Oil Industry in Gaines County. The first oil lease in Gaines County was in 1912 and the first drilling occurred in 1925. Ten years later the Landreth Company brought in the first producing well. In 1936 Amerada Oil Company opened up the Seminole Pool, a major field that yielded 350 wells within a decade. Less than 50 years after that discovery, Gaines County had produced over one billion barrels of crude oil. With several active fields, Gaines ranks as one of the top oil producing counties in Texas. The petroleum industry accounts for much of this area's prosperity. 1979 #3683