Friction coefficient: a significant parameter for lost circulation control and material selection in naturally fractured reservoir

Lost circulation of working fluid into formation fractures is one of the most common and costly problems encountered during the development of petroleum and geothermal resources. Fracture plugging strength and efficiency with loss control material determine the effect of lost circulation control. This paper proposes an integrated method for optimal material selection. The key mechanical parameter of loss control material is determined based on mathematical model and simulation on fracture plugging strength and efficiency. The developed fracture plugging strength model accounts for the shear failure of fracture plugging zone. Simulation with coupled computational fluid dynamics and discrete element method is conducted for fracture plugging efficiency accounting for particles transport and capture in fracture. Model and simulation results show that friction coefficient is the key material mechanical parameter for fracture plugging effect. Laboratory experimental results show that rigid particle with lower roundness, fiber with higher tensile strength and elastic particle with higher deformation rate lead to larger friction coefficient and should be selected as loss control material. Reasonable combination of rigid granule, fiber and elastic particle can create a synergistic effect to achieve the optimal friction coefficient and fracture plugging effect. Material selection strategy is determined and has been successfully applied to field case study in Sichuan Basin, China