Round Mountain Oil Field - Geology

Geology

Oil in the Round Mountain Field comes from four primary pools, the Freeman-Jewett, Pyramid Hill, Vedder, and Walker. Each resides in a sedimentary formation equivalently named, and are listed from top to bottom in stratigraphic sequence. The Freeman-Jewett and Pyramid Hill are of Miocene Age; the Vedder of Oligocene; and the lowest-lying productive unit, the Walker formation, was deposited during the Eocene and Oligocene. Of these units, the Vedder has been by far the most productive, with over 50 million barrels of oil being extracted.

The field is bounded on the northeast by a fault which serves as a structural trap since it is upgradient from the oil pools. Basement rocks underneath the productive units are of Jurassic age, and at around 4,000 feet (1,200 m) are not particularly deep for a Kern County oil field. The deepest well on the field is the Killingsworth "Alma" No. 6, at 4,418 feet (1,347 m), which reached the granitic basement.

Oil from the field generally heavy, with API gravity ranging from 13 at the Sharktooth and Alma areas to 22 in the Jewett pool in the Main Area. Waterflooding and cyclic steam processes have been used to retrieve some of the heavier petroleum since the early 1960s.