The influence of sedimentary rock fabrics on subsurface fluid flow: origin of quartz cement distribution in sandstones

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The proposed research aims to investigate the influence of the structures in sedimentary rocks on fluid flow. Sedimentary rocks are not regular masses of grains or crystals. Instead, they are heterogeneous, containing a variety of structures at multiple scales, including the microscopic alignment of grains and cm- to metre-scale layers, making-up the fabric of rocks. The geometry of fluid-filled pore spaces in between the grains is similarly heterogeneous, and therefore fluids within the rocks will not flow equally in all directions. As an example, fluid flow across sedimentary layers is typically less than flow along layers, but it is not always clear why this is so. The pore and grain fabric is described quantitatively by applying microscope image analysis and statistical techniques to sections of rock that are oriented in various directions. Flow measurements in these directions are also made, and the quality of flow, or permeability of the rock, can then be related to the rock fabric. The focus will be on sandstones that are cemented to varying degrees by quartz that crystallizes around grains, filling formerly open pores in the process. Since that pore space could otherwise be occupied by fluids (oil, gas, water), the distribution of quartz cement is of great interest to build conceptual and applied models of subsurface fluid reservoirs. This research is of fundamental importance to learn more about the controls on fluid flow in the subsurface, such as the flow of water through aquifer layers, the migration through sedimentary rocks of mineral-rich solutions, or how oil and gas is transported in hydrocarbon reservoirs. Quartz cement in particular is considered to be the most effective cement replacing pore space in sandstone hydrocarbon reservoirs (including many oil&gas fields in Canada), and increased understanding of its distribution is directly applicable to improve the utilization and management of these resources.