Dynamic Simulation of Mud Losses into Fractured Formations Using ABAQUS Software

Mud losses into fractured formations are the most common mud losses encountered in drilling fractured formations, and they are most complex and most difficult to control. Since mud losses into fractured formations are difficult to predict accurately in field operations, the success rate of bringing them under control is relatively low. Based on the principles of damage mechanics, the initiation of fracturing and propagation of the fracture during mud losses was simulated using the cohesive module of the ABAQUS software, and a 3D model describing the dynamic process of mud losses into fractured formations was established. The dynamic patterns of mud losses into fractured formations was obtained by analyzing the shape of fractures, the well circumferential stress and the pore pressures during mud losses. The study results showed that as the time of mud losses went on, the effect of the propagation pressure on the opening of a fracture was gradually weakening at first and then was increasing. As the opening of the fracture increased, the length of the fracture was increasing more and more slowly. The propagation of a fracture into which the mud was losing caused circumferential compressive stress around the mouth of the fracture (near the 0° position) to gradually decrease, while the circumferential compressive stress perpendicular to the mouth of the fracture was increasing. Pore pressures near the wellbore were affected by the invasion of drilling fluid, and were gradually increasing with time.