The Prediction Model And Evaluation Of Hydraulical Fracture Of High Rank Coal Reservoirs

China is one of the most abundant coal bed methane reserves, there are the worst mine gas disasters at the same time. There was a complex tectonic evolution history in main coal-bearing basins of china. There are complex structures of the coal seams with poor permeability. The full swing of the China's coal-bed methane resources of commercial development has been serious impacted, so developing scientific research work of the coalbed methane development technology in the major coal-bearing basins in china is necessary. Hydraulic fracturing technology of the coal-bed methane is technology migration of hydraulic fracturing in the oil and gas field. It is the most economical and the most widely used measure of the coal reservoirs'enhanced transformation. However, given the special conditions of coal reservoirs, the technology also needs to be further improved.The Zhengzhuang and FanZhuang blocks in the south of the QinShui basin are the target areas for studying in this paper. on the basis of reservoir properties and the systematic analysis of coal-forming geological conditions, the rupture and extension mechanism of hydraulic fracturing cracks within the coal under the conditions of hydraulic fracturing of had been analyzed, the theory of a variety of disciplines that were coal bed methane geology, rock mechanics, hydraulic fracturing, numerical simulation had been applied in the paper. The multi-fracturing cracks mathematical models are constructed under the conditions of the high rank coal reservoirs of coal bed methane wells. The region of the fracturing effects and extraction parameters of coal-bed methane wells have been evaluated through the model.Major research results include:1) The fractures'morphologies of vertical wells which had been through fracturing mainly are vertical cracks associated with T-fracture;2) The Poisson's ratio of the high rank coal seam in the study area is higher than surround rocks'. It goes against controlling the crack propagation. Variation range of the filtration in coal bed is greater than oil reservoir. There is high filtration loss in the coal bed. Filtration occurs mainly at the macro fissures.3) The multi-fracturing cracks mathematical models for the study area are constructed.4) The suitable length of the fracture is between 135m~155m, the width is 0.018m, and the optimal value of pump displacement should be controlled between the 6m3 and 8m3.