Reservoir space types and their controlling factors in ultra-deep sandstones: A case of Bashijiqike Formation in Kelasu Belt of Kuqa Depression, Tarim Basin, NW China

As a result of complex diagenetic evolution, a reservoir with extremely low porosity and low permeability has been formed in the ultra-deep sandstones of Bashijiqike Formation of Cretaceous in Kelasu belt of Kuqa depression,... [ view full abstract ]

As a result of complex diagenetic evolution, a reservoir with extremely low porosity and low permeability has been formed in the ultra-deep sandstones of Bashijiqike Formation of Cretaceous in Kelasu belt of Kuqa depression, Tarim Basin, NW China. It would be very useful to the research on the origin and distribution of good reservoir to analysis the origin and controlling factors of pores and fissures. Based on the identification of many cast slice and fluorometric slice, and using field emission scanning electron microscope and confocal microscope, eight types of pores and two kinds of fissures in the sandstone reservoir of Bashijiqike Formation, which we believed is a kind of pore reservoir, have been identified according to its shape, scale and origin. It was mainly dominated by primary pores, which is a result of complex geological process as follows: (1) it was shallow buried for a long time in earlier stage, so there is not present a porosity-decreasing effect during weak compaction; (2) the earlier cements could save some primary intergranular volumes; (3) the porosity-decreasing effect of tectonic compression is more than that of created fissures; (4) the secondary pores formed by later dissolution is the main factors which increased the reservoir spaces