Power and signal transmission using insulated conduit for permanent downhole installations

Abstract

An apparatus and method is presented for establishing electrical connection to permanent downhole oilfield installations using an electrically insulated conducting casing. Current is caused to flow in the casing by a source on the surface connected to the casing. One or more permanent downhole installations are electrically connected to the casing, and the electrical connection to the casing is used to power the downhole installations. The downhole installations also inject a signal into the insulated casing that passes via the casing to a surface readout which detects and records the downhole signals.

We claim:  
     
         1 . A method for transmitting at least one electrical signal to or from at least one downhole device in a well, the method comprising the steps of: 
 providing an electrically conductive conduit in the well;    electrically insulating a section of the conduit by encapsulating a section of the conduit with an insulative layer and insulating the encapsulated section of conduit from an adjoining section of the conduit by a conduit gap;    introducing the electrical signal within the insulated section of conduit;    providing a return path for the electrical signal; and    coupling the downhole device to the insulated section.    
     
     
         2 . The method of  claim 1  wherein the step of introducing the electrical signal is performed via inductive coupling.  
     
     
         3 . The method of  claim 1  wherein the step of introducing the electrical signal is performed via direct coupling.  
     
     
         4 . The method of  claim 1  wherein the electrical signal includes power signals.  
     
     
         5 . The method of  claim 1  wherein the electrical signal includes communication signals.  
     
     
         6 . The method of  claim 5  wherein the step of introducing the electrical signal is performed by one of the downhole devices.  
     
     
         7 . The method of  claim 5  wherein the step of introducing the electrical signal is performed by a surface device.  
     
     
         8 . The method of  claim 7  further including the step of inductively coupling the surface device to the insulated section of conduit.  
     
     
         9 . The method of  claim 7  further including the step of directly coupling the surface device to the insulated section of conduit.  
     
     
         10 . The method of  claim 1  wherein the step of electrically insulating a section of conduit further comprises the step of disposing a second conduit gap to form a completely electrically insulated conduit section.  
     
     
         11 . The method of  claim 10  further including the step of inductively coupling the surface device to the insulated section of conduit.  
     
     
         12 . The method of  claim 10  further including the step of directly coupling the surface device to the insulated section of conduit.  
     
     
         13 . The method of  claim 10  further including the step of inductively coupling at least one of the downhole device to the insulated section of conduit.  
     
     
         14 . The method of  claim 10  further including the step of directly coupling at least one of the downhole devices to the insulated section of conduit.  
     
     
         15 . The method of any one of claims  1 - 14  wherein the return path for the electrical signal is provided through the earth formation surrounding the well.  
     
     
         16 . The method of any one of claims  1 - 14  wherein the step of providing a conductive conduit comprises providing electrically conductive casing permanently installed in the well via cementation.  
     
     
         17 . The method of  claim 16  wherein the cement is of a highly conductive formulation.  
     
     
         18 . The method of  claim 16  or  17  wherein the return path for the electrical signal is provided through the cement.  
     
     
         19 . The method of  claim 18  further including the step of retrieving the electric signal from the insulated section of conduit.  
     
     
         20 . The method of  claim 19  wherein the step of retrieving is performed by inductive coupling.  
     
     
         21 . The method of  claim 19  wherein the step of retrieving is performed by direct coupling.  
     
     
         22 . The method of  claim 1  wherein the step of introducing the electrical signal within the insulated section of conduit is performed via coupling through a second conductive conduit.  
     
     
         23 . The method of any one of claims  1 - 14  further including the step of providing an outer electrically conductive layer on the insulated conduit.  
     
     
         24 . The method of  claim 23  wherein the return path for the electrical signal is through the outer conductive layer.  
     
     
         25 . The method of any one of claims  1 - 24  wherein the conduit gap is disposed within the insulative layer.  
     
     
         26 . An apparatus for transmitting at least one electrical signal to or from at least one downhole device in a well, the apparatus comprising: 
 an electrically conductive conduit installed in the well;    insulation means for electrically insulating a section of the conduit, the insulation means comprising an insulative encapsulation layer around the section of the conduit and a conduit gap insulating the insulated section of the conduit from an adjoining section of the conduit;    means for introducing the electrical signal within the insulated section of the conduit;    means for providing a return path for the electrical signal; and    means for electrically connecting the downhole device to the insulated section of the conduit.    
     
     
         27 . The apparatus of  claim 26  wherein the means for introducing the signal employs inductive coupling.  
     
     
         28 . The apparatus of  claim 26  wherein the means for introducing the signal employs direct coupling.  
     
     
         29 . The apparatus of  claim 26  wherein the electrical signal includes power signals.  
     
     
         30 . The apparatus of  claim 26  wherein the electrical signal includes communication signals.  
     
     
         31 . The apparatus of  claim 30  wherein the electrical signal is sourced by the downhole device.  
     
     
         32 . The apparatus of  claim 30  wherein the electrical signal is sourced by a surface device.  
     
     
         33 . The apparatus of  claim 31  wherein the surface device is connected to the insulated section via inductive coupling  
     
     
         34 . The apparatus of  claim 31  wherein the surface device is directly coupled to the insulated section.  
     
     
         35 . The apparatus of  claim 26  wherein the insulation means further comprises a second conduit gap disposed to form a completely electrically insulated conduit section.  
     
     
         36 . The apparatus of  claim 35  wherein the surface device is inductively coupled to the insulated section.  
     
     
         37 . The apparatus of  claim 35  wherein the surface device is directly coupled to the insulated section.  
     
     
         38 . The apparatus of  claim 35  wherein the downhole device is inductively coupled to the insulated section.  
     
     
         39 . The apparatus of  claim 35  wherein the downhole device is directly coupled to the insulated section.  
     
     
         40 . The apparatus of any one of claims  26 - 39  wherein the return path for the electrical signal is through the earth formation surrounding the well.  
     
     
         41 . The apparatus of any one of claims  26 - 39  wherein the conductive conduit comprises electrically conductive casing permanently installed in the well via cementation.  
     
     
         42 . The apparatus of  claim 41  wherein the cement is of a highly conductive formulation.  
     
     
         43 . The apparatus of  claim 41  or  42  wherein the return path for the electrical signal is through the cement.  
     
     
         44 . The apparatus of  claim 43  further comprising means for retrieving the electric signal from the insulated section of conduit.  
     
     
         45 . The apparatus of  claim 44  wherein the means for retrieving comprises inductive coupling.  
     
     
         46 . The apparatus of  claim 44  wherein the means for retrieving comprises direct coupling.  
     
     
         47 . The apparatus of any one of claims  26 - 46  wherein the means for introducing the electrical signal within the insulated section of conduit comprises a second conductive conduit.  
     
     
         48 . The apparatus of any one of claims  26 - 39  wherein the conductive conduit further comprises an outer electrically conductive layer.  
     
     
         49 . The apparatus of  claim 48  wherein the return path for the electrical signal is through the outer conductive layer.  
     
     
         50 . The apparatus of any one of claims  26 - 49  wherein the conduit gap is disposed within the insulative layer.