In 1959, Pure Oil Company made sensational simultaneous discoveries of the first major oil and gas accumulations from the Mississippian in the Paradox fold and fault belt at Lisbon and McIntyre Canyon Units. These discoveries indicated that the tectonics of the pre-salt flowage structures in the province could and would be solved. A massive exploration program was launched, but during the intervening years, only three relatively minor discoveries have been made in pre-Pennsylvania rocks. Two of these are associated with the Lisbon structural complex.

Similarities between the Persian slat anticlines and those of the Paradox basin had long been recognized and the idea of parallel, but offset, pre-salt structures was the basis on which large blocks were leased. Many operators were wary of seismic problems associated with salt flowage and(or) solution; however, Pure persevered and, in 1957, demonstrated at Big Flat field that seismic mapping was feasible and that the Mississippian could contain oil. This led the Pure's successful survey at Lisbon.

Drilling has shown that the thickened salt core of the Lisbon Valley surface anticline occupies the crestal graben of an offset-toward-the-southwestern pre-salt anticline. Mississippian fault traps closed against salt have been found on the upthrown blocks on each side of the graben. Largest of these is the Lisbon Unit with 1,800 ft. of effective closure. In addition to the Mississippian, oil production has been obtained from the Devonian Ouray and McCracken but early promise of these formations as important objectives has not materialized.

One well, now abandoned, has produced oil from the Paradox salt.

Post-salt Pennsylvania producing potential is indicated by two shut-in wells from multiple Hermosa sandstones on the downthrown block of the surface anticline which is closed against salt. Several wells within the Lisbon Unit have also tested "shows" of oil on drill-stem test of the Ismay.

The Lisbon Valley-Dolores trend is only one of the five major salt flowage structural trends of the Paradox basin. Traps similar those at Lisbon can be expected to be associated with other salt anticlines. A conservative estimate of the ultimate gross value of recoverable hydrocarbons from the Lisbon anticline is anticline $100,000,000. Search in similar accumulations is indeed warranted!

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