Erin Anderson
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B.Sc. (Honours) Thesis
(PDF - 86 Mb)
Fluid flow and reservoir quality are affected by lithologic heterogeneities that cause permeability changes in sedimentary successions. Determining the style and timing of cementation within siliciclastic sedimentary outcrops is of paramount importance when addressing the controls on lithologic heterogeneity. This is important in ancient fluvial deposits since they often form aquifers and hydrocarbon reservoirs.
At Rainy Cove (Minas Basin, Nova Scotia), lithological heterogeneity in the siliciclastic sedimentary successions of the Upper Triassic Wolfville Formation is expressed by the preferential erosion and preservation of the coastline. I hypothesize that observed variations in erosion at the study location were a result of differences in cementation texture between sandstone lithofacies. To test my hypothesis, I investigate the lithologic characteristics (measured sections, facies analysis, gamma ray and permeability measurements) and cementation textures (microscopy and cathodoluminescence) in a series of coarse-grained, vertically stacked alluvial and fluvial successions from the Wolfville Formation. The discussion on the cause of lithological heterogeneity can be expanded to address fluid flow and reservoir quality.
Six lithofacies were identified: (F1) matrix-supported clastic breccias from alluvial debris flows, (F2) clast to matrix supported conglomerates, (F3) pebbly to clean sandstones, (F4) silty sandstones, (F5) clays, and (F6) paleosols. All lithofacies are cemented by carbonate with blocky, granular, and dogtooth textures and exhibit dull cathodoluminescence. Cements are interpreted to have precipitated in a burial diagenetic environment. The samples have relatively low permeability, ranging from 32.78 to 276.53 mD. The cements have the same overall characteristics between samples and the observed textures are not limited to any single lithofacies. This suggests that cementation style is not the main control on the differential preservation of outcrop sections at Rainy Cove. Pervasive cementation contributes to the poor reservoir quality of the Wolfville Formation at Rainy Cove.
Keywords:Wolfville Formation, Rainy Cove, Triassic, fluvial braided channel systems, carbonate cementation, reservoir quality.
Pages: 108
Supervisor: Grant Wach