The Hitchcock field in Galveston County, Texas, is an example of the commercial accumulation of oil through combined structural and stratigraphic closure. The producing sand is middle Miocene in age, presumably equivalent to the true Oakville farther updip. The structure of the field is that of a broad, flat dome dipping gently away on three sides while on the fourth side, the east, the trap for oil accumulation is insured by complete lensing-out of the producing sand. The gas cap is very small and several of the highest wells in the field have a high gas-oil ratio. The water level in the field has been ascertained by electrical log and by core examinations. This water level is at 5,158 feet. The field is further complicated by a graben area in the north between two fault of small throws which lower the sand in the graben below the water level and thus serve as a northern boundary to production. A comparison of the structural and isopach maps presented herewith shows the interesting coincidence of the highest part of the gentle dome with the region of equal thickness of the sand. This may serve as an indication of the presence of the structure during deposition.

The Miocene beds above the producing sand have been erratically deposited and stratigraphic fluctuation is very prominent between each well. The presence of apparent faults is conceived in the primary study of the electrical logs; however, these faults are created merely by the erratic deposition of sediments. The only true faults in the field are the two north of the producing area and which are shown on the accompanying contour maps and cross sections.