疏松砂岩气藏渗透率敏感性实验研究

压敏、速敏、水敏的联合作用是疏松砂岩储层二次伤害的主要原因。利用松散岩心的套筒取心制样技术,对疏松砂岩油藏的露头岩心取样,通过疏松砂岩油藏应力敏感实验,模拟了不同驱替压差和驱动流速下储层的压敏、速敏、水敏变化,研究了疏松砂岩气藏特殊的渗透率敏感性机理。实验结果表明：疏松砂岩储层的渗透率越低,压敏越明显,压敏主要发生在应力变化的初始阶段,一般处在投产早期的近井地带,因此,多井低产、均衡开采将有利于稳产;疏松砂岩储层可动水会加剧压敏效应,因此随着压实和出水,中—低渗储层将转变为局部低渗—特低渗储层;疏松砂岩储层渗流过程中,微粒的运移同时具有疏通提渗和堵塞降渗的双重效应,在岩心尺度上,速敏体现在测试渗透率的异常升高,对于实际生产井,当气井产量发生显著变化时,可认为近井地层发生了微粒运移引起的速敏效应,即地层出砂。

Experiment study on permeability sensitivity in loose sandstone gas reservoir

The alliance of stress sensibility,velocity sensibility and water sensibility plays an important role in secondary damage of loose sandstone reservoir.Using the technology of taking core samples in casing pipe and the simulation of stress,velocity and water sensitivity variation in different displacement pressure and flow rate,this paper studies the special percolation mechanism of loose sandstone gas reservoir.The results show that the lower the permeability is,the more obvious the stress sensitivity will be.Stress sensitivity occurs mainly in the initial stage when the pressure changes,such as early production stage near wellbore zone,which means that low yield and balanced producing will be good for stable production.Water sensitivity caused by mobile water in loose sandstone reservoir increases the effect of stress sensitivity,which means as the compaction and effluent discharging,middle-low permeability reservoir will turn into local low and extra-low permeability reservoir.During the percolation process of loose sandstone reservoir,particle migration has dual effects such as dredging and blockage.In core scale,velocity sensitivity reflects in the abnormal increase of testing permeability.For actual production well,the velocity sensitivity known as the formation sand production caused by particle migration near wellbore occurs when the production of gas well significantly changes.