Why was there oil under Texas and was there more? Wildcatters
would come to Texas and drill hole after hole. Some became rich, but
some lost everything. The area that we now call Texas, has accumulated
oil many times since the Paleozoic. Invading seas created coral reefs.
These broad shallow shelves created conditions ideal for oil
accumulation from the Paleozoic to Cenozoic.
So, even though drillers were finding oil, the oil was not from the
same sources. For example, the oil in East Texas was caused mainly by
Mesozoic (green colors on the map) to Cenozoic (yellow to orange)
sediments. In West Texas, the oil is mainly from late Paleozoic reef and
limestone structures. The geology of the state is important to
reconstruct where the oil was formed and where the oil is today.