Fine characterization of the reservoir space in deep ultra-low porosity and ultra-low permeability glutenite in Bozhong Sag

With the application of automatic mineral quantitative identification system (QEMSCAN), modular automated processing system (MPAS), multi-scale micro CT, thin section identification, constant-rate mercury injection and other experimental techniques, the reservoir space in deep ultra-low porosity and ultra-low permeability glutenite of Kongdian Formation in the Bozhong Sag were characterized in two and three dimensions, and the influencing factors of the permeability of glutenite reservoir were studied in detail. The experimental results show that the glutenite in the study area has millimeter, micron and nanometer pores. For the samples with relatively large porosity, there are relatively more interparticle pores and interparticle dissolution pores in the reservoir. On the basis of the three-dimensional pore-throat network model, the most part of the pore radius ranges from 0.3 to 10 μm and the roar channel radius mainly ranges from 0.5 to 8.0 μm. The pore-throat distribution is mainly three forms: banded, contiguous and isolated. The pore throats of reservoirs with good reservoir properties are mostly continuous in three-dimensional space, and the reservoirs with relatively poor permeability contain more isolated large pores. The fluid mobility of porous reservoir is closely related to throat radius, pore-throat shape, coordination number and other parameters. Fractures improve the physical properties of glutenite obviously, and also provide a channel for the acid solution to the reservoir and promotes the formation of dissolution pores. Comprehensive study showed that the fluid flow of the glutenite in the Bozhong Sag is controlled by the fracture and the pore-throat connectivity. The cementation of clay and carbonate minerals in the reservoir has an important influence on the pore structure and permeability.