PROBABILISTIC CALCULATION OF THE STRUCTURAL RELIABILITY OF DRILL STRINGS ON CURVED WELL SEGMENTS

摘要

We obtain in the framework of random quantity theory a model for calculating the reliability of the drill string with respect to the static strength criterion. On the curved well segments, this string is subject to tension and bending with torsion. We take as the reliability index the probability that the limit state of the string will not reach the yield strength of the material. We find the mathematical expectation of the outer diameter of the string with respect to the given normative reliability index, which depends on the ratio of the expenditures on the planned and emergency replacement of the string. We study the sensitivity of the reliability of the string to the scatter of the strength characteristics, the loads, and the dimensions for the case when the initial values are normally distributed.