development and redevelopment projects.
Use of Perforation-Tunnel Permeability To Assess Cased Hole Gravelpack Performance
Authors: Burton R. C. 
Published: December 2007

Summary
This paper proposes a method for comparing the effectiveness of cased hole gravelpacks. The method employs effective perforation tunnel permeability as the primary indicator of gravelpack effectiveness.
Completion pressure losses in cased hole gravelpacked wells are subdivided into categories and systematically reviewed to show the relative importance of alternative design features. From this information, perforation tunnel permeability is shown to be the major determinant of completion skin and flow efficiency in cased hole gravelpacked wells. The technique is shown to be useful in both low velocity (darcy) and high velocity (non-darcy) flow regimes.
Field examples are used to show how this technique can be used to diagnose design flaws and improve well performance results. These examples show that effective perforation tunnel permeabilities in cased hole gravelpacked wells are significantly lower than surface measured gravel permeabilities. This has important implications for well design and remedial candidate selection.
A Model To Predict Wireline Formation Tester Sample Contamination
Authors: Akram A. H. , Halford F. R. , Fitzpatrick A. J. 
Published: December 2007

Summary
Wireline formation testers (WFTs) collect fluid samples for pressure-volume-temperature analysis through a probe set against the borehole wall. Filtrate contamination is reduced prior to sampling by either pumping the mixture of filtrate and reservoir fluid from the formation to the borehole or flowing the mixture into one or more WFT chambers. The cleanup is monitored at the surface. The time to reach the level of acceptable contamination (LAC) depends on the depth of invasion, pumpout rate, and various fluid and rock properties.
Generalized guidelines predict time to first oil based on simple volumetrics but do not predict the rate of cleanup. Excessive cleanup time increases costs and the risk of differential sticking of the tool/cable. In some cases it may not be practical to attempt the operation as the LAC may take too long to achieve.
A numerical simulator was used to investigate the characteristics of the contamination level versus time curve and to define the variables governing cleanup.
The model was validated using data from five wells from two fields with differing rock and fluid properties. One hundred and fifty simulation runs were made with different invasion depths, flow rates, and rock and fluid properties.
An equation was developed for field use that estimates filtrate contamination fw as a function of cleanout time t.
An alternative approach for WFT sampling is also suggested, using not one but two probes. With this method, both cleanup time and the final level of filtrate contamination can be substantially reduced.