Carbon dots enhanced ultra‐low‐density fluorescence proppants with both high‐compressive strength and anti‐deformation ability

Abstract The polymer ultra‐low‐density proppants are critical to the development of slick‐water fracture technology, but which were prone to obvious deformation under high pressure in the fractures. To increase the stiffness of the styrene‐divinylbenzene copolymer (SDB) and obtain desired ultra‐low‐density (ULD) proppants, carbon dots (CDs) were introduced in‐situ considering their characteristics as the zero‐dimensional carbon nanomaterial. Taking the compressive strength and axial deflection, and so forth into consideration, the synthesis conditions of CDs modified SDB microspheres (CDs‐SDBs) were optimized. Taking the graphite modified SDBs (MG‐SDBs) as a reference, the density of CDs‐SDBs did keep almost constant at about 1.1800 ~ 1.1899 g·cm ⁻³ with the increase of CDs amount. The CDs‐SDBs not only possess high‐peak pressure (41.5 N) but also minute axial deflection (0.090 mm). The advantages of CDs‐SDBs over MG‐SDBs become even more pronounced under higher pressure, which can withstand closure pressure of 80 MPa with a small crush ratio of 4.47%. CDs‐SDBs exhibit significant photoluminescence performances with maximum excitation and emission wavelengths of 634 nm and 554 nm. Highlights CDs‐SDBs as ULD proppants with high strength and anti‐deformation were developed. Advantages of CDs‐SDBs become more pronounced under high‐closure pressure. With increasing of CDs amount, apparent density of CDs‐SDBs keep almost constant. Axial deflection of CDs‐SDBs is only 0.09 mm under 41.5 N. The crush ratio is only 4.47% under 80 MPa closure pressure.