Prediction of fracture pressure at coal segment of CBM horizontal wells: with seam No. 3 in Fanzhuang in Qinshui basin as an example

In order to solve the wellbore fracture problems of coal bed methane (CBM) wells, a formula based on the mechanical methods and the maximum normal stress theory for calculating the collapse pressure for the horizontal wells was established to calculate the critical fracturing pressure of the horizontal wellbore. The formula was used to forecast the critical fracturing pressure for the horizontal well in Qinshui Fanzhuang 3^#CBM field. The results show that the drilling fluid density should be controlled within the 3.28 g/cm³ in drilling process of horizontal wells to prevent formation from being pushed open; and the minimum fracture gradient in fracturing horizontal well is 3.22 MPa/hm.