Modeling transport and bridging behavior of lost circulation materials in a hydraulic fracture

Lost circulation of drilling fluid is one of the most common and costly problems in drilling operations. This highlights the importance of wellbore strengthening treatment sthat can utilize lost circulation materials (LCMs) to seal fractures associated with the wellbore. In this work, a numerical model accounting for the deformation of surrounding rock, fluid flow in the fracture, fracture propagation, and the transport of LCMs is presented to investigate the wellbore strengthening, from the fracture initiation to the fracture arrest, due to plugs formed by LCMs. The equations governing the rock deformation and fluid flow are solved by the dual boundary element method and the finite volume method, respectively. The transport of LCMs is solved based on an empirical constitutive model in suspension flow, and several characteristic quantities are derived by dimensional analysis. It is found that two dimensionless parameters, dimensionless toughness and normalized initial particle concentration, control the migration of LCM particles. The numerical results show that the dimensionless toughness influences the entrance and bridging of LCMs while the initial concentration controls the location of the particle bridging. When the initial concentration is larger than 0.8, the particle bridging tends to occur near the fracture entry. Conversely, when the initial concentration is less than 0.8, the particle bridging occurs near the fracture tip. This work provides an effective tool to predict the LCM transport and plugging in the wellbore strengthening process.