Rate gyro wells survey system including nulling system
First Claim
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1. A method of obtaining a survey in a well borehole subject to deviation from the vertical which comprises the steps of:
- a) positioning in a well borehole a rate gyro having an axis of rotation coincident with a sonde which supports said rate gyro, and moving said sonde along the well borehole and taking measurements at spaced locations to determine a reference north measurement by combining measurements made with said rate gyro at opposite azimuthal positions with respect to said axis of rotation;
b) measuring the direction of gravity along the sonde as it moves in the well borehole;
c) determining from said measurements at least two dimensions of the position of the sonde in the well borehole; and
(d) determining the quality of said at least two determinations of the position of the sonde in the well borehole.
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Abstract
A method for well borehole survey is set out. A sonde supports X and Y accelerometers and X and & sensors on a rate gyro having a Z axis aligned with the sonde. On a slickline, or within a drill string, the sonde is used to measure four variables, these being Gx and Gy, Ax and Az. This enables well azimuth and inclination to determined. Measuring depth enables a survey to be made.
74 Citations
23 Claims
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1. A method of obtaining a survey in a well borehole subject to deviation from the vertical which comprises the steps of:
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a) positioning in a well borehole a rate gyro having an axis of rotation coincident with a sonde which supports said rate gyro, and moving said sonde along the well borehole and taking measurements at spaced locations to determine a reference north measurement by combining measurements made with said rate gyro at opposite azimuthal positions with respect to said axis of rotation; b) measuring the direction of gravity along the sonde as it moves in the well borehole; c) determining from said measurements at least two dimensions of the position of the sonde in the well borehole; and (d) determining the quality of said at least two determinations of the position of the sonde in the well borehole. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of obtaining a survey in a well borehole subject to deviation from the vertical which comprises the steps of:
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a) positioning in a well borehole a rate gyro having an axis of rotation coincident with a sonde which supports said rate gyro, moving said sonde along the well borehole and making two orthogonal signal measurements at spaced locations, and determining a reference north measurement from said orthogonal signal measurements; b) measuring the direction of gravity along the sonde during movement in the well borehole by making an additional two orthogonal signal measurement; and c) determining from said measurements at least two dimensions of the position of the sonde in the well borehole. - View Dependent Claims (9, 10, 11, 12)
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13. A method of performing a survey of a well borehole comprising the steps of:
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a) positioning an elongate sonde in a well borehole having a rate gyro therein rotating about an axis and forming an output indicative of north, and wherein said rate gyro is supported by a housing rotatable between first and second positions separated by 180°
of housing rotation and said output indicative of north comprises N measurements are made at a first sonde position, then the housing is rotated by 180° and
another N measurements is made where N is an integer;b) positioning the sonde at spaced locations along a well borehole; c) measuring the direction of the sonde along the well borehole; and d) combining the measurements to form a well borehole survey. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification