Borehole collapse and lost circulation are two main failure modes of borehole. To prevent lost circulation, the mud weight needs to be smaller than an upper limit so that tensile stress on the borehole wall is smaller than the tensile strength of rocks , and an upper limit so that stresses on the borehole wall is within shear failure criterion. To prevent borehole collapse, the mud weight needs to be big enough so that the stress state on the borehole wall doesn’t reach yield condition. Based on rigorous mechanics principles, GEOANT developed the software WELLPATH that can recommend appropriate mud weight windows for any deviated borehole and in-situ stress conditions.
