Electromagnetic pipe inspection with azimuthal defect evaluation

Abstract

Aspects of the subject technology relate to systems, methods, and computer-readable media for azimuthal defect evaluation through electromagnetic pipe inspection tools. A tool for monitoring an integrity of a well tubular can comprise a transmitter station with transmitter coil(s) configured to excite eddy currents in the well tubular. The tool can comprise a receiver station with receiver coil(s) to measure electromagnetic fields generated by the eddy currents. The tool can generate tool measurements in a first dimension that is axial depth, a second dimension that is azimuth, and a third dimension that is radial depth based on the measured electromagnetic field. At least one of the transmitter and receiver coils can have a polarization axis orthogonal to an axis of the well tubular. Further, one of the transmitter station and the receiver station comprises only non-azimuthal sensors.

What is claimed is: 
     
         1 . A tool for monitoring an integrity of a well tubular comprising:
 at least one transmitter station comprising at least one transmitter coil configured to excite eddy currents in the well tubular;   at least one receiver station comprising at least one receiver coil configured to measure an electromagnetic field that is generated in part by the eddy currents and is sensitive to a thickness of the well tubular; and   one or more processors configured to generate tool measurements in a first dimension that is axial depth in relation to the tool disposed in the well tubular, a second dimension that is azimuth in relation to the tool disposed in the well tubular, and a third dimension that is radial depth in relation to the tool disposed in the well tubular based on the measured electromagnetic field;   wherein:
 at least one of the transmitter coil and the receiver coil has a polarization axis orthogonal to an axis of the well tubular; and 
 one of the transmitter station and the receiver station comprises only non-azimuthal sensors. 
   
     
     
         2 . The tool of  claim 1 , wherein the receiver station comprises a plurality of radially-oriented receiver coils arranged at different azimuthal directions to span a circumference defined with respect to the tool. 
     
     
         3 . The tool of  claim 1 , wherein the receiver station comprises a plurality of azimuthally oriented receiver coils arranged at different azimuthal directions to span a circumference defined with respect to the tool. 
     
     
         4 . The tool of  claim 1 , wherein the transmitter station comprises a plurality of radially oriented transmitter coils arranged at different azimuthal directions to span a circumference defined with respect to the tool and the transmitter coils are excited either independently or simultaneously. 
     
     
         5 . The tool of  claim 1 , wherein the transmitter station comprises a plurality of azimuthally oriented transmitter coils arranged at different azimuthal directions to span a circumference defined with respect to the tool and the transmitter coils are excited either independently or simultaneously. 
     
     
         6 . The tool of  claim 1 , wherein the transmitter station comprises two axial coils and the two axial coils are either:
 excited with the same polarity to provide an equivalent axial transmitter; or   excited with opposite polarity to provide an equivalent radial transmitter.   
     
     
         7 . The tool of  claim 1 , wherein the transmitter station comprises one axial coil mounted on a body of the tool. 
     
     
         8 . The tool of  claim 1 , wherein the transmitter station and the receiver station are disposed at different axial positions such that the tool measurements can be generated at multiple radial depths. 
     
     
         9 . The tool of  claim 8 , wherein the well tubular is an innermost tubular of a plurality of tubulars and the tool measurements generated at multiple radial depths comprise a shallow depth of investigation sensitive to anomalies on the innermost tubular and the tool measurements generated at multiple radial depths comprise a deeper depth of investigation in relation to the shallow depth of investigation that is sensitive to anomalies on an outer tubular of the plurality of tubulars with respect to the innermost tubular. 
     
     
         10 . The tool of  claim 1 , wherein at least one of the transmitter station and the receiver station comprises extendable arms, spring-loaded pads, or packers coupled to a body of the tool to move one or more coils of either or both the transmitter station and the receiver station towards an inner wall of the tubular. 
     
     
         11 . The tool of  claim 1 , wherein the transmitter station is disposed on the a mandrel of the tool and the receiver station is disposed on one of extendable arms, spring-loaded pads, or packers to move one or more coils of the receiver station towards an inner wall of the tubular. 
     
     
         12 . The tool of  claim 1 , wherein the tool comprises a plurality of transmitter stations and corresponding first and second transmitters stations of the plurality of transmitter stations are disposed symmetrically on opposing sides of the receiver station and the first and second transmitters are either excited with the same polarity to form an equivalent axial transmitter or with opposite polarity to form an equivalent radial transmitter. 
     
     
         13 . The tool of  claim 1 , wherein transmitter and receiver coils are wound around cores made of high magnetic permeability material. 
     
     
         14 . The tool of  claim 1 , wherein the at least one receiver coil is coupled to an electromagnetic shield made of a material with an electrical conductivity or magnetic permeability to affect azimuthal focusing. 
     
     
         15 . The tool of  claim 1 , wherein at least one of the transmitter station and the receiver station further comprises at least one radially oriented coil placed within an electromagnetic shield and mounted on a rotating head. 
     
     
         16 . The tool of  claim 1 , wherein the at least one transmitter coil is excited with continuous-wave current with at least one frequency. 
     
     
         17 . The tool of  claim 1 , further comprising a navigation module comprising a tri-axial accelerometer or gyroscope to detect an azimuth of the tool with respect to a reference and the one or more processors configured to generate display data images indicative of a true azimuth determined based on the azimuth of the tool. 
     
     
         18 . A method for monitoring an integrity of a well tubular comprising:
 disposing a tool in proximity to the well tubular, the tool comprising:
 at least one transmitter station comprising at least one transmitter coil configured to excite eddy currents in the well tubular; 
 at least one receiver station comprising at least one receiver coil configured to measure an electromagnetic field that is generated in part by the eddy currents and is sensitive to a thickness of the well tubular; and 
 one or more processors configured to generate tool measurements in a first dimension that is axial depth in relation to the tool disposed in the well tubular, a second dimension that is azimuth in relation to the tool disposed in the well tubular, and a third dimension that is radial depth in relation to the tool disposed in the well tubular based on the measured electromagnetic field; 
 wherein:
 at least one of the transmitter coil and the receiver coil has a polarization axis orthogonal to an axis of the well tubular; and 
 one of the transmitter station and the receiver station comprises only non-azimuthal sensors. 
 
   recording voltages at the at least one receiver coil at different axial locations, azimuthal locations, and multiple depths of investigation of the well tubular based on the measured electromagnetic field that is generated by the eddy currents;   generating the tool measurements based on the voltages recorded at the at least one receiver coil; and   displaying the measurements as 2-D images with the first dimension of the axial depth and the second dimension of the azimuth in relation to the tool disposed in the well tubular, and each 2-D image of the 2-D images has a different depth of investigation.   
     
     
         19 . The method of  claim 18 , wherein the receiver station comprises a first receiver coil and a second receiver coil disposed 180 degrees apart and differential voltage measurements between the first receiver coil and the second receiver coil are made based on excitation of the transmitter station with a known and controlled signal. 
     
     
         20 . The method of  claim 18 , wherein the receiver station comprises a first receiver coil and a second receiver coil adjacent to the first receiver coil and differential voltage measurements between the first receiver coil and the second receiver coil are made based on excitation of the transmitter station with a known and controlled signal.