Analysis on characteristics and influence factors of transitional facies shale pore in Ningwu basin

In order to study the pore characteristics and influence factors of transitional facies shale in Shanxi Formation of Ningwu basin, the shale in Shanxi Formation was systematically sampled to carry out the SEM analysis, low temperature nitrogen adsorption experiment, TOC content test, maturity(R_max) test, the whole rock mineral X diffraction analysis and porosity test, then the pore types, pore characteristics and influencing factors are discussed. The results show that pores in transitional shale of Shanxi Formation mainly consist of intergranular pores, intercrystalline pores, organic matter pores, organic matter primary pores and dissolution pores and fractures. The pore radius is primarily between 2 nm to 50 nm, and the shapes of the pores inclue open-wedge pores, parallel-plate pores, conical tube pores, ink bottle pores, etc. The average porosity of the shale is 3.64%, the average pore radius is 7.78 nm, the average BET surface area is 11.70 m²/g, and the average total pore volume is 0.0222 cm³/g, indicating a strong storage and adsorption. The shale pores have obvious fractal characteristics,and the fractal dimension is 2.61~2.77,which is positively correlated with the percentage of micropore volume; the shale pore development is influenced by TOC content, maturity(R_max) and mineral composition.