基于岩石力学特性的钻井液优选研究——以鄂尔多斯盆地长7页岩地层为例  

Optimization of drilling fluid based on rock mechanics characteristics——by taking the Chang 7 shale formation in the Ordos Basin as an example

作　　者：余海棠[1] 庄严[2] 梁利喜[2] 丁乙[2] YU Haitang;ZHUANG Yan;LIANG Lixi;DING Yi(Yanchang Oilfield Co.,Ltd.,Yan’an 716000,Shaanxi,China;State Key Laboratory of Oil&Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu 610500,Sichuan,China)

机构地区：[1]延长油田股份有限公司,陕西延安716000 [2]西南石油大学油气藏地质及开发工程国家重点实验室,四川成都610500

出　　处：《石油地质与工程》2023年第5期109-114,119,共7页Petroleum Geology and Engineering

摘　　要：钻井液稳定井壁性能是决定页岩地层能否安全高效钻进的基础,常规评价方法主要针对钻井液化学性能,但页岩井壁垮塌的本质是力学失稳。基于此,通过硬度、抗压强度等多项岩石力学参数对钻井液进行优选,与常规钻井液性能评价方法相比,本方法可实现钻井液保持页岩力学强度及井壁稳定性的量化评价,更具有现场应用价值。钻井液与页岩接触,水相介质进入页岩,与内部黏土发生水化作用,导致页岩硬度与抗压强度均出现明显下降,造成井壁失稳;同时,钻井液作用48 h后的页岩地层坍塌压力当量密度增加了0.43 g/cm^(3),增加了井壁失稳的可能性,使安全密度窗口大幅变窄,不利于安全钻进。通过对比优化后的钻井液对目标页岩地层硬度、抗压强度和坍塌压力的影响程度,优选出具有良好效果的钻井液体系,为研究区及其他地区同类地层的钻井液优选提供依据。The ability of maintaining wellbore stability of drilling fluid is the basis for safe and efficient drilling.Conventional evaluation methods mainly focus on chemical properties of drilling fluid,but the essence of shale wellbore collapse is mechanical instability.Therefore,the drilling fluid is optimized through rock mechanics parameters such as hardness and compressive strength.Compared with conventional evaluation methods on drilling fluid performance,this method is able to achieve quantitative evaluation of shale mechanical strength and wellbore stability,with more on-site application value.After the interaction between drilling fluid and shale,aqueous phase enters into shale,contacting with clay mineral and causing hydration.As a result,shale hardness and compressive strength both show clear decline,leading to wellbore instability.Meanwhile,after 48 hours contacting with drilling fluid,collapse pressure in shale formation increases by 0.43 g/cm^(3),increasing the possibility of wellbore instability and reducing the safe density window,which is no good for drilling.By comparing the impact of the optimized drilling fluid on the hardness,compressive strength,and collapse pressure of the target shale formation,a drilling fluid system with good performance is selected,which can provide a basis for the optimization of drilling fluid of similar formations in the study area and other areas.

关 键 词：页岩 岩石力学 坍塌压力 钻井液 

分 类 号：TE254[石油与天然气工程—油气井工程]