Sally M. Benson¹

(1) Earth Sciences Division, Lawrence Berkeley Laboratory, Berkeley, CA

ABSTRACT: Effects of Reservoir Heterogeneity on Pressure Build-up and Fall-Off at CO2 Injection Wells

Observation of pressure build-up and fall-off in injection wells is one of the common methods for monitoring the progress of an injection operation. Evaluation of these data can be used to detect changes in the near-bore permeability and in some cases, to track migration of the flood front. Reservoir heterogeneity and gravity override may influence the applicability of the methods used for interpreting these parameters, particularly in the case of CO2, which is considerably less viscous and less dense than the resident formation fluids. This study uses the numerical simulator TOUGH2 to investigate pressure build-up and fall-off responses in heterogeneous brine-filled reservoirs. These results are compared to pressure build-up and fall-off in homogeneous formations and a new approximate analytical solution for calculating pressure buildup at CO2 injection wells. Based on these comparisons, conclusions are made regarding the effect of formation heterogeneity and gravity override on the pressure transient responses and the extent to which these data could be valuable for monitoring the progress of CO2 injection operations.

This work was supported by laboratory directed research and development funds at Lawrence Berkeley National Laboratory under U.S. Department of Energy Contract No. DE-AC03-76SF00098.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado