ABSTRACT: Hydrogeological Trapping Model of the Milk River Gas Field

LIES, HENNING K., Hydro Petroleum Canada Ltd., Calgary, Alberta, Canada

The Milk River gas field is the largest single gas accumulation in the Western Canadian Sedimentary Basin, with recoverable reserves estimated at 5 tcf. This hydrodynamically trapped gas field positioned on the Sweet Grass Arch covers over 140 townships and has no updip structural closure.

A steady-state, finite-element, numerical fluid flow model covering an area of 24 by 24 townships (Townships 1-24, Range 24W3-19W4M) was constructed. The three-dimensional water flow from the Belly River to Bow Island was modeled. The primary input data included structure, formation thickness, and aquifer permeabilities. The permeabilities of the aquitards were varied until a good match was obtained with observed water potentials.

The resulting potentiometric surface of the Milk River Formation was combined with the structure, using the UVZ method, and the gross pay of the Milk River gas field was determined. Because the gas pool interfered with the water flow, the model was rerun to account for the changes in the aquifer and aquitard permeabilities resulting from the presence of the gas.

The model demonstrated that adequate modeling of an aquifer requires that a minimum of three layers be included and that aquitard permeabilities be determined. In addition, the presence of large hydrocarbon pools will alter the water flow and thus need to be accounted for.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)