Mostly gas is produced in the Piceance basin of western Colorado. The basin, containing about 4,000 square miles, is well defined by the Tertiary-Cretaceous outcrop contact beyond which are the surrounding elevated areas. The basin is in the early stages of development with a density of only one well for every 19 square miles. The lack of pipeline outlet prior to 1956 resulted in slow development, but now three pipelines serve the area, and drilling activity has been at an accelerated pace. Of the total wells drilled, approximately one half are capable of producing gas from the Tertiary and Upper Cretaceous rocks. Owing to the thickness of the section (22,000 feet to the basement), only eight wells have tested the pre-Upper Cretaceous section.
Most accumulations of gas are due to stratigraphic traps. The paucity of subsurface data is the cause for the present disagreement among geologists on the stratigraphy and geologic history. Tentative correlations from the outcrops on the periphery of the basin are carried across the basin, particularly of the Mesaverde and upper Mancos beds, with a discussion of how the depositional history complicates the problem. The development history, which includes the identification of the multiple gas-producing zones, indicates that this basin will become one of the important gas-producing areas of the Rocky Mountains.
Figures & Tables
The first article in this book is the address that introduced the technical program of the 46th Annual Meeting of the AAPG. The organization and presentation of this symposium volume was developed in an orderly geographic continuity. Modern concepts of structural form and the sequence of tectonic events are carefully reported all along the mountainous western margins of the American continents. The relationship of this structural knowledge to the accumulation of oil and gas is constantly emphasized in the 26 papers contained herein.