Coal structure model and fracturing effect of Yanchuannan coalbed gas field

coal structure is the key factor affecting the fracturing effect of coalbed methane well. It is very important to accurately predict the distribution of coal structure and clarify the influence degree of different coal structure combination types on fracturing reform to improve the adaptability of fracturing technology. Based on the core drilling and logging response curve of Yanchuannan coalbed gas field, we established the recognition template of coal structure to recognize and divide the coal structure pattern, and clarified the distribution rules and main control factors of different patterns, as well as analyzed the transformability of different coal structure combination modes. The results show that the coal structure in the gas field can be divided into hard coal and soft coal, vertically, the coal body structure presents the combination mode of “two categories and five types”: single layer structure (single layer hard coal, single layer soft coal), multilayer structure (upper hard coal-lower soft coal, upper soft coal - lower hard coal, upper soft coal-middle hard coal-lower soft coal);The formation of different modes is affected by the structure and deposition, and the distribution on the plane is dominated by single-layer hard coal, single-layer soft coal mainly develops in the northeast and near the central fault zone of the gas field, and other types develop locally near low-order faults. On the whole, the difficulty of fracturing reconstruction is: single layer soft coal > soft and hard coal combination structure coal > single layer hard coal, which is consistent with the law of development effect. When the thickness of hard coal is more than 60% in the soft and hard coal combination structure, the cumulative gas production is better. The differences of the above coal body structure modes lead to limitations of conventional fracturing technology. Based on the difference of the transformation effect of different coal structure modes, targeted fracturing optimization suggestions are put forward to improve the development effect. The research results have a good guiding significance for the optimization of Engineering sweet spot section and fracturing scheme in the later stage of gas field fracturing construction.