bluuebunny/crossref_metadata_2025_split huggingface dataset:
Technical Screening Guides for the Enhanced Recovery of Oil
Authors: Taber J. J. , Martin F. D. 
Published: December 2007

ABSTRACT
The technical screening guides which are used to select enhanced oil recovery methods are described. The background and logic behind the various criteria are covered, and a brief description of each method is included. Economics are discussed, but the emphasis is on the technical guidelines.
A distinction is made between the oil properties and reservoir characteristics required for each process. Generally, steamflooding is applicable for viscous oils in relatively shallow formations. At the other extreme, CO2, nitrogen, and hydrocarbon miscible flooding work best with very light oils at depths great enough for miscibility to be achieved. Both steamflooding and in-situ combustion require reservoirs of fairly high permeability. Chemical flooding processes (polymer, alkaline or surfactant) are applicable for low-to-medium viscosity oils where depth is not a major consideration. However, at great depths, the higher temperature may present problems in the degradation or consumption of some of the chemicals.
Current values of the technical screening guides for the more common enhanced recovery procedures are given in tabular and graphical form. By the use of a simple graphical technique, it is shown that there is a complete spectrum of enhanced oil recovery methods available for all oils, ranging from the very lightest to the heaviest oil or tar sand.
A Three-Dimensional Well Planning Method for HDR Geothermal Wells
Authors: Scholes Haydn 
Published: December 2007

ABSTRACT
This paper presents a method for planning sections of directionally drilled wells in three dimensions where azimuth and inclination is specified at the end points. It describes the implementation of the algorithm in a computer code and its use at the Camborne School of Mines Geothermal Energy Project for planning a proposed third well in an existing hot dry rock geothermal reservoir.
Combining Production History and Petrophysical Correlations to Obtain Representative Relative Permeability Data
Authors: Meads Roosevelt , Bassiouni Zaki 
Published: December 2007

ABSTRACT
Prediction of gas reservoir performance under water drive is very sensitive to relative permeability data. Gas-water relative permeability ratio (Kg/Kw) at different values of water saturation (Sw) can be derived from production history. This technique provides data considered the most representative of reservoir characteristics since it reflects actual reservoir performance. However, the developed (Kg/Kw) vs Sw curve is only valid in the higher range of water saturation and in the absence of water coning and other forms of water intrusion. The valid portion of the curve can be used to calibrate a generalized correlation. The calibrated correlation is then used to derive relative permeability data over the entire water saturation range. The technique discussed can also be applied to oil-water systems.
Recovery Efficiency of Enhanced Oil Recovery Methods: A Review of Significant Field Tests
Authors: Hammershaimb E. C. , Kuuskraa V. A. , Stosur George 
Published: December 2007

ABSTRACT
This paper analyzes past enhanced oil recovery (EOR) projects to determine how well they have performed as a function of reservoir and process variables. In total, over 100 key tests covering the following six major enhanced oil recovery techniques are analyzed: Steam Drive, In-Situ Combustion, Carbon Dioxide Flooding, Polymer Flooding, Surfactant/Polymer Flooding, and Alkaline Flooding.
The analysis includes, by technique and geographical area: The range of oil recovery due to EOR in barrel s per acre-foot and as a percentage of oil remaining in-place.A comparison between predicted performance and actual oil recovery.An examination of the performance of different EOR processes within each of the six techniques.An analysis of the relation of reservoir parameters and process variables to oil recovery.
Limitations on the Use of Single- and Multiple-Rate Horner, Miller-Dyes-Hutchinson, and Matthews-Brons-Hazebroek Analysis
Authors: Larsen Leif 
Published: December 2007

SUMMARY
A major objective of this paper is to present methods to determine the range of applicability of Horner and Miller-Dyes-Hutchinson analysis for a variety of reservoir shapes, outer boundary conditions, and producing times. This concerns limitations on the end of semilog data caused by approximations of the drawdown transient, and not limitations on the beginning of such data caused by effects in or near the wellbore. The results, based on derivatives of dimensionless pressures, also have some bearing on the use of drawdown type curves to analyze buildup data. Moreover, they imply that the "producing time" used in Horner analysis, or in type-curve analysis based on Agarwal's effective drawdown time, can be limited by tDA =0.08 for closed reservoirs. This is important when use of later portions of test data are essential to obtain valid results.
Limitations on the use of standard methods to determine the distance to the nearest boundary in closed reservoirs, both for short and long producing times, are also investigated. From an example presented, it is evident that exact doubling of the semilog slope is not necessary to determine this distance, but such doubling simplifies the analysis. This is important since exact doubling only occurs under favorable conditions.
Both Horner and Matthews-Brons-Hazebroek analysis have natural extensions from single- to multiple-rate buildup data. This leads to a formula relating the extrapolated pressure to the average reservoir pressure through a sum of Matthews-Brons-Hazebroek functions. Using the results from the first part of the paper, it follows that a single-rate Horner plot can be used if all drawdown transients have lasted longer than tDA = 0.08, even if a longer producing time is needed to reach pseudosteady state.
The Role of Well Log Interpretation in Well Completion of Naturally Fractured Reservoirs
Authors: Hirakawa S. , Yamaguchi S. 
Published: December 2007

ABSTRACT
In planning well completion methods of wells in naturally fractured reservoirs, some problems relating to fractured zones must he considered and solved.
At first, an accurate detection of fractured zones plays an important role for the decision of completion methods. The former part of this paper presents two kinds of possible algorithm for analyzing well logs in a naturally fractured oil or geothermal reservoir. These two kinds of algorithm are applied to actual logs for the detection and quantitative evaluation of fractured zones and their availability is shown.
Secondaly, when one decides the full string completion, the completion schemes such as perforation zone must be investigated, for they affect the production performance of fractured reservoirs. The latter part of this paper mainly describes the effects of perforated zone on the production performance with typical examples of natural or artificial water drive reservoir problems.
Fluid-Loss Control in the Naturally Fractured Buda Formation
Authors: Hall B. E. , Houk S. G. 
Published: December 2007

ABSTRACT
The Buda fonnation is a naturally fractured limestone. Initial production is limited by low matrix permeability and possible plugging of existing natural fractures during the drilling and completion of the wells. Consequently, proppant fracturing is an integral part of the completion of Buda wells.
Within the last year. Gulf Oil Exploration and Production Company has completed 12 wells in the Buda lime. During the fracturing treatments, 4 screenouts occurred on the first 7 wells treated. Laboratory data indicated that a different fluid loss program minimize screenouts in naturally fractured reservoirs. This technology was applied to the Buda wells. Using 100 mesh particles in conjunction with fine oil soluble resins, only 1 screenout was observed in the next 5 treatments. Laboratory data, treatment design, and well performance are presented in this paper.
Effect of Wettability on Two-Phase Relative Permeabilities and Capillary Pressures
Authors: Heiba A. A. , Davis H. T. , Scriven L. E. 
Published: December 2007

ABSTRACT
The percolation theory of two-phase relative permeability at low capillary numbers (SPE 11015) is further developed to account for the physics of intermediate and mixed wettability in reservoir rocks. The elements of the theory are: a network representation of porespace connectivity; a distribution function description of porespace geometry; capillary pressure (i.e. quasistatic) and wettability criteria of allowability of the invading phase to poresegments according to their throat or body size; a Bethe network approximation to pore space connectivity, to estimate occupancy-conditioned poresize distributions that follow from the preceding elements and lead to occupancy-conditioned distributions of segment volumes (for saturations) and hydraulic conductances (for permeabilities); and a Bethe network transport path conductivity function for creeping flow of each phase that occupies continuously connected pore-segments. Also included is the volume occupied by virtually stationary thin films and pendular structures of the more strongly wetting liquid. Wettability is expressed in the capillary pressure criterion of allowability and acts through the pore-filling sequence in any displacement process. The theory reveals how pore-filling sequences depend on capillary pressure.
The theory predicts the saturation-dependent and saturation-history-dependent capillary pressure and relative permeability relations measured by Morrow and coworkers in uniformly wet porous media. Applied to reservoir rock in which a fraction of poresegments previously occupied by oil have become oil-wet, the theory, with that fraction a variable, accounts for the continuous spectrum of capillary pressure and relative permeability curves encountered in reality.
Parameter estimation from limited data will be treated elsewhere. The theory is so founded that it can be extended to three-phase relative permeabilities, as will be reported in a sequel.
Fundamentals of Relative Permeability: Experimental and Theoretical Considerations
Authors: Heaviside John , Black C. J. J. , Berry J. F. 
Published: December 2007

ABSTRACT
Studies investigating the validity of the conventional description of two phase immiscible flow are reported. Laboratory techniques for relative permeability determination have been applied in well controlled experimental conditions to strongly wetting systems. The tests enable a definite description of drainage and imbibition displacement processes. Concurrently a numerical model, based on the conventional macroscopic flow equations was developed to simulate the dynamic displacement tests. The purpose was threefold; 1) To study the concept of relative permeability 2) To simulate the physical processes occurring during unsteady state displacement tests 3) To use the model to assist in the provision of laboratory data more relevant to reservoir simulation.
The results show the relative permeability concept is valid for drainage displacement. For imbibition processes the concept is not strictly valid and the macroscopic flow equations are limited in their ability to describe the physical process. Consequently the relevance of laboratory data derived using this conventional theoretical framework is limited and its applicability to the reservoir will depend upon the selection of the appropriate tests. Guidelines as to the selection of the laboratory tests suitable for the different occasions are given and illustrated with a small number of field cases.
Exact Kinematic Analysis of Pumping Units
Authors: Svinos J. G. 
Published: December 2007

ABSTRACT
A new pumping unit Kinematic Analysis method was developed for the calculation of position, velocity, acceleration of the polished rod, and torque factors as functions of crank angle. This method can also be used to calculate the angular position, velocity and acceleration of any part of the pumping unit mechanism.
It is more accurate than previous methods because it produces exact results. It can be used to compare pumping units, and can analyze units with varying crank speeds. It can improve gearbox torque analysis by including inertia effects, and can allow the use of conventional dynagraphs for the prediction of downhole dynagraphs.
Controlling Numerical Diffusion in Reservoir Simulation Using Flux Corrected Transport
Authors: Carr A. H. , Christie M. A. 
Published: December 2007

Abstract
Flux Corrected Transport (FCT) is a technique developed to reduce numerical diffusion around shock fronts which has not previously been used in reservoir engineering. The first section of this paper describes the application of FCT techniques to solving a one dimensional waterflooding problem, and shows how to include FCT in an IMPES simulator. A second feature of our program is the implicit timesplit treatment of capillary pressure effects. A comparison between laboratory data and simulator results is included, and good agreement is obtained.
Random Choice Method for Treating the Convection-Diffusion Equation
Authors: Li K. M. G. 
Published: December 2007

ABSTRACT
A numerical method is developed for solving the convection-diffusion equation arising from the conservation equations used to represent miscible displacement processes. This method is superior to the conventional finite difference methods in that it introduces only a negligible amount of numerical dispersion, in contrast to the significant numerical smearing introduced by most finite difference techniques.
The construction of the method is based on the method of operator splitting; the first fractional step solves the convection equation with zero diffusion, whereas the second step accounts for the diffusive part of the convection-diffusion equation. Unlike conventional finite difference methods, which approximate the convection term by some form of upwind differencing scheme, the present approach calculates the convective flow by the random choice method in the first fractional step. The advantage of this approach is that it propagates the solution correctly without smearing out the displacement front, regardless of the grid size. This desirable feature is absent in most finite difference techniques, and as a result they are unable to model the physical dispersion accurately. In the second fractional step of the method, the parabolic character of the diffusion term is appropriately approximated by the conventional central differencing scheme.
The combined scheme is unconditionally stable. Extensive numerical tests show that the method is able to approximate the convection-diffusion equation accurately without introducing any significant numerical dispersion. No spurious oscillation is observed even at small values of the diffusion coefficient. In the limit when the diffusion coefficient approaches zero, a perfectly sharp displacement front is calculated. Extension of the method to multidimensional problems is possible by the use of operator splitting, which reduces the problem to fractional steps of locally one dimensional problem.
Front Tracking for Petroleum Reservoir Simulation
Authors: Glimm James , Lindquist Brent , McBryan O. A. , Plohr Bradley , Yaniv Sara 
Published: December 2007

ABSTRACT
The front tracking method gives high quality solutions for problems with important discontinuities. The method has been applied to several model problems in reservoir simulation. Results are given for quarter 5-spot studies in an areal reservoir and the water coning problem in a vertical cylindrical section surrounding a production well. Both problems were treated as incompressible flow in the absence of capillary pressure. We have studied miscible and immiscible displacement for frontal mobility ratios of 1 and 5. Validation studies include mesh refinement, grid orientation and orthogonal coordinate changes.
A New Equilibrium Coefficient Correlation Method for Compositional Simulators
Authors: Chien M. C. , Lee Sheng-Tai 
Published: December 2007

ABSTRACT
A new equilibrium coefficient or K-value correlation useful in compositional simulation studies was developed to reduce computing times in phase equilibrium calculations while retaining good accuracy in the calculated results. This correlation is based on the convergence pressure concept. Unlike previous works, the mixture critical pressures are correlated from binary critical pressures, the convergence pressures are correlated by treating the mixture as a pseudo-binary mixture, and the functional form of this correlation was derived by considering the asymptotic behavior of K-values. In the low pressure region, it reduces to the Chao-Seader correlation. In the near critical region, it conforms to the critical exponent theory. The correlation is related to the overall fluid composition explicitly, and requires no iteration.
This correlation has been tested for three different reservoir fluid systems. The K-values calculated using the new correlation are in good agreement with those using the calibrated Peng-Robinson Equation of State (P-R EOS). The average deviation is less than 3% for the reservoir fluid systems studied. Slim tube displacement simulations, using CO2 and nitrogen as the displacing fluid, were also performed for the three reservoir fluid systems to validate the correlation developed. The predicted oil production rates using the new correlation to calculate phase equilibria are in good agreement with those using P-R EOS. The average deviation is less than 3%; at the same time, the computational cost is reduced by 4 – 14 times.
Some Observations on Field-Scale Simulation of the In-Situ Combustion Process
Authors: Coats K. H. 
Published: December 2007

ABSTRACT
This paper describes and illustrates a method for ensuring sustained combustion in coarse-grid, field-scale simulation using a kinetic-based model. For the example problem treated, as in several unreported cases, the method considerably extends the grid block size which can be tolerated without severe grid size effects. The method is applicable only in cases where one accepts the assumption that no free oxygen passes unreacted through the combustion front.
The paper also presents and discusses results of very fine-grid one-dimensional simulations. Comparison of these fine-grid results with coarse-grid 1D results shows, for the particular problem data used, an unexplained, significant increase in amount of oil cracked with grid block size increased over the range of .5 feet to 10 feet.
2D areal, 5-spot pattern simulations show that the 9-point difference scheme very significantly reduces a large grid orientation effect in 5-point simulation of the combustion process.
A Consistent Method for Calculating Transmissibilities in Nine-Point Difference Equations
Authors: Coats K. H. , Modine A. D. 
Published: December 2007

ABSTRACT
In the past few years there has been increased interest in modeling miscible and thermal recovery processes by the use of reservoir simulation models. The prediction of sharp saturation or temperature fronts resulting from these processes has shown that these simulators can in many cases be very sensitive to grid orientation. One method for minimizing the effect of grid sensitivity is to describe the difference equations with a nine-point rather than the standard five-point finite difference approximations. Inherent in the use of the nine-point approximations is the necessity for calculating consistent transmissibility coefficients. Previously published methods for calculating these coefficients do not have general applicability to heterogeneous reservoirs and/or various irregular grid spacings. This paper presents a method for calculating nine-point transmissibilities for a general heterogeneous system with unequal grid spacing.
Using Local Grid Refinement in a Multiple-Application Reservoir Simulator
Authors: Heinemann Z. E. , Gerken Günter , von Hantelmann George 
Published: December 2007

ABSTRACT
This paper describes the application of dynamic local grid refinement in a multiple application reservoir simulator. Using this procedure generally enables a significant reduction of the total number of blocks necessary for a good reservoir description.
This procedure is combined with a number of EOR-options, automatic selection, variable in time of the implicitly computed variables, an ordering scheme for the equations devised specifically for the characteristics of local grid refinement, and several procedures for the solution of the system of equations. Together these features create a tool which is capable of providing quick and economic solutions to the problems encountered in reservoir simulation.
Nested Factorization
Authors: Appleyard J. R. , Cheshire I. M. 
Published: December 2007

ABSTRACT
A new iterative technique for the solution of the linear equations arising in finite difference reservoir simulations is described. The method comprises a novel preconditioning for the Conjugate Gradient and Orthomin iteration procedures. Nested Factorization differs from the more commonly used incomplete Cholesky factorizations in that it does not form the preconditioning matrix from strictly upper and lower factors. Instead, it constructs block lower and upper factors using a procedure which adds one dimension at a time to the preconditioning matrix. The factorization procedure conserves material exactly for each phase at each linear iteration, and accomodates non-neighbour connections (arising from the treatment of faults, completing the circle in 3D coning studies, numerical aquifers, dual porosity/permeability systems etc.) in a natural way. A number of versions of the Nested Factorization algorithm are compared with other published methods for a series of 2D and 3D problems. It is found that the Nested Factorization algorithms are all roughly comparable and that all compare very favourably with other published methods in terms both of computing speed and storage requirements.
Results of Pressure Transient Well Testing in Appalachian Gas Reservoirs
Authors: Kimmel S. L. , Fulton P. F. 
Published: December 2007

ABSTRACT
Pressure transient tests in hydraulically fractured low permeability natural gas wells require special analytical techniques. Linear flow must be identified before formation permeability can be determined. Proper test design based upon demonstrated well behavior can reduce testing costs and improve confidence in the results obtained. The analytical methods are described. Results from twenty-six pressure transient tests are presented.
Foamed Sand Provides Improved Stimulation Results from Devonian Shale
Authors: Strang D. L. , Norton J. L. 
Published: December 2007

ABSTRACT
Generally, water saturations in the Devonian Shale are low. Production records indicate minimal, if any, water in the areas producing gas or gas and oil. This low water saturation appears to be the key to stimulating the shale, especially in the oil-producing areas.
The introduction of water in the stimulation fluid appears to reduce the permeability to oil, which is reflected in poorer production. The relative permeability reduction seems to be more of a problem than particle migration or clay swelling and could explain the good initial results from straight nitrogen treatments. However, the lack of a proppant, even with low closure stress, leads to very rapid declines.
Water-base stimulation fluids appear to increase water saturation in the Devonian Shale. Use of 90+ quality foam with sand should provide a method of minimizing saturation changes while creating a propped fracture. Initial results indicate this technique provides better sustained production increases in the Devonian Shale.
This paper defines areas of production, describes the geology and presents physical data of the Devonian Shale. It also compares results of several types of treatments that have been used in the Devonian Shale. These results indicate 90+ quality foam with sand should provide an improved stimulation technique for this formation.