Numerical Simulation of Borehole Wall Strengthening Using ABAQUA

The borehole wall strengthening technology has in recent years been becoming an important means of enhancing the compressive strength of formations all over the world. This paper discusses a two-dimensional model for borehole wall strengthening based on the software ABAQUS, and the working mechanism of and factors affecting borehole wall strengthening through numerical simulation. It has been found that plugging materials, after bridging the fractures in the formations, laterally press the formations on both sides, increasing the peripheral stresses of the borehole which have the maximum increase between the lower angles of 0° and 30°. After the redistribution of the peripheral stresses, the fracture pressure of the formation is increased, and the easy-to-fracture point is deviated from its original position. In certain fracture openings, the wider the fractures, the more severe the lateral formations are pressed, and hence the better the strengthening of the borehole wall. Anisotropy of geo-stresses, positions of the bridging by plugging agents and borehole pressures all play important roles in affecting the peripheral stresses. The more severe the anisotropy, and the higher the borehole pressure, the higher the peripheral stress increments after bridging. Bridging spots of the plugging agents that are much closer to the borehole wall mean better strengthening effects; with the bridging spots moving towards the apexes of the fractures, the borehole wall strengthening dies away.