Geology of Texas Panhandle oil and gas field

Oil is found in formations along the flanks of an old buried granite ridge trending northwest and southeast. Gas is found in formations along and on the crest of this ridge. The beds are arched over the ridge as a result of compaction of sediments or diastrophic movements, or both. The shallow Permo-Pennsylvanian non-red beds are divided into five zones from bottom up: "granite wash," dolomitic arkose, coarse white dolomite, fine brown dolomite, and anhydrite. The first four are oil and gas reservoirs. Oil usually accumulates where the porous portions of these four zones intersect a plane slightly above sea-level. There is definite demarcation between the sweet and sour gas. This results from the gravitational separation of the heavy hydrogen sulphide into that portion of the gas situated low on the ridge. At the time of accumulation of oil and gas, the eastern end of the ridge was higher, generally, than the western, resulting in the greatest accumulation of sour gas in the northwest, while only sweet gas accumulated in the southeast. This condition also accounts for the heaviest oil being on the northwest. Subsequent tilting now gives the axis of the ridge a southeast plunge.