Evolution of pore space in tight sandstone: The roles of dissolution, calcite cementation, and clay growth

Pore space transforms through mineral precipitation and dissolution, providing insights into the dynamic changes in the pore structure of rocks over time. In this paper, we quantified the levels in the diagenetic alteration of tight sandstone in the Qingshankou Formation from the Upper Cretaceous in the Songliao Basin and illustrated the evolutionary processes of pore type and pore size distribution, along with porosity and permeability, with dissolution, calcite cementation, and clay growth. More important, we investigated the microscopic observation and pore size distribution of sandstone exhibiting varying levels of dissolution, calcite cementation, and clay growth and found that mineral precipitation and dissolution were inhibited in pores < 1 mm in diameter. This phenomenon may be attributed to fluid migration between sandstone and the adjacent shale. Instead of observing the preferential precipitation of minerals above and dissolution below the critical pore size, as the interfacial energy effect suggests, we anticipate that fluid from the adjacent shale preferentially migrates to the relatively large pore throat system of the sandstone, leading to mineral precipitation or dissolution. Moreover, we verify that porosity varies linearly and permeability varies as a power function with the diagenetic alteration levels. This study links the state of diagenetic alteration and pore structure of sandstones, which provides the possibility for reservoir evaluation in the geological history period.