A physical model of outburst elimination boundary after hydraulic fracturing in coal-bed methane well

In order to forecast hydraulic fracturing range and define effective outburst elimination boundary,the meth- ods of ground stress simulation technology,micro seismic real-time monitoring data and gas drainage parameters analy- sis were applied to build the physical models of fracture extending & hydraulic fracturing boundary and to determine different dangerous regions on rhombus well pattern by analyzing the control range of hydraulic fracturing,fracture mor- phology and stress distribution before and after hydraulic fracturing in single coal-bed methane wells with low permea- bility coal reservoir at Luan mining area. The results showed that the fracturing area of single hydraulic well was similar to an elliptical shape;the main fracture extended along the direction of the maximum horizontal principal stress;the fracturing area was divided into five boundaries including laying sand zone,final desorption zone,fracture zone,pene- tration zone and gas surge zone;the stress value around fracturing zone along σH and σh raised about 19% and 7% , and stress value in fracturing zone declined about 15. 5% and 9. 5% ;the boundary physical model of hydraulic fractu- ring was consistent with the results of ground stress simulation. In a standard gas drainage operation,the boundary of effective outburst elimination which was smaller than fracturing boundary was consistent with the laying boundary of proppant. Outside of effective outburst elimination boundary may exist outburst dangerous area, but inside of the boundary,rhombus well pattern by 200 m by 125 m arrangement is better for the mine gas prevention and control of the corresponding area.