华北牛东地区深井抗高温防塌钻井液技术研究与应用

Research and Application of Anti-high-temperature and Anti-collapse Drilling Fluid in Deep Well in Niudong Area of North China

华北油田牛东地区油层埋藏深,井底温度超过200℃,且钻井中易发生井壁失稳等复杂事故,常规钻井液体系稠化严重、防塌性能不足。基于深部地层岩样X射线衍射、扫描电镜组构分析结果,进行了深部地层井壁失稳机理及对策研究,结果表明牛东地区深层岩样黏土矿物含量较低,微裂缝发育,钻井液滤失是井壁失稳的主要原因。通过实验优化构建了两性离子聚磺抗高温防塌钻井液体系,并优选了刚性及可变形封堵防塌剂,形成了适合牛东地区的两性离子聚磺抗高温防塌钻井液体系,在牛东101井目的层段(井底温度207℃)进行了试验应用。室内评价结果表明,两性离子聚磺抗高温防塌钻井液体系在240℃热滚前后具有良好的流变、滤失性能,加入复配的刚性及可变形封堵防塌剂后砂床滤失量降低80%以上。现场应用过程中,钻井施工正常,电测一次成功,与邻井同井段相比,平均井径扩大率从56.74%降低为9.6%,实现了安全钻井的目标。该体系及其现场应用技术对牛东地区甚至其他高温超深井钻井具有非常重要的参考意义。

The oil layer in Niudong area of Huabei Oilfield is deeply buried,and the temperature at the bottom of the well exceeds 200℃. Due to developed cracks,accidents such as wellbore instability in drilling are frequently encountered. The conventional drilling fluid system can be severely thickened and the anti-collapse performance is insufficient. Based on the X-ray diffraction and scanning electron microscopy(SEM)analysis results of rock sample in deep formation,the mechanism and way to deal with wellbore instability were studied. The results showed that clay mineral content of the rock samples in Niudong area is low with micro-crack development. Therefore,drilling fluid filtration is the main mechanism for wellbore instability. The high temperature resistant zwitterionic polysulfonation anti-collapse drilling fluid (HTRZPACDF) system was optimized,and the rigid and deformable plugging anti-collapse agents were selected. The HTRZPACDF system suitable for the Niudong area was established. Field application in the target formation of the Niudong 101 well was conducted,where the bottom hole temperature was 207℃. The results of laboratory test showed that the HTRZPACDF system had good rheology and fluid loss performance before and after 240°C hot rolling,and the sand fluid loss was reduced by more than 80% with the addition of rigid and deformable plugging anti-collapse agent. During the field application,drilling proceeded smoothly,and the electrical measurement was successfully conducted. Compared with the adjacent wells,the average well diameter expansion rate decreased from 56.74% to 9.6%,achieving the goal of safe drilling. The successful application of the system and its field application technology had an important significance for drilling in Niudong area and even other high temperature ultra-deep wells.