莺琼盆地钻井井壁稳定性定量风险评价

Quantitative risk assessment of wellbore stability of Yingqiong Basin

黄熠 胜亚楠 管志川 罗鸣 李文拓 邓文彪1

中海石油（中国）有限公司湛江分公司，广东 湛江 524057 中国石油大学（华东）石油工程学院，山东 青岛 266580

Zhanjiang Branch of CNOOC Ltd., Zhanjiang 524057, China School of Petroleum Engineering, China University of Petroleum, Qingdao 266580, China

南海莺琼盆地前期作业实践表明，钻井施工过程中工程风险事件发生概率较高，处理难度大，井壁失稳问题尤其突出，严重制约了安全高效钻井。针对这一问题，文中开展了莺琼盆地钻井井壁稳定性分析：首先，建立井壁稳定性计算模型输入地质力学参数不确定性的量化表征方法，得到地质力学参数概率分布；然后，生成符合各参数概率分布特征的随机数，并将其代入压力当量密度定量计算模型，得到压力当量密度预测结果，进而通过正态信息扩散估计得到地层坍塌及破裂压力当量密度概率分布；最后，基于定量风险评价方法实现对地层井壁稳定性的定量评价与分析。实例分析表明，基于该方法得到的风险评价结果与实际风险发生情况相吻合，说明该方法可进行有效风险预测，有助于保障安全高效钻井作业。

Drilling practice of Yingqiong Basin in the South China Sea shows that the probability of drilling engineering risk is high, and no satisfied treatment has been found already. In order to solve this problem, the quantitative assessment method of wellbore stability is studied. Firstly, a quantitative characterization method of the uncertainty of the geomechanical parameters input in the borehole stability calculation model is established, and the probability distribution of the geomechanical parameters is obtained. Then, based on the Monte Carlo simulation method, the random number which accords with the probability distribution characteristics is substituted into the calculation model to obtain the calculation results of formation fracture and collapse pressure, and the probability distribution of formation collapse and fracture pressure is obtained according to the diffusion estimation of normal information. Finally, based on the quantitative risk assessment method, the quantitative assessment and analysis of formation wellbore stability are realized. The case study shows that the risk assessment results based on this method are consistent with the actual risk occurrence, which indicates that the method established in this paper can predict the risk and help to ensure safe and efficient drilling operations.

10.6056/dkyqt201903024