页岩储层射孔水平井分段压裂的起裂压力

目前，页岩储层水力压裂裂缝起裂和扩展机理研究已成为国内外水力压裂研究领域的重要课题，射孔水平井分段压裂技术是其高效开发的主要手段。针对目前部分裂缝起裂压力模型在计算射孔水平井横向裂缝起裂时破裂压力过低、严重偏离实际的问题，基于Hossain模型和Fallahzadeh模型，建立了新的水平井射孔孔道表面的应力分布模型；同时开展了水平井分段压裂的诱导应力分布研究和不同压裂工艺条件下复合地应力的分析；进而针对页岩储层的岩性特征，建立了考虑诱导应力条件下，页岩储层射孔水平井水力压裂在岩石本体起裂、沿天然裂缝剪切破裂和沿天然裂缝张性起裂3种方式下的起裂压力计算模型，提出了页岩储层水力裂缝起裂方式和起裂压力的判别方法。该成果对于页岩储层水力压裂裂缝起裂机理的研究和现场应用具有一定的指导意义。

Initiation pressure of multi stage fracking for perforated horizontal wells of shale gas reservoirs

Fracture initiation and propagation of hydraulic fracturing treatment stimulation of shale gas reservoirs has become a focus in this research field globally. Currently, multi stage fracking for perforated horizontal wells is a major technology in improving the fracking efficiency. However, when some existing initiation pressure models are used to calculate the transverse fracture initiation of perforated horizontal wells, the initiation pressure is excessively low and seriously deviates from the actual value. To solve this problem, we took the models developed by Hossain and Fallahzadeh as the basis, and built a new model of the stress distribution on the wall of perforation tunnel in horizontal wells. In addition, we studied the induced stress distribution of multi stage fracking for horizontal wells, and analyzed the composite geostress under different fracking conditions. Furthermore, based on the shale reservoir lithology and considering the induced stress, we built the model of calculating the initiation pressure for three initiation modes in the hydraulic fracturing of perforated horizontal wells in shale formations, respectively the initiations in rock as well as the shear and tension initiation along natural fractures. In addition, we put forward the method for distinguishing the initiation mode and pressure of hydraulic fracturing for shale reservoirs. This achievement is of guiding significance to both the research of initiation mechanism and the field application of hydraulic fracture treatment in shale reservoirs.