Method of Manufacturing a Logging Tool for a Borehole

Abstract

Methods of manufacturing a logging tool for a borehole are provided. In an embodiment of the present invention, shields are disposed to prevent or reduce circulating electrical currents from causing a voltage difference that would adversely affect the measured voltage difference between two adjacent electrodes. Groups of sensors, e.g., two or more, may be placed within the shield. The shields may have any cross-section shape. A magnetic field source is disposed proximate the electrodes such that the magnetic field source is oriented to generate a magnetic field substantially orthogonal to an imaginary line intersecting each pair of electrodes. A voltage measuring circuit is electrically coupled to the plurality of electrodes and configured to measure a voltage difference between each pair of electrodes.

What is claimed is: 
     
         1 . A method of manufacturing a logging tool for a borehole, the method comprising:
 disposing pairs of voltage sensing electrodes in a sensing device;   forming shields interposed between each of the pairs of voltage sensing electrodes, wherein the shields are configured to isolate each of the pairs of voltage sensing electrodes from ambient electrical current flow between the pairs of voltage sensing electrodes;   coupling the sensing device to a tool body configured to be inserted into the borehole, wherein the sensing device is configured to detect radial flow of conductive fluid entering or leaving an interior wall of the borehole, and wherein the sensing device is configured to detect the conductive fluid flow adjacent the borehole interior wall.   
     
     
         2 . The method of  claim 1 , wherein the shields are interconnected. 
     
     
         3 . The method of  claim 1 , wherein each of the shields comprises a conduit configured to allow fluid to flow therethrough. 
     
     
         4 . The method of  claim 1 , wherein each of the voltage sensing electrodes is a point electrode. 
     
     
         5 . The method of  claim 1 , wherein each of the voltage sensing electrodes is a longitudinal electrode. 
     
     
         6 . The method of  claim 1 , wherein each pair of electrodes substantially covers opposing sides of the respective shields. 
     
     
         7 . The method of  claim 1 , wherein the sensing device is a sensor loop. 
     
     
         8 . The method of  claim 1 , further comprising disposing a magnetic field source in the sensing device proximate the electrodes, wherein the magnetic field source is oriented to generate a magnetic field substantially orthogonal to an imaginary line intersecting each pair of electrodes. 
     
     
         9 . The method of  claim 8 , wherein the magnetic field source is an alternating magnetic field source. 
     
     
         10 . The method of  claim 8 , wherein the disposing the magnetic field source further comprises:
 disposing a first coil of wire in the sensing device proximate the electrodes; and   disposing a second coil of wire in the sensing device proximate the electrodes and offset from the first coil of wire.   
     
     
         11 . The method of  claim 10 , wherein the disposing the magnetic field source further comprises disposing a ferromagnetic material between the first coil of wire and the second coil of wire. 
     
     
         12 . The method of  claim 1 , further comprising electrically coupling a respective resistor between each pair of electrodes. 
     
     
         13 . The method of  claim 12 , wherein the electrically coupling is performed before the disposing the electrodes and the disposing the resistors. 
     
     
         14 . The method of  claim 1 , wherein the electrodes are regularly spaced in the sensing device. 
     
     
         15 . The method of  claim 14 , wherein first and second electrodes in each electrode pair are spaced about 0.3 inches or less from each other. 
     
     
         16 . The method of  claim 1 , wherein the sensing device has a substantially oval shape.