Pressure Behavior of Layered Reservoirs with Crossflow

Abstract

Abstract Experience with a large number of well tests has shown that the analysis of some field tests using currently available interpretation models is not satisfactory. Marked departure from homogeneous behavior is evident and none of the available heterogeneous models, such as the double porosity models, yields a convincing interpretation. This is particularly apparent when the pressure derivative behavior is examined. In this paper, a new analytical solution is presented that describes the pressure response of a well intercepting a layered reservoir with crossflow. The model is designed to describe a system of alternating beds of relatively high permeability contrast. The interpreation models currently in use (homogeneous reservoir, two layers without crossflow, double porosity reservoir) are shown to be limiting forms of the new solution which is therefore a more general description of transient pressure responses. The layered reservoir behavior is discussed in terms of the pressure and the derivative of pressure. The limits of applicability of the homogeneous and the double porosity solutions for analysis of tests in layered formations are clearly defined. The new model is used to analyze an actual field case and a good match is obtained when no other solution is found to be applicable. In addition to the usual well and reservoir parameters (total permeability thickness product, skin and wellbore storage constant), analysis yields quantitative information on the storativity and permeability of the contrasting layers.