Pressure Behavior of a Well in an Anisotropic Reservoir

Abstract

Abstract Transient pressure tests used to define linear boundaries within a reservoir are affected by anisotropy. This anisotropic behavior of the flow in natural rocks can create major obstacles in characterizing the reservoir. In their mathematical development, conventional methods of analysis use the principle of superposition and direct mirror imaging of wells, which are normally applicable only to isotropic systems. The method of images was used to generate type-curves for a well located in various multiple-sealing-fault systems and inside closed rectangular reservoir. The transient pressure behavior of a well located anywhere between two parallel sealing boundaries can also be analyzed by type curves. Some research studies have considered anisotropic flow regions. This paper is concerned with well imaging in anisotropic media for (a) a single well near a single no-flow boundary, and, (b) a single well near a constant pressure line. An imaging method is used to find the image well location, and then a general step-by-step solution is derived which accounts for wellbore storage and skin effects. Type-curve plots of dimensionless pressure and dimensionless pressure derivative are generated. They clearly show the effect of the anisotropy ratio on the transient pressure response. The application of the proposed general solution is carried out by solving some simulated examples. The calculated distance from well to boundary was found to be in good agreement with the input value of distance to the boundary for the simulated cases.