Physicochemical forces exert non-neligible effects on the migration of micro-particles in channels. Experiments, analytical and non-resolved computational fluid dynamics models have failed to decipher the dynamic behaviors of these particles when carried by fluid flow. In this paper, particle-scale numerical simulation is conducted to study the adhesive micro-particle migration process during duct flow in channels with a large characteristic dimension ratio and those with relatively small such ratio based on the coupled lattice Boltzmann method-discrete element method. The interaction between particle and fluid flow is dealt with by the immersed moving boundary condition. For micro-particle migration in duct flow, the effects of hydrodynamic force, adhesive force and particle concentration on the aggregation of particles are investigated. Based on the concept of hydrodynamic and adhesive force ratio, a stable aggregation distribution map is proposed to help analyze the distribution and size of the formed agglomerates. For micro-particle migration in channels with small characteristic dimension ratio, the general particle migration process is analyzed, which includes single particle retention, followed by particle capture, and the migration of large agglomerates. It is concluded that two factors accelerate single particle retention in a curved channel. Moreover, it is established that higher fluid flow rate facilitates the formation of large and compact agglomerate, and blockage by this can cause severe damage to the conductivity of the channel.

Reorientation of fractures and high production improvement are observed and illustrated by fields and theoretical researches. During the refracturing treatments, it is important to get familiar with the enhanced oil recovery mechanics of fracture reorientation and distribution of residual oil. Mechanisms of fracture reorientation are discussed in order to design the parameters of reoriented fractures in numerical simulation. To furtherly evaluate the oil recovery of different angles of reoriented fractures, geological and numerical models are simulated using data of the actual reservoir with rhombus inverted nine spot well pattern, different angles of reoriented fracture are designed for both corner and edge wells to obtain the enhanced oil recovery. Results show that potential of production increase is highly impacted by the well pattern and angles of fractures and meanwhile impacted by distribution of residual oil and formation properties. Oil enhancement potential is significantly different with fracture reorientation angles in refracturing treatment: cumulative produced oil for corner wells is symmetrical around the angle of 0° and reaches the highest at the angles of positive and negative 23°; for the edge wells, it is also symmetrical around the angle of 0° while reaches the highest cumulative oil at the angles of positive and negative 90°. The difference shows that optimal angles exist for reoriented fractures during refracturing design and with proper induced reoriented fractures, more oil will be recovered for field restimulation treatments.