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ABSTRACT: Merrill Avenue Gas Field, an AVO Success

HILL, DAVID R., and PRENT H. KALLENBERGER,* Union Oil Company of California, Bakersfield, CA

Merrill Avenue gas field, location 40 mi northwest of Fresno, California, was discovered in July 1989 by Union Oil Company of California. The discovery well, Union 1 O'Banion, was completed in the Upper Cretaceous Blewett sand, and tested at a rate of 6.7 MMCFD.

Subsequent drilling has defined a complex stratigraphic pinch-out trap with approximately 20 bcf recoverable reserves.

Pre-drill regional mapping in the area indicated a rapid pinch out of the Blewett sand interval from west to east. Two speculative seismic lines and proprietary seismic data showed a strong seismic anomaly associated with the pinch-out zone. Further analysis of this seismic anomaly showed a large increase in reflection amplitude with increasing angle of incidence over the prospect area and a decrease in amplitude with offset in the vicinity of a nearby dry hole. Modelling results substantiated these observations.

The 1 O'Banion well was located on a Union proprietary seismic line in a position to test the center of the seismic anomaly. The well encountered 195 ft of Blewett sand, with the upper 64 ft gas saturated.

Integration of new seismic data and subsequent development wells show that Blewett sands thin to zero in a complex and abrupt manner within the Merrill Avenue area. Amplitude vs. offset information has proven to reliably indicate the presence of both sand and producible gas. Increasing AVO signatures are characteristic of areas of producible gas, whereas sand-poor and wet zones are distinguished by a decreasing AVO signature.


AAPG Search and Discovery Article #91016©1992 AAPG-SEPM-SEG-EMD Pacific Section Meeting, Sacramento, California, April 27-May 1, 1992 (2009)