Abstract: Bo re hole breakout is an important method to measure the orientation of earth stress. For inhomogeneous rocks, actual orientation of break out usually deviates from the minimum compressional st ress predicted by idealistic elastici ty. We use a Weibull dist ribution to describe the scat ter of mechanical property of rocks, and apply the RFPA method to simulate the bore hole breakout in inhomogeneous rocks to study theiro rientation dist ribution and possible errors. It is also shown that the RFPA method has broad future of application.

Key words: Bore hole breakout, RFPA method, Stress measurement