The Asphalto field is in Kern County on the western side of the San Joaquin Valley. It lies about 2 mi. east of McKittrick, and approximately half-way between the old McKittrick field toward the west and the Elk Hills “24 Z” pool toward the east.
The discovery well, the E. A. Bender “Standard Oil Co.” No. 18, in Sec. 23, T. 30 S., R. 22, E., M.D.B.&M., was spudded November 17, 1962, on an 80-acre farm-out from the Standard Oil Company of California and was completed for an initial production of 312 BD of 37° gravity oil from the interval 5,612-5,672 feet. Since then, over 60 wells have been completed in the field for average production in excess of 13,000 BOPD from about 600 acres. Cumulative production to December 31, 1964, is about 8,000,000 barrels of oil and 10,000,000 Mcf of gas. Peak production was over 17,000 BD in September, 1963.
The trap for the accumulation is formed by the shale-out of the upper Miocene Asphalto-Stevens Sands on the southeastern plunge of the McKittrick Front structure. Clues to the possible presence of the reservoir were given by the trend of the sandstones in the Elk Hills “24-Z” pool, and by the presence of thin laminae of oil-stained sandstones in the equivalent shale intervals of 3 wells straddling the area and about 1½ mi. apart.
Three sandstones are present and have been named respectively the Asphalto I, Asphalto II, and Asphalto III Sands. Only the uppermost Asphalto I Sand is productive in the discovery well, the lower sandstones being wet. However, subsequent wells have found all three sandstones productive at various locations, but toward the south and east, they merge into one thick sandstone body making their separation difficult.
Structurally, the field forms an elongated structural saddle at “N” point with some shallow closure of its own. Local unconformities and successive overlap immeasurably complicate attempts to unravel the structure and stratigraphy in any great detail. Generally, “N”-point structure is valid for the sandstones, but differs from lower horizons in detail. The Olig structure above is greatly different.
The discovery of the Asphalto field has given new impetus to exploration in the southern San Joaquin Valley and is certainly a classic example of a major discovery in a highly explored area.