Evaluation of Fracturing Effects and Analysis of Key Influences in Coal Bed Methane Reservoirs Based on Grey Correlation Theory

C6 reservoir in the Ordos Basin is mainly composed of medium fine-grained arkose with a burial depth of 1500–2000 m. The pore structure of reservoir space is complex, the throat is fine and the sorting is poor. The average permeability of the reservoir is 0.01–100.00 mD, and the porosity is generally less than 19%. It is a low permeability reservoir. Based on the geological and engineering parameters of the reconstructed well and the post-fracturing effect data, the influence degree and law of geological and engineering parameters on the fracturing effect are comprehensively analyzed by using the method of grey correlation theory. A multi-factor analysis model combining the status and trends of system development with information utility is developed to explore the weights of fracturing parameters that affect hydrocarbon productivity after fracturing. The analysis using a single method lacks determination of each applicability, and the results obtained often deviate from the actual project. In our study, firstly, the grey-correlation method model and entropy-method model are established to get two kinds of weights. Secondly, two types of weights are merged into a combined weight. Eventually, the in-situ data of 100 horizontal wells in the C6 formation of the Q block are substituted into the model. And the primary and secondary relationships of the influential factors are clarified according to the result. The correlation and influence degree between each influencing factor and fracturing effect are clarified. Taking the Block C reservoir in the Q block as an example, the fracturing design parameters are optimized, and further clarify the influencing factors and laws of the C6 horizon reconstruction effect in Block C, B, E, D, A, and other blocks of the Q block, which is based on grey correlation theory and method. It provides a reference and guiding method for the optimization of well fracturing design in this block.