bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mobilization of Waterflood Residual Oil by Miscible Fluids
Authors: Holm L. W. 
Published: December 2007

Summary
A study was conducted to determine how residual oil left by a waterflood is mobilized by miscible or low-interfacial-tension (IFT) fluids. Crude oils were used in the oil-displacement experiments with cores and sandpacks. In most previous investigations, refined oils were used. The residual crude oil was distinguished from injected oils by tagging of one or the other with olefins—hydrocarbons that are not present in crude oils but are easily and quantitatively distinguishable by analytical chromatographic techniques.
The study shows that residual crude oil left by a waterflood is more accessible to an injected miscible fluid than is a residual refined oil, presumably through crude-oil-wetted surfaces of the rock. The results of laboratory coreflood displacements of residual or mobile refined oils (decane, soltrol, mineral oil, etc.) are not representative of reservoir formations containing indigenous crude oil. The displacement of residual crude oil by solvent is more efficient than displacement of refined oil by that solvent. Also, the displacement of residual oil by an oil or solvent at favorable mobility ratio occurs as a bank of oil production at a high flowing oil saturation approaching one minus the immobile water saturation. This saturation in a given porous medium at oil breakthrough depends on the viscosity of the residual oil.
Elastomers Are Eliminated in High-Pressure Surface-Controlled Subsurface Safety Valves
Authors: Morris A. J. 
Published: December 2007

Summary
Industry well completions are currently limited by the uncertain finite life of elastomers. The useful life of subsurface equipment with elastomeric seals is shortened by temperature, pressure, amines, acids, and completion fluids.
All-metal, hydraulically operated surface-controlled subsurface safety valves (SCSSV's) that meet and exceed all regulatory requirements and standards are now available with no elastomeric seals. This fully developed design, awarded the Special Meritorious Award for Engineering Innovation in May 1983, has been completely laboratory and field tested and is being used in critical service well completions.
Development of subsurface high-pressure completion equipment indicates that at 10,000-psi [69-MPa] working pressure; elastomers perform at minimum acceptable levels. The longevity of subsurface completion equipment is limited and uncertain. Combining sound engineering principles with state-of-the-art metallurgy, reducing galling tendencies of high-nickel/chrome alloys, and using diffused-surface alloys have resulted in the technology for all-metal hydraulically operated equipment. This technology is expandable to an entire subsurface completion system without any elastomers.
Effects of Wellbore Storage and Skin on Vertical-Permeability Testing
Authors: Kamal M. M. 
Published: December 2007

Summary
Knowledge of the vertical permeability is needed to determine the optimal depletion scheme of most reservoirs. Current methods often render vertical-permeability tests uneconomical to conduct and/or to analyze, and methods are not available for test design. This paper presents a new method, based on type curves, to design and analyze vertical-permeability tests in the presence of wellbore storage and skin at both the active and measurement perforations. The method uses early-time data and thus reduces the test time and improves the economics of vertical-permeability testing. The new method is simple to use and practically eliminates the need for numerical simulators. A step-by-step example describing the design and analysis of a vertical-permeability test demonstrates the use of this method.
Tip Screenout Fracturing: A Technique for Soft, Unstable Formations
Authors: Smith M. B. , Miller W. K. , Haga J. 
Published: December 2007

Summary
Several special stimulation techniques have been proposed for soft, unstable formations. One example is a combination of acid and proppant, which leaves the acid channels full of sand. This paper discusses an alternative completion technique that involves only normal sand fracture procedures and is effective where acid is ineffectual or undesirable. Because the procedure is aimed primarily at creating short, high-conductivity fractures in soft formations, its use can be extended to any formation where such a treatment is practical and economically feasible.
The fracture design is based on intentionally screening out the tip of the fracture with sand and then continuing to pump slurry to increase the fracture width and to pack the fracture with proppant to obtain high conductivity. Because this involves severe risk of a premature screenout, and because failure to achieve the tip screenout will not yield the desired stimulation, special prefracture tests are required to determine fracture design variables. The implementation and analysis of these tests are discussed, along with the theory behind the fracture design schedule. This theory is then compared with fracture pressure data and production performance from two wells completed in an Upper Cretaceous chalk formation in the Norwegian Sector of the North Sea.
Hydrodynamic Conditions of Hydrocarbon Accumulation Exemplified by the Carboniferous Formation in the Lublin Synclinorium, Poland
Authors: Zawisza Ludwik 
Published: December 2007

Summary
Groundwater movement in a selected aquifer of a sedimentary basin in the Lublin synclinorium is considered on the basis of rock and fluid data, and conditions of migration and accumulation of hydrocarbons are presented. The problem of groundwater movement is solved analytically, taking into consideration variable density of water and variable permeability of rocks.
A modified theory is advanced to define more precisely the position of potential oil and gas traps. The theory introduced here is more universal than Hubbert's theory because it accepts both the variability of the oil, gas, and water density (static effect) and the groundwater motion (dynamic effect). The suggested method of determining the positions of potential hydrodynamic petroleum traps is comparatively simple to apply and gives good results in regions with high hydraulic gradients and high variability of salinity and hydrocarbon densities.
Application of Fracture Design Based on Pressure Analysis
Authors: Nolte K. G. 
Published: December 2007

SummaryThis paper describes case studies of fracturing pressure analysis for the Wattenberg field of the Denver basin and the Cotton Valley sand of east Texas. The studies show the benefits of pressure analysis and controlled pressure designs for fracture treatments. In addition, procedures for measuring fracturing pressures and considerations for the successful execution of minimal viscosity treatments are presented.
Triple-Porosity Systems for Representing Naturally Fractured Reservoirs
Authors: Abdassah Doddy , Ershaghi Iraj 
Published: December 2007

SummaryThis study develops an improved model for analysis of pressure transient tests of naturally fractured reservoirs. The development was prompted by observations of actual well tests that showed anomalous slope changes during the transition period and where the behavior could not be explained by dual-porosity models.Geometrical configurations studied include both the strata model, where horizontal matrix layers are separated by fractures, and the uniformly distributed blocks, which are separated by an orthogonal set of fractures. These systems were assumed to be under gradient flow conditions. In both cases, two separate sets of matrix properties were assumed. The formulation of response was solved semianalytically. The solutions included the earlytime effects of both the afterflow and skin.Observations made from the theoretical predictions are that the fracture-controlled early times and portions of the transition period will resemble the behavior of a dual-porosity system. The latter part of the transition zone, however, exhibits slope changes; the duration is a function of λ1/λ2 (ratio of interporosity flow coefficients for the two matrix types) and ω1/ω2 (ratio of fluid capacitance coefficients).A correlation developed on the basis of numerous sensitivity runs allows the estimation of ω1/ω2 and λ1/λ2 with the times that correspond to the onset of anomalous slope changes. Because an infinite-acting slope may develop before the matrix blocks of the lowest λ show their existence during the anomalous slope changes, recognition of the various matrix properties emphasized in this study will also safeguard against extrapolation of incorrect late-time curves.
Incomplete LU Preconditioners for Conjugate-Gradient-Type Iterative Methods
Authors: Simon Horst D. 
Published: December 2007

Summary
In recent years, such conjugate-gradient-type methods as orthomin have been used very successfully with various preconditioners to solve the unsymmetric linear systems that arise in reservoir simulation. Here these successful iterative methods are combined with a new set of preconditioners that have been derived from some powerful algorithms in direct sparse Gaussian elimination. The SPARSPAK implementations of minimum degree and nested dissection algorithms have been modified to yield incomplete LU factorizations. Their application to reservoir simulation problems is investigated here.
Effects of Gas Composition and Geothermal Properties on the Thickness and Depth of Natural-Gas-Hydrate Zones
Authors: Holder G.D. , Malone R.D. , Lawson W.F. 
Published: December 2007

Summary
When natural gas and water contact at low temperature and high pressure, gas hydrates can form. In colder climates (such as Alaska, Northern Canada, and Siberia) and beneath the oceans, conditions are appropriate for gas-hydrate formation. This paper gives the depths and potential thicknesses of such hydrate formations as a function of the geothermal gradient, gas composition, and where appropriate, permafrost thickness. pressure gradient, and ocean-bottom temperature.

Analysis of Reservoir Conditions Where Hydrates Are Likely To Form
An accurate model for predicting hydrate equilibrium as a function of gas composition, temperature, and pressure has been used to generate hydrate-stability data. Figs. 1 through 6 present depth-vs.-temperature profiles for the earth and indicate hydrate-stability zones. The variables studied included permafrost thickness, geotherinal radients, gas composition, and pressure gradients on land and ocean depth, ocean-bottom temperature, and gas composition beneath the ocean. Except for the gas composition. these variables allow the pressure/temperature conditions in the earth to be determined. Together with gas composition, pressure and temperature determine whether hydrates are stable. These variables are cross-correlated so that any combination of permafrost thickness, gas composition, and geothermal permafrost thickness, gas composition, and geothermal gradient can be evaluated. Correlations presented in Figs. 7 through 11 show the effect that these variables have on hydrate-stability-zone thickness. All results were calculated with a computer program of excellent accuracy that calculates the minimum pressure required for hydrate stability given temperature, T, and gas composition. If the pressure calculated by the program is lower than the pressure determined from the pressure gradient in the pressure determined from the pressure gradient in the earth, the hydrates are stable; otherwise, the hydrates are not stable. Results of the depth/temperature studies are presented in Figs. 1 through 6 as outlined below. Table 1 shows the default values used for these calculations. These values are considered to be representative. Where differences in values are likely, the effects of changes in these values have been given in Figs. 1 through 11. The values studied are not the only possible conditions in the earth. The ranges of values used were chosen because they represent conditions where hydrates can form, but some values, such as geothermal gradient and average surface temperature, can vary with location.
P. 1379
Predicting Liquid Gradient in a Pumping-Well Annulus
Authors: Hasan A. Rashid , Kabir C. Shah , Rahman Rehana 
Published: December 2007

SummaryThis work proposes a hydrodynamic model for estimating gas void fraction, fg, in the bubbly and slug flow regimes. The model is developed from experimental work, involving an air/water system, and from theoretical arguments. The proposed model suggests that prediction of fg, and hence the bottomhole pressure (BHP), is dependent on such variables as tubing-to-casing-diameter ratio, densities of gas and liquid, and surface tension. Available correlations do not include these variables as flexible inputs for a given system.Computation on a field example indicates that slug flow is the most dominant flow mechanism near the top of liquid column at the earliest times of a buildup test. As buildup progresses, transition from slug to bubbly flow occurs in the entire liquid column. Beyond the afterflow-dominated period, the effect of bubbly flow diminishes as gas flow becomes negligibly small. Comparisons of BHP's are made with the proposed and available correlations. Because the proposed model predicts fg between those of the Godbey-Dimon and Podio et al. correlations, BHP is predicted accordingly.
Evaluation of Oil Properties in After-Tax Dollars
Authors: Powell Douglas H. 
Published: December 2007

Abstract
Why do we talk about "pre-tax dollars" and "after-tax dollars"?
In choosing its investments, management today usually asks the question, "How soon will we have a full return of our investment after all income taxes?"
Contrary to our intentions, every business venture that we enter into today has some unseen "net profits interests" who get a major percentage of our net profits but stand none of our net losses if the venture is unsuccessful. This refers, of course, to the fact that, under the present rates of income taxes, the United States Government and the State of California (or some other state) get approximately 50 per cent of the net profits (if any) of any venture of a large corporation and varying percentages in the cases of small corporations, partnerships and individuals.
Field property valuations are ordinarily submitted on a strictly engineering basis, arriving at the present worth of the net cash recovery before income taxes for the estimated life of the property.
To convert these pre-tax dollars to the after-tax dollars so often wanted by management in weighing one proposed investment against another, it is necessary to estimate the income taxes payable by years. In an extractive industry such as ours, statutory depletion is an important element in this computation, as are the depreciation deduction and method of financing also. These computations are ordinarily done by accountants versed in income taxes.
This paper is presented to explain how accountants and petroleum engineers must sometimes work together to get the final solution desired in making a valuation of oil and gas properties in after-tax dollars.

Introduction
Income taxes have reached such high rates that all important business transactions made today are entered into only after consideration has been given to the impact of income taxes on the final net results. Most agreements are drawn in such a manner as to minimize income and other taxes as much as possible and avoid the payment of any unnecessary taxes.
A New Approach to Interference Test Analysis
Authors: El-Khatib Noaman A. F. 
Published: December 2007

Summary
The line-source solution of the diffusivity equation is differentiated and rearranged so that a linear relation between the variables is obtained. A plot of log tp′ vs. 1/t yields a straight line whose intercept and slope are used to estimate the transmissivity, kh/μ, and the storativity, hϕct, respectively. The method is extended to handle two-rate tests, including buildup tests, and can be used for the analysis of the combined data of the two periods.
Revised Bean Performance Equation for East Baghdad Oil Wells
Authors: Al-Attar H. H. , Abdul-Majeed G. H. 
Published: December 2007

Summary
A comparison of the existing correlations for the determination of multiphase fluid-flow performance through a wellhead choke is made. The comparison is based on statistical analysis with production data from 155 well tests, 20 of which are from the East Baghdad oil field. The comparison indicates the relative strengths and weaknesses of each correlation and should aid in the selection of a satisfactory correlation for different applications. No one method is found to be most accurate in all ranges of flow variables. The best overall comparison, however, is obtained with the Gilbert correlation that predicted measured production rates within an average error of 6.19%. This correlation is then revised in two forms to fit the observed data from the East Baghdad oil wells best.
The Utility of CO2 as an Energizing Component for Fracturing Fluids
Authors: Garbis Sam J. , Taylor J. Lawrence 
Published: December 2007

Summary
The use of CO2 as an energizer in hydraulic fracturing fluids has increased dramatically in the past few years. The history of CO2 usage for this application is discussed briefly, and CO2 is compared with the other commonly used energizer, N2. The design considerations for using CO2 in a fracturing treatment, both as a minor (energizer) and a major (foam) component, are presented. Special consideration is devoted to CO2 foam because CO2 is pumped as a compressible liquid that changes to a gas downhole. This paper presents the calculations required to estimate the surface liquid CO2 volumes and injection rates needed to obtain the desired downhole foam properties. Also, the instrumentation required to meter the liquid CO2 safely and accurately is discussed.
Field results further evidence CO2's utility in hydraulic fracturing. This discussion includes a comparison of fracture stimulation with and without CO2 as an energizer as well as treatments that compare CO2 -energized fluids with N2-energized fluids. Economic considerations of pumping CO2 vs. N2 vs. no energizer are discussed. Conclusions suggest what further study is required to help improve design techniques and when CO2 should be considered as a component of a fracture stimulation treatment.
Quantitative Analysis of Factors Influencing Vertical and Lateral Fracture Growth
Authors: Settari Antonin 
Published: December 2007

Summary
This paper presents contributions to the modeling of the vertical and lateral propagation of hydraulic fractures. The first part presents a method for the quantitative analysis of factors controlling vertical height growth in three-dimensional (3D) fracture propagation. Included are confining stress contrast, elastic stiffness contrast, fracture toughness, and influence of settled (or buoyant) proppant on height growth. A composite propagation function was formulated that can be implemented in a pseudo3D model of fracture geometry or in hand calculations. The second part extends the formulations of the lumped models for lateral fracture growth to handle dynamic conditions existing in the field. The new formulation can handle variable injection rates, fluid rheology changes, and multiple fluids and includes fracture toughness at the tip. The results are presented in the form of dimensionless charts, and their use is explained through an example.
Log Analysis Techniques for Quantifying the Permeability of Submillidarcy Sandstone Reservoirs
Authors: Kukal G. C. , Simons K. E. 
Published: December 2007

Summary
A gradational diagenetic change from the "tubular" primary pore network of conventional sandstones to a pore geometry consisting of secondary-solution pores interconnected by narrow "slot-like" flow paths in low-permeability sandstones has necessitated the formulation of revised log-derived permeability equations. The equations are derived from Lower Mesaverde group core data and are tested for limitations by extrapolation to a. shallower Mesaverde interval and to a remote Travis Peak (Hosston) interval. An alternative method involving invasion inferences from a log-derived filtration index is used to complement the permeability analysis.
Development of an Efficient Algorithm for the Calculation of Two-Phase Flash Equilibria
Authors: Abhvani A. S. , Beaumont D. N. 
Published: December 2007

Summary
This paper details the development of an efficient algorithm for the calculation of two-phase equilibrium in multicomponent hydrocarbon systems with an equation of state (EOS). A number of numerical solution algorithms are evaluated for speed and robustness. To ensure generality, the compositions used in the study range from a synthetic 3-component fluid to a real 20-component reservoir fluid, and the calculations are performed at different positions on the fluid-phase diagram.
The results of the study are used in the construction of a stable and efficient algorithm. Although the method was developed with reservoir engineering applications in mind, it should also be applicable in chemical, process, and petroleum engineering.
Influence of Downhole Conditions on the Leakoff Properties of Fracturing Fluids
Authors: Ford William G. F. , Penny Glenn S. 
Published: December 2007

SummaryFluid loss under dynamic conditions, considering such realistic conditions as low-permeability core samples and extreme shear conditions, has been examined and is reported in this paper. Dynamic data of fluid loss as a function of time, pressure, and temperature have been developed.
Estimation of the Permeabilities and Skin Factors in Layered Reservoirs With Downhole Rate and Pressure Data
Authors: Shah Piyush C. , Karakas Metin , Kuchuk Fikri , Ayestaran Luis C. 
Published: December 2007

SummaryThis paper addresses the problem of estimating horizontal and vertical permeabilities, skin factor, and average fluid pressure within the drainage area in each layer in a multilayered reservoir in the presence of formation crossflow between the layers and commingling through the wellbore. A multistep testing procedure is proposed that involves downhole measurement of the pressure and fluid flow rate. The measurements are made successively above the individual layers as transients are induced in the reservoir. A history-matching procedure is used to analyze the data from the entire multistep test simultaneously. The performance of this approach is compared with that of separate, conventional interpretation of each step in five examples with synthetic data. The simultaneous analysis benefits from the synergy between the steps and consistently yields better estimates.A linearized sensitivity analysis is developed to determine the probable errors in the parameter estimates. It indicates whether a given set of measurements with a given level of measurement noise contains sufficient information to determine the individual parameters uniquely.
Effect of Solvent on Steam Recovery of Heavy Oil
Authors: Shu W. R. , Hartman K. J. 
Published: December 2007

Summary
Solvents and light ends of crudes are frequently used as diluents to facilitate pumping and pipeline transportation of heavy crudes. The use of solvent alone for in-situ recovery of heavy oil tends to be limited because of its high cost; however, the use of solvent as an additive to steam processes has been tested both in the laboratory and in the field. The results of these tests are mixed. In this study, we use numerical experiments to delineate the recovery mechanism of a steam-slug process when solvents are present. A good understanding of the mechanism will help provide an interpretation of the conditions under which solvents can improve steam oil recovery. The study focuses on the use of small quantities of solvent—i.e., no more than 10% of the steam volume.