地质条件变化对涪陵页岩气井压裂的影响及对策

Influence of geological condition change on shale gas well fracturing in Fuling and its strategy

由于埋深、构造等地质条件发生改变,页岩气井压裂面临新的问题和挑战。涪陵区块平面及纵向上地质力学条件、深度和构造位置等变化,给水平井分段压裂工艺实施及压后效果带来一系列影响。文中分析总结本区域储层地质条件的具体变化,评估了各因素变化对压裂改造的影响,特别是埋深增加、复杂构造环境等对压裂工艺实施的综合影响;明确了由于深度、构造等变化,导致地应力、闭合应力及内聚力增加。另外,岩石塑性破坏影响,使得净压力消耗增加、有效净压力降低、剪切区面积减小、人工裂缝带层理剪切区域扩展受限,进而可能影响储层有效改造体积及压后效果。最后从分段分簇、压裂配套材料及泵注程序等方面提出了页岩气井压裂工艺参数优化的总体策略和具体方向。

Because of the change of the geological conditions such as the buried depth and geological structure, the hydraulic fracturing for shale-gas wells is facing new problems and challenges. The change of geological mechanics condition, depth and structure position of the Fuling Block both in the plane and vertical directions has brought about a series of effects on the fracturing technique for horizontal well. Analyzing and summarizing the specific change of reservoir geological conditions, the influence of various factors on the fracturing transformation is evaluated, especially the influence of the buried depth and complex structure environment on the fracturing process. Due to the depth and structure changes, there is a significant increase in in-situ stress, closure stress and cohesion. The plasticity damage of rock results in the net pressure consumption increase, the effective net pressure reduction, shear area decrease, and limited bedding shear zone expansion of hydraulic fracture, which may affect the storage layer effective transformation volume and pressure effect. The overall strategy and the specific direction of optimizing fracturing techniques for shale-gas wells are presented from the following aspects, the cluster space, the matching material of fracturing, and the pumping program.