致密砂岩水平井组同步压裂过程中诱导应力场变化规律

水平井组同步压裂过程中多井多裂缝导致的诱导应力对压裂设计、复杂裂缝的形成有重要影响，但目前对诱导应力场变化规律的研究相对较少。为此，建立了双井多缝诱导应力场数学模型，并利用线性叠加原理和矢量表征方法，得到了不同裂缝参数及井距时两井中间位置处诱导应力场的变化规律。研究发现，布缝方式、裂缝宽度、裂缝长度和井距对诱导应力场的影响程度各不相同:诱导应力场对裂缝长度与井距的变化最为敏感；相邻两井中间位置处产生的诱导应力最大，井筒井壁位置产生的应力最小，欲使压裂裂缝转向形成复杂裂缝系统，需要布缝方式、裂缝长度、裂缝宽度与井距相互匹配。大牛地气田DP43井组现场井下微地震监测结果证实了上述研究成果，从而也解释了水平井组拉链式布缝同步压裂可以获得高产的原因。水平井组诱导应力场变化规律的清楚认识，为致密砂岩水平井组合理设置井距与优化压裂设计方案提供了依据。 

The Principle of Induced Stress Change Caused by Multi-Wells and Multi-Fractures during Synchronous Fracturing of Cluster Horizontal Wells in Tight Sandstone Gas Reservoirs

During synchronous fracturing of horizontal well clusterd, the induced stresses generated by multiple wells and fractures may significantly affect fracturing design and the formation of complex fractures. Few studies have been conducted related to patterns of changes in induced stress fields. In the study that concerns itself with this topic, the mathematic model for the horizontal stress field between wells was constructed. By using linear superposition and vector representation, patterns of changes in induced stress fields between two wells at different fracture parameters and well spacing were highlighted. Research results demonstrated variable impact based on factors on induced stress field. To be more specific, the induced stress fields were extremely sensitive to changes in fracture lengths and well spacing. The maximum induced stress could be observed at the central point between two neighboring wells, whereas the minimum stress could be observed at the sidewalls. To divert fractures to generate complicated fracture systems, it was necessary to establish suitable matching among fracturing techniques, fracture length, width and well spacing. Underground micro-seismic monitoring results in Daniudi DP43 well cluster verified accuracy of above research results. In addition, these results might also provide an acceptable explanation for the high productivity of synchronous fracturing operations in zippered fractures of horizontal well clusters. Generally speaking, a clear understanding of changes in induced stress fields in horizontal clusters might provide a reliable foundation for the determination of optimal well spacing and a fracturing program for horizontal well clusters to develop tight sandstone formations.