Preparation and Performance of Multifunctional Self-Aggregating Modified Quartz Sand Proppant for Coalbed Methane Channel Fracturing.

A multifunctional self-aggregation modified quartz sand support agent (MRQS) was prepared by a simple dry coating method for coal seam gas fracturing channels. The organic coating is composed of KH550, OTMS, H-PDMS and microcrystalline wax, which transforms the surface of the raw sand from super hydrophilic to hydrophobic (contact angle is 91.8°), thus providing a driving force for the spontaneous aggregation of particles in aqueous fluids. MRQS shows excellent anti-reflow stability, which does not dissipate after ultrasonic oscillation for more than 10 min, while raw sand can only withstand 3 min. Atomic force microscopy (AFM) analysis shows that the interface adhesion of MRQS under low load is tripled (106.7 nN vs. 32.0 nN), which explains its stronger aggregation intensity. In the temporary sealing test, MRQS forms a stable and low-permeability sealing layer at the narrow crack, raising the sealing pressure to 0.23 MPa, while the original sand cannot achieve effective sealing. The crack diversion ability test shows that MRQS still maintains a diversion capacity of 1.62 μm2·cm under a closed stress of 45 MPa, and the attenuation curve is gentle. Although the initial value is slightly lower than that of raw sand (1.88 μm2·cm), the overall performance is comparable. The static loss test shows that MRQS extends the filtration time of 200 mL filtrate to 439 s, which is 2.04 times that of the original sand. This simple dry coating strategy prepares a multifunctional support agent, which combines self-aggregation, temporary sealing, filter loss control and high stress stability, providing a practical solution to improve the fracturing performance of coal seam gas (CBM).