Depositional Modelling of the Upper Mannville (Lower Cretaceous), East-Central Alberta: Implications for the Recognition of Brackish Water Deposits
Published:January 01, 1988
Daryl M. Wightman, S. George Pemberton, Chaitanya Singh, 1988. "Depositional Modelling of the Upper Mannville (Lower Cretaceous), East-Central Alberta: Implications for the Recognition of Brackish Water Deposits", Reservoir Sedimentology, Roderick W. Tillman, K. J. Weber
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Thick (15 to 35 m, 49 to 115 ft) sandstones in the upper Mannville (Aptian to early Albian) in east central Alberta have several genetic origins. In the western part of the study area, thick sandstones have formed by the stacking of fluvial channel deposits. The variable thickness and irregular distribution of the sandstones on cross sections support the presence of multiple paleochannels. Oil saturation and reservoir pressure data corroborate this interpretation in the Hairy Hill area.
In the eastern part of the study area, sandstones of similar thickness have formed by an amalgamation of channel and marine shoreline facies and by the stacking of crevasse splay deposits in brackish water bays. Ichnological and palynological data confirm that the upper Mannville becomes more marine in the eastern part of the study area. It is concluded that during upper Mannville time, the streams in the west were flowing into a marine embayment which lay to the east.
Brackish water deposits have predictive value, as they signal the change from continental to marine sedimentation. Based on the upper Mannville, several criteria have been proposed for the interpretation of these environments in core. The presence of syneresis cracks, pyrite and siderite and a limited assemblage of certain trace fossils and marine microplankton together indicate a marginal marine setting. These criteria are complementary and represent a multidisciplinary approach which the authors advocate for the recognition of paleoenvironments.
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This volume is a collection of papers which focus on the sedimentology of siliciclastic sandstone and carbonate reservoirs. The papers were selected to show how detailed sedimentologic descriptions, when combined with engineering or other subsurface geologic techniques, yield reservoir models which may be used for reservoir management during field development and during secondary or tertiary enhanced oil recovery. In all the papers the framework for the field descriptions relies heavily of full-diameter cores. In addition to conventional 4-inch-diameter cores, frozen and rubber-sleeve cores were utilized in one or more of the studies. In addition to cores, at least one other geologic or engineering technique is integrated into each study. This integration of sedimentologic descriptions with other techniques gives rise to synergism.