In the mid-1990s, EnLink's founders recognized the inefficiencies then inherent in large-scale GHP installations being executed using conventional labor-intensive processes. Since the founders had extensive experience with coiled tubing technologies in the oilfield, they realized that a loop-insertion approach exploiting a coiled tubing unit could yield significant benefits in both quality and costs for the EHX component of GHP systems.

Accordingly, EnLink designed and produced a coiled tubing loop insertion unit and consequently developed a new set of technologies and processes that allowed GHP installers to dramatically reduce both the amount of footage required in an EHX and to reduce the time required to insert the earth loops.

• Easy operation: since all controls are within easy reach, only one operator is required to effortlessly maneuver the CTU from hole to hole, even in cramped areas
  
  
• Time-saving: because the loop reel is part of the CTU, installers don't waste time manually moving loops
  
  
• The high pressure grout pump is included as an integral part of the CTU, eliminating the need for an additional piece of equipment
  
  
• Mounted on rubber crawler tracks, the CTU can easily move around on soft and muddy drill sites
  
  
• Higher productivity: the CTU can be used to simultaneously loop and grout behind multiple drilling rigs
  
  
• Higher drilling penetration rates: no sinker bar or rebar weight is required, so that holes as small as 3½” diameter (instead of the typical 6" hole) can be drilled, which results in significantly better drilling penetration rates in challenging conditions
  
  
• Improved efficiency: smaller hole size also means a tighter fit between loop and earth, offering better thermal transfer properties to improve loop efficiency by up to 25%, reducing the required footage in a given EHX installation to achieve the desired heat transfer level, and also reducing the quantity required of expensive thermally conductive grout
  
  
• Lower disposal costs: less EHX footage also implies less drilling fluid, grout, and cuttings

EnLink currently has a fleet of six CTU units. Each rig is a self-propelled, track-mounted unit positioned directly over a previously drilled borehole. The steel coiled tubing on the CTU effortlessly and quickly pushes the polyethylene pipe, including EnLink's specially designed U-bend, to the bottom of the hole. If necessary, water can be jetted through a hole in a side pocket of the U-bend to help get past borehole obstructions (such as sand bridges) that cannot be overcome by conventional loop insertion methods.

When the U-bend reaches the bottom of the hole, grout is then pumped through the CTUs insertion pipe.
The CTU insertion pipe is then pulled free of the U-bend pocket and retracted as the grout is being pumped, leaving the grouted loop in the borehole. The loop is thus grouted completely and consistently from the bottom of the hole as drilling mud and other materials are displaced upward. There is no need to make another trip downhole with tremmie pipe.

EnLink's CTU works equally well with all thermal enhanced or environmentally sanctioned grouts. Our optional grout system helps ensure that any grout you select is thoroughly mixed and pumped. The CTU enables loop installation to be performed at least twice as fast as historical methods, allowing a crew of only one or two men to install and grout as many as 10 ground loops per day.