Quantitative analysis of pore genetic types in the Silurian clastic rocks in the Tarim Basin: A case study of the Kepingtage Formation in well Shun9

The identification of pore genetic types in clastic reservoirs affects reservoir prediction. The Silurian reservoirs in the Tarim Basin mainly include primary-secondary composite pores and micro-pores. It is difficult to identify their genetic types by conventional cast thin section observation. A case study was made in the Silurian reservoirs in well Shun9 based on cast thin section observations. Primary pores decrease to a similar extent under compression in formations of similar lithologies buried to similar conditions, resulting in similar residual primary pore contents. We studied the lithologic features and measured porosity of formations with similar burial depths, and quantitatively determined the contents of pores of different genetic types. Primary residual intergranular pores account for less than 4.6% (measured porosity 3.2%-14.6%) in the Silurian reservoirs in well Shun9. Present reservoirs with medium and low porosities were formed due to secondary dissolution, and the reservoirs with high porosities were mainly composed of secondary pores. The quantitative analysis is helpful for the identification of pore genetic types.