Abstract: Integration of Surface Geology and Borehole Geophysics for Reservoir Characterization in the Monterey Siliceous Shales for the Purpose of Facilitating Improved Recovery Designs

DHOLAKIA, SNEHA K., ATILLA AYDIN, DAVID D. POLLARD, MARK D. ZOBACK, COLLEEN BARTON, and BRUCE J. BILODEAU

Surface studies of the low permeability siliceous shales of the Monterey Formation at Chico Martinez Creek in southern San Joaquin Valley and subsurface data from Buena Vista Hills field, an active oil field nearby, were successfully integrated for the purpose of improved characterization and recovery in reservoirs with similar settings. First, it was deciphered from outcrop studies that brecciated-fault zones and associated fracture systems are the most significant conduits for petroleum migration pathways. Brecciated zones occur predominantly parallel to bedding in porcelanite units and are bounded above and below by siliceous shale beds. This observation suggests a mechanism of brecciation based on a delicate interplay among lithology, diagenesis, deformation, and perhaps, hydrocarbon maturation. This interplay results in a petroleum-filled compound breccia zone of several meters in thickness, in which the boundaries of the individual zones are partially obliterated by subsequent deformation. Second, petroleum-filled breccia zones are interpreted in borehole images and caliper logs from several wells using the knowledge gained from the geological and geomechanical studies.

This project demonstrates that using geology and geomechanics together with borehole geophysics is a powerful tool for hydrocarbon recovery as well as exploration.

Search and Discovery Article #90945©1997 AAPG Pacific Section Meeting, Bakersfield, California