利用测井资料预测水平井压裂裂缝形态

Predicting the Shape of Hydraulic Fracture of Shale Gas Horizontal Well in Sichuan with Log Data

水平井压裂裂缝形态复杂,预测难度较大。建立水平井压裂裂缝起裂数学模型;考虑水平井井周裂缝应力和流体的实际状态,根据断裂力学理论给出水平井井周裂缝尖端的应力强度因子的计算方法,按照Irwin延伸扩展准则判断裂缝是否延伸,遍历计算起裂点及其扩展点并不断迭代求解直至满足约束条件,建立裂缝延伸扩展数学模型;提出了用测井资料预测压裂裂缝长、宽、高的方法,建立用测井资料预测水平井压裂裂缝形态的方法。针对四川页岩气水平井,研究了用测井资料计算岩石力学参数和地应力方法,对四川页岩气水平井H1-3井压裂裂缝形态进行了预测,预测结果与微地震监测结果进行对比,表明水平井H1-3井预测结果能够反映近井周围压裂裂缝的延伸情况。

The shape of hydraulic fracture in horizontal well is complex and its prediction is difficult, so, first, the mathematics model for initiation of hydraulic fractures is established. Second, the calculation method for stress intensity factor of horizontal wellbore fracture tip accounting for horizontal wellbore fracture stress and the actual state of fluid is given based on fracture mechanics theory, and whether the fracture is expanded or not is judged according to Irwin＇s expansion criteria, the initiation point and expansion point is calculated by ergodic way until the constraint condition is satisfied, thus fracture expansion model is established. Third, the method of predicting length and width ＆ height of the hydraulic fracture based on the logging data is established. Finally the method of predicting the shape of hydraulic fracture in horizontal well is established. The method calculating rock mechanical parameters and in-situ stress of shale gas horizontal wells in Sichuan with log data is studied, the shape of hydraulic fracture for shale gas horizontal well H1-3 in Sichuan is predicted, the predicted result is compared with the Micro Seismic Monitoring result, comparison shows predicted result of horizontal well H1-3 can reflect the expansion behavior of hydraulic fracture near wellbore.