Patent ID: 6041509
Filing Date: 2000-03-28
Classification: E21B

Abstract:
A method of determining the space position of the axis of a cased well, said method comprising the steps of:providing a down-the-hole instrument-inclinometer having a sensor of the angle of rotation of said down-the-hole instrument-inclinometer, a sensor of the zenith angle of the longitudinal axis of the well being surveyed, and a plurality of azimuthally stabilizing spring-loaded arcuate elements:placing the down-the-hole instrument-inclinometer at the mouth of the well being surveyed;azimuthal stabilizing of said instrument at said well mouth in such a manner that any point on the surface of said instrument does not change its azimuthal direction while running said instrument into said well, and an azimuthal deviation of the longitudinal axis of said well causes said instrument to rotate round its longitudinal axis, using said plurality of spring-loaded elements, through an angle equal to the angle of azimuthal deviation of said longitudinal axis of said well;fixing the azimuthal direction of said azimuthally stabilized instrument and determining the datum point for measuring said angle of rotation of said instrument round its longitudinal axis in response to an azimuthal deviation of said longitudinal axis of said well;running said instrument into said well;measuring the magnitude of the zenith angle of said longitudinal axis of said well using said zenith angle sensor;obtaining the processed output data from said sensor of the zenith angle of said instrument, said data being indicative of the magnitude of the zenith angle of said longitudinal axis of said well during said measurement of said angle;measuring, by means of said sensor of the angle of rotation of said instrument, the magnitude of said angle of rotation of said instrument round its longitudinal axis with respect to said datum point, said rotation resulting from an azimuthal deviation of said longitudinal axis of said well during said running-in of said instrument;obtaining the processed output data from said sensor of the angle of rotation of said instrument, said data being indicative of the magnitude of said angle of rotation of said instrument round its longitudinal axis during said measurement of the magnitude of said angle, said magnitude being equal to the magnitude of the azimuthal deviation of said longitudinal axis of said well; anddetermining the space position of said longitudinal axis of said well by processing said output data on the magnitude of said zenith angle and of said angle of the azimuthal deviation of the longitudinal axis of said well, obtained from said measurements.