Abstract:
According to one aspect of the invention, there is provided a method for drilling a hole into the ground and installing a geothermal transfer loop. A drilling apparatus is positioned at a desired location. The drilling apparatus includes a rotating and vibrating apparatus, such as a sonic drill, for rotating and vibrating a hollow drill string into the ground. The hollow drill string having an inner space. A hole is drilled to a desired depth by rotating and vibrating the hollow drill string into the ground and discharging fluid into the inner space of the hollow drill string. A geothermal transfer loop is lowered into the inner space of the hollow drill string and the drill string is removed from the ground. The method may also include discharging grouting material into the hole.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to the geothermal heat exchange systems, and in particular, to the installation of geothermal transfer loops with sonic drills.  
         [0002]     Geothermal heat exchange systems are environmentally friendly, energy efficient heating and cooling systems. As such, there is a rising demand for geothermal heat exchange systems for both commercial and residential properties. There is therefore a need for a quick and efficient method of installing the geothermal transfer loops used in many geothermal heat exchange systems.  
       SUMMARY OF THE INVENTION  
       [0003]     According to one aspect of the invention, there is provided a method for drilling a hole and installing a geothermal transfer loop. A drilling apparatus is positioned at a desired location. The drilling apparatus includes a rotating and vibrating apparatus for rotating and vibrating a hollow drill string into the ground. The hollow drill string having an inner space. A hole is drilled to a desired depth by rotating and vibrating the hollow drill string into the ground while discharging fluid into the inner space of the hollow drill string. A geothermal transfer loop is lowered into the inner space of the hollow drill string and the drill string is removed from the ground. The method may also include discharging grouting material into the hole.  
         [0004]     According to another aspect of the invention, there is provided a method of drilling a hole and installing a geothermal transfer loop. A drilling apparatus is positioned at a desired location. The drilling apparatus includes a rotating and vibrating apparatus for rotating and vibrating a hollow drill string into the ground. The hollow drill string having an inner space. A hole is drilled to a desired depth by rotating and vibrating the hollow drill string into the ground while discharging a fluid into the inner space of the hollow drill string. A geothermal transfer loop is lowered into the inner space of the hollow drill string. The geothermal transfer loop is filled with a second fluid and a portion of the geothermal transfer loop is straight. The straightened portion of the geothermal transfer loop is lowered first. Weights are attached to the geothermal transfer loop. The hollow drill string is vibrated out of the ground while grouting material is simultaneously discharged into the inner space of the hollow drill string. The geothermal transfer loop is operatively connected to a heat exchanger.  
         [0005]     This invention provides the advantages of being able to drill cased holes faster and in litholgies that are often difficult for conventional drill rigs to drill in. This invention also provides the further advantage of being able to more accurately control and monitor the grouting process.  
         [0006]     This invention provides the further advantage of being able to lower the geothermal transfer loop supplied in coils by eliminating the problem of the coils catching on mud on the side of the hole because the hole is cased. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     In the Drawings:  
         [0008]      FIG. 1  is an elevational, partly in section view of a drilling rig drilling a hole, using a method according to the invention;  
         [0009]      FIG. 2  is an elevational, cross-sectional diagram illustrating pressurized fluid carrying drill cuttings to the ground surface, using a method according to the invention;  
         [0010]      FIG. 3  is an elevational, cross-sectional diagram illustrating the lowering of a geothermal transfer loop into the hole, using a method according to the invention;  
         [0011]      FIG. 4  is an elevational, cross-sectional view of a rig grouting the hole, using a method according to the invention; and  
         [0012]      FIG. 5  is an elevational view of a geothermal exchange loop connected to a heat exchanger, using a method according to the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]     Referring to the drawings, and first to  FIG. 1 , this shows a method of drilling a hole  12  into the ground  14  according to a preferred method of the invention. A drilling apparatus  20  is mounted on a movable vehicle  50 . The vehicle  50  is moved to a desired drilling location and the drilling apparatus  20  is placed in a desired drilling position. A drill pipe  22  is threadedly connected to the drilling apparatus  20  at a first end  23 , and the drill pipe  22  is threadedly connected to a drill bit  28  at a second end  24 . The drill pipe  22  is hollow and is open at both ends  23  and  24 . In this example, the drill bit  28  is a ring bit that is concentric with drill pipe  22 . This combination of drill pipe  22  and drill bit  28  forms an open ended drill string  30 . There is a cavity or inner space  35  encompassed by the drill string  30 .  
         [0014]     The drilling apparatus  20  is a rotary and vibratory apparatus such as a sonic drill. Sonic drills are known in the art and accordingly are not described in more detail herein. Examples of sonic drills are described in my earlier U.S. Pat. No. 5,027,908 and U.S. Pat. No. 5,409,070 which are hereby incorporated by reference. The drilling apparatus rotates and vibrates the drill string  30  into the ground  14 . A hose  42  hydraulically connects a pressurized fluid pump apparatus  40  to the drilling apparatus. A pressurized fluid is pumped by the pressurized fluid apparatus or pump  40  along the hose  42 , through the drilling apparatus  20 , and into the inner space  35  of the drill string  30  as indicated by arrow  44  during the drilling process. In this example of the method, the pressurized fluid is water but water with added components such as polymer or clay may also be used. The fluid has a pressure range of between 10-5000 psi, with the preferred pressure range being between 500-2000 psi. This pressure facilitates faster drilling in ground conditions that would otherwise block the flow of pressurized fluid out of the drill bit  28 .  
         [0015]     A column of fluid  37  fills the inner space  35  acting as a plug in the drill string  30 , impeding the entry of ground materials into the inner space  35 . The diameter of the hose  42  is less than the diameter of the inner space  35 , thereby preventing the pressurized fluid from being pushed back through the hose in response to high pressure spikes created when the pressurized fluid impacts the ground  14  in the hole  12 . The vibrating drill string  30  causes the pressure in the fluid column to oscillate at the same frequency that the drill string is vibrated at. The pressure spikes thus created causes the fluid column to act in a manner similar to a water hammer, thereby adding an additional drilling force.  
         [0016]     At minimum, sufficient pressurized fluid is pumped into the inner space  35  to form a fluid column  37  that impedes the entry of ground materials into the inner space  35 . However, additional pressurized fluid may be pumped into the inner space  35  in order to carry cuttings up the annulus  13 , between the drill string and the hole, to the ground surface  15 , as illustrated in  FIG. 2 . Arrow  44  indicates the direction of the flow of pressurized fluid into the ground  14  through the inner space  35  of the drill string  30 . The excess pressurized fluid is pushed down and around the drill bit  28  and up the annulus  13  towards the surface as indicated by arrows  45  and  46 . The pressurized fluid carries cuttings as it moves up the annulus  13  to the ground surface  15  where the pressurized fluid and cuttings are expelled from the hole  12  as indicated by arrows  47  and  48 .  
         [0017]     As the depth of the hole increases, additional drill pipes (not shown) may be added to the drill string  30  in sequence. Each additional drill pipe has a first end and a second end. The additional drill pipes are hollow and open at both ends. The first ends of the additional drill pipes are threadedly connected to the drilling apparatus  20  and the second ends of the additional drill pipes are threadedly connected to the drill string  30 . The additional drill pipes may then be rotated and vibrated into the ground, thereby increasing the length of the drill string  30  and the depth of the hole  12 . The additional drill pipes may be added manually or with an automated drill pipe handling apparatus. Once the hole  12  has been drilled to a desired depth the drill string  30  is disconnected from the drilling apparatus  20 , leaving a hole  12  which is cased by the drill string  30 , as illustrated in  FIG. 3 . A geothermal transfer loop  70  is lowered into the hole  12  through the inner space  35  of the drill string  30 , as indicated by arrow  44 . It is to be noted however, that in other examples of the method the drill string  30  may be removed prior to the lowering of the geothermal transfer loop  70  into the hole  12 .  
         [0018]     The geothermal transfer loop is preferably filled with a fluid prior to being lowered into the hole  12 . In this example of the method, the geothermal transfer loop  70  is a high density polyethylene tube and is filled with water. The fluid adds weight to the geothermal transfer loop  70  and prevents the geothermal transfer loop  70  from collapsing in any fluid column that may remain in the inner space  35  of the drill string  30 . Weights  75  may also be attached to the geothermal transfer loop  70  to facilitate the lowering of the geothermal transfer loop  70  into the hole  12 . The lead portion  71  of the geothermal transfer loop  70  may be straightened to aid in keeping the geothermal transfer loop  70  at the bottom of the hole  12  during grouting and withdrawal of the drill string  30 . In this example of the method, the weight  75  is an elongated piece of steel bar that has been attached to the lead portion  71  of the geothermal transfer loop  70  by wiring  76  around the steel bar and the geothermal transfer loop. The steel bar performs the dual function of a weight and a means for straightening the lead portion  71  of the geothermal transfer loop  70 . Once the geothermal loop  70  has been completely lowered the drill string is removed from the hole  12  and the hole is grouted. The hole  12  may be grouted with the drill string  30  remaining in the ground  14  or after the drill string  30  has been removed from the ground.  
         [0019]     In this example of the method, grouting is accomplished by the tremie line method as illustrated in  FIG. 4 . A tremie line hose  80  is lowered into the hole  12 . The tremie line hose is comprised of a steel pipe section  82  at a first end and a flexible tube section  81  at a second end, the steel pipe section  82  being the lead end of the tremie line  80  lowered into the hole  12 . A pump  86  pumps thermally conductive grouting material  120  from a reservoir  88  along the tremie hose line  80  to the bottom of the hole  12 . The grouting material  120  encompasses the geothermal transfer loop  70 . As the hole  12  is filled from the bottom up, a tremie line hose reel  87  pulls the tremie line hose  80  out of the hole  12 , so as to maintain the lead end of the of the tremie line hose  80  below the grouting material  120 . This process is continued until the hole  12  has been filled with grouting material  120  and the grouting material encompasses the portion of the geothermal transfer loop  70  which is below the ground surface  15 .  
         [0020]     In other examples of the method, grouting may be accomplished by the pressure grouting method. Pressure grouting may be accomplished by attaching a grout line to the top of the of the drill string  30  or a grout line can be attached to the swivel on the drill head. As the drill string  30  is removed from the ground, grouting material is simultanoeusly pumped into the inner space  35  of the drill string  30 . The grouting is topped up once the casing has been removed. In some cases grouting may not be required, for example in silty or sandy soils which collapse about the geothermal loop when the drill string is removed.  
         [0021]     Once the grouting process is completed, either by the tremie line method or the pressure grouting method, the geothermal transfer loop  70  may be operatively connected to a heat exchanger  100 , as illustrated in  FIG. 5 . The geothermal transfer loop  70  may also be operatively connected below the ground surface, in series, to additional geothermal transfer loops below the surface. The series geothermal transfer loops are then connected to a communal heat exchanger.  
         [0022]     It will be understood by someone skilled in the art that many of the details provided above are by way of example only and can be varied or deleted without departing from the scope of the invention as set out in the following claims.