EFFECT OF MUD FILTRATE INVASION OF APPARENT PRODUCTIVITY IN DRILL STEM TESTS IN LOW PERMEABILITY GAS FORMATIONS.
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The objective of this study is to present the results of a study which has been performed to investigate these problems. In particular, it was desired to determine the effect of mud filtrate invasion on the results from a drill stem test. It has long been suspected that the invasion of mud filtrate into a low permeability formation can cause relative permeability and capillary pressure changes in the invaded zone which can significantly alter the formation response during a DST. These effects could probably be detected if the final shut-in period during the DST were long enough to reach the correct semilog straight line with slope inversely proportional to true formation permeability. To examine the effects of mud filtrate invasion in more detail, a two-phase, two-dimensional, fully implicit reservoir simulator was used to simulate drill stem tests. The input data for the computer model have been obtained from special core analyses, open hole logs and drill steam tests from the Falher standstone in Western Canada.
author list (cited authors)
Holditch, S. A., Lee, W. J., Lancaster, D. E., & Davis, T. B.
complete list of authors
Holditch, SA||Lee, WJ||Lancaster, DE||Davis, TB