Method and System for Forming a Non-Circular Borehole

Abstract

System and methods for creating shaped, non-circular boreholes in rocks especially for use with geothermal heat pump applications and for increasing wellbore support in applications such as horizontal oil and gas drilling are described. The systems and methods when applied to geothermal heat pumps create an elliptical shaped hole that is optimized for placing heat transfer tubes with a minimum of grout used. The significantly reduced cross-sectional area of the elliptical borehole also increases the overall drilling rate in rock and especially in hard rocks. In horizontal hard-rock drilling, creation of a horizontal non-circular borehole or modification of a circular borehole to a non-circular geometry is used to stabilize the borehole prior to casing insertion, and may also allow the use of lower mud pressures improving drilling rates. The system uses a non-contacting drilling system which in one embodiment uses a supersonic flame jet drilling system with a movable nozzle that swings between pivot points. In a second embodiment the elliptical shaped hole is created by an abrasive fluid or particle bearing-fluid or air jet drill that moves between pivot points. In another embodiment a non-contacting drill can use dual parallel nutating nozzles that create a pair of overlapping circular holes. The non-circular shaped hole is created by either the high temperature flame or water-particle jet or chemically active fluid jet as it removes rock material by erosion, dissolution and or thermal spalling. Modifications of circular boreholes to a generally elliptical shape can also be done using milling or jetting techniques.

1 . A method of forming a drill hole having a substantially non-circular shaped cross-section, comprising: 
 providing a means for forming the substantially non-circular-shaped cross-section drill hole; and    using said means to form the substantially non-circular-shaped cross-section drill hole.    
     
     
         2 . The method of  claim 1  wherein the drilled hole is formed in rocks for the purpose of preparing the rocks for a geothermal heat pump application.  
     
     
         3 . The method of  claim 1  wherein the drilled hole is formed in rocks for the purpose of increasing the mechanical stability of the borehole.  
     
     
         4 . The method of  claim 1  wherein the drilled hole is formed in rocks for the purpose of stabilizing the formation during the drilling and completion of a well for oil and gas exploration or production.  
     
     
         5 . The method of  claim 1  wherein said means for forming the substantially non-circular-shaped cross-section drill hole comprises a swivel mechanism configured to swivel a drill head nozzle assembly.  
     
     
         6 . The method of  claim 5  wherein the swivel mechanism is configured to swivel the drill head along an arc in a direction transverse to a longitudinal line aligned along the drill hole depth.  
     
     
         7 . The method of  claim 5  wherein the throw of the swivel mechanism is configurable to control the length of the elliptical portion of the drill hole.  
     
     
         8 . The method of  claim 5  wherein the rate of movement of the drill head in a swiveling motion is adjustable.  
     
     
         9 . The method of  claim 1  wherein said means for forming the substantially non-circular-shaped cross-section drill hole comprises a non-contacting drilling tool.  
     
     
         10 . The method of  claim 1  wherein said means for forming the substantially non-circular-shaped cross-section drill hole comprises a substantially slotted jet nozzle drill head configured to form a jet having a length longer than the jet width.  
     
     
         11 . The method of  claim 1  wherein said means for forming the substantially non-circular-shaped cross-section drill hole comprises a flame jet drilling tool.  
     
     
         12 . The method of  claim 1  wherein said means for forming the substantially non-circular-shaped cross-section drill hole comprises a superheated water or steam tool.  
     
     
         13 . The method of  claim 1  wherein said means for forming the substantially non-circular-shaped cross-section drill hole comprises an abrasive water jet tool.  
     
     
         14 . The method of  claim 13  wherein the abrasive water jet includes entrained particles.  
     
     
         15 . The method of  claim 1  wherein said means for forming the substantially non-circular-shaped cross-section drill hole comprises a particle jet drill using mud as the drilling fluid.  
     
     
         16 . The method of  claim 1  wherein said means for forming the substantially non-circular-shaped cross-section drill hole comprises a chemical drilling tool using a fluid containing a chemically erosive fluid.  
     
     
         17 . The method of  claim 16  wherein said erosive fluid is a basic or an acidic solution.  
     
     
         18 . The method of  claim 1  wherein said means for forming the substantially non-circular-shaped cross-section drill hole comprises a drill body having a diameter that is smaller than the minimum width of the non-circular hole.  
     
     
         19 . The method of  claim 1  wherein said means for forming the substantially non-circular-shaped cross-section drill hole comprises a drilling tool having a dual nutating drilling nozzles.  
     
     
         20 . The method of  claim 19  wherein said drilling tool is configured to drill using particulates delivered with a high velocity fluid.  
     
     
         21 . The method of  claim 1  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises a drilling tool having a dual rotating drilling nozzles.  
     
     
         22 . The method of  claim 21  wherein said drilling tool is configured to drill using particulates delivered with a high velocity fluid.  
     
     
         23 . A method of forming a drill hole having a substantially non-circular shaped cross-section, comprising: 
 forming a circular cross-section bore hole with a first drilling tool; and    forming extended regions on two sides of the circular cross-section bore using a second drilling tool, so as to form two lobes extending from the circular cross-section bore.    
     
     
         24 . The method of  claim 23 , wherein said second drilling tool is configured for a milling operation.  
     
     
         25 . The method of  claim 23 , wherein said second drilling tool is configured for a jet drilling operation.  
     
     
         26 . The method of  claim 23 , wherein said drill hole having a substantially non-circular shaped cross-section is a horizontal drill hole.  
     
     
         27 . The method of  claim 23 , wherein said drill hole having a substantially non-circular shaped cross-section is a non-vertical drill hole.  
     
     
         28 . The method of  claim 23 , wherein said first drilling tool is selected from the group consisting of: a rotary bit, an auger, a rotary impact, a percussion or sonic drill, a coiled tubing drill, and combinations thereof.  
     
     
         29 . The method of  claim 23 , wherein said second drilling tool is configured to drill using a process selected from the group consisting of: contact drilling, non-contact drilling, rotary bit, grinding, abrasion, particle abrasion, spallation, sonication, scraping, cutting, melting, and fusing.  
     
     
         30 . The method of  claim 23 , wherein a supply of power for the second drilling tool is derived from the rotation of the first or second drilling tool, hydraulic flow of fluids, air flow, electrical means, thermal means, or chemical means.  
     
     
         31 . The method of  claim 30  wherein the hydraulic flow of fluids comprises flow of circulating fluids or muds.  
     
     
         32 . The method of  claim 23  wherein the second drilling tool operates concurrently with the primary drilling tool.  
     
     
         33 . The method of  claim 23  wherein the second drilling tool operates while the primary drill string is still in the wellbore.  
     
     
         34 . The method of  claim 23  wherein the second drilling operation occurs during the removal of the drill string of the primary drilling operation.  
     
     
         35 . The method of  claim 23  wherein the second drilling operation occurs after the removal of the drill string from the primary drilling operation.  
     
     
         36 . The method of  claim 1  wherein downhole instrumentation is used to determine the orientation of the stresses in the rock, the orientation of the BHA, or the orientation of the BHA relative to the stresses during the course of producing the non-circular well bore.  
     
     
         37 . A drilling rig for forming a drill hole having a substantially non-circular-shaped drill hole cross-section, comprising: 
 a drilling support system configured for connection with a drill head; and    a drill head configured for connection with the drilling support system having a means for forming the substantially non-circular-shaped drill hole cross-section.    
     
     
         38 . The rig of  claim 37  wherein the rig is configured to form a drill hole in rocks for the purpose of preparing the rocks for a geothermal heat pump application.  
     
     
         39 . The rig of  claim 37  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises a swivel mechanism configured to swivel a drill head nozzle assembly.  
     
     
         40 . The drilling rig of  claim 39  wherein the swivel mechanism is configured to swivel the drill head along an arc in a direction transverse to longitudinal line aligned along the drill hole depth.  
     
     
         41 . The drilling rig of  claim 39  wherein the throw of the swivel mechanism is configurable to control the length of the non-circular portion of the drill hole.  
     
     
         42 . The drilling rig of  claim 39  wherein the rate of movement of the drill head in a swiveling motion is adjustable.  
     
     
         43 . The drilling rig of  claim 37  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises a non contacting drilling tool.  
     
     
         44 . The drilling rig of  claim 37  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises a slotted jet nozzle drill head configured to form a jet having a length longer than the jet width.  
     
     
         45 . The drilling rig of  claim 37  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises a flame jet drilling tool.  
     
     
         46 . The drilling rig of  claim 37  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises a superheated water or steam tool.  
     
     
         47 . The drilling rig of  claim 37  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises an abrasive water jet tool.  
     
     
         48 . The drilling rig of  claim 47  wherein the abrasive water jet includes entrained particles.  
     
     
         49 . The drilling rig of  claim 37  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises a particle jet drill using mud as the drilling fluid.  
     
     
         50 . The drilling rig of  claim 37  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises a chemical drilling tool using a fluid containing a chemically erosive fluid.  
     
     
         51 . The drilling rig of  claim 50  wherein said erosive fluid is a basic or an acidic solution.  
     
     
         52 . The drilling rig of  claim 37  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises a drill body having a diameter that is smaller than the minimum width of the elliptic hole.  
     
     
         53 . The drilling rig of  claim 37  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises a drilling tool having a dual nutating drilling nozzles.  
     
     
         54 . The drilling rig of  claim 53  wherein said drilling tool is configured to drill using particulates delivered with a high velocity fluid.  
     
     
         55 . The drilling rig of  claim 37  wherein said means for forming the substantially non-circular-shaped drill hole cross-section comprises a drilling tool having a dual rotating drilling nozzles.  
     
     
         56 . The drilling rig of  claim 55  wherein said drilling tool is configured to drill using particulates delivered with a high velocity fluid.  
     
     
         57 . The method of  claim 1  wherein the substantially non-circular-shaped cross-section drill hole has a L/W ratio greater than 1.0.  
     
     
         58 . The method of  claim 1  wherein the substantially non-circular-shaped cross-section drill hole has L/W ratio between 1.05 and 10.  
     
     
         59 . The method of  claim 1  wherein the substantially non-circular-shaped cross-section drill hole is substantially asymmetric.