Is Fluid Flow in Paleozoic Formations Affected by the Rocky Mountain Thrust Belt, West Central Alberta?

P. Kent Wilkinson

The hydraulic influence that a thrust belt may have on basinal formation-fluid flow is not well understood. The hydraulic nature of such a structural zone has important exploratory implications in the adjacent foothills and plains regions. In order to develop an appreciation of the nature of hydrocarbon migration and distribution in the vicinity of a major thrust belt, fluid potentials within the Cordillera and associated sedimentary basins must be identified to determine if hydraulic communication exists between the two regions. Work completed to date in the West Central region of Alberta has indicated several significant flow features within Paleozoic Formations East of the disturbed zone. Ongoing work is attempting to determine the relationship, if any, between these f atures and the adjoining thrust belt.

Potentiometric and water chemical analyses from Paleozoic aquifers combined with geological data have indicated areas of preferential and restricted flow. Upward flow through vertical hydraulic conduits can be identified between the Leduc and overlying Nisku Formations based on the location of a Leduc potentiometric minimum. This potentiometric low coincides with a relative thinning of the intervening Ireton shale aquitard. Similarly, greater hydraulic gradients and two separate pressure-depth profiles combined with an increase in Ireton shale thickness suggest two Leduc reef platform areas where hydraulic communication and fluid flow are restricted. Preliminary mapping within the Cordillera suggests that fluids within the basinal sediments are partially sourced from both the Foothill and Thrust Belt regions. Therefore, it appears that the Thrust Belt region has some influence on regional flow features within the basinal Paleozoic formations.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995