Abstract: The Structure and Production of a New Fault Block Discovery, Fractured Monterey Shale Zone, Northwest Lost Hills Oil Field, Kern County, California

HECTOR, SCOTT, Gary Drilling Co., Davis, CA

In 1998, a new fault block discovery was made at Northwest Lost Hills oil field. Nine wells now produce oil and gas out of fractured Monterey Shale from the fault block. Electric logs show a 500 ft repeat section in the Antelope Shale section of the Monterey. The reverse faults encountered appear to be located near the axis of the Lost Hills Anticline. In this area, the anticline plunges to the northwest.

The nine "high block" wells are much more prolific than wells to the west and east that produced from much lower structural positions. Pay zone depths are typically from 3200 ft to 3600 ft. Recent drilling has proven the existence of at least three large thrust faults in the area. The productive area appears to be a zone of failure near the anticlinal axis, also known as a "pop-up" block.

Maximum pay thickness in the high block to date is 400 ft. None of the nine wells drilled to date have seen a complete section (550-750 ft) of the Antelope Shale member of the Monterey. All wells are cut by at least one of the major faults. Artificial stimulation by hydraulic fracturing is necessary to obtain commercial production. A typical well will have two or three stages of fracing with placement of 75,000 to 150,000 lbs of proppant sand per frac. Initial production rates vary from 30 to 60 BOPD of 30-gravity crude oil. GOR's are typically between 1500 and 2500. Wells are flowed on small bean sizes (3/64 to 5/64 in) to maximize reservoir energy and lower water cut. Gas is presently being flared due to the distance of the field from natural gas pipelines.

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