Dolomitisation of the Lower-Middle Ordovician Yingshan Formation in the Tazhong area, Tarim Basin, western China

The origin of heterogeneous sucrosic dolomite reservoir of the lower Permian Qixia Formation, NW Sichuan Basin, China

“…The exploration of the Lower Permian Qixia Formation in the NW Sichuan Basin, a large superimposed petroliferous basin in SW China, has revealed a kind of unique heterogeneous sucrosic dolomite. This kind of dolomite is characterized by coexistence of medium-and coarse-grained sucrosic dolomites with varied textures and physical properties, different from the characteristics of heterogeneous sucrosic dolomite reported in previous literatures (Bai et al, 2016;Choquette and Hiatt, 2008;Gaswirth et al, 2007;Giorgioni et al, 2016), and being worthy of basic scientific research. In addition, this kind of heterogeneous sucrosic dolomite is interpreted to be a good reservoir, and its buried depth can reach over 7000 m, with a maximum test production capacity of more than 1 million m 3 /d and a high-yield commercial gas flow of more than 100 × 10 4 m 3 (Shen et al 2015;Xiao et al, 2020a).…”

“…The massive homogeneous dolomite is the most ubiquitous sucrosic dolomite ever reported, and it is characterized by relatively uniform texture and grain size, and accordingly homogeneous physical properties (e.g., porosity and permeability). By the contrast, the heterogeneous dolomite has long been highly controversial for its genetic mechanism and reservoir-forming mechanism due to the heterogeneity (Bai et al, 2016;Choquette and Hiatt, 2008;Gaswirth et al, 2007;Giorgioni et al, 2016). The genetic mechanism mainly includes the heterogeneous composition and texture of original limestone ( Giorgioni et al, 2016;Iannace et al, 2011Iannace et al, , 2014, the heterogeneous dolomitization and cementation caused by complex diagenetic fluids (Choquette and Hiatt, 2008;Gaswirth et al, 2007), and the heterogeneous dissolution and precipitate filling (Bai et al, 2016;Jiang et al, 2016;Zhu et al, 2015).…”

“…By the contrast, the heterogeneous dolomite has long been highly controversial for its genetic mechanism and reservoir-forming mechanism due to the heterogeneity (Bai et al, 2016;Choquette and Hiatt, 2008;Gaswirth et al, 2007;Giorgioni et al, 2016). The genetic mechanism mainly includes the heterogeneous composition and texture of original limestone ( Giorgioni et al, 2016;Iannace et al, 2011Iannace et al, , 2014, the heterogeneous dolomitization and cementation caused by complex diagenetic fluids (Choquette and Hiatt, 2008;Gaswirth et al, 2007), and the heterogeneous dissolution and precipitate filling (Bai et al, 2016;Jiang et al, 2016;Zhu et al, 2015). The reservoir-forming mechanism is also diverse, including hydrothermal fluid (Liu et al, 2017), meteoric water (Bai et al, 2016), hydrocarbon-bearing fluids in the burial stage (Zhu et al, 2015), and thermochemical sulfate reduction (TSR) (Jiang et al, 2016).…”