Geological modeling-based productivity response characteristics of the CBM well in Baode unitⅠ

Coalbed methane resource conditions and reservoir physical conditions are the basis of CBM exploration and exploitation. The geological modeling of CBM reservoir was carried out to clarify the spatial distribution of coal reservoir, and explain the difference of single well productivity, which can provide theoretical basis for selection and well drilling. This paper took Baode unit I as research object. Based on the measured data of gas content and well test permeability, the inversion model of gas content and permeability in the study area was established by using support vector machine algorithm(SVM) and transformed F-S permeability calculation formula, and the gas content and permeability logging interpretation of 162 CBM wells were completed. Furthermore, the modeling of gas content and permeability were established by using stochastic modeling method. The modeling results show that the gas content of coal seam 4+5 was 2.0-5.2 m³/t, averaging 3.3 m³/t, the gas content of coal seam 8+9 was 2.4-9.2 m³/t, averaging 5.1 m³/t; the permeability of coal seam 4+5 was (0.8-9.8)×10^-3 μm², averaging 6.1×10^-3 μm², the permeability of coal seam 8+9 was (2.8-11)×10^-3 μm², averaging 7.3×10^-3 μm². In general, it is a CBM development unit with low gas content, high permeability. Planar distribution characteristics of equivalent gas content, resource abundance, and adsorption saturation of coal reservoir in study area were analyzed based on the established geological model. Then, the geological conditions of two typical wells(B1-X1 and B1-X2) were compared and analyzed, the results show that the parameters of well B1-X1 were better than those of well B1-X2. From the cross-well section and the production curve, it can be seen that the productivity difference between two wells mainly includes two aspects: one is resource condition, the gas content and resource abundance of well B1-X1 are better than those of well B1-X2, and the low adsorption saturation in well B1-X2 makes gas desorption more difficult. On the other hand, it is reservoir physical conditions. The permeability of well B1-X1 is better than that of well B1-X2, which is beneficial to the seepage of coalbed methane and forms a high yield. Among them, the difference in permeability is a key parameter that affects CBM exploitation, and CBM resource abundance and adsorption saturation are important factors for evaluating CBM wells to maintain high and long-term stable production.