工作液对低渗气藏产能影响机理及储层保护

Effect mechanism of working fluid on productivity of low permeability gasreservoir and reservoir protection

东海低渗气藏储层黏土矿物差异明显,导致储层损害机理各异、与外来流体接触后对产能影响认识不清,储层保护研究缺少机理支撑。针对上述问题,以东海H气田实际钻完井液体系开展储层损害机理研究,通过采用气体作为驱替介质、延长循环时间、建立初始含水饱和度等方法优化动态损害评价实验。在此基础,建立了钻完井液侵入深度与表皮系数数学模型,系统分析钻完井液体系对气层的损害机理,评价损害程度。最终综合地质因素、储层损害机理优选H气田储层保护技术。实验结果表明,钻完井液初期侵入速度快,5 d后基本稳定;钻完井液侵入主要发生水锁、配伍性及固相堵塞孔喉等损害;优化暂堵颗粒、增加返排压差能够有效降低钻完井液对储层损害程度。研究成果为低渗气藏高效开发、产能释放提供基础支撑。

The difference of clay minerals in low permeability gas reservoirs in the East China Sea leads to different formation damage mechanisms,unclear understanding of the impact on productivity after contact with foreign fluids,and lack of mechanism support for reservoir protection research.In view of the above problems,the mechanism of reservoir damage was studied with the actual drilling and completion liquid system of H gas field in the East China Sea.The dynamic damage evaluation experiment was optimized by using gas as displacement medium,extending cycle time and establishing initial water saturation.Furthermore,a mathematical model of mud filtration depth and skin factor is established to analyze the mechanism and significance of the productivity damage caused by drilling and completion fluid system.Finally,reservoir protection technology for H gas field is selected.The experimental results show that the initial fluid invasion speed is fast,and it remains unchanged after 5 days.The productivity impairment is mainly caused by snap-off,water compatibility,and pore-throat blockage.Choosing the right solid particles and increasing fluid pressure can effectively reduce the damage due to drilling and completion fluid.The research results provide a fundamental guide to increase the productivity of low-permeability gas reservoir.