Optically-controlled switching of power to downhole devices

Abstract

A well having optically controlled switching, the well including a power cable run along a tubular string in a borehole, one or more downhole devices attached to the tubular string, one or more optically-controlled switches arranged downhole, where each switch is coupled between the power cable and one of the one or more downhole devices to enable or disable a flow of power to the downhole device, and a switch controller coupled to the one or more optically-controlled switches via an optical fiber, where each of the one or more optically-controlled switches are independently controllable.

What is claimed is: 
     
         1 . A well having optically-controlled switching, the well comprising:
 a power cable run along a tubular string in a borehole;   one or more downhole devices attached to the tubular string;   one or more optically-controlled switches arranged downhole, wherein each switch is coupled between the power cable and one of the one or more downhole devices to enable or disable a flow of power to the downhole device; and   a switch controller coupled to the one or more optically-controlled switches via an optical fiber, wherein each of the one or more optically-controlled switches are independently controllable.   
     
     
         2 . The well of  claim 1 , wherein at least one of the downhole devices includes a capacitive electrode. 
     
     
         3 . The well of  claim 1 , wherein at least one of the downhole devices includes a galvanic electrode. 
     
     
         4 . The well of  claim 1 , wherein at least one of the downhole devices includes a multi-turn loop antenna. 
     
     
         5 . The well of  claim 1 , wherein at least one of the downhole devices is an electric motor. 
     
     
         6 . The well of  claim 1 , wherein the switch controller is arranged at the surface. 
     
     
         7 . The well of  claim 1 , further comprising an optical fiber current sensor coupled to at least one of the optically-controlled switches that measures a current of the corresponding downhole device. 
     
     
         8 . The well of  claim 1 , further comprising optical fiber voltage sensor coupled to at least one of the optically-controlled switch that measures a voltage of the corresponding downhole device. 
     
     
         9 . The well of  claim 1 , wherein the power cable is a multi-conductor cable. 
     
     
         10 . The well of  claim 1 , wherein the tubular string is electrically insulated. 
     
     
         11 . The well of  claim 1 , wherein the tubular string is a casing string cemented within the borehole. 
     
     
         12 . The well of  claim 1 , further comprising a processing unit which determines a formation characteristic. 
     
     
         13 . A permanent electromagnetic (EM) monitoring method, comprising:
 positioning a tubular string having a power cable and one or more downhole devices attached thereto in a borehole;   controlling the flow of power to each of the downhole devices via one or more optically-controlled switches arranged downhole, wherein each switch is coupled between one of the one or more downhole devices and the power cable; and   controlling the one or more optically-controlled switches with a switch controller, the switch controller being coupled to the one or more optically-controlled switches via an optical fiber, and wherein each of the one or more optically-controlled switches are independently controllable.   
     
     
         14 . The method of  claim 13 , further comprising cementing the tubular string and downhole devices in the borehole. 
     
     
         15 . The method of  claim 13 , further comprising monitoring characteristics of the downhole devices. 
     
     
         16 . The method of  claim 15 , wherein the characteristic includes one of the group of an electrical current, an electrical voltage, a temperature, or a vibration. 
     
     
         17 . The method of  claim 16 , wherein the monitoring the electrical current is performed by an optical fiber current sensor coupled to one of the optically-controlled switches. 
     
     
         18 . The method of  claim 16 , wherein the monitoring the electrical voltage is performed by an optical fiber voltage sensor coupled to one of the optically-controlled switches. 
     
     
         19 . The method of  claim 13 , further comprising controlling one of a voltage, current, or waveform of the downhole devices with the corresponding optically-controlled switch. 
     
     
         20 . The method of  claim 13 , wherein one of the downhole devices includes a multi-turn loop antenna, the method further comprising measuring an electromagnetic signal with the multi-turn loop antenna. 
     
     
         21 . The method of  claim 13 , wherein one of the downhole devices includes an electric motor, the method further comprising controlling the electric motor. 
     
     
         22 . The method of  claim 13 , further comprising determining a formation characteristic with a processing unit.