MULTIPROBE WIRELINE FORMATION TESTER PRESSURE BEHAVIOR IN CROSS-FLOW-LAYERED RESERVOIRS

This paper presents new analytic solutions for the pressure behavior o f the multiprobe wireline formation tester in layered reservoirs with crossflow, where the rock and fluid properties may change vertically a s a function of z. These solutions are applicable to layered systems t hat can be unbounded and/or bounded by no-flow and/or constant-pressur e boundary planes in the z direction. The system is assumed to be unbo unded in the x and y directions. New solutions are also presented for the multiprobe wireline tester in single-layer reservoirs. All solutio ns are presented in the Laplace transform domain; the tool line volume storage and skin effects can therefore be easily incorporated. The ne w solutions are derived by utilizing the reflection and transmission c oncept of electromagnetics to solve fluid-flow problems in three-dimen sional layered reservoirs, where nonhomogeneity is in only one directi on. The Green's function for a point source in a three-dimensional lay ered system is presented by using the reflection and transmission meth od. The point-source solution is sufficiently general that it may be a pplied to a wide variety of fluid-flow and well-testing problems invol ving single-phase flow. The solutions are applied to two layered-reser voir examples. The first example is for a six-layer moderately stratif ied reservoir. The second one is for a twenty-layer highly laminated r eservoir, where the permeability contrast among the layers is very hig h. These two examples provide some ideas for the pressure behavior of the multiprobe wireline formation tester in layered reservoirs.