Oil and gas exploration in the Raton Basin
— William R. Speer

The history of exploration for oil and gas in the Raton Basin has been cyclical and is currently in a relatively quiescent stage. The Raton Basin has long been considered one of the better frontier areas for petroleum exploration in the Rocky Mountains. Yet at the present time it is the only major Laramide-aged structural and stratigraphic basin in the Rockies that does not have commercial production. It has great thick-nesses of organic-rich marine shales to serve as source beds for petroleum generation. These beds overlie, underlie and inter-finger with massive sandstones of beach and nearshore origin that could serve as reservoir beds. These sands are in turn interbedded with coastal plain, paludal, estuarine and lagoonal sediments with both source and reservoir potential. The geological history of marine transgression and regression which deposited this rock sequence is an integral part of the same Late Cretaceous sequence which produced the majority of oil and gas accumulations in the Rocky Mountains. The deeper Mesozoic and Paleozoic possibilities can be only speculative, as the subsurface control within the confines of the deeper Basin is limited to the data provided by only thirteen tests which penetrated below the Jurassic beds.

The geologic factors point primarily toward stratigraphic entrapment, but there are also structural possibilities. All of the obvious structural features have been drilled, but in several cases cannot be said to have been adequately tested. In addi tion limited drilling has suggested less obvious structural con-trols which will become apparent when the drilling density is increased. This low drilling density is probably the single most important reason why there is no production in the Raton Basin today. There are approximately 2,150 mi within the area of the Raton Basin as defined by the Trinidad Sandstone outcrop-1,194 in Colorado and 956 in New Mexico (Fig. 1). All of the recorded holes penetrating at least to the Cretaceous Trinidad Sandstone within the same area number less than 100. This figure includes a substantial number of coal exploration holes which are clustered in limited areas. Utilizing these figures, the drilling density is about one test per 20 mi, an extremely low density compared to other productive Rocky Mountain basins.

This paper discusses the structure and stratigraphy of the Raton Basin, its drilling history and problems associated with the drilling, and the potential of some of the more favorable stratigraphic horizons.