The Oakridge oil field is located atop the Oakridge Mountains 2 miles east of the Torrey Canyon oil field and 3½ miles southeast of the town of Piru.

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The producing zone was discovered by Union "Oakridge" 1-3 ("Simi" 17) which recovered 1,700 feet of clean 23° oil on a one-hour, 8-minute formation test from the interval 2,851 to 2,926 feet. As "Oakridge" 1-3 prospected ahead, "Oakridge" 2-10 was drilled and completed in the "Luisian" zone, pumping 390 B/D, 8% cut, 21.7°, 129 Mcf. from the interval 2,852-3,298 feet. Potential productivity of the "Luisian" sands was first indicated by oil showings cored in Union Wildcats "Simi" 10 and 15. The discovery well was located to test these showings in a higher structural position.

The generalized section is as follows: lower Mohnian shale, Luisian siltstone, Luisian sand, Topanga and Vaqueros sand, Sespe sand.

The so-called "Luisian" production comes from foraminiferal Luisian sands above an angular unconformity and from unfossiliferous marine sands below which are thought to be Topanga and Vaqueros undifferentiated. The most prolific wells are down structure near the discovery well, since the producing sands become thinner and siltier up structure to the north and west. A troublesome wedge of intermediate water sand directly underlies the unconformity, with increasing thickness north and west.

Oil accumulation is on an asymmetric, unfaulted, easterly plunging nose, with reason for closure on the west unknown, but believed to be stratigraphic. Dips on the steep north flank average 60°-70°, on the south flank 30°-35°. In the west end of the field the east plunge is gentle, becoming more abrupt on the east. This simple structure lies beneath the folded Santa Susana thrust, with a complex folded and faulted Miocene section above the fault as seen on the surface.

The field is being actively developed and 33 wells produce approximately 3,800 B/D. No dry holes have been drilled, and no definite limits proved, except at the north. A shallow low-pressure oil sand discovered in the east end of the field by Union "Oakridge" 11-3 remains for further evaluation.

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