Paper: Update on Operations Of the Sheep Mountain CO2 Unit

ARCO Oil and Gas Company started producing the nation's first large-scale natural carbon dioxide (C02) reservoir on January 31, 1983, from the Sheep Mountain Unit located in Huerfano County, Colorado. With the installation of a 330 MMCFD capacity pipeline, completed in January 1983, this CO2 has become an important source for future enhanced recovery projects in the West Texas area. This paper describes the Sheep Mountain reservoir, including a geological history, and the current theories for CO2 creation and migration in the Dakota and Entrada formations. A comparison of CO2 fluid properties to hydrocarbon fluid properties is presented, followed by a discussion of the producing characteristics of the wells and the conditioning processes employed before the CO2 is placed in the pipeline. An account of the problems encountered since start up and the resulting or proposed solutions is also included.