摘要
An ultralow-density composite proppants suitable for SC-CO 2 fracturing were prepared • High sphericity, apparent density ≤1.18 g/cm 3 , and crushing rate ≤ 2.31% at 69 MPa • Sedimentation rate is 6 times slower than that of ceramsite in SC-CO 2 environment • Maintaining a relatively high conductivity of 6.98 μm 2 ·cm under 96.5MPa : Conventional proppants used in supercritical carbon dioxide (scCO 2 ) fracturing suffer from rapid settling and poor fracture conductivity due to the extremely low viscosity of scCO 2 , which severely limits proppant transport and fracture effectiveness. To overcome these limitations, an ultra-low density poly(methyl methacrylate)/graphite (PMMA/G) composite proppant suitable for scCO 2 fracturing was prepared via in situ suspension polymerization. The physicochemical, mechanical, and thermal properties, as well as fracture conductivity and scCO 2 resistance, were systematically characterized. Incorporation of 2.0 wt.% graphite significantly enhanced compressive strength (crush rate≤2.31% at 69 MPa), thermal stability (glass transition temperature increased to 129.53 °C), and sphericity (≥0.90), while maintaining an apparent density≤1.18 g/cm 3 . After 12 h of exposure to scCO 2 , the composite proppant exhibited minimal swelling and retained structural integrity with only a slight increase in crush rate. Sedimentation tests showed a settling velocity of 3.55 cm/s—approximately six times slower than that of conventional ceramic proppants—demonstrating excellent suspension and transport capability. Furthermore, the PMMA/G proppants maintained a relatively high fracture conductivity of 6.98 μm 2 ·cm under 96.5 MPa, confirming their outstanding load-bearing performance. These results demonstrate that the PMMA/G composite proppant provides a promising material solution for efficient and sustainable scCO 2 fracturing in unconventional reservoirs. Download: Download high-res image (263KB) Download: Download full-size image
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