Characterization of Nonmarine and Shallow Marine Sediments Using Electrofacies and Advanced Volumetric Methods, Eastern San Joaquin Valley: ABSTRACT

Abstract

The Delmontian Chanac and Pliocene Etchegoin Formations of the Kern Front field, Kern County, California, were studied to relate log response to lithofacies in nonmarine and transitional marine depositional environments. Six wells in a roughly north-south cross section were analyzed by the Multiwell Faciolog data-reduction technique. A lithology-sensitive data base created by the bulk-density, neutron-porosity, gamma-ray (also a relative grain-size indicator), and effective photoelectric cross section index logs was calibrated using detailed core and side-wall data. VOLAN volumetric analyses, using wireline-log data including EPT measurements, then provided reservoir property measures of porosity, permeability, and saturation. Ten electrofacies were identified, including three types of claystone, a siltstone, and six types of sandstone. A spectrum of sandstone composition ranged from very argillaceous to somewhat clayey with carbonaceous stringers to silty to relatively clean. Two sands showing gas effect were also defined. The thin-bedded shaly Chanac strata are characterized by rapid vertical and horizontal changes in lithology, which make well-to-well correlations difficult. The beds were deposited chiefly as fluvial channels and alluvial fans with interbedded lutites representing overbank or ephemeral lacustrine deposits. Many channels are stacked. Etchegoin strata are composed of an upward-coarsening shoreface sequence, culminated by seaward-prograding tidal channels. Stratigraphy at leastmore » partly controls the trap and complicates steamflood efforts.« less