Integrating strike-slip tectonism with three-dimensional basin and petroleum system analysis of the Salinas Basin, California

Abstract

The Salinas Basin is a strike-slip basin in central California with stratigraphy dominantly composed of Miocene Monterey Formation. Despite a long history of oil production, aspects of petroleum system development in the basin remain poorly understood. Of the seven main oil fields, one—San Ardo field—has produced more than 500 million bbl of oil or 99% of all oil found in the basin. The evolution of this basin was profoundly influenced by strike-slip movement on the Rinconada Fault, which bisected the depocenter beginning circa 15 Ma. To address the influence of strike-slip motion on petroleum system development, we constructed a three-dimensional (3-D) basin and petroleum system model that incorporates strike-slip displacement. Seismic reflection profiles from a 3-D survey reveal four main tectonic stages that correspond to events in petroleum system evolution. Petroleum generation from type II kerogen source rock began circa 11 Ma, approximately 4 m.y. after strike-slip faulting began to offset a once-contiguous sedimentary depocenter. Two separate petroleum provinces—an eastern one and a western one—developed, and the fault zone likely was a conduit for petroleum, if nonsealing. Most accumulated petroleum was derived from the eastern pod of active source rock because of greater sedimentary burial east of the fault. Our model roughly replicates the skewed distribution in oil-field size. Factors controlling field size distribution include trap size and connectivity to source.