Reducing error contributions to gyroscopic measurements

Abstract

A method and system for reducing error contributions to gyroscopic measurements is provided. The method includes receiving a plurality of signals indicative of at least one component of the Earth's rotation substantially perpendicular to a portion of a wellbore and a component of the Earth's rotation substantially parallel to the portion of the wellbore. The plurality of signals is generated by one or more gyroscopic sensors within the portion of the wellbore. The method further includes calculating, using the plurality of signals and using one or more signals indicative of the Earth's rotation rate and one or more signals indicative of the latitude of the one or more gyroscopic sensors within the portion of the wellbore, a mass unbalance offset for the one or more gyroscopic sensors.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. patent application Ser. No. 13 / 243,989, filed on Sep. 23, 2011 and incorporated in its entirety by reference herein, which is a continuation of U.S. patent application Ser. No. 12 / 363,465, filed Jan. 30, 2009 and incorporated in its entirety by reference herein, now issued as U.S. Pat. No. 8,065,087.BACKGROUNDField[0002]The present application relates generally to systems and method for reducing error contributions to gyroscopic measurements from a wellbore survey system and / or determining the position or orientation of the survey system relative to the Earth.Description of the Related Art[0003]Many wellbore gyroscopic survey systems that are currently in service are based on angular rate measurements taken about two axes only, denoted the x and y axes, that are both substantially perpendicular to the direction along the wellbore (referred to as the “along-hole axis”) and substantially pe...

AI Technical Summary

Benefits of technology

The patent describes a method for reducing errors in gyroscopic measurements in a wellbore. The method involves receiving signals from gyroscopic sensors in the wellbore that indicate the rotation of the Earth perpendicular to the wellbore and parallel to the wellbore. These signals are combined with information about the rate of rotation of the Earth and the location of the sensors to calculate a mass unbalance offset. This offset is then used to control the downhole tool in the wellbore, reducing errors in the measurements. Overall, this method improves the accuracy of gyroscopic measurements in wellbore construction.

Problems solved by technology

While azimuth can be determined using a strapdown system, the process takes considerably longer to implement without the facility to index the gyro.

However, the mechanical complexity and consequent size of such a system preclude it as a viable option for down-hole application.

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