Stochastic error analysis of misalignment between axis of inclinometer and trajectory in process of measuring while drilling

In order to describe the trajectory error derived from measurement while drilling more accurately, the error caused by misalignment between axis of inclinometer and borehole axis was analyzed by error analysis theory and calculated by Lagrange interpolation method. The results indicate that the misalignment error should be included into the scope of stochastic error. According to the characteristics of this kind of error item, it will take equal effect on inclination and azimuth of the survey results. And the distribution feature of this stochastic error belongs to the uniform distribution. Through analysis and comparison, this stochastic error produces much less uncertainty compared with systematic error. The center of stochastic error ellipsoid at a survey station is close to this survey station. With the increase of the gap, the distance between the center of stochastic error ellipsoid and the corresponding survey station increases too. The dimension of ellipsoid also takes the same variation tendency.