Nanomicron heterogeneous topic——Pore size suspended particle retention law and seepage field characteristics

The development of oil and gas field is a typical multi-phase percolation process. Water injection, gas flooding, chemical flooding, fracturing and other technologies will lead to the migration and plugging of mineral particles in the reservoir pores, and then affect the exploitation of the reservoir and the ultimate recovery efficiency. Therefore, it is of great significance to study the migration and flow field of suspended particles during their migration and retention in porous media. However, existing studies on the migration and retention of suspended particles in porous media mainly focus on the damage to permeability caused by the migration and retention of particles, which do not reflect the process of particle migration, nor can they reflect the relationship between particle blockage and flow field changes in pore networks. The microscopic visualization model and the Micro-Particle Image Velocimetry (Mirco-PIV) technology were used to analyze the particle retention and flow field changes in the main channel and boundary region of the two-dimensional porous glass model, and the laws were summarized. The experimental results show that the initial flow velocity in the main channel is higher, but because the particle retention in the main channel is more than that in the boundary zone, the continuous injection of particles leads to the decrease of the flow velocity in the main channel, disturbing the original flow field and resulting in "spot" flow field. It also reduced the main channelto a lower flow rate in the medium term than the boundary zone. This also indicates that particles are transported more efficiently in the high flow zone. The distribution characteristics of the retention observed are mainly retention near the side wall, and aggregation occurs in the main channel under relatively high concentration conditions, all of which lead to effective plugging of the pores. The phenomenon of retention, aggregation and interweaving was not considered in the previous plugging experiments. In this paper, for the first time, the interaction process between particles and flow field is provided, and direct evidence for visualization in two-dimensional conditions is given. In addition, the particle distribution characteristics show that the core mechanism of blockage is observed to be the retention near the side wall, the narrowing of the effective flow radius and the concentration of high concentration in the main channel. The original theory does not cover this problem, and should be revised accordingly in the future. The process and characteristics of suspended particles' retention and flow field in porous media were studied by the combination of microscope and Micro-PIV, and the variation rules were revealed.