Correction of Cross-Component Induction Measurements for Misalignment Using Comparison of the XY Formation Response

Abstract

Measurements are made with a multicomponent logging tool in an earth formation. The measurements are inverted without using a selected cross-component measurement. The model is then used to predict the value of the selected cross-component. A misalignment angle of the tool is estimated from the predicted and actual values of the selected cross-component.

1 . A method of estimating a parameter of interest of an earth formation, the method comprising: 
 (a) conveying a logging tool into a borehole in the earth formation;    (b) obtaining a plurality of multi-component resistivity measurements using the logging tool;    (c) inverting the multi-component resistivity measurements without using a particular cross-component to give a resistivity model;    (d) using the resistivity model to provide a simulated value of the particular cross-component; and    (e) using the simulated value of the particular cross-component and an actual value of the particular cross-component for estimating a misalignment angle in the logging tool.    
   
   
       2 . The method of  claim 1  wherein inverting the multi-component measurements further comprises using a search technique.  
   
   
       3 . The method of  claim 1  further comprising obtaining multi-array induction measurements and using the multi-array induction measurements in the inversion.  
   
   
       4 . The method of  claim 1  wherein inverting the multi-component measurements further comprises: 
 (i) using a first subset of the measurements to estimate a horizontal resistivity of the formation, and    (ii) using the estimated horizontal resistivity and another subset of the measurements to estimate a vertical resistivity of the earth formation.    
   
   
       5 . The method of  claim 1  wherein inverting the multi-component measurements further comprises using a separation of modes.  
   
   
       6 . The method of  claim 1  wherein the particular cross-component is selected from (i) an XY component, and (ii) an XZ component.  
   
   
       7 . The method of  claim 1  wherein determining the misalignment angle further comprises using an average value of the particular cross-component and an average simulated value of the particular cross-component.  
   
   
       8 . The method of  claim 1  further comprising using the misalignment angle and the multi-component measurements to estimate the parameter of interest of the earth formation.  
   
   
       9 . The method of  claim 8  wherein the parameter of interest is at least one of (i) a horizontal conductivity, (ii) a vertical conductivity, (iii) a horizontal resistivity, (iv) a vertical resistivity, (v) a relative dip angle, (vi) a strike angle, (vii) a sand fraction, (viii) a shale fraction, and (ix) a water saturation.  
   
   
       10 . An apparatus for estimating a parameter of interest of an earth formation, the apparatus comprising: 
 (a) a logging tool configured to be conveyed into a borehole in the earth formation and which is configured to obtain a plurality of multi-component resistivity measurements; and    (b) a processor which is configured to: 
 (A) invert the multi-component resistivity measurements without using a particular cross-component to give a resistivity model;  
 (B) use the resistivity model to provide a simulated value of the particular cross-component; and  
 (C) use the simulated value of the particular cross-component and an actual value of the particular cross-component to estimate a misalignment angle in the logging tool.  
   
   
   
       11 . The apparatus of  claim 10  wherein the processor is configured to invert the multi-component measurements using a search technique.  
   
   
       12 . The apparatus of  claim 10  wherein the processor is configured to invert the multi-component measurements using: 
 (i) a first subset of the measurements to estimate a horizontal resistivity of the formation, and    (ii) the estimated horizontal resistivity and another subset of the measurements to estimate a vertical resistivity of the earth formation.    
   
   
       13 . The apparatus of  claim 10  wherein the processor is configured to invert the multi-component measurements by using a separation of modes.  
   
   
       14 . The apparatus of  claim 10  wherein the particular cross-component is selected from (i) an XY component, and (ii) an XZ component.  
   
   
       15 . The apparatus of  claim 10  wherein the processor is configured to estimate the misalignment using an average value of the particular cross-component and an average simulated value of the particular cross-component.  
   
   
       16 . The apparatus of  claim 10  wherein the processor is further configured to use the estimated misalignment angle and the multi-component measurements to estimate the parameter of interest of the earth formation.  
   
   
       17 . The apparatus of  claim 16  wherein the parameter of interest is at least one of (i) a horizontal conductivity, (ii) a vertical conductivity, (iii) a horizontal resistivity, (iv) a vertical resistivity, (v) a relative dip angle, (vi) a strike angle, (vii) a sand fraction, (viii) a shale fraction, and (ix) a water saturation.  
   
   
       18 . The apparatus of  claim 10  further comprising a wireline configured to convey the logging tool into the borehole.  
   
   
       19 . The apparatus of  claim 18  further comprising a motor configured to rotate the logging tool to the plurality of rotational angles.  
   
   
       20 . The apparatus of  claim 10  wherein the logging tool is part of a bottomhole assembly (BHA) configured to be conveyed into the borehole on a drilling tubular.  
   
   
       21 . A computer readable medium used with an apparatus for evaluating an earth formation, the apparatus comprising: 
 (a) a logging tool configured to be conveyed into a borehole in the earth formation which is configured to obtain a plurality of multi-component resistivity measurements;    the medium comprising instructions which enable a processor to    (b) invert the multi-component resistivity measurements without using a particular cross-component to give a resistivity model;    (c) use the resistivity model to provide a simulated value of the particular cross-component; and    (d) estimate a misalignment angle in the logging tool by using the simulated value of the particular cross-component and an actual value of the particular cross-component.    
   
   
       22 . The medium of  claim 20  further comprising at least one of (i) a ROM, (ii) an EPROM, (iii) an EAROMs, (iv) a flash memory, and (v) an Optical disk.