基于可靠度理论的井壁稳定性定量评价方法

非常规深层油气资源勘探开发是目前的热点，由于钻井地质环境复杂、井壁稳定性差，导致钻井复杂及故障频发，严重制约了油气资源勘探的安全高效开发。针对该问题，本文开展了相关研究，建立了一种井壁稳定性定量评价方法。首先分析和完善了现有地层坍塌及破裂压力计算模型；在此基础之上，建立了地层坍塌及破裂压力不确定性定量表征方法；同时，综合考虑高温高压环境、井径不规则、排量不稳定等不确定性因素对ECD计算结果的影响，基于不确定度理论建立了ECD不确定性定量表征方法；在上述两方面研究的基础上，建立了定量评估井壁稳定性的分析模型，解决了井壁失稳的识别难题，实现了井壁稳定性的定量评价，可以有效降低井下复杂发生率、提高钻井效率、缩短钻井周期，为钻井施工降本提速提供技术支持。

Quantitative evaluation method of wellbore stability based on reliability theory

The exploration and development of unconventional deep oil and gas resources is a hot spot at present. The complex drilling geological environment and poor wellbore stability lead to frequent drilling faults, which seriously restricts the safe and efficient development of oil and gas resources exploration. To solve this problem, a quantitative evaluation method of wellbore stability is established in this paper. Firstly, the existing calculation models of formation collapse and fracture pressure are analyzed and improved. On this basis, the quantitative characterization method of uncertainty of formation collapse and fracture pressure is established. At the same time, considering the influence of uncertain factors such as high temperature and high pressure environment, irregular well diameter and unstable displacement on ECD calculation results, a quantitative characterization method of ECD uncertainty is established based on uncertainty theory. On the basis of the above two aspects, the analysis model for quantitative evaluation of wellbore stability is established, the identification problem of wellbore instability is solved, and the quantitative evaluation of wellbore stability is realized, which can effectively reduce the incidence of downhole complexity, improve drilling efficiency, shorten drilling cycle, and provide technical support for cost reduction and speed-up of drilling construction.