Key Factors for Inhibiting Fracture Propagation during Leakage Control under Pressure

In order to minimize lost circulation time while drilling through fractured formations, lost circulation plugging materials are generally used to prevent fracture propagation under pressure. So far, however, no further analysis has been performed on the key factors that arrest or inhibit fracturing. In this paper, a related study was conducted. First, analysis was conducted on fracture pressure variation after leakage control. Second, a formula for the fracture terminations and a stress intensity factor induced by fracture pressure was derived using the principle of superposition. And third, the influencing factors of the stress intensity factor were analyzed. It is shown that the stress intensity factor decreases with the increase of plugging length, drilling fluid viscosity, and the decrease of the plugging permeability, and consequently arrest/inhibition of propagation conditions are gradually satisfied. The stress intensity factor increases as fracture length or subsurface pressure increases or plugging location gradually approaching fracture terminations. The higher the stress intensity factor is, the more difficult the fracture inhibition. The functional relationships between the stress intensity factor induced by fracture pressure and other parameters are as follows. The formula shows approximately a cubic relationship with plugging length and location, linear relationship with drilling fluid viscosity and subsurface pressure, approximately a logarithmic relationship with plugging permeability, and power relationship with fracture length. In summary, fracture propagation can be stopped through optimizing circulation lost materials and improving drilling fluid properties if the fracture length and subsurface pressure are constant or out of control during pressured leakage control.