Analysis of Pressure Data of Vertically Fractured Injection Wells

摘要

This study investigates the flowing and shut-in pressure behavior of a fractured well located in a square drainage region with the outer boundary at a constant pressure. The fracture plane lies on one of the diagonals of the square. The results can be used to analyze pressure data for a five-spot pattern when the fracture orientation is most favorable (from the viewpoint of sweep efficiency). Comparisons with the results in the literature (which assume that the fracture orientation is unfavorable) are given. It is shown that the fracture orientation must be considered in the analysis of pressure data for the following conditions: (i) small values of fracture penetration ratio, (ii) large flowing times prior to shut-in, and (iii) large values of fracture flow capacity. New insights into the application of type curve analysis to estimate drainage volumes are presented. The drainage volume can be obtained from a pressure fall-off test only if the flowing times prior to shut-in are large. The estimate of the drainage volume obtained by type curve matching pressure build-up data can be erroneous even if producing times are long. Claims in the literature regarding the determination of the drainage volume by type curve matching appear to be based on unrealistic expectations. The flowing pressures were obtained by a Crank-Nicolson Galerkin procedure. Analytical expressions to evaluate the integrals of the basis functions used in this study are given. (ERA citation 05:000119)