The Use of Wireline Pressure Measurements to Refine Reservoir Description, Main Body B Waterflood, Elk Hills Oil Field, Kern County, California
WILSON, MARK, Bechtel Petroleum Operations, Inc., Tupman, CA, CHET LOVE, Scientific Software Intercomp, Bakersfield, CA, MAURICE FISHBURN, Department of Energy, Los Angeles, CA, and MICHAEL HUMPHREY, Chevron, U.S.A., San Ramon, CA
The Main Body B, one of five large Stevens sand reservoirs at Elk Hills, occupies the eastern half of the 31S anticline. Early in the production history of this reservoir, the Elk Hills unit initiated peripheral water injection to maintain reservoir pressure. Water injection has proceeded at a rate approximately equal to the voidage created by oil and gas production and has moved water upstructure creating an oil bank. Bechtel Petroleum Operations Inc., the current unit operator, drills five to ten new wells each year to fully exploit this oil bank.
In 1985, the unit added wireline pressure measurements to the open-hole logging programs of these infill wells for the purpose of evaluating the net effect of injection into and production from the Main Body B reservoir. A typical well provides the opportunity to obtain 8-10 pressures from the Main Body B. To date, the Unit has measured wireline pressures in more than two dozen wells.
The wireline measurements have shown a broader than expected range of formation pressures (1600 +/- psi to 4200 +/- psi). The pressures show that this is a layered reservoir with little vertical pressure communication between some of the layers. In some parts of the reservoir, wireline pressures indicate horizontal continuity of the layers between wells and in other areas pressure differences between adjacent wells may indicate faults or cementation barriers. Permeabilities calculated from the sampling drawdown are the same order of magnitude as brine permeabilities obtained from core and show that higher-pressured layers of the reservoir have lower permeability. These observations fundamentally alter performance evaluation of the Main Body B waterflood.
AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)