Method and system for downhole object location and orientation determination

Abstract

A downhole device is provided that is intended to be co-located with an optical fiber cable to be found, for example by being fixed together in the same clamp. The device has an accelerometer or other suitable orientation determining means that is able to determine its positional orientation, with respect to gravity. A vibrator or other sounder is provided, that outputs the positional orientation information as a suitable encoded and modulated acoustic signal. A fiber optic distributed acoustic sensor deployed in the vicinity of the downhole device detects the acoustic signal and transmits it back to the surface, where it is demodulated and decoded to obtain the positional orientation information. Given that the device is co-located with the optical fiber the position of the fiber can then be inferred. As explained above, detecting the fiber position is important during perforation operations, so that the fiber is not inadvertently damaged.

1 . An apparatus, comprising:
 i) an orientation detector arranged to detect the orientation of the apparatus;   ii) a vibrational and/or acoustic source arranged to produce vibrational or acoustic signals in dependence on the detected orientation of the apparatus, the produced vibrational or acoustic signals representing the detected orientation; and   iii) a clamp for clamping optical fiber to wellbore tubing or casing, the orientation detector and the vibrational and/or acoustic source being disposed within the clamp such that when in use the clamp is co-located with the optical fiber;   wherein the clamp clamps the orientation detector against or near to the optical fiber, the orientation detector being co-located with the optical fiber within the clamp such that any orientation that is then determined for the orientation detector also corresponds to the optical fiber and hence the position of the optical fiber around the wellbore tubing or casing can then be inferred.   
     
     
         2 . An apparatus according to  claim 1 , wherein the orientation detector is a three-axis accelerometer, wherein the accelerometer detects the orientation of the apparatus with respect to the direction of gravity. 
     
     
         3 . An apparatus according to  claim 1 , wherein the orientation detector comprises one or more offset rotatably mounted magnetic masses, and a magnetic detector arranged to detect a rotational orientation of the offset magnetic masses. 
     
     
         4 . An apparatus according to  claim 1 , wherein the orientation detector is a relative bearing sensor. 
     
     
         5 . An apparatus according to  claim 1 , wherein the vibrational or acoustic source is an impulse source that generates vibrational or acoustic impulses at one or more frequencies corresponding to respective one or more detected orientations. 
     
     
         6 . An apparatus according to  claim 1 , and further comprising a sealed case within which the orientation detector and the vibrational and/or acoustic source are contained. 
     
     
         7 . An apparatus according to  claim 1 , and further comprising control circuitry arranged to receive an orientation signal from the orientation detector, to determine the orientation of the apparatus in dependence on the orientation signal, and to control the vibrational or acoustic source so as to produce vibrational or acoustic signals encoding the determined orientation. 
     
     
         8 . A distributed acoustic sensor system, comprising an optical fiber deployed along a well bore and a signal processing apparatus arranged to receive optical backscatter and/or reflections from along the optical fiber and to process such backscatter and/or reflections to determine vibrational and/or acoustic signals incident on the optical fiber, the optical fiber being collocated at one or more positions along the well bore with an apparatus according to  claim 1 , vibrational or acoustic signals from said apparatus being detected by said distributed acoustic sensor system and processed to thereby determine the orientation of the apparatus. 
     
     
         9 . A system, comprising:
 i) a downhole and/or a remote device, wherein the downhole and/or remote device is an apparatus according to  claim 1 , the downhole and/or the remote device being provided with at least one vibrational transducer and arranged to produce vibro-acoustic signals pertaining to the downhole and/or remote device or its environment; and   ii) a fiber optic distributed acoustic sensor system, comprising an optical fiber deployed downhole and/or remotely and arranged to listen for the vibro-acoustic signals produced by the downhole and/or remote device;   wherein the fiber optic distributed acoustic sensor system communicates information from the downhole and/or remote device to the surface or local vicinity of the fiber optic distributed acoustic sensor system.   
     
     
         10 . A method, comprising:
 i) providing a downhole and/or a remote device, wherein the downhole and/or remote device is an apparatus according to  claim 1 , the downhole and/or remote device further having at least one vibrational transducer and arranged to produce vibro-acoustic signals pertaining to the downhole and/or remote device or its environment; and   ii) operating a fiber optic distributed acoustic sensor system comprising an optical fiber deployed downhole and/or remotely so as to listen for the vibro-acoustic signals produced by the downhole and/or remote device;   wherein the fiber optic distributed acoustic sensor system communicates information from the downhole and/or remote device to the surface or local vicinity of the fiber optic distributed acoustic sensor system.   
     
     
         11 . A distributed acoustic sensor system, comprising an optical fiber deployed along a well bore and a signal processing apparatus arranged to receive optical backscatter and/or reflections from along the optical fiber and to process such backscatter and/or reflections to determine vibrational and/or acoustic signals incident on the optical fiber, the optical fiber being collocated at one or more positions along the well bore with an apparatus, vibrational or acoustic signals from said apparatus being detected by said distributed acoustic sensor system and processed to thereby determine an orientation of the apparatus, said apparatus, comprising:
 a sealed case, the sealed case having contained within it:
 i) an orientation detector arranged to detect the orientation of the apparatus; and 
 ii) a vibrational and/or acoustic source arranged to produce vibrational and/or acoustic signals in dependence on the detected orientation of the apparatus, the produced vibrational and/or acoustic signals representing the detected orientation, the vibrational and/or acoustic source in use imparting the vibrational and/or acoustic signals to the sealed case; and 
 iii) control circuitry arranged to: receive an orientation signal from the orientation detector, determine the orientation of the apparatus in dependence on the orientation signal, and control the vibrational and/or acoustic source so as to impart the vibrational and/or acoustic signals encoding the determined orientation to the sealed case for detection external to the sealed case by said distributed acoustic sensor system. 
   
     
     
         12 . A system according to  claim 11 , wherein the orientation detector is a three-axis accelerometer. 
     
     
         13 . A system according to  claim 12 , wherein the accelerometer detects the orientation of the apparatus with respect to the direction of gravity. 
     
     
         14 . A system according to  claim 11 , wherein the orientation detector comprises one or more offset rotatably mounted magnetic masses, and a magnetic detector arranged to detect a rotational orientation of the offset magnetic masses. 
     
     
         15 . A system according to  claim 11 , wherein the orientation detector is a relative bearing sensor. 
     
     
         16 . A system according to  claim 11 , wherein the vibrational or acoustic source is an impulse source that generates vibrational or acoustic impulses at one or more frequencies corresponding to respective one or more detected orientations. 
     
     
         17 . A system according to  claim 16 , wherein the impulse source is an electromechanical tapper. 
     
     
         18 . A system according to  claim 11 , and further comprising a clamp for clamping the optical fiber to tubing or casing, the orientation detector and the vibrational and/or acoustic source being co-located within the clamp with the optical fiber. 
     
     
         19 . A system according to  claim 11 , wherein the control circuitry includes a microprocessor. 
     
     
         20 . A system according to  claim 11 , wherein the apparatus is arranged to be one of:
 battery powered, powered by a non-chemical energy storage mechanism or powered by a power wireline from the surface.