Abstract: The Sulphur Mountain Oil Tunnels

CHAUVEL, JEAN PAUL, Retired, Unocal, Ojai, CA

The oil tunnels of Sulphur Mountain were located four to eight miles northwest of Santa Paula along the northern margin of California's Ventura Basin. They were part of the abandoned Santa Paula Oil Field, and they were dug northerly into the steep south flank of Sulphur Mountain. Oil pioneers were lured to this site by vigorous oil seeps.

Professor Benjamin Silliman, Jr. wrote about this phenomenon in 1865 saying that: "The oil is struggling to the surface at every available point, and is running down the rivers for miles and miles." Josiah Stanford discovered the Santa Paula Field in 1866 when he dug an 80-foot tunnel in Wheeler Canyon near one of the most active oil springs. An economic depression and lack of a sizeable oil market delayed further digging until 1889. Between 1889 and 1892, at least 53 tunnels were dug, most of them under contract for Union Oil Company of California and its predecessor companies. About 2.5 miles of tunnels were dug, the longest being 1940 feet. They had a one percent gradient which allowed produced fluids to flow to the tunnel’s portal where it was collected, separated, and shipped.

Produced oil came from fractures and thin sandstone beds within the late Miocene Sisquoc Formation which is exposed in the overturned limb of the Sulphur Mountain anticline. Tunnel production prior to their abandonment in 1997 was 6 to 8 BOPD and about 750 BWPD. The API gravity of this oil ranged from 26.9 to 30.3 degrees.

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