The principal objective of this project was to determine the influence of diagenetic and structural features at the reservoir/caprock interface on transmission of CO2 into and through the caprock. The study focused mainly on the influence of deformation structures and fractures on fluid flow. The project team investigated interfaces in three different reservoir/seal pairs. The first stage of the project involved a brief field campaign to perform basic descriptions of the interfaces and conduct detailed sampling. The second stage involved laboratory analysis of the samples to describe their petrographic, geochemical, mechanical, and petrophysical properties. Finally, the descriptive information acquired in the first two steps was used as input data for a detailed coupled thermal hydrologic mechanical chemical modeling investigation of the implication for transmission across the storage zone/caprock interface. Some of the findings of this study are that differences in permeability at the reservoir-caprock interface caused by deformation bands and fractures have a large impact on fluid flow and that seals have the capacity to store large quantities of CO2 if permeable fractures terminate below the top of the seal.
This project helps to improve monitoring capabilities by using information obtained from rock outcroppings and core samples of proposed CO2 clastic formations and overlying mudstone confining zones to determine the characteristics of the interface zone. This is contributing to better storage technology thus reducing CO2 emissions to the atmosphere. Specifically, the project is using these data to develop conceptual models of the behavior of formation-confining zone interfaces and, in particular, sandstone/mudstone contacts.
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