Deep Structures and Their Possible Impact on Sediment Deposition and Natural Gas Production, Medicine River Area, West-Central Alberta: Stratigraphic Framework Review, 2005

The Red Deer-Buck Lake area of west-central Alberta has been a prolific producer of conventional oil and gas. In recent years, the focus of exploration has shifted from conventional oil and gas toward drilling for shallow unconventional gas, including coalbed methane. Studies show that deep structures in this area vary greatly, act differently and have a profound impact on sedimentation. Gas production from the Devonian, Mississippian, Jurassic and Cretaceous has a certain relationship with these deep structures. To some degree, the deep structures that influence the formation of coalbed hostrocks may control the distribution of unconventional gas.

Geophysical logs were intensively employed during this study. The picking protocol of the 41 correlation markers is briefly described, and 12 600 new, internally consistent stratigraphic picks, 15 structural cross-sections (elevation as datum) and more than 80 structural and isopach contour maps are provided. The stratigraphic correlation, database management and geological analysis were greatly assisted by advanced software.

The Medicine River area is floored by three northeast-trending Precambrian basement domains. Five large blocks appear to have had slightly different motions during Phanerozoic time. Seven basement lineaments appear to have affected the sedimentary strata. The characteristics of the successions from the Devonian Wabamun top to the Lower Tertiary are described, and the zero edges and subcrop areas of the Mississippian and Jurassic formations are defined.

Huge volumes of natural gas have been produced from Devonian, Mississippian, Jurassic and Cretaceous reservoirs in this area, particularly along the Rimbey Arc, downdip of the Mississippian and Jurassic zero edges, and along intensively fractured belts. The Drumheller, Carbon-Thompson, Ardley and Upper Manville are relatively well developed in the Medicine River area. Prospective areas have been identified for each of the coal zones based on the structure analysis and study of production history.