低渗透致密砂岩气藏保护技术研究与应用

分析了低渗致密气藏的损害机理与保护措施,认为低渗透致密砂岩气藏在钻井过程中的损害因素主要是水敏损害和水锁损害,其次为固相颗粒堵塞损害。为此,针对试验区块提出了“合理的屏蔽暂堵-强抑制-防水锁” 保护气层技术思路,进行了水锁损害机理与预防方法研究;以自行研制的气层专用保护剂为主剂,研制出了保护气层的钻井完井液配方,并进行了现场试验。实验表明,岩样被水侵之后,渗透率明显降低。因此,对于低渗透岩样,在钻井过程中,尽量避免滤液侵入储层;研制的保护气层钻井完井液配方抑制性强（页岩回收率为97.8%）,岩样气体渗透率恢复率高（大于80%）,能有效减小钻井液对气层的水敏和水锁损害。现场试验表明,该钻井完井液体系抑制能力强,气层保护效果较好。

Study and Application on Protection Techniques for Low-permeability Tight Sandstone Gas Reservoir

On the basis of analysis of the formation damage mechanism of low-permeability tight gas reservoirs, it is recognized that the damage factors of low-permeability tight sandstone gas reservoirs during drilling is water-sensitive damage and water-locking damage, as well as solids particle invasion. A technical plan of " adequate shielded temporary plugging, strong inhibition and water-locking prevention " is put forward for the field test area. The water-locking damage mechanism and corresponding preventive measures are studied. Special drilling and completion fluid formulae for gas reservoir protection are developed with the self-developed special gas-reservoir protection agents as the main additives. The lab and field test results show that the core permeability is dramatically declined with the water invasion. So efforts should be tried to prevent the filtrates from entering the gas reservoirs during drilling. With strong inhibition (with shale recovery rate of 97.8%), the newly developed drilling and completion fluids for gas reservoir protection has a high recovery rate of gas permeability (over 80%), and can effectively reduce water sensitivity and water-locking damage to the gas reservoir.