Correlation Sections Prepared by the Geological Names and Correlations Committee of the A.A.P.G. Castaic Junction Field, Los Angeles County: ABSTRACT

Abstract

The Humble Oil and Refining Company discovered Castaic Junction in January, 1950, with its fifteenth California wildcat. The discovery well, Newhall Land and Farming Company No. 1, was completed from 11,792-11,841 feet, flowing 156 barrels of 34.2° API gravity oil, gas-oil ratio 3,945, tubing pressure 825 pounds, ¼-inch positive choke, 2.8 per cent salt water. After drilling through a continuous upper Miocene shale section from 8,000-10,900 feet, the well encountered a lower Mohnian gas-condensate sand at 11,638 and an oil sand at 11,775 feet. Subsequently, N. L. & F. 2, located 3,000 feet west-northwest of the discovery, was completed from 100 feet of net gas-condensate sand between 11,198 and 11,371 feet. These wells are producing from the deepest known sa d in the field, Reservoir 21. N. L. & F. 3, located down structure, 2,400 feet southeast of the discovery well, encountered a new reservoir sand near the top of the Mohnian stage of the upper Miocene. Three additional wells have been completed in this sand which has been designated Reservoir 10. Net oil-stained sand and conglomerate range in thickness from 95 feet in N. L. & F. 3 to 221 feet in N. L. & F. 4. A minimum oil column of 998 feet has been proved in Reservoir 10 with no bottom water yet encountered. There is an apparent natural stratification of oil, structurally low wells producing 18.5° gravity oil increasing to 21.3° gravity higher on the structure. In August, 1951, N. L. & F. 6, located 726 feet north of N. L. & F. 3, drilled through Reservoir 10 End_Page 2632------------------------------ and discovered a new upper Mohnian sand, Reservoir 15, approximately 1,000 feet below the base of Reservoir 10. Formation tests of this new reservoir indicate excellent productivity of between 27° and 29° gravity oil and condensate. Subsurface information is so limited to date that the mechanics of reservoir closure are not definitely known. Since the field lies on the southeasterly plunging Del Valle nose, the most logical cause seems to be either strong cross faulting between the Del Valle and the Castaic Junction fields, or merely the development of stratigraphic traps by lensing sands along the anticlinal structure. The highly lenticular nature of the sands and the general structure are depicted on the cross sections and maps. A strong northward shift of the subsurface structural axis is apparent. Current production is approximately 1,100 barrels per day with individual well potentials ranging from 450 to 750 through ¼-inch choke. End_of_Article - Last_Page 2633------------