南海西江油田古近系泥页岩地层防塌钻井液技术

Anti-Sloughing Drilling Fluid Technology for the Paleogene Shale Stratum of the Xijiang Oilfield in the South China Sea

张伟国 狄明利 卢运虎 张健 杜宣

ZHANG Weiguo DI Mingli LU Yunhu ZHANG Jian DU Xuan

中海石油（中国）有限公司深圳分公司，广东深圳 518067 中海油田服务股份有限公司，河北三河 065201 油气资源与探测国家重点实验室（中国石油大学（北京）），北京 102249 中国石油大学（北京）石油工程学院，北京 102249

CNOOC China Limited, Shenzhen Branch, Shenzhen, Guangdong, 518067, China China Oilfield Services Limited, Sanhe, Hebei, 065201, China State Key Laboratory of Petroleum Resources and Prospecting (China University of Petroleum (Beijing)), Beijing, 102249, China College of Petroleum Engineering, China University of Petroleum (Beijing), Beijing, 102249, China

为了解决南海西江油田古近系泥页岩地层钻井过程中出现的井下掉块和阻卡等问题，进行了防塌钻井液技术研究。通过地层矿物组分、理化特性和力学参数分析，明确了古近系泥页岩地层井眼失稳机理；建立了维持井壁稳定的钻井液密度与岩石黏聚力关系图版，确定了保持井壁稳定的最低岩石黏聚力；为提高泥页岩经钻井液浸泡后的强度，优选了抑制剂和封堵剂并确定了其加量，得到了新防塌钻井液配方。研究发现，钻井液滤液进入地层引起泥页岩强度降低，是该油田古近系泥页岩地层井眼失稳的主要原因；在KCl–聚合物钻井液中加入2.0%聚铵盐、0.5%纳米二氧化硅和3.0%碳酸钙配成的新防塌钻井液，泥页岩岩样在其中浸泡10 d后黏聚力可达8.8 MPa，满足预计工期内岩石内聚力大于8.7 MPa的要求。研究认为，新防塌钻井液具有较好的抑制性、封堵性和良好的防塌效果，能有效减小井径扩大率，从而解决南海西江油田古近系泥页岩地层钻井中出现的井眼失稳问题。

In order to address the problems of borehole caving, blockage and sticking while drilling the Paleogene shale formation in the Xijiang Oilfield of the South China Sea, technical research has been carried out on anti-sloughing drilling fluids. Through analyses of stratigraphic mineral composition, physicochemical properties and mechanical parameters, the mechanisms of wellbore instability in the Paleogene shale formation have been clarified, and have established the relationship chart between the drilling fluid density required for maintaining wellbore stability and rock cohesion, so as to determine the minimum rock cohesion index required to sustain wellbore stability. In order to improve the strength of surrounding shale immersed in drilling fluid, a new anti-sloughing drilling fluid formula was obtained through selection of proper inhibitor and plugging agent as well as their optimal dosages. The research showed that the intrusion of drilling fluid filtrate would lead to the reduction of shale strength, which is the main reason for the wellbore instability of Paleogene shale formation in this oilfield; After immersing for 10 days in the new anti-sloughing drilling fluid added by 2.0% polyammonium salt, 0.5% nano-silica and 3.0% calcium carbonate into KCl-polymer drilling fluid, the rock sample still has the cohesive force of 8.8 MPa, which satisfies the required rock cohesion of greater than 8.7 MPa in the expected period. According to the comprehensive analysis, the new anti-sloughing drilling fluid featured by good inhibition, plugging and anti-sloughing effect, it can solve the problems encountered during Paleogene shale drilling in the Xijiang Oilfield of the South China Sea, and effectively control the borehole enlargement rate.

国家自然科学基金面上项目“高温高应力盐膏层弯曲井筒围岩失稳机理与控制理论研究”（编号：51774305）、石油化工联合基金（A类）重点支持项目“超深井井筒安全构建工程基础理论与方法”（编号：U1762215）资助

https://doi.org/10.11911/syztjs.2019103