Effect of fracture behavior variables on hydraulic fracturing optimization by adding graphene nanosheets to sand/water mixtures: A molecular dynamics approach

Hydraulic fracture is one of the promising techniques for the breakage of rock without blasting, thus the investigation of its internal mechanism is helpful to develop forecasting system for ground pressure. In this study, molecular dynamics (MD) method was used to describe the effect of graphene nanosheets (GNS) (with different edges) on the hydraulic fracturing process. More specifically, in the MD box, we simulated the effects of GNS on rock substrates, the mixtures of H2O and sand, and sands that deviate from the specified atomic substrates. Therefore, we calculated the parameters, such as temperature, total energy and mutual forces of atomic structures. In these simulations, mixture fluid is simulated by sand particles and water molecules with the Universal Force Field (UFF). Physically, adding GNS to mixture fluid caused a decrease in the number of trapped sand particles in the fracture of rock matrix. The sand particles removed from rock matrix fracture. This atomic phenomenon optimized the hydraulic fracturing process and reduced operating costs. Numerically, in our simulations, the atomic structures' temperature and potential energy converged to 300 K, and -479 eV (respectively). Furthermore, trapped sand particles in MD simulations decreased to 14 particles using GNS. Our results show that the trapped sand particles reached their minimum rate (14 particles) by 2.5% atomic ratio of GNS inserting into the initial atomic mixture fluid. This atomic behavior results from the energy of the interactions between sand particles, and rock substrate. The interaction energy between the sand particles and the substrate reduced to a -32.38 eV by adding GNS to original H2O-sand mixture. This atomic evolution caused the volume of trapped sand particles reached to minimum value in the presence of GNS with optimum atomic ratio.

Automated summary

This study investigated the effect of graphene nanosheets (GNS) on the hydraulic fracturing process using molecular dynamics simulation. The results showed that adding GNS to the mixture can optimize the hydraulic fracturing process and reduce operating costs.