Method for removing hydrate plug from a flowline

Abstract

A method of drilling through a blockage in a flowline using a remotely controlled electrically operated drilling tool that comprises a drill bit, a steering means, a pumping means, and a propulsion system wherein the drilling tool is connected either directly or indirectly to an electric cable and the drill bit is mounted on the steering means, the method comprising: introducing the drilling tool into the flowline; actuating the electrically operated propulsion system to move the drilling tool through the flowline to the location of the blockage; actuating the electrically operated steering means so that the drill bit is aligned with the blockage; actuating the electrically operated drill bit so that the drill bit engages with and drills through the blockage; and actuating the electrically operated pump so that when the drill bit engages with the blockage, fluid that is present in the flowline adjacent the blockage is passed over the cutting surfaces of the drill bit and cuttings from the blockage are transported away from the cutting surfaces of the drill bit suspended in the fluid.

1 - 28 . (canceled) 
     
     
         29 . A method of drilling through a blockage in a flowline using a remotely controlled electrically operated drilling tool that comprises a drill bit, a steering means, a pumping means, and a propulsion system wherein the drilling tool is connected either directly or indirectly to an electric cable and the drill bit is mounted on the steering means, the method comprising:
 introducing the drilling tool into the flowline;   actuating the electrically operated propulsion system to move the drilling tool through the flowline to the location of the blockage;   actuating the electrically operated steering means so that the drill bit is aligned with the blockage;   actuating the electrically operated drill bit so that the drill bit engages with and drills through the blockage; and   actuating the electrically operated pump so that when the drill bit engages with the blockage, fluid that is present in the flowline adjacent the blockage is passed over the cutting surfaces of the drill bit and cuttings from the blockage are transported away from the cutting surfaces of the drill bit suspended in the fluid.   
     
     
         30 . A method as claimed in  claim 29  wherein the flowline is a subsea flowline and the drilling tool is passed into the flowline either (i) through a surface entry point and a riser (with the drilling tool suspended from the electric cable), or (ii) through a subsea entry point in the flowline. 
     
     
         31 . A method as claimed in  claim 30  wherein a flowline intervention riser is deployed from a floating vessel and is latched to the subsea entry point and the drilling tool is lowered to the subsea entry point from the floating vessel, through the flowline intervention riser, with the drilling tool suspended from the electric cable. 
     
     
         32 . A method as claimed in  claim 30  wherein a subsea electric cable is laid alongside the flowline and is connected to an electric cable that runs from the surface through an umbilical wherein the subsea electric cable is provided with a wet-connect electrical connection point for the drilling tool, and wherein the drilling tool and sufficient additional electric cable to enable the drilling tool to reach the blockage is delivered to the wetconnect electrical connection point via a remotely controlled submersible vehicle (ROV); the drilling tool is connected to the wet-connect electrical connection point via the additional electric cable; and electricity is transmitted to the drilling tool via the umbilical, the subsea electric cable and the additional electric cable. 
     
     
         33 . A method as claimed in  claim 29  wherein the drilling tool comprises an elongate housing having a diameter in the range of 2 to 24 inches and a length in the range of 10 to 60 feet wherein the elongate housing comprises a plurality of housing segments that are joined together by flexible joints or flexible connectors and wherein the length of each segment of housing is in the range of from 1 to 10 feet and the flexible joints or flexible connectors provide an angular deviation of up to 90°, for example, up to 45° between adjacent housing segments such that the drilling tool is capable of negotiating bends in the flowline having a radius of less than 5 pipe diameters, in particular, bends having a radius of less than 3 pipe diameters. 
     
     
         34 . A method as claimed in  claim 29  wherein a drill bit is provided at the rear of the drilling tool that is actuated when withdrawing the drilling tool from the blockage or from the flowline. 
     
     
         35 . A method as claimed in  claim 29  wherein an electric motor is located in the elongate housing of the drilling tool and is capable of actuating a means for driving the drill bit. 
     
     
         36 . A method as claimed in  claim 29  wherein the steering means for the drill bit is a continuously variable bent-sub or is a continuously rotatable steerable system that is capable of adjusting the bit orientation relative to the longitudinal axis through the drilling tool by from 0 to 10°, for example, 0 to 5° thereby allowing the trajectory of the borehole that the drilling tool drills through the blockage to be adjusted. 
     
     
         37 . A method as claimed in  claim 33  wherein the propulsion system is a traction means that is connected either directly or indirectly to the elongate housing of the drilling tool wherein the traction means comprises tractor feet, pads or wheels that are capable of being extended in a radial direction into engagement with the walls of the flowline (or into engagement with the walls of the bore hole that is drilled through the blockage) and that are adapted to move the drilling tool through the flowline (or borehole). 
     
     
         38 . A method as claimed in  claim 29  wherein the drilling tool is retrieved by pulling on the electric cable and/or by running the propulsion system in reverse such that the drilling tool moves in the reverse direction through the borehole that has been drilled through the blockage and then in a reverse direction through the flowline. 
     
     
         39 . A method as claimed in  claim 33  wherein the elongate housing of the drilling tool has a fluid passage having an inlet that is in close vicinity to the drill bit and an outlet that is at or near the rear of the drilling tool and the pumping means draws the suspension of drill cuttings through the inlet of the fluid channel and discharges said suspension via the outlet into the flowline behind the drilling tool. 
     
     
         40 . A method as claimed in  claim 39  wherein the fluid passage is in fluid communication with a discharge conduit that extends longitudinally behind the drilling tool, preferably, at least 10 metres behind the drilling tool, such that the cuttings are deposited at a distance behind the drilling tool. 
     
     
         41 . A method as claimed in  claim 33  wherein the drilling tool is provided with a junk basket located behind the housing of the drilling tool for collecting cuttings wherein the junk basket is joined to the elongate housing of the drilling device via a flexible joint or flexible connector. 
     
     
         42 . A method as claimed in  claim 33  wherein the housing of the drilling device is provided with a fluid reservoir that contains a treatment chemical, the fluid reservoir is in fluid communication with an outlet of the housing that is located at or near the drill bit, and an electrically operated pump is provided within the housing of the drilling device for pumping the treatment fluid from the fluid reservoir to the outlet, and wherein the pump is actuated so that the treatment fluid is discharged from the outlet and is delivered to the blockage. 
     
     
         43 . A method as claimed in  claim 30  wherein a tubing is run from the surface for delivering a treatment chemical to the blockage wherein the tubing either runs alongside the electric cable or the electric cable is arranged within the tubing. 
     
     
         44 . A method as claimed in  claim 29  wherein the electric cable has a borehole running therethrough and a treatment chemical is delivered to the blockage in the flowline through the borehole. 
     
     
         45 . A method as claimed in  claim 29  wherein the drill bit is a non-expandable bit and the cutting surfaces on the drill bit are sized to form a borehole having a diameter of from 3 to 12 inches, preferably, 3 to 6 inches. 
     
     
         46 . A method as claimed in  claim 29  wherein the drill bit is an expandable drill bit, the drilling tool is passed through the flowline with the drill bit in a non-expanded state and, when the drilling tool has reached the blockage, the drill bit is expanded to a diameter that is at least 0.125 inches less, preferably at least 0.25 inches less than the internal diameter of the flowline. 
     
     
         47 . A method as claimed in  claim 46  wherein the drilling tool is provided with an expandable reamer or expandable underreamer that is located immediately behind the drill bit and is capable of being expanded to a diameter that is at least 0.125 inches less, preferably at least 0.25 inches less than the diameter of the flowline and wherein the expandable reamer or underreamer is either deployed when the drilling tool is being withdrawn from the borehole that has been drilled through the blockage or as the borehole is being drilled through the blockage. 
     
     
         48 . A method as claimed in  claim 29  wherein the drilling tool is provided with sensors that are electrically connected to recording equipment at the surface via electrical conductor wire(s) or segmented conductor(s) in the electric cable wherein the sensors either continuously or intermittently transmit signals to the surface and the signals received at the surface are monitored and electrical signals are transmitted from the surface to the drilling tool in response to these sensor signals to control the operation of the drilling tool.