Mathematical concept - Stress Cloud - can predict borehole failure

A theoretical model of borehole failure has been developed which predicts the conditions for pressure-induced lost circulation (hydraulic fracturing) and borehole collapse. The model can be used to calculate the conditions of borehole failure in vertical and directional wells under normal and tectonic in situ conditions. The results show that deviation and hole direction can significantly influence both lost circulation and borehole collapse. The study concludes with an illustration on how this theoretical model can be used to select proper mud weights to prevent borehole failure. Borehole instability is a continuing problem which results in substantial yearly expenditure by the petroleum industry. As a result, a major concern of the drilling engineer is keeping the borehole wall from falling in or breaking down. Detailed attention is paid to drilling fluid programs, casing programs, and operating procedures in drilling a well to minimize these costly problems. In addition to the costs associated with borehole stability while drilling, borehole stability has a substantial impact on production problems.