Wengang Li1,Edreese Alsharaeh2,Mohanraj Krishnan2,Abdullah Garni1
Saudi Aramco1,Alfaisal University2
Wengang Li1,Edreese Alsharaeh2,Mohanraj Krishnan2,Abdullah Garni1
Saudi Aramco1,Alfaisal University2
Frac proppants, usually silica sand or ceramic spheres, have been widely applied in both conventional and unconventional oil gas production operations, with an essential function of supporting the created fractures by hydraulic pressure to keep the hydrocarbon flowing. To stand for high stress, enhancement of proppants has been performed by coating methods. Commercial resin coated proppant are mainly fabricated with novolac or epoxy resin, where the hardness and pressure resistance of product are limited by resin properties, and the pressure/temperature resistance are determined by the natural properties of commercial resins.<br/>This paper demonstrated a novel method to fabricate coated proppants for HTHP applications by surface polymerization methods and dual coating protocol. The sand particles were firstly coated with polystyrene-polymethyl methacrylate copolymer (PS-PMMA) composite with commercial graphene (CG) (first composite layer) and subsequently coated with epoxy-CG composite (second composite layer). Chemical, mechanical, thermal and morphological characterizations for the composite layers and dual-coated sand proppants were investigated in detail by Fourier transform-infrared spectroscopy (FT-IR), nano-indentation, thermogravimetric (TGA), optical, and scanning electron microscopic (SEM) techniques.<br/>The fabricated silica sand based proppant can hold 12-14k psi pressure and the thermal stability of the dual coating has reached as high as 368 <sup>o</sup>C. The elasticity (E), hardness (H), and the fracture toughness (K<sub>c</sub>) of the dual coating (PS-PMMA/DVB)-(Epoxy-CG) have been investigated with a maximum of 7.78 GPa, 0.34 GPa, and 3.22 MPa m<sup>1/2</sup> respectively. A 3-D morphology effect has also been observed to further enhance proppant mechanical property, fulfilled by poly(styrene-methyl methacrylate)/divinyl benzene) (PS-PMMA/DVB) plus epoxy resin dual coating.<br/>This surface polymerization coating method has been established on silica sand with wide range of size, 20/40 mesh to 100 mesh and nano-sand. The mechanically and thermally reinforced dual-coated sand particles with very high-stress resistance will be successful proppants for hydraulic fracture operations.