川西致密砂岩气层保护技术——进展与挑战

FORMATION DAMAGE CONTROL TECHNOLOGY FOR TIGHT GAS SANDSTONE RESERVOIRS IN WESTERN SICHUAN BASIN: DEVELOPMENTS AND CHALLENGES

为了解决妨碍致密砂岩天然气勘探开发中的地层损害问题 ,以川西致密砂岩气藏为研究对象开展了国家重点科技攻关。项目研究立足于钻井完井中有效地保护天然裂缝 ,以屏蔽式暂堵技术思想作指导 ,通过建立井筒周围原地裂缝参数预测技术、裂缝性致密储层的敏感性和损害评价技术 ,基本形成了适于裂缝性致密砂岩气层保护的钻井—完井—增产配套技术系统 ,关于裂缝性致密砂岩气层开发获得了“保护与改造并举 ,二者相得益彰”的新认识。文章分析了面临的技术—经济—环境方面的严重挑战 ,提出要不断完善适应各种复杂地质对象的能力 ,在保护致密气层新技术开发中应特别注重与环境保护需求的结合。

Tight gas sandstone reservoirs in western Sichuan Basin are characterized with low energy, complex in macro- and micro-structures, and extreme sensitivity to environmental variations. Being congenitally deficient and liable to impairments, the damages of these reservoirs are very difficult to remove completely. With the above considerations, this work initiated from effective protection of natural fractures during drilling and completion. In the light of temporary shielding principles, a technical system of drilling-completion-stimulation for vertical wells, accompanied by methods of predicting fracture parameters close to bore-hole, and by core lab evaluations on sensitivity and working fluids damage, has been formed. The practices contribute an insight into the strategy that damage control and reservoir stimulation can be integrated for gas production from these reservoirs. Based on the discussion on technical, economical and environmental situations, this paper suggests that new and improved technology should be developed in order to cope with more complicated geologic situations such as deep tight gas reservoirs and abnormally low pressure gas reservoirs. It is also pointed out that environmental protection should be an especial concern in the research and application of formation damage control technology in drilling and completion operations.