Numerical Modeling and Analysis of Lost Circulation on Drilling-Induced Fracture

The wellbore induced fracture often leads to wellbore leakage in deep and ultra-deep drilling, and the dynamic changes in drilling fluid leakage pressure and leakage channels are crucial for the selection of plugging technology and optimization of lost circulation materials. In order to study dynamic changes of leakage channels caused by induced fracture during drilling process, based on the fluid solid coupling effect, a numerical model of wellbore induced fracture leakage caused by drilling was established based on combining Fluid Pipe Elements (FPEs) with Cohesive Zone Model (CZM). The leakage pressure and channels at the wellbore fracture site were analyzed under different displacement, drilling fluid density and viscosity conditions. The research results indicate that the combination of FPEs and CZM can effectively simulate the process of induced wellbore fracture and leakage during drilling, which verifies the accuracy of this numerical model. As the displacement, drilling fluid density, and viscosity increase, the critical leakage pressure at wellbore fracture also increases. Under the same operating conditions, the effect of displacement and drilling fluid density on wellbore fracture is significantly higher than that of viscosity. As the displacement, drilling fluid density, and viscosity increase, the fracture width and length correspondingly increase. The research results have important reference significance for the selection of plugging technology and optimization of lost circulation materials in deep and ultra-deep drilling.