基于水化损伤的硬脆性泥页岩应力分布研究  

Study on Stress Distribution of Hard and Brittle Shale Based on Hydration Damage

作　　者：谢涛 刘海龙 张晓诚 张磊 窦蓬 Xie Tao;Liu Hailong;Zhang Xiaocheng;Zhang Lei;Dou Peng(Tianjin Branch,CNOOC(China)Limited,Tianjin 300452,China)

机构地区：[1]中海石油(中国)有限公司天津分公司,天津300452

出　　处：《石油工业技术监督》2021年第12期50-54,共5页Technology Supervision in Petroleum Industry

摘　　要：引入了考虑水化作用的弹性模量损伤张量,基于硬脆性泥页岩考虑水化损伤作用时井眼周围的应力-应变本构关系,结合数值或解析方法求解了非均匀应力条件下硬脆性泥岩的井周应力分布规律。以渤中某油田X井为例进行井周水化应力分布及坍塌压力分析。计算发现:钻开100 h后,水化损伤造成的地层刚度下降明显,井壁失稳首先发生在井壁内部,在最小地应力方位坍塌风险更大;水化膨胀性能对应力分布影响程度有限,仅在井壁附近对切向应力有微弱影响;硬脆性泥页岩的坍塌主要与水化损伤导致的岩石刚度性能下降和岩石强度参数劣化有关;该井段坍塌周期较短,井径扩大率最大为6.5%,现场使用钻井液密度偏小,建议加强钻井液封堵性的前提下适当提高钻井液密度。该模型一定程度上揭示了硬脆性泥页岩的水化坍塌机理,为类似地层安全高效钻进提供了理论依据。The elastic modulus damage tensor considering hydration is introduced. Based on the stress-strain constitutive relation of hard brittle shale around borehole considering hydration damage, the stress distribution law of hard brittle shale around borehole under non-uniform stress condition is solved by numerical method combined with analytical calculation. The distribution of hydration stress and collapse pressure around the well X in Bozhong oilfield are analyzed. It is shown that: After drilling for 100 hours, the decrease of formation stiffness caused by hydration damage is obvious. The wellbore instability first occurs inside the wellbore, and the risk of collapse is greater in the minimum in-situ stress direction. The effect of hydration expansion of shale on the stress distribution is limited,and the tangential stress is only slightly affected near the wellbore. The collapse of hard brittle shale is mainly related to the decrease of rock stiffness and the deterioration of rock strength parameters caused by hydration damage. The collapse period of this well section is short, and the maximum diameter expansion rate is 6.5%. The density of drilling fluid used on site is small. It is suggested that the density of drilling fluid should be appropriately increased on the premise of strengthening the plugging ability of drilling fluid. The model reveals the hydration collapse mechanism of hard brittle shale to a certain extent, and provides a theoretical basis for safe and efficient drilling in similar formations.

关 键 词：硬脆性泥页岩 水化损伤 弹性模量 本构关系 应力分布 

分 类 号：TE52[石油与天然气工程—油气田开发工程]