多分层煤层压裂起裂压力及起裂位置研究

Analysis on fracturing and initiation pressure and initiation location in multi slicing seam

针对重庆松藻矿区煤层分层多、埋深和倾角变化大,导致煤层压裂参数选择和抽采钻孔布置存在盲目性的问题,采用最大拉应力理论的断裂失效准则,通过理论分析建立了多分层煤层压裂的起裂压力计算模型,并就倾角和埋深对煤层压裂起裂压力和起裂位置影响规律进行试验研究。结果表明:煤层压裂的起裂压力在埋深相同时均不随煤层倾角的改变而改变,而在倾角相同时与煤层埋深呈线性增加关系,与理论计算的起裂压力随煤层倾角和埋深的变化规律相一致。多分层煤层压裂起裂位置均位于软分层中,近水平煤层中形成网状裂缝,无明显主裂缝存在,随倾角增大,倾斜煤层中易形成明显主裂缝,主裂缝周围网状裂缝逐渐减少。

According to multi slicing of the seam,deep depth and high varied inclination in Chongqing Songzao Mining Area,there were a blindness problem existed in the selection of the seam fracturing parameters and the layout of the coalbed methane boreholes. The broken failure criterion of the maximum tensile stress theory was applied to establish a model to calculate the initial pressure of the fracturing pressure for the multi slicing seam with the theoretical analysis. An experiment Analysis was conducted on the inclination and deep depth affected to the seam fracture initiation pressure and the initiation location. The results showed that when at a same depth,the initiation pressure of the seam fracturing would not be changed with the inclination changed. When at a same inclination,the initiation pressure of the seam fracturing would be in a linear increased relation to the seam depth and would be same to the theoretical calculated initiation pressure with the variation law of the seam inclination and depth. The initiation location of the multi slicing seam fracturing would be in a soft slice.Net type cracks would be formed in the horizontal seam and there were no obvious major crack existed. With the inclination increased,there would be obvious major cracks formed in the inclined seam and the net type cracks around the major cracks would be steadily reduced.