The East White Point oil field is located in south-central San Patricio County, Texas, on the Gulf Coastal Plain of South Texas, being situated approximately midway between Galveston and Brownsville, 20 miles inland from the Gulf of Mexico, and 5 miles northward across Nueces Bay from the city and deep-water port of Corpus Christi. Subsequent to the discovery of oil in the 5,600-foot sand by the Plymouth Oil Company in February, 1938, the field has been subjected to continuous development. As of January 1, 1941, approximately 240 oil and gas wells have been completed in the four productive sands between the depths of 4,000 feet and 5,900 feet, which wells have yielded approximately 5½ million barrels of oil.

Within the scope of this paper, the strata encountered in the drilling of the majority of the wells below a depth of 4,000 feet in the subsurface have been grouped in the Oligocene formation and the authors have restricted their study to the beds included in the interval below that depth and above the 5,600-foot (principal oil-producing) sand. Isopach and other geologic studies of the several sand and shale zones have presented some very interesting problems. The intermittent and periodic structure-making movements, and likewise the periods of quiescence, are reflected in the sedimentary intervals of the respective strata. The most outstanding feature of the stratigraphy, however, is the well developed erosional topography on the top of the 5,400-foot (Zone E) sand. Isopach maps of th s stratum display the typical features of degradation and planation common to the erosion cycle of normal rivers in an area being subjected to cyclic rejuvenation. Similar maps of the overlying 5,300-foot (Zone D) shale reflect the effects of the deposition over the eroded topography. As suggested by the reconstructed terraces, and slopes attendant thereto, three periods of uplift and erosion are propounded. The erosional unconformity thus established, and advocated by the authors, offers additional criteria and evidence for the following: first, offlap or regression of the Gulf of Mexico at the close of Frio time, with the consequent development of stream drainage and erosional topography on the land surface; second, the location of an ancient Gulf of Mexico at some distance removed fro the present location of the East White Point Field following the deposition of the 5,400-foot sand; and third, the delineation of the top of the Frio formation at the erosional break in the stratigraphy.

End_of_Article - Last_Page 932------------