Down here on the Gulf Coast, I suspect most old time oilfield hands carried a rusty knife, because oilfield work here will corrode one in your pocket. Sweat + saltwater + corrosive chemicals + 12 hour shifts. But really, most likely one of the larger patterns - large stockman or trapper or a large hawkbill like above. I live in oil country, and have never seen any old timer carry that wildcat driller pattern.
Having roughnecked some myself, I can tell you - the ideal knife in all ways for offshore drilling rig work is a Spyderco Endura. So back in the day, they probably used the largest slipjoint they could find. A sodbuster would have been a good choice. Buck 110 when those came out.