Cyclic Steaming in Heavy Oil Diatomite

Abstract

ABSTRACTChevron currently uses cyclic steaming as a recovery method to produce economically its heavy oil diatomite resource in the Cymric field, San Joaquin Valley, California. A highly instrumented, cyclically steaming well from this field was simulated in this study to delineate important production mechanisms, to optimize operations, and to improve reser­ voir management. The model was constrained, as much as possible, by the available measured data.Results show that fluid flow from the well to the reservoir is primarily through the hydraulic fracture induced by the in­ jected steam. Parameters with unique importance to model­ modeling cyclic steaming in diatomites are: ( 1) induced fracture dimension (length and height), (2) matrix permeability, (3) oil/water capillary pressure, (4) grid size perpendicular to fracture face, and (5)producing bottomhole pressures. Additionally, parameters important for conventional steam injection processes, such as relative permeabilities and injected steam volume, quality, and rate, are important for diatomites also. Oil production rates and steam/oil ratios calculated by this model compare reasonably with field data.