Sensitivity studies of resistivity monitoring for shallow enhanced recovery processes - A numerical case history

Enhanced Oil Recovery (EOR) processes have been monitored using gas analysi s, geophysical logging, observation wells (pressure and temperature), well testing methods, seismic velocity tomography, and inversion of deformation measurements. Each of these methods has various strengths and weaknesses. M ost EOR processes involve large changes in the formation resistivity becaus e of the introduction of a fluid phase with a different electrical conducti vity, or because of a large temperature change. These massive changes in su bsurface conductivity may be monitored remotely using subsurface-to-surface resistivity techniques to investigate propagation of fluid fronts and grow th of affected zones with time. In this paper, we present general requireme nts for resistivity techniques in EOR monitoring, typical electrode install ations to reduce noise and seasonal variations, and approaches to the inver sion of three-dimensional (3D) EOR resistivity problems. Sensitivity analys es for a real reservoir case subjected to EOR are presented, and a method o f rapid design evaluation for resistivity monitoring is outlined. It appear s that that the analysis tools and the technology is now adequate to system atically develop electrical monitoring for various EOR applications.