Research on the Calculation Method of Wall Fracture Pressure in the Horizontal Section of Horizontal Wells Along Coal Seam
For the prediction of wellbore fracture pressure in horizontal section of coalbed methane horizontal well along coal seam,the influence of wellbore orientation and well deviation has not been considered,and there is a large gap between the actual fracture pressure of the formation.In this paper,the force of the wellbore of coalbed methane horizontal well is analyzed.Due to the influence of coal seam cutting and bedding,the hydraulic fracture is mainly tensile fracture.Therefore,combined with the maximum tensile stress criterion,and the parameters of coal reservoir formation pressure,the hypothesis method and the elimination method are used to comprehensively analyze.Based on the constraints of vertical principal stress,maximum horizontal principal stress,minimum horizontal principal stress,reservoir pressure,rock tensile strength,rock Poisson's ratio,effective stress coefficient of coal measures,horizontal well orientation and well circumferential angle,the prediction model of wellbore fracture pressure of horizontal well along coal seam is established.and it is applied to the design of fracturing pump injection program of X-03 horizontal well group in Gaoping mining area.The accuracy of the model is 92.80%,the overall sand addition rate of horizontal section is 110%,and the daily gas production is over 10000 m3.
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