低渗透油藏水平井压裂理论及现场工艺探讨

水平井井筒应力分布和岩石破坏准则构成了水平井压裂裂缝起裂数学模型,利用迭代法对模型进行了求解.分析表明,井筒方位角不同,最小水平主应力和垂直主应力对裂缝的起裂压力影响规律不同,在井筒方位角为0时最不容易起裂,而在井筒方位角为90°时最容易起裂.现有的裂缝延伸模型中,全三维裂缝延伸模型计算结果与Fracpro-PT软件计算结果具有很好的一致性,适合水平井压裂裂缝延伸模拟,裂缝间距较长时,多条裂缝延伸模型可以在考虑裂缝之间干扰的基础上结合单裂缝延伸模型建立.现场多条裂缝压裂可以总结为限流法压裂和分段压裂两种,限流法施工相对简单,改造强度相对较小,分段压裂改造强度大,但工具设备和工艺要求高,现场水平井压裂作业时应根据现场情况选择合适的压裂工艺.图4表1参14

Horizontal well fracturing technology for reservoirs with low permeability

The horizontal well stress distribution and the rock failure criterion constitute a fracture initiation mathematical model, which was solved by the iteration method. Minimum horizontal principal stress and vertical principal stress have different influences on the fracture initiation pressure when the horizontal well orientation angle is different: the fracture is least likely to initiate when the angle is 0 and is easiest to initiate when the angle is 90°. The simulation result of 3-D hydraulic fractures propagation model matches well with the Fracpro-PT software, and it is suitable to simulate horizontal well fractures propagation. If the fracture interval is long, a multi-fracture propagation model could be built taking into account of the fractures interaction and the single fracture propagation model. Field horizontal well fracturing technology can be summarized as limited entry treatment and staged fracturing treatment, the limited entry treatment is simple with smaller reformation intensity; the staged fracturing treatment has higher reformation intensity but requires advanced facilities. The fracturing technology should be chosen according to the field situation.