松南气田泥岩井壁失稳形式及失稳机制的微观数字化分析  

Micro Digital Analysis on Instability Form and Mechanism of Mudstone Borehole Wall in Songnan Gas Field

作　　者：石秉忠 张栋 褚奇 SHI Bingzhong;ZHANG Dong;CHU Qi(Sinopec Research Institute of Petroleum Engineering Co.Ltd.,Beijing,102206,China)

机构地区：[1]中石化石油工程技术研究院有限公司,北京102206

出　　处：《石油钻探技术》2023年第1期22-33,共12页Petroleum Drilling Techniques

基　　金：中国石化基础前瞻项目“基于微观分析的钻井液对岩石作用机理研究”(编号:P20047-1)资助。

摘　　要：针对松辽盆地松南气田青山口组、泉头组和登娄库组泥岩井壁失稳的问题,运用高精度CT扫描数字化成像技术建立了数字岩样,并应用岩石微观结构数字图像数值分析方法提取物性参数,通过综合对比不同地层泥岩矿物组成、理化性能,以及泥岩经蒸馏水、不同钻井液处理剂溶液和现场钻井液浸泡后内部微观结构损伤变化等,揭示了泥岩井壁失稳的形式及其机制。3组泥岩岩样黏土矿物含量平均达到34.56%,且以伊/蒙混层、伊利石为主,均具有较强的毛细管自吸水化作用;因组构特征不同,水化损伤微观裂变扩展、裂变过程及其破裂模式与程度存在明显差异;裂变扩展过程决定了次生裂缝的走势与强度,从而决定了泥岩地层井壁宏观上的失稳形式主要是片状剥离和掉块坍塌;不同测试液抑制泥岩水化的作用机理不同,其效果存在明显差异,预防泥岩水化的关键是有效控制或阻缓水分子侵入。分析结果表明,采用数字化成像分析技术进行井壁稳定性评价时,在岩样微观结构损伤的直观刻画、定量描述及对比分析等方面具有明显优势;泥岩地层井壁失稳形式及失稳机制的揭示,为松南气田钻井液处理剂的优选和钻井液配方的优化提供了科学依据。The Qingshankou Formation,Quantou Formation,and Denglouku Formation of Songnan Gas Field in Songliao Basin have unstable mudstone borehole walls.Considering this problem,the digital rock samples were established by high-precision CT scanning-based digital imaging technology,and the physical properties of the samples were extracted by numerical analysis of the digital rock microstructure image.A comprehensive comparative analysis was conducted in terms of the mudstone mineral composition,and physical and chemical properties of formations,as well as the microstructure damage variations in the rock samples caused by the physical and chemical actions when they were soaked in distilled water,solutions of different drilling fluid additives,and on-site drilling fluids.In this way,the instability forms and mechanisms of mudstone borehole walls were revealed.The results demonstrated that for the mudstone samples from the three formations,the content of clay minerals reached 34.56%on average,and they were mainly composed of mixed illite/smectite and illite,which all had strong hydration of spontaneous capillary imbibition.Due to different fabric characteristics,there was a great difference in the micro-fission expansion,fission process,and fracture mode and degree of hydration damage.The fission expansion process determined the trend and strength of secondary fractures,which further decided the macroscopic instability forms of mudstone borehole walls were mainly sheet stripping and falling block collapse.The mechanisms of various test fluids inhibiting the hydration of mudstone differed,and their effects also demonstrated significant differences.Hence,effectively controlling or inhibiting the intrusion of water molecules was the key to preventing the hydration of mudstone.The analysis suggests that the digital imaging analysis technology has great advantages in evaluating borehole wall instability regarding the intuitive characterization,quantitative description,and comparative analysis of the microstructure damage to the

关 键 词：泥岩 井壁失稳 微观结构 水化作用 CT扫描 松南气田 

分 类 号：TE21[石油与天然气工程—油气井工程]