关键词: 页岩气, 井漏, 堵漏, 环境保护

Abstract: 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.