Reserch On CBM Reservoir Multi-pulse Fracturing Mechanism And Technology

Coal-bed methane(CBM) is one of the world’s most reliable alternative energy besides coal, petroleum and natural gas, of which the United States, Canada and other countries have realized commercial development and utilization. The rational development of CBM has great significance in energy strategy for China because of its rich coal-bed gas resources. However, the technological development of CBM is still in the experimental stage, is not only because the domestic coal-bed features low saturation, permeability and pressure with complicated coal-bed reservoir structure, but also the reservoir reconstruction technology based on Hydraulic fracturing can not fully meet the requirements of development. Thus, this paper focus on CBM reservoir multi-pulse fracturing mechanism and corresponding technologies.This paper, based on the pilot test of High Energy Gas Fracturing in CBM development and the analysis of coal-bed characteristics., elaborates the study of fracture length conducted by multi-pulse fracturing, energy utilization rate of fracturing charge, rock mechanics parameters of coal-bed and multi-pulse fracturing technology via the case study of Qinshui, Zhengzhuang block.According to the establishment and analysis of CBM multi-pulse fracturing length calculation model, we can obtain that the larger the amount of fracturing charge. the longer the time of gas energy roling in the formation, the longer the fracture within the range of reasonable peak pressure. Through the research and analysis of computing model of fracturing charge energy efficiency, we can acquire, in the shallow coal-bed methane, that using totally enclosed fracturing well head and multi-stage loading structure can effectively reduce the loss of energy of work done on the liquid column and effectively improve the energy efficiency of fracturing charge that produce longer and more crack formation systemAccording to the referring to the measured date of longitudinal wave and shear wave time of coal seam, the model of coal seam shear wave time was built through liner empirical formula method, the undetermined coefficient method and Critensen prediction method. Afterwards, the model was optimized by comparative analysis and error analysis methods. The formula of rock mechanics of coal seam was modified by the optimized model and the stress of coal seam was obtained by the hydraulic fracturing method. The above researches lay a foundation for the layer of CBM multi-pulse fracturing and selection of the fracturing parameters.Based on the study of CBM multi-pulse fracturing mechanism, the multistage control device, the time-lapse ignition control device and charge structure were studied and the technology process of CBM reservoir totally enclosed multi-pulse fracturing was designed. This technology was applied to the construction site and the effect was evaluated after construction. This technology provides a new way for CBM development in China.