Double-porosity response of horizontal wells during linear flow periods

Abstract

In this work the diagnostic properties of the square-root derivative type curve is discussed for a double-porosity reservoir. It is not possible to distinguish between two competing physical models by derivative analysis alone. The pressure behaviour of a restricted entry horizontal well in a double-porosity reservoir is investigated. There is a possibility of experiencing three linear flow periods: a fracture linear flow, a flow that is equivalent to an early homogeneous reservoir flow, and a late linear flow. The applicability of the square-root of the time derivative as a diagnostic tool is demonstrated on real field data. If only two of the three possible linear flow periods appear in a given test, then it is difficult to distinguish between a restricted entry effect and a double-porosity effect. A transition between fracture flow and “equivalent” homogeneous reservoir behavior will appear on a square-root derivative type curve as two horizontal lines. A transition between an early linear and a late linear flow period will have the same appearance. In either case the vertical separation between the horizontal lines has an important physical interpretation. To better distinguish between the two models, a conventional tandem square-root of time plot is used as an additional diagnostic tool.