Study on coal-rock microstructure and it’s relationship with fracturing fluid design

In order to more intuitively and quantitatively analyze the microstructure of coal-rock,the design of the fracturing fluid is guided through the understanding of the microstructure to improve the efficiency of the fracturing fluid and reduce the damage of coal reservoir.In this paper,microstructural analysis methods，such as microphotometer,scanning electron microscopy,and CT are used to establish coal structure fracture diagrams with different dimensions and angles,and to quantitatively analyze fracture parameters.Based on microscopic photometer,scanning electron microscope and CT:the main crack length and main crack width of different blocks of coal samples are very different;cleats have obvious isotropy and are prone to cracks in communication;the distribution of cracks is complex,making the cracks sensitive to complex stress profiles and changing stress field during fracturing;cracks have anisotropy and heterogeneity,increasing the chance of fracturing fluid damage.Quantitative analysis shows that:the coal samples in different blocks have different compositions.The different compositions of the coal samples come from different geological functions.At the same time,they also lead to different fluids effects.The CT software can calculate the porosity and permeability of the tested samples statistically.The porosity of sample is 2.68% and the permeability is 6.65×10-3 μm2.It is similar to the porosity-permeability experimental structure and confirms the remarkable characteristics of low permeability and low permeability in coal seams.Wetting and sorption experiments and other data prove that different coal structures and components are the causes of different fracturing fluids’ performance.Intuitive structural micrographs and quantitative data analysis can guide the research direction of fracturing fluids for fracturing fluids and provide the basis for fracturing fluid design.