Adaptive parameter estimation for static and dynamic wellbore surveys

Abstract

Survey measurement compensation terms are determined for dynamic wellbore surveys. The compensation terms may be applied to either static or the dynamic surveys to obtain compensated survey measurements.

We claim: 
     
         1 . A wellbore surveying method comprising:
 making dynamic surveying measurements while rotating a drill string in a wellbore;   making static surveying measurements when drilling has temporarily stopped and the drill string has been pulled off of a bottom of the wellbore;   comparing the dynamic surveying measurements and the static surveying measurements to compute at least one dynamic surveying compensation term;   applying the dynamic surveying compensation term to subsequent dynamic surveying measurements to obtain compensated dynamic surveying measurements; and   computing at least one survey parameter from the compensated dynamic surveying measurements.   
     
     
         2 . The method of  claim 1 , wherein a measured depth of the dynamic surveying measurements is within about 15 m of a measured depth of the static surveying measurements. 
     
     
         3 . The method of  claim 1 , wherein the comparing comprises computing a difference between dynamic surveying measurements and the static surveying measurements to compute the least one dynamic surveying compensation term. 
     
     
         4 . The method of  claim 1 , wherein the applying comprises subtracting the dynamic surveying compensation term from the subsequent dynamic surveying measurements to obtain the compensated dynamic surveying measurements. 
     
     
         5 . The method of  claim 1 , wherein the dynamic surveying compensation term is an axial magnetometer compensation term. 
     
     
         6 . The method of  claim 1 , wherein the dynamic surveying compensation term is a toolface offset compensation term. 
     
     
         7 . The method of  claim 6 , wherein the comparing further comprises computing a time shift offset between magnetometer measurements and accelerometer measurements in the dynamic surveying measurements. 
     
     
         8 . The method of  claim 1 , wherein the dynamic surveying compensation term is at least one of an axial or cross-axial accelerometer compensation term. 
     
     
         9 . A wellbore surveying method comprising:
 making dynamic surveying measurements while rotating a drill string in a wellbore to drill, the dynamic surveying measurements including at least cross-axial magnetometer measurements;   fitting the cross-axial magnetometer measurements with a second-degree polynomial equation of an ellipse;   evaluating the fit to determine a cross-axial magnetometer measurement compensation; and   applying the cross-axial magnetometer measurement compensation to the cross-axial magnetometer measurements to compute a compensated transverse magnetic field measurement or compensated cross-axial magnetometer measurements.   
     
     
         10 . Them method of  claim 9 , further comprising saving a predetermined number of the cross-axial magnetometer measurements to a buffer, wherein the fitting comprises fitting the cross-axial magnetometer measurements saved in the buffer. 
     
     
         11 . The method of  claim 9 , wherein a center of the ellipse is offset from a center of a cross axial plane and major and minor axes of the ellipse are rotationally offset by a nonzero angle from measurement axes in the cross axial plane. 
     
     
         12 . The method of  claim 11 , wherein:
 the evaluating the fit comprises determining at least a first translational transformation that translates the ellipse to the center of the cross axial plane and a second rotational transformation that rotates the ellipse to align the major and minor axes of the ellipse with measurement axes in the cross axial plane; and   the applying comprises applying the first translational transformation and the second rotational transformation to the cross-axial magnetometer measurements to obtain the compensated transverse magnetic field measurement.   
     
     
         13 . The method of  claim 11 , wherein the major and minor axes of the ellipse are not equal to one another. 
     
     
         14 . The method of  claim 13 , wherein
 the evaluating the fit comprises determining at least a first translational transformation that translates the ellipse to the center of the cross axial plane, a second rotational transformation that rotates the ellipse to align the major and minor axes of the ellipse with measurement axes in the cross axial plane, and a third gain transformation that scales the ellipse such that the major and minor axes are equal to one another; and   the applying comprises applying the first translational transformation, the second rotational transformation, and the third gain transformation to the cross-axial magnetometer measurements to obtain the compensated transverse magnetic field measurement.   
     
     
         15 . The method of  claim 14 , wherein the compensated transverse magnetic field measurement is equal to the major and minor axes of the ellipse after the application of the first translational transformation, the second rotational transformation, and the third gain transformation to the cross-axial magnetometer measurements. 
     
     
         16 . The method of  claim 9 , further comprising:
 making static surveying measurements when drilling has temporarily stopped and the drill string has been pulled off of a bottom of the wellbore, the static surveying measurements including at least static cross-axial magnetometer measurements; and   applying the cross-axial magnetometer measurement compensation to the static cross-axial static magnetometer measurements to obtain compensated static cross-axial magnetometer measurements.   
     
     
         17 . A downhole tool comprising
 a downhole tool body configured to rotate in a wellbore;   a triaxial accelerometer set and a triaxial magnetometer set deployed in the tool body; and   a processor deployed in the tool body, the processor configured to cause the triaxial accelerometer set and a triaxial magnetometer set to make corresponding triaxial accelerometer and triaxial magnetometer measurements while the downhole tool body rotates in the wellbore, fit cross-axial ones of the triaxial magnetometer measurements with a second-degree polynomial equation of an ellipse, evaluate the fit to determine a cross-axial magnetometer measurement compensation, and apply the cross-axial magnetometer measurement compensation to the cross-axial magnetometer measurements to compute a compensated transverse magnetic field measurement or compensated cross-axial magnetometer measurements.   
     
     
         18 . The downhole tool of  claim 17 , wherein the processor is further configured to:
 determine at least a first translational transformation that translates the ellipse to the center of the cross axial plane and a second rotational transformation that rotates the ellipse to align the major and minor axes of the ellipse with measurement axes in the cross axial plane; and   apply the first translational transformation and the second rotational transformation to the cross-axial magnetometer measurements to obtain the compensated transverse magnetic field measurement.   
     
     
         19 . The downhole tool of  claim 17 , wherein the processor is further configured to:
 determine at least a first translational transformation that translates the ellipse to the center of the cross axial plane, a second rotational transformation that rotates the ellipse to align the major and minor axes of the ellipse with measurement axes in the cross axial plane, and a third gain transformation that scales the ellipse such that the major and minor axes are equal to one another; and   apply the first translational transformation, the second rotational transformation, and the third gain transformation to the cross-axial magnetometer measurements to obtain the compensated transverse magnetic field measurement.   
     
     
         20 . The downhole tool of  claim 17 , wherein the processor is further configured to:
 compare certain ones of the triaxial accelerometer and triaxial magnetometer measurements made while the downhole tool body rotates in the wellbore with corresponding ones of triaxial accelerometer and triaxial magnetometer measurements made while the downhole tool body is static in the wellbore to compute at least one dynamic surveying compensation term;   apply the dynamic surveying compensation term to subsequent triaxial accelerometer and triaxial magnetometer measurements made while the downhole tool body rotates in the wellbore to obtain compensated dynamic surveying measurements; and   compute at least one survey parameter from the compensated dynamic surveying measurements.