El Segundo field is about 14 miles southwest of the central portion of thecity of Los Angeles, immediately adjacent to the town of EI Segundo and theStandard Oil Company's EI Segundo refinery site. The field is served andbisected by several major highways connecting the beach cities on the west sideof the Los Angeles Basin. The exact location of the field and its position withrespect to other producing areas is shown on the map covering this portion ofthe Basin (Fig. 1). The Republic Petroleum Co; discovered the first commercial production in thearea when it completed its EI Segundo No.1 (sec. 18, T. 3 S. R. 14 W.) at adepth of 7402 ft. on Aug. 24, 1935, flowing at the rate of about 400 bbl. perday, 28? gravity oil. The producing horizon in this well consists of about 72ft. of conglomerate and schist conglomerate situated below the nodular shale.(Miocene). The true (or solid) schist (Franciscan) was encountered andpenetrated some 20 ft. in the bottom of the hole. This paper gives a report on the history of development and oil production todate, and also submits the writer's interpretation of structural conditions asdetermined from such development. The limited development, together with thecomplex and variable nature of the producing horizon, makes any interpretationof the structure at present only tentative, and any forecast for a given wellextremely hazardous History of Oil and Gas Production The EI Segundo field has produced approximately 1,920,000 bbl. of oil. It has27 producing wells and 14 drilling wells or locations. The present daily rateof production is about 13,400 bbl. The production history of the field to dateis shown in Table 1. The principal companies operating or owning leases in thisfield are: Caminol Company, Geo. F. Getty, Inc., Ohio Oil Co., RepublicPetroleum Co., Pacific Western Oil Corporation, Royalty Service Corporation, Richfield Oil Corporation; Standard Oil Company of California, The TexasCompany, Union Oil Company.