--> Reservoir Geology of a Transgressively Filled, Multi-Stage Valley-Fill Complex, Sundance and Edson Gas Fields, Viking Formation, Alberta, by S. A. J. Pattison; #90986 (1994).

Datapages, Inc.Print this page

Abstract: Reservoir Geology of a Transgressively Filled, Multi-Stage Valley-Fill Complex, Sundance and Edson Gas Fields, Viking Formation, Alberta

Simon A. J. Pattison

Valley-fill deposits in the Viking Formation (Albian) of west-central Alberta are located over an area of approximately 2000 sq km (20 township blocks: T51-55, R18W5-21W5) forming a laterally extensive, but thin, valley-fill complex. The Sundance and Edson valley fill complex is 2-15 m thick, and is completely encased by the marine mudstones of the Joli Fou Formation below, and by the Lower Colorado shales above. Four gas fields have been discovered in the valley-fill deposits, with cumulative production approaching 200 Bcf of gas. Over 250 well logs and 37 cores were examined in order to unravel the depositional environments, geological history and reservoir geology of the valley-fill complex. Four distinct facies associations were recognized in the valley-fill; bay head delta sandst nes, estuarine mudstones, transgressively reworked shoreface siltstones and sandstones, and tidal inlet/channel sandstones. The high resolution sequence stratigraphy reveals two distinct episodes of valley filling during stillstands superimposed onto an overall transgression. Both the NE fill and the SW fill show a tripartite facies geometry.

Fine-to medium-grained sandstones of the bay head delta and medium-grained sandstones of the tidal inlet/channel facies associations were identified as the main reservoir sandstones. The tidal inlet/channel sandstones have 15-20 percent porosity, 100-1000 mD of permeability, and a maximum thickness of 15 m. Top, lateral and base seal is provided by facies changes into estuarine mudstones and by the encasing marine mudstones. Four stratigraphically trapped gas fields are thus observed.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994