Method for calculating gyroscopic wellbore surveys including correction for unexpected instrument movement

Abstract

A method for calculating a gyroscope survey is disclosed. The method includes measuring outputs of gyroscopes and accelerometers in a survey instrument. An instrument rotational movement is determined from the outputs of the gyroscopes. If the rotational movement exceeds a predetermined threshold, an instrument attitude is calculated from the gyroscope measurements, using the most recent alignment measurement to initialize the attitude measurement. Instrument alignment is calculated from the output of the accelerometers and gyroscopes when the threshold is not exceeded. In one embodiment, alignment is calculated using Kalman filtering. In a particular application, azimuth and inclination of a wellbore are determined at selected positions from the alignment and/or attitude measurements. The wellbore azimuth and inclination are used in one embodiment to calculate the wellbore trajectory along its length.

Dependencies are inferred from the claim text.