Effect of an Invaded Zone on Pressure Transient Data From Multi-Probe and Packer-Probe Wireline Formation Testers in Single and Multilayer Systems

摘要

A three-dimensional r-θ-z single-phase fully-implicit finitedifferencemodel for a vertical well has been developed toexamine how the presence of invaded zones affects the multiprobeand packer-probe pressure measurements in single-layerand multilayer (crossflow) systems. Invasion zones aremodeled as composite zones concentric with the wellbore, thathave different rock and fluid properties (permeability,porosity, viscosity and compressibility) from those of thenative uninvaded formation.The results show that for multi-probe wireline testers, thesink (or the flowing) and horizontal probe pressure responsesare highly affected by the invaded region properties, while thevertical probe pressures are mainly influenced by theproperties of the uninvaded zones. For packer-probe testers,similar results are obtained; i.e., the vertical probe pressuresare mainly influenced by the properties of the uninvadedzones, while the packer interval pressures at early times areinfluenced by the invaded zone properties. It is shown that ifthe invaded zones are incorporated into the interpretationprocess using the model developed in this work, simultaneousmatching of spatially available wireline formation testerpressure data sets using nonlinear regression can provideestimates of both invaded and uninvaded zones parameters. Asynthetic example of a multi-probe test is presented to confirmthe theory and procedures developed in this work.