分级堵漏技术在鄂尔多斯盆地东部的应用

为了解决鄂尔多斯盆地东部刘家沟组-石千峰组地层的井漏问题，通过扫描电镜分析岩心样品、X衍射分析岩屑样品和对区域地质资料的研究，发现高含伊利石和绿泥石、低含高岭土和蒙脱石的刚性地层遇水失稳和网状缝发育是引起该区井漏严重和堵漏困难的主要原因。从抑制裂缝壁遇水失稳和用含不同直径刚性颗粒的桥塞型复合堵漏剂封堵不同宽度裂缝的思路出发，通过实验室优化和室内模拟实验，形成了分级堵漏剂配方及分级堵漏技术。分级堵漏剂主要成分包含0.4%～0.5%生物凝胶增稠剂、5%～7%钻井液用复合堵漏剂Ⅱ和含刚性颗粒不等的桥塞型复合堵漏剂。通过8口井现场应用表明，分级堵漏技术能够封堵裂缝宽度小于6 mm的裂缝性复杂井漏，堵漏后漏点地层承压高，满足后续钻井施工承压要求，且在堵漏后至完井期间未发生井漏。研究结果表明，分级堵漏技术适合鄂尔多斯盆地东部刘家沟组-石千峰组复杂裂缝性井漏，值得进一步推广。 

Study and Application of Mud Loss Control Technique with Graded LCMs in the East of Ordos Basin

SEM experiment on core samples, X-ray diffraction experiment on drilled cuttings, as well as studies on regional geology data were performed in an effort to solve mud loss problem encountered in drilling the Liujiagou formation-Shiqianfeng formation in the east of Ordos Basin. The experimental result and the studies show that destabilization of rigid formations in contact with water and reticular fractures developed in the rigid formations are the main causes of severe mud losses and difficulties in controlling mud losses in this area. The rigid formations have high contents of illite and chlorite, and low contents of kaolinite and montmorillonite. It was decided to inhibit the destabilization of fractures in the formation in contact with water and to plug the fractures of different sizes with compounded bridging lost circulation materials (LCMs) containing particles of different sizes. A graded LCM slurry and techniques of using the LCM slurry were developed through laboratory experiment. The graded LCM contains 0.4%-0.8% bio-gel thickening agent, 5%-7% compounded LCM Ⅱ and rigid particles. Application of this LCM slurry on 8 wells showed that this technique was able to effectively plug mud losses into fracturs of 6mm in width. After the mud losses were stopped, the pressure bearing capacity of the loss zone became high enough to satisfy the needs of subsequent drilling operation, and no mud losses ever happened thereafter. The experimental results show that the graded LCM is suitable for controlling mud losses into complex fractured formations in the Liujiagou formation – Shiqianfeng formation in the east of Ordos Basin, and is worth popularizing.