纹层状泥灰质陆相页岩压裂裂缝扩展机理研究

Investigation on the Hydraulic Fracture Propagation Mechanism of Lime-Clay Lamina in Continental Shale

纹层状岩心水平层理呈现密度大,胶结强度小的特点,在水力压裂过程中,弱胶结层理容易“捕获”压裂裂缝,使其沿层理面扩展,从而增大裂缝带宽,但会限制裂缝在缝高方向上扩展。裂缝相对简单时,压力曲线呈现出较为平稳的形态。在裂缝相对复杂时,压力曲线表现出较为明显的波动,水平应力差越小,声发射事件数增加,剪切裂缝占比增加,裂缝相对更复杂。

The horizontal bedding of the lamellar cores has the characteristics of high density and low cementation strength. In the process of hydraulic fracturing, weakly cemented bedding is easy to “capture” the fracturing fracture, so that it expands along the bedding plane, thereby increasing the fracture bandwidth. But it will limit the crack propagation in the direction of the fracture height. When the fracture is relatively simple, the pressure curve shows a relatively stable shape. When the fractures are relatively complex, the pressure curve shows obvious fluctuations. The smaller the horizontal stress difference is, the more acoustic emission events are. The proportion of shear fractures increases and the fractures are relatively more complex.