A Historical Perspective of Anadarko's CBNG Exploration and Development Success in the Rocky Mountain Region

Brad Miller and Steve Ruhl. Anadarko Petroleum, P.O. Box 1330, Houston, TX 77251-1330, phone: 832 636 8743, [email protected]

Anadarko Petroleum has been actively exploring and developing coal bed reservoirs in the Rocky Mountain region for the last 15 years. Their current production is 110 MMCFPD from 700 operated wells. Exploration efforts on Cretaceous marine and Tertiary intermountane deltaic depositional settings have yielded two geologic play types with economic success from coal reservoirs. The Cretaceous play type is represented by the Helper and Clawson areas in the southwestern Uinta basin of central Utah. These areas were identified in the early 1990s and are in a mature stage of development. They are characterized as multiple high gas content bituminous coal seams ranging from thickness of 1 to 20' thick and distributed over a gross interval of 300 feet. These reservoirs are generally at depths of the 2000 from 4500' and require fracture stimulation with initial per well water production ranging 50 to 400 BWPD.

The second play type is represented by the County Line Field, consisting of the Big Mike and Big George Federal Units located in the central Powder River Basin of Wyoming. These areas were identified in the mid- 90's and currently under field development. This play type is characterized by low gas content sub-bituminous coal seam with thicknesses exceeding 100' at average depths of 1100'. Wells are completed open-hole with common water rates of 700 to 1200 BWPD. Critical to these play types are strategies for managing produced water. Various methods such as under ground injection, surface impoundments, irrigation utilization and aquifer recharge are employed in the Anadarko projects.