Abstract

The Tucumcari Basin of east-central New Mexico is an asymmetric structural depression that existed as a depositional basin from the Atokan (Early Pennsylvanian) through the Wolfcampian (Early Permian). The deepest parts of the Tucumcari Basin are in elevator basins along the northern margin of the basin. Depth to Precambrian basement may exceed 12,000 ft in the deepest parts of these elevator basins. On the shelf areas to the south of the elevator basins, depth to Precambrian ranges from 2,000 to 5,000 ft in most places.

Pennsylvanian strata contain the most significant source rocks in the Tucumcari Basin. They contain more than sufficient amounts of organic carbon for petroleum generation and are thermally mature. Underlying Mississippian strata contain insufficient levels of organic carbon. Post-Pennsylvanian strata are either thermally immature or contain insufficient organic carbon.

Pennsylvanian shales are good to excellent source rocks of gas, oil, and condensate. Source facies are dark-gray to black shales and shaly coals. Shales in the elevator basins are thicker and have enhanced TOC levels. Within the elevator basins, the shales have TOC levels in excess of 2 percent in most places and in the 6 to 10 percent range over large areas. Shaly coals, unknown from outside the elevator basins, have TOC levels approaching 50 percent.

Thermal maturity of Pennsylvanian strata is also enhanced within the elevator basins. Throughout the shelf areas, source facies are only marginally mature. Within the elevator basins, however, deeper burial resulted in enhanced thermal maturity and the Pennsylvanian source facies are within the oil and condensate windows.