The Monterey Formation of the Santa Ynez Unit, Part II: Fractures, Borehole Images, and Production
D. F. Lockman and J. R. Schwalbach
The Santa Ynez Unit (SYU), operated by Exxon, USA, comprises sixteen Federal OCS leases in the western portion of the Santa Barbara Channel, offshore California. The three accumulations, Hondo, Pescado, and Sacate fields, are trapped in a large complex of east-west trending anticlines. The Hondo and Harmony platforms produce from the Hondo structure, and the Heritage platform produces from the Pescado structure. Hondo platform production began in 1981, and approximately 130 MBO and 200 BCF have been produced. Drilling began from Harmony and Heritage platforms in 1993.
The primary reservoir is the Miocene Monterey Formation, consisting of very thin interbeds of fine-grained siliceous mudstones, cherts, porcelanites, and carbonate rocks. The majority of the recoverable reserves are contained in and produced from the extensive, high-permeability fracture network.
Part of our formation evaluation program emphasizes fracture characterization and quantification by integrating a number of new technologies. We have calibrated borehole images to approximately 1000 feet of continuous cores from the main producing zones. This enables us to quantify levels of fracturing in wells without core, and to develop strategies for selective perforation of the most highly-productive intervals. Production logs and wireline formation tests provide valuable information about the relation between fluid entry to the well bore and fracture distribution. Borehole images also provide valuable information about fracture orientations, bed orientations, locally-developed chert folds, and lithofacies.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California