Erectable arm assembly for use in boreholes

Abstract

An erectable arm assembly for use in a borehole, the erectable arm assembly comprising a main body and an arm member, the arm member being able to move between a collapsed position in which the assembly can be removed from the borehole and an erected position, the erectable arm assembly being adapted to house a fluid drilling assembly comprising a fluid cutting device and a flexible hose drill string such that the arm member during erection can contain at least part of the fluid drilling assembly, and when in the erected position the arm member is able to guide the fluid cutting device towards the borehole wall, the assembly further including at least one sensor for monitoring the arm member or the fluid drilling assembly.

1 . An erectable arm assembly for use in a borehole, the erectable arm assembly comprising a main body and an arm member, the arm member movable between a collapsed position in which the assembly can be removed from the borehole and an erected position, the arm assembly being adapted to house a fluid drilling assembly comprising a fluid cutting device and a flexible hose drill string such that during erection the arm member can contain at least part of the fluid drilling assembly, and when in the erected position the arm member is able to guide the fluid cutting device towards the borehole wall, the assembly further including at least one sensor for monitoring the arm member or the fluid drilling assembly.  
     
     
         2 . The assembly of  claim 1 , wherein the fluid cutting device can be retracted into the arm member.  
     
     
         3 . The assembly of  claim 2 , wherein a said sensor is adapted to detect when the fluid cutting device has been retracted into the arm member.  
     
     
         4 . The assembly of  claim 3 , wherein the sensor comprises an electromagnetic sensor which is adapted to detect the presence of the fluid cutting device.  
     
     
         5 . The assembly of  claim 3 , wherein the sensor comprises an electric sensor which is adapted to the presence of the fluid cutting device.  
     
     
         6 . The assembly of  claim 1 , wherein a said sensor is adapted to detect the angle of erection of the arm member relative to the main body.  
     
     
         7 . The assembly of  claim 6 , wherein the sensor comprises a tilt transducer.  
     
     
         8 . The assembly of  claim 6 , comprising an hydraulic or pneumatic ram for moving the arm member between the collapsed position and erected position, the arm member being attached at one end to the main body and at the other end to the arm member and wherein the sensor is adapted to determine the extension of the ram.  
     
     
         9 . The assembly of any one of the preceeding claims, including guides to guide the flexible hose drill string through the main body and the arm member.  
     
     
         10 . The assembly of  claim 9 , wherein a said sensor is able to detect the position and/or direction of travel of the flexible hose drill string.  
     
     
         11 . The assembly of claim any one of the preceding claims, which further includes a compass for detecting the azimuth of the arm member.  
     
     
         12 . The assembly of any one of the preceding claims, wherein the arm member is formed from at least two arm members coupled together to provide a larger degree of curvature for a drill string  
     
     
         13 . The assembly of  claim 1 , wherein the arm member has at least one fluid cutting nozzle thereon to cut a slot in the bore wall as the arm is erected, the at least one nozzle being adapted to be connected to a supply of high pressure fluid.  
     
     
         14 . The assembly of any one of the preceding claims, wherein the main body is elongate and the arm member is pivotally attached to the main body such that it can move about a pivot axis between the collapsed and the erected position.  
     
     
         15 . The assembly of  claim 14 , wherein the arm member in the collapsed position sits entirely within or substantially within the main body.  
     
     
         16 . A method for forming at least one lateral borehole from an existing borehole, the method comprising lowering an erectable arm assembly into the borehole to a desired position, the assembly having a main body and an erectable arm member, positioning a self-advanceable fluid cutting device to be supported by the arm member at least as the arm member is erected, operating the fluid cutting device to self advance the fluid cutting device from the arm member and into the side wall of the borehole to form a lateral bore in a direction dictated by the position of the arm member in the borehole.  
     
     
         17 . An erectable arm assembly for use in a borehole, the assembly comprising a main body and an arm member which can move between a collapsed position where the assembly can be installed and removed from the borehole, and an erected position where the arm member can guide a fluid drilling assembly towards the borehole wall.  
     
     
         18 . The assembly of  claim 17  wherein when the arm member is in the erected position, the main body and the arm member define a guide for turning the fluid drilling assembly through an angle of about 90° within a radius of less than about 300 mm.