Numerical Simulation Of Asymmetric Vertical Cracks And Analysis Of Pressure Drop After Pressure

Because of the complex geological structure and low permeability of coal seam,it must be transformed by hydraulic fracture to achieve the high field.In the process of fracturing and production,the formation probability of asymmetric vertical cracks is very big.In order to achieve the increasing producion purpose of the coalbed methane well,it is necessary to bulid the targeted and the whole simulation technology of asymmetric vertical cracks.According to the asymmetric vertical cracks,this paper uses the model and the pressure decline analysis technology to solve the crack geometry parameters.The principal results are as follows:(1)It utilizes the monitering means of fracture such as microseisms and potentiometry to show the objective existence of asymmetric vertical cracks.Starting from the formation mechanism of hydraulic fracturing cracks,considering the geological structure features of coal seam,this paper discusses the reason of asymmetric vertical cracks,the stress formula is given when the initiation location of fracture is not ideally.(2)Based on the digestion and absorption of the model of the conventional vertical cracks,considering the characteristics of the asymmetric vertical cracks,this paper analyzes and gives all kinds of net stress formula,establishes the simulation models of a single wing,wings,even as many vertical cracks in the first time and designs the corresponding numerical algorithm of the models.(3)Based on the pseudo 3 dimension model of the conventional vertical cracks,combined with flow distribution equation,establishes the pressure decline analysis of post-fracturing models of a single wing,wings,even as many vertical cracks,introducing mathematical fitting method to calculate the fitting pressure and gives the corresponding numerical algorithm of the models.(4)Against the above models,this paper gives the correspoding software and it is applied in the field.We compare the calculation results which are caculated by the above models with the results retained by microseisms monitering,the simulation results are satisfied with the need of the engineering.The simulation results of the above models are compared with each other,complement and perfected each other mutually,it forms a complete simulation technology of asymmetric vertical crack fracture.