This study presents an analysis of annular backpressure \)aria/ion,$ associated with Contro[[ed gas kick.r and their pronounced eflect on casing strings and exposed underlying formations. A mathematical model describing the volumetric behavior of an extraneous gas as it is transported from reservoir to s[o-face conditions under changing temperamres and pre.r,sures has been programmed in a Kingston FORTRAN 11 language for digital computer analysis. The gases under investigation typify Gulf Coast reservoir gases within a Q,6 !Q0.,7 rnfw-ifir or flvitv rfmoo~h~p~Qg~Q.rn r--.,.-~. -..., . -.-aoutput has been substantiated by actual field cases of gas kicks encountered in Gulf Coast wells. ,h~AO,,"!nnm,,wt
A mathematical model particularly suitable for secondary recovery predictions is described. The model is based upon the flow lines generated by the superposition of line sources and sink solutions and is easily adaptable to arbitrary well patterns and fluid displacement mechanisms. Nonunity mobility ratios and reservoir stratification may be modeled. The model may be used with relatively small digital computing equipment. Previous models of this type have used the generated flow lines to outline "flow bundles", thus requiring a prior knowledge of the geometric shape of each of these bundles so that the flow through each could be computed. The modeling method described does not require any such prior knowledge of these flow lines since the volumetric flow in a stream bundle is computed as each chosen streamline is generated. This feature makes the model particularly adaptable to arbitrary well patterns. patterns. Examples are given to show the application of this model to both single and multiphase flow. Introduction Streamline models of secondary recovery projects result from the use of line source and sink solutions to the diffusivity equation to represent injection and production wells. Muskat described these solutions and their application to simplified problems. He used semi-analytic techniques to problems. He used semi-analytic techniques to obtain breakthrough sweep efficiencies for regular, dispersed injection patterns at a mobility ratio of 1. Collins described a finite-difference approximation for determining streamlines for unit mobility ratios in arbitrary well patterns. Both Muskat and Collins described image-well techniques for mathematically bounding the area being studied. Collins' finite-difference method is particularly adaptable to the use of a high-speed computer for obtaining streamlines and travel times along streamlines. Higgins and Leightons have described a technique for approximating the waterflood recovery of oil using streamlines generated by single-fluid how models (such as the method described by Collins). Their technique uses these streamlines to divide the total flow area into "stream channels", which flow in parallel between injection and production wells. Each stream channel is divided into a number of recovery rectilinear flow cells, in series, which closely approximate the shape of the stream channel. Through the use of shape factors determined for each flow cell, a Buckley and Leverett type of frontal displacement in each stream channel is computed. Combining the results from all stream channels gives the waterflood production history by this method. Once the stream channels, the flow cells, and the shape factors have been determined, a single computer program is used to obtain the production history. production history. Hauber has also described a method using stream channels formed by single-fluid streamlines. In this method, the cross-sectional area of each stream channel, as a function of length along a center streamline, is determined mathematically from the stream function, and an integration technique is used to determine the flow through each stream channel. Hauber applied this method to piston-like displacement in a five-spot injection piston-like displacement in a five-spot injection pattern. pattern. The stream-channel concept has been used and elaborated upon in subsequent publications dealing with the displacement of oil by fluids of unequal mobilities. This use of stream channels requires a prior knowledge of the single-fluid streamlines for the well spacing to be studied, so that flow cells and their shape factors, or the area functions of the channels, may be determined. The purpose of this paper is to describe a method which produces equivalent results but requires no prior knowledge of the streamlines or stream channels to be used. It is not necessary to know the eventual destinations of the "stream channels" in order to obtain production histories for arbitrary well patterns and either of the types of displacement patterns and either of the types of displacement mechanism mentioned above. SPEJ P. 7
The pdf file of this paper is missing the tables and figures. Abstract Empirical PVT correlations are presented for estimating bubblepointpressure, solution gas-oil ratio, oil formation volume factor, and isothermal compressibility. To develop the above correlations, the data base consisted of ninety-eight PVT laboratory analyses for Colombian crude oils. The gas-oil ratios, gas gravities, oil gravities, and formation volume factors involved in the development of the correlations are the result of one, two and three-stage flash separation as recorded from PVT samples analyzed in the laboratory. The effect of separator conditions on the prediction of the bubble-point pressure, solution gas-oil ratio and oil formation volume factor is studied. Anew correlation that corrects the separator solution gas-oil ratio for separator conditions is provided. Improved correlations for estimating the bubble-point pressure, based on the corrected separator solution gas-oil ratio, are developed. In addition, total solution gas-oil ratio and oil formation volume factor correlations based on separator data are presented. Since the stock-tank gas-oil ratio and stock-tank gas gravity are not usually measured in the field, these correlations represent a realistic form of estimating PVT properties. Although the correlations presented are based on Colombian crude oils and gases, consideration should be given to their applicability to all types of gas/oil mixtures with API gravities ranging between 18 to 44.9 (single stage separation), 14.3 to 29.0 (two stage separation) and 40.3 to 44.1 (three stage separation). Introduction An accurate knowledge of Pressure-Volume-Temperature (PVT) properties is essential in reservoir and production engineering calculations. Estimation of reserves, determination of oil reservoir performance, recovery efficiency, production optimization and design of production systems are some of the areas which require precise determination of a fluid's physical properties at different conditions of pressure and temperature. Ideally, the physical properties of the reservoir fluids are determined experimentally in the laboratory. However, due to economical and/or technical reasons, quite often this information cannot be obtained from laboratory measured values. In this case, PVT properties must be estimated from empirically derived correlations. Several correlations have been proposed for determining the PVT properties of reservoir fluids. Some of the most widely used correlations are: Standing's, Lasate, Calhoun, Trube's, Chew-Connally's, Beal's, Glaso's, Vazquez-Beggs, Beggs-Robinson's, Dokla-Osman, Petrosky-Farshad, and Petrosky-Farshad. These correlations are based on reservoir fluid samples from certain specific regions of the world. Because of the varying compositions of crude oils from different regions, prediction of PVT properties from empirical correlations may not provide satisfactory results when they are applied to hydrocarbons behaving differently from the fluid samples on which the correlations were based. Previous studies have shown that extrapolation of empirical PVT correlations should beundertaken with caution. P. 311
Selected parameters in gravity drainage of oil mining have been studied. Like others, this method of oil recovery is affected by fluid and rock properties. Furthermore, the recovery is influenced by other parameters such as length, diameter, number of holes and the inclination angle of the drainage holes. A laboratory model of a gravity drainage system was designed and constructed to simulate a reservoir drainage area. The reservoir parameters were scaled down for the experiments. The model was saturated with a 35 degree API oil. A pressure of 40p~i (276 kPa) was maintained in the reservoir as the depleted reservoir pressure. Drainage holes were drilled from the bottom of the reservoir. The holes were drilled 45 and 90 degrees from horizontal. A total of five (5) drainage holes were monitored at various times and the recovery was monitored in three (3) separate stages. First, the model was allowed to produce conventionally from the top (primary recovery) and production was monitored. In the second stage, the model was produced by maintaining a constant injection pressure (secondary recovery). Finally, the model was produced by gravity drainage at the constant depleted reservoir pressure.In each stage, the parameters were varied and production monitored. The experimental data from the laboratory model proved that the hole angle of inclination was the most critical factor to the rate of recovery than the other parameters. The diameter of the hole was found to be the least effective parameter in terms of recovery. The make up of the laboratory reservoir matrix materials and its mode of construction will certainly affect the rate and amount of oil recovery from the drainage holes. The overallReferences and Illustrations at end of paper.439 results of the experiments using this specific laboratory reservoir matrix showed that, for optimum conditions of the most effectnre pnxameters 87% of the in-place oil was recovered by the drainage ho1e technique of oil mining compa.::ed to 37% recovery by the conventional (primary and secondary) method. The net increase in total production was 50% due to gravity drainage. The total recovery of oil in place by primary and secondary followed by gravity drainage was 91%, of which 37% accounts for primary and secondary recoveries, and 54% due to gravity drainage.
Sengupta, Sujit Kumar, Cities Service Co., Hayatdavoudi, A., University of Southwestern Louisiana, Tiab, J.O., University of Oklahoma, Kalra, Satish Kumar, LeBlanc, James L., and Schluntz, E.K., University of Southwestern Louisiana Members SPE-AIME Abstract Recent investigations have established the fact that authigenic clays may be dislodged during the enhanced oil recovery operations. However no mechanical stabilization of these clays along with chemical treatments has been fully used or investigated. The mechanical unstability of the clays is due to stress variation at the pore surfaces of the reservoir rock during the flow of pseudoplastic fluid such as polymer, etc. An pseudoplastic fluid such as polymer, etc. An equation has been derived which shows the relationship between the stress developed and the radial distance from the well bore at constant injection pressure. The analysis of this equation shows that the stress is maximum near the well bore and decreases rapidly with distance. Graphs have been plotted to show further the effect of flow rate and power law coefficient on the stress. Introduction The pseduoplastic fluid flow through porous media has gained considerable importance because of their increasing uses as displacing fluid for improved recovery technique. The behavior of the movement of these types of fluid is quite different than ordinary fluid (i.e. Neutonian fluid). These fluids in fact adds to the permeability reduction as a result of pore throat blockage near the well bore which plays an important role in success or failure of improve oil recovery project, by injection of pseudoplastic fluids. To consider, the behavior pseudoplastic fluids. To consider, the behavior of the movement of the pseudoplastic fluid, consideration of the stress development at the junction of the rock pore surface and the fluid will lead a better understanding. See Figure (1) To consider the theory of relation between stress and radial distance, we have to proceed in two steps, first, study the stresses that are developed if the fluid is flowing in an open space without any constriction, second, to study the effect of the development of these stresses in porous media. porous media. The viscosity correlation of the pseudoplastic fluid can be written as (1) and for the power law model (2) From equation (1) and (2) we have (3) The flow of fluid (pseudoplastic fluid) through porous media is given by porous media is given by (4) where at a continuous injection, where the pumping of fluid has already started (5) substituting equation (3) and (5) in equation (4) we have ......(6) p. 245
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