ABSTRACT: Diagenetic Features in Basal Sands of the Upper Mississippian Kiskatinaw Formation, Alberta
KIRKLAND, IAN K., and IAN E. HUTCHEON, University of Calgary, Calgary, Alberta, Canada
Examination of drill cores and thin sections in a 4660 sq. kilometers area adjacent to the north- and east-trending erosional edge indicates that reservoir quality in Kiskatinaw basal sands has been strongly controlled by diagenetic processes.
Numerous macroscopic diagenetic features are observable in cores. Early diagenetic features include pyrite and siderite nodules that commonly have laminations draped over them, pyritized burrows, and branches or woody material whose interiors were rotted out and infilled by anhydrite. Tight streaks in more porous sands and in deeper sands farther from the subcrop edge are pervasively cemented by early anhydrite cement with minus-cement porosities up to 40%. Anhydrite also occurs in the cores of some siderite nodules.
Shale clasts in the Kiskatinaw are unstable and most have been illitized; many have been impinged upon or progressively altered, in
During burial diagenesis, dissolution of the extensive early anhydrite cement occurred, commonly leaving behind remnant blebs of anhydrite, giving the rocks a mottled appearance. Stylolites are common in the basal sands, but usually appear to be only crinkled shale laminations, representing insignificant rock volume loss through pressure solution. Liesegang bands are an additional interesting burial diagenetic feature.
In the Detloff gas field diagenesis appears to have been limited by residual oil/bitumen, as only small amounts of later cements have reduced porosity created by anhydrite dissolution. Bacteria sulphate reduction is occurring in the transition zone of the Josephine field resulting in reservoir destruction and extensive pyrite and clay mineral formation.
AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)