川南页岩气钻井井漏特征及堵漏技术研究与应用

川南页岩气井区地质地貌复杂，缝洞发育明显，各层段恶性漏失频发，堵漏工作难度大，复杂处理周期长，钻井提速受到严重制约。针对上述工程地质难题，开展了川南地区页岩气钻井井漏特征分析和井漏防治技术现状评价，系统阐述了桥塞堵漏、水泥堵漏、多相混输堵漏、遇水快速凝固堵漏、油基钻井液堵漏等技术工艺的封堵效果。川南页岩气井区以裂缝性漏失为主，纵向上呈明显的“三段式”特征。表层地层井漏治理难度大，尚未得到很好解决；中部地层采用随钻、桥堵、水泥堵漏和清水强钻工艺，井漏防治效果较好；下部地层存在承压堵漏无效、龙马溪组溢漏同存的难题。研究形成了复合桥塞堵漏、桥塞+高滤失堵漏、桥塞+水泥浆堵漏、凝胶+水泥浆堵漏等综合堵漏工艺技术，通过集成应用，整体堵漏成功率提高至56%，治漏成效显著。针对当前仍存在的表层漏失处理工艺受限、井漏治理时间长、缺乏精确的漏层诊断技术等问题，建议开展漏失层诊断等技术攻关，研发漏失通道适应能力强的堵漏新材料、新工具及配套工艺。

Leakage Characteristics of Shale Gas Wells Drilled in Southern Sichuan and Plugging Technology Research and Application

The geological landform is complicated in the shale gas zone of Southern Sichuan with development of obvious fractures and cavities. Serious leakage of drilling mud frequently happened at various layers, causing difficulties for plugging work. The long period for treatment of the complicated conditions severely impaired acceleration of drilling rate. To solve those engineering geological bottlenecks, the efforts were focused to analyze the leakage characteristics of shale gas wells drilled in Southern Sichuan and evaluate the current conditions of leakage prevention technology, while systematically elaborating the effects of various technological process for well leakage, such as bridge-plug plugging, cement plugging, multiphase mixed injection plugging and rapid solidification plugging, and oil-based drilling fluid plugging. Leakage was mainly of the fractural property in the shale gas zone of Southern Sichuan, with the obvious characteristic of vertical “three segments”. Treatment of well leakage for the surface formation was difficult. It was still to be solved satisfactorily. As for the middle formations, bridge-plug plugging, cement plugging and clear water enhanced drilling process could achieve good results for leakage prevention. Plugging the leakage under pressure had no effect on the lower formation while spill and leakage co-existed for Longmaxi Formation. The study led to a comprehensive plugging process technology, such as compound bridge-plug plugging, bridge plug + high fluid loss plugging, bridge plug + cement slurry plugging, and gel + cement slurry plugging. The whole plugging success rate was brought up to 56 percent of the basis of integrated application, making a remarkable plugging achievement. Focusing on the existing problems for the surface formation, such as the limited process for treatment of well leakage, long duration for handling leakage, and lack of precise leaking formation diagnosis technology, it is proposed to make study of leaking formation diagnosis technology and develop the new plugging materials and tools suitable for the leaking channels as well as the series of the related processes.