多孔介质中菌体的滞留聚集效应

RETENTION AND AGGREGATION OF BACTERIA IN POROUS MEDIUM

菌体在储层中的滞留聚集是微生物与原油发生作用从而实现提高采收率的前提。滞留的菌体不仅有利于微生物与原油发生作用，而且可对孔道中的流体起到微观调剖作用。通过实验向微观仿真孔隙模型中注入菌体悬浮液，借助图像采集系统观察菌体在多孔介质中的滞留聚集现象，发现随菌体悬浮液注入时间的延长，流体的驱动压力呈阶梯状逐渐上升，驱血液中的菌体含量下降到一定值后趋于相对稳定。分析认为多孔介质中孔道形状、水流速度、菌体浓度等使菌体在孔道中的滞留聚集现象显著，造成驱出液的菌体浓度值低于注入液的菌体浓度值。孔道中滞留的菌体数量和菌体堆积强度达到一定值时流体的驱动压力升高，迫使流体携带菌体流向其他孔道，从而使菌体在多孔介质中的波及体积增大，有利于扩大菌体与原油的接触范围。因此微观尺度下不可忽略孔道中菌体的滞留聚集对流体的影响。

Retention and aggregation of the bacteria in the reservoir is the premise of the reaction between microbe and oil, which enhances the recovery. Retained bacteria could not only help the reaction between microbe and oil, but also realize the microscopic profile control of the fluid in the porous channel. In the experiment, bacteria suspension is injected into artificial micro-model of pore, and the retention and aggregation of bacteria in porous medium is observed through image acquisition system. The experiment shows that the driving pressure of fluid takes a stair-stepping increase along with the prolonged injection time of bacteria suspension and goes steady after the bacteria content in the droved fluid falls under certain value. The analysis shows that shape of channel, flow velocity and bacteria concentration in porous medium reinforces the retention and aggregation of bacteria in pores and throats, so that the bacteria concentration in the droved fluid is lower than that in the injected fluid. When the bacteria retention amount and accumulation intensity reaches a critical value, the drive pressure of fluid increases and bacteria is forced by the fluid to flow into other channels, so that the sweeping volume of bacteria in porous medium increases and the contact between bacteria and oil expands. The influence of bacteria retention and aggregation on fluid in channel should not be neglected under micro examination.