| dc.description.abstract | In order to achieve the goal for geological storage of CO2, important assessment factors for reservoir rocks include not only suitable geological structure, thickness and depth, but also high porosity and permeability. This study is aimed to determine porosity and permeability, mineral compositions and pore structures of reservoir sandstones by using porosity/permeability measurement, thin section and SEM analysis. Characteristics and influencing factors of porosity and permeability of reservoir sandstones in Miaoli area were studied, so as to evaluate their storage potential for CO2 sequestration. Samples from seven different sandstone formations in Miaoli area were collected, including Beiliao Sandstone, Kuanyinshan Sandstone, Tongkeng Formation, Shangfuchi Sandstone, Guandaoshan Sandstone, Yutengping Sandstone and Cholan Formation. According to the analytic results, Shangfuchi Sandstone exhibits the highest porosity (20.8%) and permeability (3.0E-13m2) under 5 MPa confining pressure as well as the largest quartz content, grain size and pore size. In addition, Tongkeng Formation stands the second place in porosity (14.8%) and permeability (3.4E-15m2) under 5 MPa confining pressure. Overall, porosity and permeability were influenced not only by burial depth, but also by mineral composition, grain fabric and diagenetic processes. Increased burial depth usually leads to increased compaction as well as decreased porosity and permeability. Furthermore, mineral composition, grain size, shape, and packing influence the connectivity and size of pores and fractures, and then the porosity and permeability. Compaction and cementation could reduce porosity and permeability, but dissolution could increase them. Primary and secondary porosity of reservoir rocks were affected during different stages of diagenetic processes.
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