The Castaic Hills field is located in Los Angeles County northwest of, and adjacent to, the Honor Rancho field. It is believed to be completely separate from the latter field both from a structural and stratigraphic standpoint although only one location separates the two areas.

The field was discovered by Ted Sterling, operator for Paul W. Trousdale's "Rynne-Fisher" well No. 1 (now Continental Oil Company's well), which was completed on September 13, 1951, from the interval 4,632-4,697 feet, flowing 233 b/d, 33° gravity, 0.1% cut, 27/64^Prime bean, 90# T.P., 485# C.P., and 185 MCF. As of September 30, 1952, 29 wells have been completed in the area, 5 wells abandoned, and several wells are still drilling.

The stratigraphy in the field is characterized by the great thickness of conglomerate and abrupt facies changes. The general geologic section above the basement granite consists of the following.

1. 1,400-2,700 feet of non-marine Saugus (Pleisto-Pliocene) conglomerate, sands, and clays

2. 1,400-1,000 feet of marine Pico with possibly some Repetto at base (Pliocene) conglomerate, sands, and siltstones

3. 6,500± feet of Modelo upper and middle Miocene sands, conglomerate, and shales, of which there are:

a. 50-200 feet of Delmontian conglomerate and siltstone
b. 1,700-2,500 feet of upper Mohnian conglomerate and sand
c. 4,500± feet of lower Mohnian shales, conglomerates, and thin sands

The producing sand (Sterling zone) is 30-220 feet thick and occurs in the uppermost part of the lower Mohnian or in basal upper Mohnian. Tar sands occur in the Saugus and Pico formations.

The field is on the steeply dipping south flank of the east-west Loma Verde (Devils Canyon) anticline, the surface axis of which is ½ mile north. The discovery well was drilled on the assumption that sands coming up toward the north on this flank would either pinch out or be faulted in such a manner that north and west closure would occur. It was expected that east closure should be provided by the large northwest-trending San Gabriel fault. This is in general what has been proved, although numerous faults made complications. It now appears that the closure on the west is caused by facies change, closure on the east by faults probably related to the San Gabriel fault, and on the north by both faulting and facies change, although this is not definitely determined. The field contai s fault blocks which affect accumulation.

The field, which is producing about 4,340 b/d (August average), is composed of about 280 proved acres with possibly 50 additional definitely proved acres to be drilled. However, with very little

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imagination, one can visualize the field being twice its present size. Also there are possibilities of deeper producing sand or sands being present and the shallow tar zones being produced.

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