Abstract:

Taking the south Qinshui basin as researching area and the 3# coal bed as the researching target, a geological model of this area was set up on the base of the characteristics of the field stress and the triaxial stress test results of coal samples from Sihe coal mine in Jincheng. Using finite element software ANSYS as the platform, this research simulated the changing law that the geological factors including ground stress and Youngs modulus of coal reservoirs influence on the initiation pressure and propagation of the fracture. The results show that the initiation pressure keeps constant when the maximum horizontal principal stress changes, but increases with the minimum horizontal principal stress increasing, and the variation range is between 10 MPa and 25 MPa. The maximum fracture length and the maximum fracture width keep unchanged with the increasing of the maximum horizontal principal stress, but decrease with the rising of the minimum horizontal principal stress and Youngs modulus. The maximum fracture length has the highest probability to range between 36 m and 83 m. The results coincide well with the field data. This achievement would provide a reference for hydrofracturing design of coalbed methane well in south Qinshui basin.

Key words: hydraulic fracturing, numerical simulation, Youngs modulus, ground stress, south Qinshui basin