The Transitional Facies Mud/Shale Pore Characteristics And Controlling Factors

In order to research the characteristics and controlling factors of the transitional facies shale nanopore, on the basis of core logging and analysis of sedimentary environment, samples from drilling cores of Taiyuan, Shanxi, and Xiashihezi Formation were collected to perform a series of experiments, including the X ray diffraction, FESEM, nitrogen adsorption desorption experiment and related chemical geochemistry experiment. The black mud / shale had developed mainly in lagoon facies, mud flat facies, delta phase, interdistributary bay microfacies, distributary depressions microfacies.The TOC value of coal measure shale is 2.47% in the study area, which is rich in organic clay and shale. But the reflectance of the mirror is slightly lower(0.58-1.37%), the average is 0.95%, and the whole is in the middle mature stage. Mineral components with quartz(average 36.3%,) and clay minerals(average 55.8%) mainly. Clay minerals are mainly illite smectite mixed layer(mean 45.9%) and kaolinite(37.7% on average). Illite has an increasing trend with the depth of the buried. Clay mineral composition characteristic response study area coal measure clay/shale is in the middle diagenetic stage A stage. Most of these pores are open in style and mainly consist of the V wedge pores with two ends open,parallel-plate pores with four sides open and ink bottle shaped hole. The main pore size range is located in 3-7 nm, 10-45 nm, 50-270 nm, The most development of micro pores in 3-7nm. The micropores of which diameters are 3-7 nm dominate the main pore specific surface.Most of the pore volume is occupied by the pores which are 3-7 nm in size.The main pore types are Intergranular pore of clay mineral, Pyrite intergranular pore, Clay minerals and intergranular pore of brittle minerals, and a small amount of internal hole. Organic matter pore is not very developed.There is a certain degree of positive correlation between content of quartz and the pore volume in each stage of the hole. In the composition of clay minerals illite smectite mixed layer on the stage of three main aperture hole has a positive contribution. The content of kaolinite and the pore showed negative correlation. Influence of TOC content on the pore characteristics is not obvious.It is because the organic shale maturity is not high, not enough to make a lot of organic hole development. The characteristics of pore development are affected by the hydrodynamic conditions, except for 42 and 54. With the weakening of hydrodynamic force, the pore volume of 3-7nm becomes larger. 10-45 nm phase pore volume becomes smaller. The sedimentary environment affects the pore development of the reservoir, and the water power condition of the reservoir can also influence the pore characteristics of the mud and shale.