A Novel Analysis Procedure for Estimating Thickness-Independent Horizontal and Vertical Permeabilities from Pressure Data at an Observation Probe Acquired by Packer-Probe Wireline Formation Testers

摘要

This paper presents a new spherical-flow cubic-analysis procedure for estimating horizontal and vertical permeabilities solely from pressure transient data acquired at an observation probe of the dual-packer-probe wireline formation testers (WFTs) for all inclination angles of the wellbore. The procedure is based on the analytical spherical-flow equation that Onur et al. ( 2004a) previously presented, and the conventional spherical-flow analysis plot of drawdown or buildup observation probe pressures. This procedure now makes it possible for one to estimate both horizontal and vertical permeabilities from observation- probe pressure data exhibiting spherical flow for packer-probe interval pressure transient tests (IPTTs). The new analysis procedure does not require one to know the formation thickness or to observe the radial flow regime at the dual-packer and/or observation probe. The procedure provides unique estimates of horizontal and vertical permeabilities from observation-probe pressure data obtained along both vertical and horizontal wellbores. However, for slanted well cases, the analysis procedure yields two possible solutions for the horizontal and vertical permeabilities. Therefore, one must use a priori information on permeabilities, from sources such as core data or pretests, to eliminate one of the solutions and identify the appropriate solution for the slanted well cases. For IPTTs that have transitional data from the spherical flow regime to late-radial flow regime, nonlinear regression analysis based on history matching of dual-packer- and/or observation-probe pressure measurements from slanted wells may also help one to estimate correct values of horizontal and vertical permeabilities. We illustrate the applicability of the proposed analysis procedure by considering two synthetic and two field packer-probe ,IPTT data sets from vertical and slanted wellbores.