Reservoir Description and Steamflood Development in the Lost Hills Field

Abstract A steamflood was developed in the Lost Hills field, located in the southwest portion of the San Joaquin Basin in California. The heavy oil reservoirs consist of shallow-marine Upper Etchegoin sands overlain by the fluvio-lacustrine Tulare formation. Steamflood development was complicated by the presence of desaturated zones in both the Tulare and Upper Etchegoin sands. Core analyses, density-neutron logs, and temperature profiles aided in the identification of three genetically different types of desaturation: 1) gravity drainage response to anticlinal growth and/or regional uplift, 2) possible paleo-oil seeps related to an unconformity, and 3) production depletion due to nearby thermal operations. Reservoir mapping indicates that the the first type of desaturation was widespread in the Upper Tulare sand. This type of desaturation not only significantly reduced the oil-in-place, but could also become a major thermal thief zone. Steamflood patterns and well completions were designed to minimize the effect of desaturation and maximize the project efficiency. The design and development of the steamflood may be applied to other partially desaturated, multiple sand reservoirs.