Publication: The Mountain Geologist, Vol. 49, No. 2, Pages 55-76
Date Published: April 2012
Title: Hydrocarbon-Water and CO2-Water Systems in the Pre-Cretaceous
Section in the New Mexico Part of the Raton Basin
Author(s): Ronald F. Broadhead
Abstract: The Raton Basin, which straddles the Colorado-New Mexico border, is an asymmetric north-south elongated Laramide (Late Cretaceous – Early Tertiary) foreland basin. The deep axis runs north-south through the western half of the basin. On the New Mexico side of the basin, coalbed methane has been produced since 1999 from approximately 800 wells in the shallow Vermejo and Raton formations (Upper Cretaceous to Lower Tertiary). The Pierre and Niobrara shales (Upper Cretaceous) have produced gas from four wells in the New Mexico part of the basin.
The pre-Cretaceous section in the New Mexico side of the basin has been sparsely penetrated by exploratory wells and thus far has not been commercially productive. Test wells have encountered shows of hydrocarbon gases, oil, and carbon dioxide (CO2) gases. Stratigraphic intervals in which reservoirs are associated with petroleum source rocks have yielded shows of hydrocarbon gases and oil. Stratigraphic units that contain reservoirs but that are devoid of petroleum source facies have yielded shows of CO2 gases. The most plausible sources of the CO2 are Tertiary-age magmas that formed the intrusive and extrusive igneous rocks that are present throughout large parts of the Raton Basin.
Pre-Cretaceous reservoir units that are associated with petroleum source rocks are the Morrison Formation and Entrada Sandstone (Jurassic), the lower part of the Sangre de Cristo Formation (Lower Permian to Upper Pennsylvanian), and the pre-Sangre de Cristo Pennsylvanian section. Source rock analyses from the Cretaceous and pre-Cretaceous sections indicate that pre-Cretaceous source rocks are in the oil window on the shallow basin flanks and are in the thermogenic dry gas window in the deeper parts of the basin. These units have yielded shows of oil and hydrocarbon gases in exploratory wells. The potential is for oil and hydrocarbon gases.
Pre-Cretaceous stratigraphic units that are devoid of petroleum source rocks are the Chinle Group and Santa Rosa Sandstone (Triassic), erosional remnants of the Bernal Formation (Upper Permian), the Glorieta Sandstone, Yeso Formation, and the upper part of the Sangre de Cristo Formation (Lower Permian). These strata contain reservoir facies and have yielded CO2 shows in exploratory wells. The potential is for CO2 and not hydrocarbons.
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