Structural and Stratigraphic Evaluation of the Southern Belgian Anticline Area, North Midway-Sunset Field, San Joaquin Basin, California

Bayer, W. Sebastian¹, Shankar Mitra², Roger Slatt², Steve S. Boljen³, Joel S. Pomerene³ (1) The University of Oklahoma, Houston, TX (2) University of Oklahoma, Norman, OK (3) Berry Petroleum Company, Bakersfield, CA

The Midway-Sunset field is located in the West Side fold belt in the San Joaquin Basin. The structures in the area, including the Midway-Sunset, Buena Vista, and Elk Hills anticlines, were formed during multiple episodes of compressive deformation, separated by periods of extension, between the Upper Miocene and present. A regional study of a 250 square mile area was conducted to understand the structure and stratigraphy within the fields. The study utilized existing geologic maps and data from over 400 wells to construct three regional structural and seven stratigraphic cross sections. One of the structural sections was kinematically reconstructed through time to understand the tectonic history. The Midway-Sunset and Buena Vista structures are interpreted as a series of parallel fault-bounded structures, cored by deeper fault-bend folds. Many of the larger structures display overturned or steep flanks. Some of the reservoir units, such as the Stevens and Potter deep water turbidite sandstones, were deposited in an active tectonic environment, so that the depositional history is closely related to the structural events. A more detailed structural-stratigraphic study was conducted to evaluate an approximately 15 square mile area within the Southern Belgian anticline. A three-dimensional structural model was constructed using six closely-spaced balanced structural cross sections constrained by dipmeter logs and surface structural data. This structural model will provide a tool to evaluate potential bypassed reservoirs in the Potter sandstone, and new targets in deeper reservoirs.