bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plugging Thief Zones in Water Injection Wells
Authors: Robertson John O. , Oefelein Frank H. 
Published: December 2007

Abstract
Standard Oil Co. of California is improving performance of its California water floods by improving vertical coverage and reducing water cycling. This program is being achieved by selectively plugging thief zones in water injection wells with a mixture of silicic acid gel and either gilsonite or silica flour. Previous field trials over a period of 10 years with many other materials and techniques had not achieved the desired results. This article discusses the theory and placement techniques of silicic acid gel and presents the results of successful plugging operations in unsegregated, multilayered reservoirs consisting of interbedded soft shales and unconsolidated sands. The operations have been successfully conducted in slotted liner completions, gravel-packed liner completions and cemented gun- or jet-perforated liner completions. The silicic acid gel is prepared in the field, and the entire operation can be conducted with a production hoist and cement truck. Results of this program show conclusively that silicic acid gel in conjunction with proper placement techniques can be utilized to effectively plug thief intervals in water injection wells. This is expected to become a major factor in improving waterflooding efficiency with a resultant decrease in operating costs and increase in net profit.

Introduction
The economic success of a waterflood in thick, multilayered sands is dependent upon the efficiency of the displacement process. Control of vertical injection coverage is necessary for the maximum oil recovery and the reduction of excessive water cycling. Effective vertical coverage can be achieved by plugging thief intervals or with subsurface controls. The Vickers zone, Inglewood oil field, Calif., is an Unsegregated, 1,500-ft thick, multilayered reservoir consisting of unconsolidated sands interbedded with soft shales (Fig. 1). The average net sand thickness in this interval is 520 ft. The porosity and permeability values range from 28 to 36 percent and 500 to 2,500 md, respectively. Most injection wells are completed with either gravel-packed or slotted liners. In unsegregated zones this type of completion precludes the use of packers and subsurface beans to control or exclude injection into thief intervals. Within this zone, thief intervals are not confined to particular stratigraphic intervals; therefore, they cannot be excluded upon completion.

General Theory: Selective Plugging
Selective plugging in injection wells is not new to the petroleum industry. Cement, colloidal clays, inert solids, paraffins, waxes, organic resins and gels have long been utilized. Opinions differ as to the benefits obtained from using a selective plugging technique since apparently only the area adjacent to the wellbore is affected.
X-Ray CT and NMR Imaging of Rocks
Authors: Vinegar H.J. 
Published: December 2007

Introduction
In little more than a decade, X-ray computerized tomography (CT) and nuclear magnetic resonance (NMR) imaging have become the premier modalities of medical radiology. Both of these imaging techniques also promise to be useful tools in petrophysics and reservoir engineering, because CT and NMR can nondestructively image a host of physical and chemical properties of porous rocks and multiple fluid phases contained within their pores. The images are taken within seconds to minutes, at reservoir temperatures and pressures, with spatial resolution on the millimeter and submillimeter level.
The physical properties imaged by the two techniques are complementary. CT images bulk density and effective atomic number. NMR images the nuclide concentration, Mo, of a variety of nuclei ( H, 19-F, 23-Na, 31-P, etc.), their longitudinal and transverse relaxation-time curves (t1 and t2 ), and their chemical shift spectra. In rocks, CT images both rock matrix and pore fluids, while NMR images only mobile fluids and the interactions of these mobile fluids with the confining surfaces of the pores.

Principles
CT uses an X-ray source that rotates around the sample to obtain one-dimensional projections of X-ray attenuation at different angles. From these projections, a crosssectional slice through the sample is reconstructed by computer. Finally. a three-dimensional image is reconstructed from sequential cross-sectional slices taken as the sample is moved through the scanner.
To obtain both density and effective atomic number, CT images are taken at two X-ray energies. One energy is high enough for the X-rays to be predominantly Compton-scattered and one is low enough for them to be mostly photoelectrically absorbed. A combination of the two images in the computer. on a pixel-by-pixel basis, generates separate images of bulk density and effective atomic number.
In NMR imaging, the sample is placed inside an intense, homogeneous, magnetic field, one preferably generated by a superconducting magnet. Radio frequency (RF) coils apply RF magnetic fields at the precise Larmor frequency to cause the particular nuclear species to precess. The RF coils then detect the signals generated by the precessing nuclei.
Spatial localization within the sample is obtained by x. y, and z magnetic-field gradient coils that cause nuclei in different parts of the sample to precess at slightly different frequencies. The resulting frequency-modulated signal is Fourier-transformed to obtain the spatial distribution of nuclear-spin density. Unlike CT, an image is obtained of the entire sample volume within the RF coil.
JPT
P. 257^
A Method for Simultaneous Determination of Permeability and Porosity in Low-Permeability Cores
Authors: Haskett Steven E. , Narahara Gene M. , Holditch Stephen A. 
Published: December 2007

Summary
A new method for simultaneously determining the permeability and porosity of low-permeability cores is described. This method uses unsteady-state gas flow, which results in rapid tests. Equations are presented that describe the pressure response as a function of porosity and permeability. Comparisons of results to numerical simulations and conventional core-analysis methods are presented that verify the method 's accuracy.
Computerized Automation of Oilfield Production Operations: An Extensive 5-Year Study Into the Costs and Benefits
Authors: Jentsch W. A. , Marrs R. D. 
Published: December 2007

Summary
Sun E&P Co. conducted an extensive 5-year study into the costs and benefits of installing and operating a supervisory-control and data-acquisition (SCADA) system. This paper briefly outlines the unit operations and the SCADA system installation, explains in detail the 5-year study, and highlights other intangible benefits provided by the system.
Temperature Dependence of L1/L2/V Behavior in CO2/Hydrocarbon Systems
Authors: Larson L. L. , Silva M. K. , Taylor M. A. , Orr F. M. 
Published: December 2007

Summary
The temperature dependence of liquid/liquid (L1/L2) and liquid/liquid/vapor (L1/L2/V) phase behavior in CO2/hydrocarbon systems is investigated with a combination of measurements of L1/L2 and L1/L2/V phase compositions and calculations of two- and three-phase behavior with the Peng-Robinson equation of state (PREOS). New phase-composition data are reported for mixtures of CO2 with normal hexadecane (C16) and squalane (C30) and for mixtures of CO2 with methane (C1) and hexadecane. Measurements of three-phase pressures for mixtures of CO2 with C14, C16, and C30 are also reported. Calculations of L1/L2 and L1/L2/V phase behavior with the PREOS are compared with all available experimental phase-composition data for CO2/C1/C16 and CO2/propane (C3)/C16 systems. The PREOS predicts such behavior with reasonable quantitative accuracy if binary interaction parameters are selected to match L1/L2 data. Details of the disappearance of L1/L2/V behavior with increasing temperature are investigated with the validated PREOS. For the CO2/C3/C16 system, three-phase behavior disappears at a tricritical point. For the CO2/C1/C16 system, the disappearance occurs at the upper critical endpoint (UCEP) for the CO2/C16 binary system. Finally, qualitative similarities between CO2/crude-oil systems and the ternary systems described here are discussed.
Effect of an Aqueous Phase on CO2/Tetradecane and CO2/Maljamar-Crude-Oil Systems
Authors: Pollack N. R. , Enick R. M. , Mangone D. J. , Morsl B. I. 
Published: December 2007

Summary
The effect of the presence of an aqueous phase on the phase behavior of the CO2/tetradecane and the CO2/Maljamar-crude-oil systems has been experimentally determined. Both the salinity and the amount of the aqueous phase were varied to test several methods of modeling. In the first technique, the amount of CO2 "lost" to the aqueous phase was determined using Henry’s law, decreasing the overall ratio of CO2 to hydrocarbons, while the Peng-Robinson equation of state (PR EOS) was used to determine the phase distribution of the hydrocarbon phases. In the second technique, the equation of state (EOS) was modified to predict the densities and compositions of not only the hydrocarbon phases, but also the aqueous phase. Simply accounting for CO2 solubility by incorporating Henry’s law, used in conjunction with the Poynting correction and an empirical factor for salinity, not only gave results nearly identical with the EOS approach, but also required less computational effort. Both methods gave good agreement with the experimental data.
Economic Considerations for Sizing Tubing and Power Cable for Electric Submersible Pumps
Authors: Powers Maston L. 
Published: December 2007

Summary
Power consumption of an electric submersible pump (ESP) installation may be categorized into three components: the energy required to perform useful work, which is equivalent to the net hydraulic load divided by the product of pump and motor efficiencies; the energy absorbed by tubing friction, which is equal to the dissipated hydraulic energy divided by the efficiency product; and power-cable electrical losses. An improved design technique is presented that brings the first two categories into economic perspective. The interrelated effects of tubing friction, power-cable resistance, and motor voltage on ESP power consumption are demonstrated, as is the degree of desirability for using a motor of the highest available voltage. An equation, useful in making economic evaluations of alternatives, is developed for calculating power consumption for combinations of tubing size, power-cable size, and motor voltage. Variations of power consumption are illustrated graphically for various combinations of these three parameters. Also illustrated is the effect of the nature of a specific net hydraulic load—i.e., the product of rate, net lift, and specific gravity. Practical examples using the design techniques developed here are presented and comparisons made to designs based on common practice.
System Analysis for Sucker-Rod Pumping
Authors: Schmidt Z. , Doty D. R. 
Published: December 2007

Summary
Pumping free gas in an oil well can significantly decrease the efficiency of a sucker-rod-pumping installation. Pump placement depth and use of a downhole gas/liquid separator (gas anchor) were found to be significant variables in improving the overall efficiency. A procedure is presented that shows when and to what degree the use of a gas anchor improves the efficiency of a sucker-rod pumping system. It was found that at lower pump intake pressures, the gas anchor usually improves efficiency, but at higher pump intake pressures, use of a gas anchor will produce no positive effect. Also, elevating the pump to the highest position that still allows proper pump loading was found to reduce the operating costs of a sucker-rod-pumping installation significantly. Finally, a procedure is presented to calculate directly the pump volumetric efficiency and required volumetric pump displacement rate.
Gas-Lift Design and Production Optimization Offshore Trinidad
Authors: Laing Cameron M. 
Published: December 2007

Summary
Through a variety of field examples, this paper describes how increased production rates were obtained from gas-lift wells. These results were achieved through a wide range of activities, including special training for production operators, optimizing gas injection rates, modifying surface piping systems, identifying and replacing defective wireline-retrievable gas-lift valves, and improving gas-lift design techniques. A major modification of a standard gas-lift design technique is discussed in detail. The modification optimizes the depth of gas injection throughout the life of a well. An empirically derived chart, which relates valve spacing to the PI of a well, is also presented.
Early-Time Tight Gas Production Forecasting Technique Improves Reserves and Reservoir Description
Authors: Neal D. B. , Mian M. A. 
Published: December 2007

Summary
For many tight gas wells producing without curtailment, the formation linear flow period can last for several years, leading to a new evaluation technique that utilizes commonly available producing rate data. This linear flow model, which states that the inverse of rate is proportional to the square root of time, leads to simple equations and graphical techniques for predicting the performance of low-permeability gas wells. The model is also useful in evaluating the reservoir quality and effectiveness of stimulation treatments. Accurate reserves and well-performance predictions can be made with as little as 6 months of production. In addition, the proposed method is easier to apply than other methods currently in use.
CASTEM—A New Automated Parameter-Estimation Algorithm for Single-Well Tracer Tests
Authors: Seetharam R. V. , Deans H. A. 
Published: December 2007

Summary
The single-well chemical-tracer (SWCT) method has been used in more than 140 tests since 1968 to determine residual oil saturation (ROS) after waterflooding. Interpretation of the test involves matching tracer data from the field by use of computer simulation programs. As the complexity of the simulator model increases, the number of trial runs needed to fit field data satisfactorily increases rapidly. The conventional fitting procedure can thus become very cumbersome and can involve prohibitive computer costs. A new method has been devised to model tests in heterogeneous formations. These rigorous simulators have been replaced by simple response functions capable of being used in a standard parameter-estimation routine. Matching the tracer data now involves function evaluations rather than full simulator runs, resulting in a large reduction in computing time.
The algorithm developed here includes many frequently used tracer test models. The new method has been used to explain both simulated and actual field data from tracer tests conducted in multilayer reservoirs. The choice of an appropriate model to explain a specific set of field data may be a qualitative decision, especially in the absence of other supportive physical evidence. However, the variation in the effective ROS predicted by the different models was found to be quite minimal and within the limits of accuracy of the test.
Dual-Burst Thermal Decay Time Logging Principles
Authors: Steinman D. K. , Adolph R. A. , Mahdavi M. , Preeg W. E. 
Published: December 2007

Summary
The dual-burst thermal-neutron-decay-time (TDT™) tool brings two enhancements to pulsed-neutron capture logging. The first is a realistic physical model of pulsed neutron decay curves that accounts explicitly for the effects of neutron diffusion and decay in both the wellbore and the formation. The second is the dual-burst system itself, which permits excellent statistical precision with minimal dead-time losses. This paper discusses the physics of the model, operation of the tool, important mathematical considerations for optimum use of the tool, and a demonstration of the tool performance in a laboratory simulation of a log-inject-log (LIL) operation.
Use of Inhibitors for Scale Control in Brine-Producing Gas and Oil Wells
Authors: Rogers L. A. , Varughese K. , Prestwich S. M. , Waggett G. G. , Saliml M. H. , Oddo J. E. , Street E. H. , Tomson M. B. 
Published: December 2007

Summary
Field and laboratory work sponsored by the Gas Research Inst. (GRI) and the U.S. DOE showed that calcium carbonate (CaCOз) scale formation in waters produced with natural gas and oil can be prevented by injection of phosphonate inhibitor into the formation, even if the formation is sandstone without calcite binding material. Inhibitor squeeze jobs were carried out on the DOE's geopressured/geothermal Gladys McCall brine/gas well and GRI's coproduction wells in the Hitchcock field. After the inhibitor squeeze on Gladys McCall, the well produced more than 5 million bbl [800× 103 m3] water at a rate of about 30, 000 B/D [4770 m3/d] without CaCOз scaling. Before the inhibitor squeeze, the well could not be produced above 15, 000 B/D [2385 m3/d] without significant scale formation. In the GRI brine/gas coproduction field tests, inhibitor squeezes have been successfully used to prevent scaling. Laboratory work has been conducted to determine what types of oilfield waters are subject to scaling. This research has led to the development of a saturation index and accompanying nomographs that allow prediction of when scale will develop into a problem in brine production. Core samples from both fields were used in laboratory studies. Analytical methods to analyze inhibitors in brine at low levels were extended. A complete history of field development and the laboratory backup experiments is included in this paper.
Evaluation of Directional Survey Errors at Prudhoe Bay
Authors: Dubrule Olivier , Nelson Philip H. 
Published: December 2007

SummaryMore than 1,000 directional surveys from wells in the Prudhoe Bay field are used to examine differences in well location at 8,000 ft [2438 m] subsea, as measured by gyroscopic and magnetic surveying instruments. The lateral, radial, and vertical errors are plotted as a function of horizontal offset. Mean lateral differences appear to be about 100 ft [30 m]. Drillstring magnetization causes magnetic surveys to read north of gyros. Vertical and radial differences are negatively correlated, are chiefly a result of inclinometer errors, and are on the order of tens of feet. The Wolff-de Wardt (WdW) error model, with small modifications, does a good job of quantifying the error magnitudes, of describing the dependence of error upon horizontal offset, and of producing the ellipses of uncertainty.
Effects of Nonlinear Reservoir Compaction on Casing Behavior
Authors: Chia Y. P. , Bradley D. A. 
Published: December 2007

Summary
Depletion of overpressured, undercompacted reservoirs can cause large reservoir pressure drops and sediment compaction, which may result in casing deformation and well failure. To predict soil and casing deformation during depletion, a finite-element model was developed. Nonlinear elastic and plastic behavior of the soils and slippage along the wellbore boundary are major advancements in this study. This axisymmetric model is composed of casing wall, cement column, slippage interface, and sediments from 11,400 to 13,200 ft [3475 to 4025 m] in depth with a radius of 3,400 ft [1035 m]. This study features a process of concurrent fluid flow, nonlinear elastic and plastic soil deformation, slippage from the wellbore boundary, and casing deformation.
The modeling results show that the decline in near-wellbore reservoir pressure during depletion causes vertical compaction in both the sand reservoirs and the confining shale formations. Slippage next to the wellbore decreases the axial shear load placed on the casing by the sediments. Nonlinear elastic and plastic soils show a greater tendency for casing deformation with depletion than do linear elastic soils. Axial strains in the casing above the yield strain eventually developed as near-wellbore reservoir pressure was allowed to decline to a minimum. Because this effect is quantified, the production rate may be held to a safe maximum so that the operating limits of the casing are not exceeded. Criteria are given to improve both completion design and production rate specification.
Complex Dielectric Interpretation of 20-MHz Electromagnetic Logs
Authors: Sims J. C. , Cox P. T. , Simpson R. S. 
Published: December 2007

SummaryAn interpretation technique for the 20 × 106-cycle/sec [20-MHz] dielectric log based on the complex Lichtenecker-Rother (LR) equation is proposed. The equation is shown to be an adequate model of quarry rocks and is applied to field logs from the California coastal basins. The results are significantly better than those obtained with other techniques. The major disadvantage is that core data are required for calibration in each reservoir.
Coiled-Tubing Logging System
Authors: Howell E. P. , Smith L. J. , Blount C. G. 
Published: December 2007

Summary
Techniques have been developed to use coiled tubing containing a seven-conductor wireline to facilitate logging operations. Equipment has been designed to permit the connection of conventional logging tools to the tubing and the recording of logs. Operating techniques have been developed and applied under various wellbore conditions. The system allows traditional log measurements in a well while wellbore conditions are controlled. Advantages of the system include reduced wellbore pressure during perforation to maximize perforation performance; lubrication during pulling or pushing a logging tool through a borehole so that a more uniform velocity can be maintained with a logging sonde; continued circulation and thus borehole stability during logging; temperature reduction for improved reliability of logging sonde electronics in hot holes; and more stable positioning of perforation equipment. The ability of coiled tubing to push tools down highly deviated or horizontal wellbores makes logging or perforating feasible in these wells. Expenses can often be reduced with coiled-tubing logging because a rig is unnecessary during many operations.
The Effects of Multiphase Flow on the Interpretation of Pressure Buildup Tests
Authors: Ayan Cosan , Lee W. J. 
Published: December 2007

SummaryA two-dimensional (2D), three-phase, variable-bubblepoint reservoir simulator was developed to simulate pressurebuildup tests involving multiple phases. The simulation indicated that nonuniform saturation distributions throughout the drainage area can cause erroneous interpretations when single liquid-phase techniques, as modified by the Perrine-Martin theory, are used for the analysis.