Fractal characteristic of microscopic pore structure of tight sandstone reservoirs in Kalpintag Formation in Shuntuoguole area,Tarim Basin

Using the fractal geometry method,the microscopic pore structures of tight sandstone reservoirs in Kalpintag Formation of Shuntuoguole area in Tarim Basin were conducted fractal characterization on the base of test analysis data such as physical property,cast thin section,scanning electron microscope and mercury injection,and the genetic mechanism of pore structure heterogeneity was investigated.The storage spaces are dominated by intergranular dissolved pore,intragranular dissolved pore and residual intergranular pore,and the throat type consists of the necking throat,lamellar throat,curved lamellar throat and tube-shaped throat.The microscopic structure type includes Type Ⅰ(fractal dimension≤2.350),Type Ⅱ(2.350<fractal dimension<2.580),Type Ⅲ(fractal dimension>2.580)and fracture type.The most favorable reservoirs with Type-Ⅰ microscopic pore structure are mainly distributed in the Upper Member of Kalpintag Formation,while the reservoirs with Type-Ⅱ and Type-Ⅲ microscopic pore structures are mainly in the Lower Member of Kalpintag Formation.The sedimentation controls the heterogeneity of microscopic pore structure,and the differences on composition and particle size of sandstone lead to differentiation of microscopic pore structures.The Lower Member of the Kalpintag Formation experiences stronger compaction and cementation but weaker dissolution than the Upper Member of the Kalpingtag Formation,and thus the microscopic pore structure of Upper Member of the Kalpintag Formation is significantly worse that of the Lower Member o the Kalpingtag Formation.The Upper Member of the Kalpintag Formation with high content of brittle mineral develops microscopic fractures due to tectonic rupture,thus the permeability is improved and the heterogeneity of microscopic pore structures is enhanced;but the Lower Member of Kalpintag Formation is characterized by attrition crushing of particles and strong compaction.

Reservoir characteristics of Donghe well No.1 in Tarim Basin

Based on the techniques of X-ray diffraction analysis, identification of the thin sections of core cast, phys- ical analysis and scanning electron microscopy analysis, this paper studied the reservoir characteristics of the Carboniferous strata in Donghe well No.1 of Tarim region. The results show that the reservoir lithology is mainly the fine-grained quartz sandstone with ferrocalcite and pyrite, mud cement-based, the permeability concentrated in 5-40 × 10-3 μm2, a small part of the high permeability up to 150-327 ×10-3 μm2 and porosity ranged from 10% to 20%. The most part of the reservoirs is low perme- ability with a small part of the layer in moderate-high permeability. The types of reservoir space include intergranular pores, intra particle-molding pores, micro-pores and cracks, which mainly are intergranular pores with the pore diameter of 15-200 μm, 95.5μm on average. And the types of the throats are comolex with the main tvne of constricted l：hroats in this area and large contribution to the permeability.