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3-D Analysis Leads to an Injection Strategy Designed to Optimize Volumetric Sweep: Cymric Field, California


1Aera Energy LLC, Bakersfield, CA
2Plains Resources Inc., San Luis Obispo, CA

Correct volumetric calculations and spatial mapping of remaining oil in a mature field presents a major technical challenge to the U.S. oil industry. This study uses 3-D technology and selected modern wells to build a 3-D volumetric model that quickly and quantitatively targets remaining oil in the Pliocene-Pleistocene Tulare reservoir at Cymric field in the San Joaquin Valley, California. This study applies 3-D technology to assess the amount of remaining oil-in-place and to develop an injection strategy that is based on the remaining pore volume to be flooded in each flow unit.

This method utilized a modern high-resolution 3-D seismic survey that identified the major fault blocks for each of the 15 reservoir sand horizons identified from well logs. The pore volume of each horizon in every fault block at 20 feet of subsea depth increments was determined from a 3-D geologic model. This data was used to construct a cumulative pore volume versus depth relationship.

A snapshot of the fluid contacts was determined for each fault block by using modern well logs to determine the steam-oil contact and oil-water contacts at a particular point in time. Differences in contacts between adjacent fault blocks provided insight into the hydraulic connectivity across the faults. Allocated injection by flow unit and fault block coupled with the date stamped steam-oil-contacts resulted in a "barrel injected-to-barrel of steam chest" relationship. The resulting calculations of pore volumes injected matched simulation for the overall steam chest volumes achieved and provided a methodology for adjusting steam targets to maximize volumetric sweep efficiency.




AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California