Estimating borehole geometry and lateral tool displacements

摘要

A method of determining a borehole geometry parameter vector (eg major and minor axes and orientation of an elliptical borehole cross section) and/or lateral tool displacement vector includes acquiring a plurality of sets of standoff measurements at a plurality of times using a downhole tool provided with a plurality (eg three) of standoff sensors (eg acoustic sensors). An azimuth sensor may be provided to acquire an azimuth measurement at the time of acquisition of each set of standoff measurements, but alternatively the azimuth is calculated. The method comprises processing a system of non-linear equations which includes variables representative of the borehole parameter vector, the lateral tool displacement vector, the plurality of sets of standoff measurements and the azimuth. The equations may be solved using a least squares technique. The method allows for simultaneous determination of borehole parameters of a borehole having a complex shape and an instantaneous displacement vector between the measurement tool and the borehole.