STOCHASTIC OPTIMIZATION TECHNIQUE FOR IN SITU STRESSES FROM THE PROBABILITY DISTRIBUTIONS OF ROCK STRENGTH AND BOREHOLE BREAKOUT WIDTH

摘要

Disclosed is a stochastic optimization method for in situ stress from a probability distribution of rock strength and a borehole wall breakout width. According to the present invention, the stochastic optimization method for in situ stress from the probability distribution of rock strength and the borehole wall breakout width simultaneously determines minimum horizontal stress (S_h) and maximum horizontal stress (S_H) applied to the borehole, comprising: a step of securing elastic wave speed logging data and image logging data (breakout width data); a step of calculating a probability distribution for rock strength from the elastic wave speed logging data; a step of calculating a probability distribution of a breakout width from the probability distribution for the rock strength; a step of calculating an objective function from a difference between the calculated probability distribution of the breakout width and dispersion of the breakout width from the image logging data; and a step of simultaneously calculating the minimum horizontal stress and the maximum horizontal stress from the objective function having a minimum value.