A Study of Reservoir Performance of the First Grubb Pool, San Miguelito Field, Ventura County, California

The San Miguelito Field of Ventura County, California, lies along the coastapproximately five miles northwest of the city of Ventura. The structure is oneof several in the Ventura anticline, a series of anticlinal folds trendingnorthwest-southeast through the San Miguelito Field. The Ventura Avenue Fieldlies to the southeast along the anticline, and Padre Canyon and Rincon Fieldslie to the northwest; the series then extends beneath the Pacific Ocean.Production is obtained from the Lower Pico and Repetto formations of Plioceneage, and oil accumulation is controlled by faulting, lithology and structure.The first well in the First Grubb Pool was completed in November, 1931, and todate 48 producing wells have been drilled on the 276 productive acres.Approximately 685 ft of net pay are contained in the eight sand bodies grossing1,220'Ft of section. Production of oil to date has been 15,600,000 bbl. A gasinjection project was instigated in April, 1940, but was discontinued inSeptember, 1949. This paper is confined to a discussion of the development and performancehistory of the First Grubb Pool of the San Miguelito Field. Location and Geology The San Miguelito Oil Field is located in Ventura County about five milesnorthwest of the city of Ventura along the coastal highway to Santa Barbara. Itis located within sections 23, 24, 25, and 30 of Township 3 North, Range 24West, San Bernardino Base and Meridian. Surface elevation in the field rangesfrom sea level to plus 1,200'Ft, and the terrain is extremely rugged. Thestructure is well defined on the surface and on the wall of the AmphitheatreCanyon where appears a so-called "text book" anticlinal section. The San Miguelito structure is an asymmetrical, elongated anticline about twomiles long and three-fourths of a mile wide. The trend of the axis of theanticline is northwest-southeast. Fig. 9 illustrates the contours and majorfaults of this structure. Dips on the southwesterly flank average about 40degrees, whereas the northeasterly flank ranges from 60 to 75 degrees. Thereare several faults striking generally east and west. These faults do not appearto affect materially the area of accumulation or performance behavior. It isbelieved that accumulation was affected by steeply dipping beds and extremelylow permeability of the northeast flank of the structure. T.P. 2951