Technology in Detail
EnLink stands out as an industry leader in GHP technology, and with 13 patents that it owns and co-owns, has made a significant contribution to the industry.
Historically, the most difficult and costly task in installing a GHP system has been drilling the vertical bore holes and inserting the closed-loop tubing that makes up the EHX. EnLink’s innovative technology addresses both of those issues.
Drilling service contractors on GHP projects typically use equipment developed for other applications, mainly water well drilling. These drilling technologies are not optimal for high production rate requirements (i.e., several hundred wells on a single site) associated with GHP installations for commercial/institutional projects. This often leads to drilling difficulties, cost overruns and significant delays.
After decades working in oilfield and geotechnical services, the founders of EnLink saw an opportunity in the GHP industry if key obstacles could be overcome. They met those challenges designing a "fit-to-purpose" drill rig and a Coiled Tubing Unit (CTU) for tube insertion and grouting specifically optimized for high production of GHP boreholes in any soil condition.
EnLink Drill
EnLink employed the development of a custom drill rig that uses five drilling technologies: mud rotary, air rotary, downhole air hammer, sonic and mud sonic. The drill rig is also optimized to handle the challenges of drilling many holes for a large-scale EHX -- predictably, rapidly, and under a variety of geologic conditions.
The EnLink Drill employs an innovative integration of components, including a multifunction drill head and automated rod/pipe handling and casing methods. Each of these components has been expertly demonstrated over many years in challenging applications. With EnLink's design, the drill operator simply selects the correct features and tools for the job at hand and consistently achieves maximum production rates, no matter the soil condition.
In commonly encountered unstable soil or overburden conditions, EnLink prevents the borehole from collapsing on itself by simultaneously inserting casing into the hole as the drill penetrates the earth — ensuring that the bored hole will remain open for the looping and grouting steps.
From the beginning, EnLink has relentlessly focused on developing and employing technological innovations that reduce the installed cost and improve the performance of EHXs. We can efficiently complete EHXs where many other drillers cannot easily or economically perform. EnLink has a dramatically better way to drill holes for large-scale EHXs.
EnLink's fit-to-purpose drill rig uses proven technologies optimized for large-scale GHP projects. This enables EnLink to efficiently drill small-diameter holes several hundred feet deep in a wide variety of soil conditions — even under extremely challenging situations where casing would be required.
Coiled Tubing Unit
A coiled tubing unit (CTU) quickly and easily inserts polyethylene pipe
loops all the way to the bottom of pre-drilled holes less than four
inches in diameter. EnLink’s proprietary CTU is used for simultaneously
installing a plastic pipe loop and a grout tremmie pipe into a previously
drilled hole, and then grouting the pipe loop in the wellbore as the tremmie
pipe is withdrawn. This technology ensures that a wellbore is completely
grouted from the bottom of the hole to the top. EnLink's highly efficient
loop insertion and grouting systems have been successfully utilized for
over five years.
Grout
One of the most important determinants of an EHX's performance - and hence
its required size and its associated cost - is the quality of the grout
used to seal each ground loop within its borehole to the adjoining earth.
EnLink's grouting system is compatible with all major grout types, and
uses a grout mixing process for uniformly blending any type of thermally
enhanced grouts in large quantities. Additionally, a bottom-up pumping
process helps ensure that the grout gets dispersed evenly and thoroughly
throughout the vertical depth of a completed borehole.
U-bend
At the bottom of every EHX ground loop is a patented U-bend. EnLink has designed a special U-bend to work in conjunction with its CTU loop insertion rig. The U-bend quickly and easily slides down a borehole.
Metering System
EnLink also has patented a unique method of metering the amount of energy extracted from or rejected to the earth in EHX heat pump installations. Accurate metering enables invoicing an end user, or allocation of charges to multiple end users if desired.