bluuebunny/crossref_metadata_2025_split huggingface dataset:
Density off Crude Oil Saturated With CO2
Authors: Marra R. Kendall , Poettmann Fred H. , Thompson Robert S. 
Published: December 2007

Summary
A correlation for determining the density of CO2/crude-oil mixtures with engineering accuracy was developed. The correlation is based on the ideal-solution principle. Apparent liquid densities for CO2 were correlated as a function of pseudoliquid system density and CO2 concentration. In the final working correlation, the pseudoliquid system density is expressed as a function of pseudoliquid hydrocarbon density and CO2 concentration. The pseudodensities are then corrected to reservoir conditions. The correlation is presented in both graphic and equation form and is easily adaptable to computer or hand-held calculator applications.
The mean error for the 154 data points used to develop the correlation is +1.39%, the average absolute error is 4.46%, and the standard deviation is 5.25%. An error analysis of the experimental data indicated that when the 20 points with the greatest deviation are removed, the mean error is +0.06%, the average absolute error is 2.8%, and the standard deviation is 2.44%.
The correlation presented provides a simple method for calculating the density of CO2/crude-oil mixtures with engineering accuracy. The densities are used for calculating FVF and swelling and in other reservoir engineering calculations.
An Analytical Simulator for Drillstem Test Interpretation
Authors: Hegeman Peter , Abbaszadeh Maghsood 
Published: December 2007

Summary
An analytical drillstem test (DST) simulator has been developed that can be used to verify the interpretation of DST's that have insufficient or poor-quality flow-rate data. The DST is modeled as a sequence of alternating pressure-specified buildup periods. With field data, it is shown that this simulator can be used to enhance the interpretation of nonsurface flowing DST's.
Hydraulic Fracturing Model Based on a Three-Dimensional Closed Form: Tests and Analysis of Fracture Geometry and Containment
Authors: Boutéca M. J. 
Published: December 2007

SummaryThe numerical model described in this paper was designed to provide a realistic three-dimensional (3D) solution for fracture propagation in minimal computation time. Comparisons with available results show good concordance for a wide range of data. The results of a parametric study are compared with the Nolte analysis of the propagation pressure.
Automatic Type-Curve Matching for Well Test Analysis
Authors: Abbaszadeh Maghsood , Kamal Medhat M. 
Published: December 2007

Summary
This paper presents a general method for automatic well test interpretation. The method matches the field data with theoretical reservoir models using a constrained, nonlinear, least-squares regression technique coupled with numerical Laplace inversion of pressure-drawdown equations. Pressure gradients are computed by forward finite-difference approximations. Hence, reservoir models whose pressure gradients are difficult to obtain analytically can be readily included. Only equations for drawdown type curves of reservoir models are needed. Simulated pressure tests and actual field data are analyzed to illustrate the application of the method. The method reduces the time required to perform well test analysis and minimizes the subjectivity of interpretation.
Criteria for Gas-Lift Stability
Authors: Asheim Harald 
Published: December 2007

Summary
Severe flow instability (heading or annulus heading) is known from operations of gas-lift systems. Here, two simple stability criteria are developed and compared with reported field data. The stability problems experienced for the cases examined would have been identified with these criteria and corrected at the design stage.

Introduction
The currently used principles for gas-lift design were established during the early 1950's. They provide relations betweengas injection pressure and the most efficient point of injection andgas injection rate and the production rate to be expected.
From these relations, standardized procedures for gas-lift design have been worked out. Works on application and optimization of the procedures have provided further insight into the interrelations between gas-lift design and economic performance.
Often-unstated assumptions of gas-lift design are that it will be possible to inject gas at a constant downhole rate and that the resultant production rate will be stable. This is not necessarily true; severe flow instability is well known in the actual operation of gas-lift systems.
Variations in pressure and flow rate are observed in all multiphase flow systems, even in pumping wells, because of redistribution of gas and liquids. They cause relatively small short-duration pressure and flow changes. Alone, this has little effect on the continuity of production. In a gas-lift system, however, it may trigger system instabilities.
API recommends that, for the sizing of pipes receiving gas-lifted production, a "surge factor" of 40 to 50% should be added to the estimated steady-state flow rate, compared with 20% for naturally flowing wells. Intended as guidelines for cases where more definite information is lacking, these numbers may indicate something about the uncertainties concerning the flow instabilities during gas lift.
Bertuzzi et al. observed that when the lift-gas input rate was reduced below a certain minimum, violent heading would occur and the liquid production would eventually cease. They postulated that "a sudden drop in pressure in the tubing brought about a sudden surge of gas into the tubing. The volume of gas surging into the tubing is dependent on the pressure and volume of gas in the annular space. If the pressure in the annular space dropped too much, gas ceased to flow into the tubing." More recently, gas-lift insta-bilities have led to shutdowns of wells in the Claymore field. This was amended by replacement of the downhole injection valve by a fixed orifice.
Flow instabilities have also been observed and analyzed for simple air-lift pumps. This is related to gas-lift instability. However, the inflow mechanisms of a gas-lift system are considerably more complicated than for an air-lift pump. Besides, the friction dampening will be much larger in a gas-lift system because of order-of-magnitude-larger flow length. Thus, the dominating mechanisms of instability will be quite different.
Simulation of PVT Experiments
Authors: Bouett L. W. , Grader A. S. , Orr F. M. 
Published: December 2007

Summary
An interactive program (PVTLAB) was written to simulate PVT experiments with a microcomputer. The simulator is a real-time representation of an actual PVT laboratory. Operations typically performed in the laboratory may also be performed with the simulator. The Peng-Robinson equation of state (PR-EOS) is used to calculate phase behavior, and the results of the calculations are displayed in color on the microcomputer monitor. The monitor graphically represents the condition of all the physical components of the PVT laboratory, including pressures, fluid levels in vessels, and the status of valves and pumps. A printed record of every action taken during a run is kept if desired. A simulated experimental error results in an appropriate termination of the run. Program structure and operation are described, and examples of simulated PVT experiments are given.
Reperforation of North Sea Electric-Submersible-Pump Wells With an ESP/Y-Tool/TCP System
Authors: Dudley R. W. 
Published: December 2007

Summary
As a result of the increasing emphasis on reducing operating costs and minimizing deferred production, a new system was designed for the reperforation of wells lifted with electric submersible pumps (ESP's). This paper describes an alternative method that can be used when a tubing-conveyed-perforating (TCP) system is required for the underbalanced reperforation of an ESP well. The method, which uses a combined ESP/Y-Tool/TCP assembly, can save about 24 hours in rig time over conventional methods. Use of the method can avoid substantial deferred or lost production, particularly when other wells requiring workovers are awaiting use of a rig at considerable cost. The system can also be used for the completion of new wells where an ESP is required from the outset and, under certain conditions, has an application during drillstem tests (DST's).
Refurbishment of the Ballast-Water System of the Gravity-Based Structure Beryl Alpha
Authors: Seume Klaus , Gilchrist James M. 
Published: December 2007

Summary
In Sept. 1985, the Beryl Alpha platform in the North Sea experienced a leak in its ballast-water system in the utility shaft 328 ft [100 m] below sea level. The importance of the ballast-water system for platform operations and the particular location of the leak led to the development and implementation of unique and extensive repair procedures. This experience may be of interest to design engineers and repair contractors. The total repair program took more than 3 years and has cost $6.5 million [£10 million*].
Formation Pressure Prediction With Seismic Data From the Gulf of Mexico
Authors: Martinez Ruben D. , Schroeder Joyce D. , King Geoffrey A. 
Published: December 2007

Summary
In this study, we derive seismic formation-pressure logs using seismic data from offshore Louisiana to delineate the distribution of overpressured zones in the subsurface. The seismic-data processing consists of velocity modeling, wavelet processing, and seismic inversion. From the acoustic impedances produced by seismic inversion, we derive seismic velocity and density logs at every seismic trace location using a relationship between sonic velocities and acoustic impedances. We use these logs to compute the seismic formation-pressure logs vs. depth. Formation-pressure logs are calculated with the assumption that compressional velocity, mean density, and depth are proportional to formation pressure. These logs are constrained at every depth by estimated matrix and fluid compressional velocities (vmax and vmin). vmax and vmin are derived from porosity and sonic well-log information.
Results include profiles of seismic-velocity, seismic-density, and formation-pressure logs for two intersecting seismic lines from offshore Louisiana. Logs from one well are used to constrain the data processing. The seismic formation-pressure sections delineate a large region of overpressured shales in the subsurface.
Experimental Study of a New type of Oil Production Platform
Authors: Kobayashi H. , Hirakawa S. , Suzuki T. 
Published: December 2007

Summary
A hybrid-type guyed tower platform composed of a steel-framed tower and a concrete caisson with oil-storage space inside and a petalous pedestal on top has been proposed. Computer analyses, laboratory tests, and an experiment at sea were performed to verify its design and construction.
A Study of Slip/Stick Motion of the Bit
Authors: Kyllingstad Å. , Halsey G. W. 
Published: December 2007

Summary
This paper deals with torsional oscillations caused by slip/stick motion of the drill-collar section. This phenomenon is associated with a large-amplitude, saw-tooth-like variation in the applied torque. "Slip/stick motion" refers to the belief that the amplitude of the torsional oscillations becomes so large that the drill-collar section periodically comes to a complete stop and does not come free until enough torque is built up in the drillstring to overcome the static friction.
A mathematical model of slip/stick motion is presented. This model includes parameters describing downhole friction effects and a simplified description of the drillstring. The effects of damping, finite rotary-table inertia, and the rotary-speed control system are discussed. Theoretical predictions are compared with measured torque signals recorded during field drilling.
This kind of drilling performance is likely to be less effective than normal drilling and may also lead to fatigue problems. This paper discusses ways to avoid severe torsional oscillations by using a more sophisticated feedback system to control the rotary speed.
Displacement of a Rich Gas Condensate by Nitrogen: Laboratory Corefloods and Numerical Simulations
Authors: Renner T. A. , Metcalfe R. S. , Yellig W. F. , Spencer M. F. 
Published: December 2007

Summary
A unique laboratory study of displacement of a rich gas condensate (from an Overthrust Belt reservoir in the western U.S.) by nitrogen and buffer gas (nitrogen plus separator gas) was conducted in slim tubes and long Berea sandstone cores at 215°F [375 K] over the pressure range 4,500 to 5,700 psia [31.0 to 39.3 MPa]. Innovative modifications and adaptations of laboratory flow equipment were required to complete this study under the severe test conditions used. Unit displacement efficiency was higher for buffer-gas injections than for nitrogen alone.
A generalized compositional model, which incorporates a modified Redlich-Kwong equation of state (EOS) for the fluid properties, was used to simulate the laboratory corefloods described above. With an appropriate estimate of the number of gridblocks required to mimic mixing effects in the cores, good matches of all measured parameters were obtained, although calculated gas breakthrough times were consistently later than observed. Compositional profiles were generally well-matched, with the largest deviations occurring for the methane and C7 + fractions. This simulator can be used for reservoir engineering studies of the fluid systems described.
New Insights Into Enriched-Air In-Situ Combustion
Authors: Moore R.G. , Bennion D.W. , Belgrave J.D.M. , Gie D.N. , Ursenbach M.G. 
Published: December 2007

Summary
This paper presents the results of 10 enriched-air in-situ combustion-tube tests performed on core from the Athabasca oil sands deposit. The tests show that at high pressures, the use of oxygen-enriched air results in increased low-temperature reactions between the oxygen and the oil, resulting in an increased fuel load and decreased burn stability. Although water injection may enhance the performance of oxygen combustion, it may also lead to increased oxygen storage in the swept zone.

Introduction
In-situ combustion, or fireflooding, is a thermal recovery technique that offers a high theoretical efficiency and uses relatively simple surface equipment. Although the process has been extensively studied in the laboratory and the field, operational problems associated with field projects, combined with the success of steam-based processes in a wide variety of reservoirs, have retarded the large-scale application of this technology.
Enriched-air injection is a modification of standard in-situ combustion technology with the potential to overcome a number of the problems that have hindered widespread field application of the process. In their excellent review of oxygen fireflooding literature, Garon et al. concluded that oxygen offers many process and operational advantages over normal air in-situ combustion. Fairfield and White discussed the advantages of using oxygen in the heavy-oil reservoirs of Saskatchewan, where field operations were hampered by severe sanding and gas locking of the production wells and by the formation of tight, difficult-to-treat emulsions. They concluded that removal of the large nitrogen volumes from the reservoir by injection of oxygen rather than normal air would not only reduce the sanding and gas-locking problems, but the greater allowable rates of oxygen injection would result in accelerated recovery schedules.
It is now generally accepted that in-situ combustion should be a follow-up process to steam stimulation if it is to be applied in cold, viscous reservoirs, such as those of northern Alberta. BP Resources Canada Ltd., in conjunction with the Alberta Oil Sands Technology and Research Authority (AOSTRA), has successfully piloted oxygen injection following steam stimulation of the Cold Lake reservoir. The application of in-situ combustion as an alternative to steam flooding has considerable merit because of its significantly higher thermal and displacement efficiencies.
This paper discusses enriched-air (95% oxygen) in-situ combustion tests conducted for AOSTRA on the Athabasca Oil Sands reservoir by the U. of Calgary In Situ Combustion Laboratory. The original objective of these tests was to evaluate the burning characteristics of enriched air at pressures up to 5520 kPa [800 psi]. The definite pressure effects noted during the initial test program, however, prompted an extension of the pressure range to 10 300 kPa [1,500 psi].
Thermal Recovery Well Test Design and Interpretation
Authors: Ambastha A. K. , Ramey H. J. 
Published: December 2007

SummaryBecause a reservoir undergoing a thermal recovery process is typically idealized as a composite reservoir, this study develops new design and interpretation equations by investigating pressure-derivative behavior of a well in a two-zone, radial, infinite or finite composite reservoir. Accurate design equations help establish the test duration required to observe a particular feature in well test data and thus the applicability of an interpretation method to determine front radius, or swept volume.This study shows that the dimensionless time to the end of the first semilog line (deviation time) based on front radius is a constant. The deviation-time method may be used if wellbore storage does not mask the first semilog line. Design equations for the time of the beginning of the second semilog line and the time to observe outer-boundary effects show that the intersection-time method is not suitable for thermal recovery well test analysis. Correlations developed for the end of pseudosteady-state behavior of the swept region should help select the correct Cartesian line to calculate swept volume. This paper also presents derivative type curves applicable for all front radii, with mobility and storativity ratios as parameters for infinitely large composite reservoirs. For closed and constant-pressure outer boundaries, the ratio of outer boundary to front radius is the third parameter.
Assigning Effective Values to Simulator Gridblock Parameters for Heterogeneous Reservoirs
Authors: Begg S. H. , Carter R. R. , Dranfield P. 
Published: December 2007

Summary
Characterization of heterogeneous reservoirs for simulation studies by use of a statistical component to the reservoir description combined with calculation of effective permeabilities is discussed through a case study of a fluvial reservoir. Inspection of whole core and logs from the Sherwood reservoir revealed that it is extremely heterogeneous, containing short shales embedded in a mixture of sands and silts. A statistical approach was used to quantify the distribution of core-plug porosity and permeability measurements to discriminate between significantly different rock types. A successive rescaling procedure was then adopted in which we first calculated effective values for each rock type from the core-plug data. These results were combined with statistics on the spatial distribution of the rock types to calculate effective values for the nonshale part of each layer. Finally, the effect of the shales on the vertical permeability was incorporated. The resulting anisotropy ratios, on the order of 10-3, were used successfully in black-oil model studies, a good match between the simulator predictions and observed production data being achieved with minimal fine tuning of the model parameters.
Effect of Borehole Size, Mudcake, and Standoff on the Photoelectric Absorption Index Measurement
Authors: Gearhart D. A. 
Published: December 2007

Summary
The photoelectric absorption index, IPe, is accepted as an accurate measurement for the description of formation lithology. The measured IPe has been shown to deviate slightly for a given lithology because of the effects of porosity. Properly calibrated and measured IPe's, however, have been observed to deviate from predicted values in practice, even considering the influence of porosity. Such departures were traced to variations in borehole size and tool standoff.
The nature of the physical method of recording an IPe does not ensure independence from the influence of the borehole environment. A series of laboratory experiments has been conducted in test formations to verify and to characterize the influence of borehole size, mudcake, and standoff on IPe measurement. A set of nomographs has been constructed that allows correction of IPe measurements for the influence of the borehole environment. With these nomographs, a more accurate interpretation of IPe can be performed.
Geochemical Logging With Spectrometry Tools
Authors: Hertzog R. , Colson L. , Seeman B. , O'Brien M. , Scott H. , McKeon D. , Wraight P. , Grau J. , Ellis D. , Schweitzer J. , Herron M. 
Published: December 2007

Summary
A geochemical logging tool (GLTSM) string, measuring natural, activation, and prompt neutron-capture gamma rays, produces logs of the most abundant and a few trace inorganic element concentrations. Direct measurements of Al concentrations are provided. A geochemically based closure model is used to derive Si, Ca, Fe, S, Gd, and Ti concentrations. The only significant spectroscopically undetermined element, Mg, is inferred by comparing measured with derived photoelectric factor. Analysis algorithms, demonstrations of accuracy and precision, and applications of geochemically derived formation properties are discussed.
A New Set of Type Curves for Well-Test Interpretation With the Pressure/Pressure-Derivative Ratio
Authors: Duong Anh N. 
Published: December 2007

Summary
This paper presents a new set of type curves used in well-test analysis for homogeneous reservoirs with wellbore storage and skin effects. When the pressure/pressure-derivative ratio (PDR) is used as a parameter in constructing the type curves, the vertical scales on both type-curve and field-data plots are identical. This automatic alignment of the vertical scale makes the new type curves easier to match and, subsequently, easier to use in the computer-aided analysis. The paper concludes that use of the new type curves reduces the uniqueness problem in pressure-transient type-curve matching, identifies the flow regimes effectively, and gives greater confidence in the results. A new method to correct the pressure buildup when drawdown type curves are used in radial-flow wells is also proposed. Two example applications, one with a long producing time and one with a short producing time before shut-in, are included to demonstrate the use of these type curves.
Analysis of Geothermal Wells With Simultaneous Logging Instruments
Authors: Davarzani J. , Sloan M. L. 
Published: December 2007

Summary
A new series of instruments has been developed for applications in geothermal wells. These instruments provide simultaneous acquisition of spinner-flowmeter, pressure, and temperature data. The hardware and the calculation methods used to determine various wellbore steam properties are described briefly and a geothermal field example with details and analysis methods is presented.
Thermal Effects in Cyclic Operation of Storage Reservoirs
Authors: Batesole Elizabeth C. , Wilkes James O. 
Published: December 2007

SummaryThis paper addresses the long-term temperature and pressure variations of natural gas that is stored cyclically in underground reservoirs to avoid the formation of gas hydrates. A detailed examination of the well and near-well reservoir emphasizes the cumulative importance of the Joule-Thomson effect over many years.
Hydrate Equilibria for Binary and Ternary Mixtures of Methane, Propane, Isobutane, and n-Butane: Effect of Salinity
Authors: Paranjpe S. G. , Patil S. L. , Kamath V. A. , Godbole S. P. 
Published: December 2007

Summary
This paper provides new experimental data on the phase behavior of gas hydrates for several binary and ternary mixtures of methane, propane, isobutane, and n-butane. After the molecular Kihara parameters for n-butane in the thermodynamic model were tuned, the predictions were in good agreement with the experimental data. The role of n-butane in hydrate formation is explained, and the effect of salinity on the phase behavior of binary mixtures of propane/n-butane is determined.