四川盆地裂缝储层钻井井漏安全起钻技术认识与探讨

Safe tripping-out technology against lost circulation in fractured reservoirs,Sichuan Basin

随着石油天然气钻探逐渐向深层、裂缝碳酸盐储层转移,钻井过程中发现了严重井漏、喷漏同存等井下复杂问题,如四川盆地高磨区块二叠系和灯影组储层、双鱼石构造二叠系,其储层裂缝发育,井漏严重,常规堵漏效果差,井底压力波动大,溢漏转化频繁,给钻井作业特别是起钻作业带来了严峻挑战。从裂缝储层钻井井漏起钻作业安全影响因素出发,定性分析了常规重浆吊灌起钻方式的缺陷,带压起钻方式的优势和不足,重点介绍了"带压起钻+重浆帽吊灌"方式的工艺流程、技术优势和关键做法,推荐采用"带压起钻+重浆帽吊灌"方式解决起钻严重井漏和井控风险的问题,通过对比得出"带压起钻+重浆帽吊灌"方式是目前裂缝储层钻井井漏起钻作业最安全、最有效的方式。从2014年4月起,"带压起钻+重浆帽吊灌"方式已在西南油气田高磨区块、双鱼石构造等地区广泛应用,应用结果表明,该方式施工便利、安全性高、钻井液漏失量大幅减少、作业时效显著提高,在四川盆地裂缝储层钻井中得到充分认可。

As drilling moves gradually to deeper fractured carbonate-rock reservoirs, it’s found that some severe lost circulation and blowout lost circulation coexist, and downhole complexities get more and more obvious. In the Permian Dengying Formation of Gaoshiti-Moxi block and the Permian of Shuangyushi structure, Sichuan Basin, fractures are developed, and lost circulation is more serious. As a result, an application of conventional plugging is poor, bottomhole pressure fluctuates greatly, and well kick and lost circulation frequently convert, which bring about some drilling challenges, especially tripping out. So, the defects of the hang's mudding off and tripping out of conventional heavy mud, and the advantages and disadvantages of tripping out under pressure were analyzed with safety influence factors of tripping out operation against lost circulation in fractured reservoirs. The technological process and advantages, and key steps of "tripping out under pressure+hang's mudding off of heavy grout" technology are presented. After some comparison, it is pointed out that, this technology is currently the most effective and safe. Since April 2014, it has already been extensively applied to Gaoshiti-moxi block and Shuangyushi structure. Results show that, it is advantageous with convenient operation and higher safety. After its application, drilling-fluid loss is reduced significantly, and operation-time efficiency is improved greatly. Its effectiveness to drill fractured reservoirs in Sichuan Basin has been sufficiently recognized.