Results of Study of Application of Buckley-Leverett Techniques in Oil-Reservoir Analysis

Abstract

Fall Meeting of the Los Angeles Basin Section, 16–17 October, Los Angeles, California Quick Methods for (1) Determining Saturation at Breakthrough (2)Approximating Relative Permeability and (3) Evaluating Preferential Wettability Abstract In this study generalizations have been devised with respect to oil-reservoir-analysis data processed by the electronic computer, from which useful relationships were obtained. These relationships are presented in a graph, the ordinate of which is the product of the ratio of the upper extremities of the permeability curves and the ratio of the viscosities. The abscissa is the fractional saturation at breakthrough. The parameters are related to the values of the permeability curves at a saturation midpoint between the irreducible water and oil saturations. Three important determinations can be made by using the graphical data:with relative permeability relationships obtained in the laboratory. saturation at breakthrough can be approximated by using the upper extremities and the midpoints of the relative permeability curves;the effect of preferential wettability can be approximated; andif the permeability data are not available a method is proposed by which relative permeabilities can be quickly approximated. By using high rates of flow in oilfield cores to minimize the end effects, upper extremities of the permeability curves and saturation at breakthrough can be measured. By means of these experimental data and the graph the midpoints can be determined; then, the approximate relative permeability curves can be drawn. Summary and Introduction As part of a study of application of the Buckley-Leverett method to an analysis of oil-reservoir performance covering a wide range of relative permeabilities and oil saturations, a method has been devised for quickly determining average water saturation at breakthrough from relative permeability data. The base for the relative permeability used in the report is either permeability to air or effective permeability to oil at the irreducible water saturation. The permeability to air also was used because of the large backlog of air permeabilities available to reservoir engineers. Basic data were calculated by an electronic computer and are presented in a single graph from which the point of breakthrough may be obtained.