Pressure Transient Analysis and Inflow Performance for Horizontal Wells

Abstract

Abstract In recent years, pressure transient behavior and inflow performance of horizontal wells have received considerable attention due to the increase in horizontal drilling. In this paper we develop an interpretation methodology for horizontal well pressure transient testing. This methodology is then applied to the interpretation of an actual horizontal well test performed in Prudhoe Bay. The complex geometry associated with horizontal wells makes interpretation of well tests a difficult task. Uniquely determining the system parameters from short time (typical times for vertical well testing) pressure tests is not possible. Combining drawdown and buildup tests, with downhole flowrate measurement is critical for proper interpretation. We also provide a solution for the Inflow Performance of a horizontal well completed in a rectangular drainage volume, where the well can be of arbitrary length and completed at any location within the drainage volume. Introduction Now forward solutions to the diffusivity equation for horizontal well geometry with varied boundary conditions are available in the literature. Moreover, Reiss and Sherrard presented performance and production data from several horizontal wells and mentioned interpretation of well test data. The interpretation of well test data from horizontal wells is a much more difficult task than its vertical counterpart. This difficulty stems from:the main search direction of the parameters usually does not coincide with the depositional environment,the three dimensional nature of the How geometry and lack of radial symmetry, andmore parameters (information) to be obtained. In addition to these difficulties, zonal variation of vertical permeability and shale distribution will make interpretation intricate. A well-defined flow period comparable to that of the infinite acting radial How period (free from storage and boundary effects) of a vertical well is not apparent for horizontal wells. This is largely due to the fact that most horizontal wells will exhibit partial penetration effects, even when they are fully perforated. This fact has already been observed by many authors, and specific methods have been proposed to identify How regimes and their durations under ideal conditions. However, it has not been shown how to extend the identification of How regimes and their usage to the interpretation of real pressure transient tests.