泸州深层页岩气呼吸性地层井漏堵漏方法及对策分析——以Y101H3-4井为例

Plugging of breathing formation in deep shale gas wells in Luzhou： Taking Well Y101H3-4 for example

摘要:

泸州深层页岩气储层埋深达4000 m，属于高压力地层，所钻遇石牛栏组地层岩性为含砂泥岩，本区内多口井钻遇高压裂缝气，溢流及井漏风险大，时常出现高套压事件；同时一些井存在采用高密度钻井液钻进至类似地层时发生漏失后又返吐的现象，给堵漏和钻进作业带来较大困难。针对该类呼吸性地层井漏，以Y101H3-4井为例，现场试验了一系列堵漏方法及措施，结果表明：常规堵漏工艺对呼吸性地层堵漏效果不佳，堵漏材料粒径难以匹配，易导致封门堵漏失败；针对同平台邻井实钻油气显示情况，合理降低钻井液密度有助于堵漏作业实施；油基水泥塞是解决此类呼吸性井漏最有效的工艺技术，但前提条件是确定合理钻井液密度，降低注水泥过程中的返吐量，防止水泥浆与钻井液直接接触污染。在泸州区块采取降密度+注油基水泥塞堵漏是解决呼吸性地层井漏的最佳方法，可快速解决该类地层的堵漏难题。

关键词:深层页岩气;呼吸性地层;井漏;堵漏;水泥塞;降密度;泸州区块

Abstract:

The depth of deep shale formation in Luzhou is about 4000m. It is typical high-pressure formation， where Shiniulan Formation drilled is a sandstone-rich mudstone. In this area， high-pressure formation gas was often encountered in drilling operations， increasing risks of gas-kick and lost circulation； meanwhile， pulsation wellbore leakage was observed while using high-density drilling mud. All these issues posed great challenges to drilling operations in this region. To address this issue， taking Well Y101H3-4 as an example， some wellbore plugging treatments were tested. Results showed that：①Typical wellbore plugging materials can not effectively plug wellbore leakage due to incompatible material-fracture sizes.②Based on drilling history of neighboring wells， reducing drilling mud density helped with wellbore plugging operations.③Oil-based cement plugging was the most effective method to deal with the formation with pulsated lost circulation at the prerequisite that proper mud density should be determined to prevent contamination due to contact between drilling mud and cement slurry. In conclusion， reducing mud density and use of oil-based cement plugging are the best method for pulsated lost-of-circulation in the Luzhou Block.

Key words:deep shale gas;breathing formation;lost circulation;wellbore plugging;cement plugging;mud density decreasing;Luzhou Block