# Physical Simulation Experiment for Visualizing Pulverized Coal Transport in Propped Fractures
## 3 Results and Discussion
### Analysis of the Migration Patterns of Pulverized Coal in Various Carrier Fluids  
Under the experimental conditions of 16-20 mesh proppant, 100-150 mesh pulverized coal particle size, and a repulsion rate of 300 mL/min, significant variations were observed in the injury rate of propped fracture conductivity, the amount of pulverized coal output, and the repulsion time of equal-volume solution when different transport fluids (distilled water, active water fracturing fluid, agglomerated fracturing fluid, and dispersed fracturing fluid) were employed for pulverized coal transport experiments (Figure 4). Figure 3: Image illustrating bonding between pulverized coal and proppant. Figure 2: Pulverized coal accumulation mode chart. (1) Injury rate of propped fracture conductivity  
The fracture conductivity injury rate is higher when the carrier fluid is distilled water than when the other three carrier fluids are employed. Notably, the injury rate of fracture conductivity in the case of dispersed fracturing fluid starts to increase significantly when the third cup of fluid is produced by driving, and the injury time is earlier than that of active water fracturing fluid and agglomerated fracturing fluid. Furthermore, the damage rate of fracture conductivity for agglomerated fracturing fluid and active water fracturing fluid shows a significant increase upon production of the fourth cup of liquid during displacement. The trend in the increase in the damage rate of the fracture conductivity follows this sequence: agglomerated fracturing fluid > active water fracturing fluid > distilled water > dispersed fracturing fluid. However, the cumulative injury rate of fracture inflow capacity for agglomerated fracturing fluid remains lower than that of the other three transport fluids. This indicates that agglomerated fracturing fluid can effectively mitigate the permeability injury caused by pulverized coal to the propped fractures. (2) Pulverized coal output  
The three stages of pulverized coal deposition--pulverized coal deposition on the surface of proppant particles (pulverized coal deposition), the narrowing of channels between proppant particles (mild clogging), and the clogging of proppant fractures by pulverized coal (severe clogging)--are illustrated in Figure 5. The deposition and plugging of pulverized coal occur more rapidly with increasing drive flow rates. The powder content in all four transport fluids reaches its peak value in the second cup of the drive output, followed by a sharp decline in the fourth cup. This decline is attributed to the higher flow rate, which leads to more severe blockage in the propped fractures and the deposition of pulverized coal, forming a barrier. Under the same replacement flow rate conditions, the output of pulverized coal exhibits this sequence: dispersed fracturing fluid > active water fracturing fluid > distilled water > agglomerated fracturing fluid. (3) Equal-volume solution displacement time  
The time required for discharging the equal-volume solution serves as an indicator of the smooth transportation of the carrier fluid within the proppant fracture from the sideline. The expulsion time for the four types of carrier fluids demonstrates an increasing trend, with agglomerated fracturing fluid requiring the shortest time, followed by active water fracturing fluid, and finally distilled water and dispersed fracturing fluid. Distilled  
Figure 4: Experimental results of pulverized coal transport, using various transport fluids. water and dispersed fracturing fluid exhibit a significant increase in expulsion time upon production of the third cup of fluid during displacement, whereas active water fracturing fluid and agglomerated fracturing fluid show a significant increase in expulsion time only upon production of the fourth cup of fluid during displacement. This suggests that distilled water and dispersed fracturing fluid experience clogging at an earlier stage, impeding the flow of the carrier fluids.