The complex geological conditions of drilling, the difficulty of formation collapse and fracture pressure prediction in South Sichuan work area lead to the complex drilling and frequent failure, which seriously restricts the safe and efficient development of shale gas. In view of this problem, this paper has carried out relevant research. First of all, the existing calculation model of formation collapse and fracture pressure is established and improved; on this basis, the sources of uncertainty in the calculation model of collapse and fracture pressure are analyzed, mainly the in-situ stress and rock mechanics parameters, which have a lot of uncertainties; then, the uncertainty of rock mechanics parameters and in-situ stress is analyzed, and its probability is determined. Finally, based on Monte Carlo simulation, the quantitative characterization method of formation collapse and fracture pressure uncertainty is established. The prediction result of collapse and fracture pressure is no longer a single curve or value, but an interval, which is more practical for drilling in complex geological environment. The results of this study are helpful to better describe the collapse and fracture pressure of complex formation and can provide more valuable reference data for drilling design.

川南工作区钻井地质条件复杂，地层塌陷困​​难，裂缝压力预测困难，导致钻井复杂，频繁失败，严重制约了页岩气安全高效开发。针对这一问题，本文进行了相关研究。首先，建立并完善了现有的地层垮塌和压裂计算模型。在此基础上，分析了倒塌和裂缝压力计算模型中的不确定性来源，主要是原地应力和岩石力学参数，具有很大的不确定性。然后，分析了岩石力学参数和地应力的不确定性，并确定了其可能性。最后，基于蒙特卡洛模拟，建立了地层垮塌和压裂压力不确定度的定量表征方法。塌陷和断裂压力的预测结果不再是单一的曲线或值，而是一个区间，对于复杂地质环境下的钻进更为实用。这项研究的结果有助于更好地描述复杂地层的坍塌和破裂压力，并可以为钻探设计提供更多有价值的参考数据。