Logging Evaluation of Coalbed Methane Reservoir and Perforation Interval Optimization

At present, the development of medium and high-rank coalbed methane (hereinafter referred to as CBM) has not yet achieved large scale benefits. One of the main reasons is that the CBM reservoirs have not been effectively stimulated. Therefore, fine logging evaluation of coal stratum and the optimization of adaptive engineering technologies for them are particularly important for increasing single well production. This paper conducts a comprehensive logging evaluation of coal stratum in Hancheng Block, such as source rock quality, reservoir quality and fracturability. Based on the adaptability analysis of engineering technologies, this paper has proposed two major methods for stimulating CBM reservoirs in Hancheng block. Since sandstone is easier to fracture than coalbed, when the lithology of the roof and floor is argillaceous sandstones and has low water content and the thickness of the intermediate mudstone interlayer is less than 1 m, the indirect fracturing method with the perforating interval across the coal bed and the roof and floor is preferred. On the contrary, high-quality coal bed perforation intervals are optimized and the “direct fracturing” method is adopted. The field practice results of more than 20 wells in Hancheng block show that the CBM production of a single well has been increased by more than 50% using this perforation stimulation method for CBM reservoirs.