Characteristics and significance of proppant in hydraulic fractures in coal reservoirs

The distribution form and internal characteristics of proppant after coal seam hydraulic fracturing determine the fracturing effect to a great extent. The proppant in the hydraulic fracture exposed in the underground roadways of the coal mine is taken as the research object. The morphology and accumulation characteristics of the proppant were observed, and the relationship between the morphology and accumulation characteristics of the proppant and its stacking process was analyzed. Then, the morphology and accumulation characteristics of the proppant obtained at the typical part of the hydraulic fracture are described, which provides a basis that restores the stacking process of the proppant. The results of this study indicate that the proppant size gradually becomes smaller with the increase of the distance from the wellbore in the horizontal fracture. In the soft coal zone, the proppant particles experience a strong collision in chaotic hydrodynamic circumstances before deposition, and the sand spreading characteristics of the proppant zone, mixed zone of proppant and pulverized coal, and coal pulverized zone are formed. The change of fracture extension form can lead to the early deposition of proppant, which is not conducive to fracture extension. The sorting and integrity of proppant particles, the adhesion of pulverized coal and the trace in coal rock are often different in different fractures, which is of guiding significance to the proppant accumulation process and the flow characteristics of fracturing fluid. The results can provide a scientific basis for the parameter of numerical simulation and engineering practice. And it has certain reference significance for the same type of fracturing design and fracturing effect prediction.