Investigation of Previously Unpublished Igneous Unit(s) in the Los Angeles Basin California: Inglewood Oil Field

Ryan, Michael W.¹, Dalton Lockman², James R. Boles³ (1) University of California Santa Barbara, Santa Barbara, CA (2) Plains Exploration & Production Company, Los Angeles, CA (3) University of California, Santa Barbara, Santa Barbara, CA

Plains Exploration encountered an igneous unit of unknown age, composition, and extent in approximately forty exploitation and development wells, at approximately 8000 feet beneath the Inglewood oil field. The Newport-Inglewood fault zone is the prominent structural feature of the Inglewood oil field and is a potential conduit for the igneous unit(s). An ongoing investigation of whether the igneous unit is deformed similarly to surrounding sediment will aid in determining age constraints. Analysis of well logs including gamma ray, SP, sonic, neutron, density and image logs reveal what we interpret to be a series of flows or intrusion events in the surrounding Sentous Sandstone which is middle Miocene in age. These events have distinct characteristics on electronic logs that have the potential to be correlated from well to well. Analyses of image logs offer a picture of what the unit contacts look like in-situ. The presence of an igneous body (s) is confirmed by conventional and sidewall core samples that are being studied in thin section and by chemical and dating methods. High kaolinite content reported in sandstones adjacent to the igneous unit(s) suggests possible hydrothermal alteration of the surrounding sediment. Analysis of mud logs for the various exploration wells and side wall cores, as well as isotopic analysis of pore waters will provide us with a better understanding of the nature of the kaolinte and temperature of crystallization.