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ABSTRACT: A Gravity Model of The Southern San Joaquin Basin Constrained by Density Data from a 24,000 Foot Well, Elk Hills, California


In this study we have constructed a density model for the Southern San Joaquin Basin using a porosity log from the deepest well in California, the UO-NPR #1 #934-29R well in the Elk Hills Naval Petroleum Reserve. We derived bulk density from the porosity log using standard industry methods. 22 discrete density layers were constructed representing the sediments of the San Joaquin Basin. Two-dimensional gravity modeling was conducted using these density constraints. The sediments by themselves produce an anomaly of -100 mgals which is 60 mgals lower that the observed residual anomaly that characterizes the west side of the Southern San Joaquin Valley. The discrepancy is resolved with substitution of a 68 km thick ophiolitic basement (3.10 g/cc) supporting the presence of the ophiolite as hypothesized in several previous studies.

Search and Discovery Article #90945©1997 AAPG Pacific Section Meeting, Bakersfield, California