Frequently Asked Questions
Frequently Asked Question (FAQ’s)
What are Vertebrae™ horizontal nested, or segmented well systems (Vertebrae Well Systems) and how do they differ from traditional single horizontal wells?
- Vertebrae Well Systems are a multi-function engineered set of nested, segmented subsurface wells oriented horizontally. Each well is isolated from the others in the same horizontal borehole and separately plumbed to the surface. The Vertebrae Well System design reduces or eliminates the potential for preferential pathway influences associated with single horizontal wells.
- Vertebrae Well Systems allow users to complete site assessments and implement a wide variety of remedial actions regardless of site obstacles. This includes the surface and subsurface infrastructure in built or natural environments, security constraints (industrial or military), issues with access to adjacent properties.
- Vertebrae Well Systems can eliminate the need for an extensive network of vertical wells and site trenching, and they also limit or eliminate business disruption along with providing a safer work environment.
- The versatility of Vertebrae Well Systems allows them to be used for extraction or injection of fluid or gases. This makes them suitable for assessment or treatment or often both.
How are the Vertebrae Well Systems delivered to the project site?
- Vertebrae Well Systems are pre-manufactured at the factory and delivered to the project site ready to be installed in a “protective” conduit on either an eight or a ten-foot diameter reel.
Who installs the Vertebrae Well Systems?
- The Vertebrae Well Systems are installed by local licensed driller’s, experienced in the installation of horizontal wells and are familiar with the specific regional geologic and local drilling conditions. EN Rx personnel are on every project site to oversee the installation of the Vertebrae Well Systems, to ensure that the wells are installed correctly, developed, grouted, and completed. This operation culminates in final field testing and sign-off.
What can Vertebrae Well Systems be used for?
- Vertebrae Well Systems can and have been used for many forms of site characterization and remediation technologies. Vertebrae Well Systems have been implemented for the injection of oxidants and reductants, AS/SVE systems, vapor mitigation, biosparge, ozone and advanced oxidation process (AOP), bio-amendments and pump and treat applications. Vertebrae Well Systems have the capability to be more than one tool in that it can be used for both data collection followed by an appropriate remediation strategy as required.
How do you design spacing and well segment lengths?
- The lengths and spacing of the individual well segments are based on the desired function of the well system, along with the estimated radius of influence (ROI) for treatment. With direction from the Engineer of Record and/or consultant we collaborate to design the Vertebrae Well Systems based on the desired remedial action plan. “System Control is the Goal”.
How is the Radius of Influence (ROI) determined?
- The ROI is largely based on prior vertical data and site specific geologic/lithologic information. In some cases, a pilot Vertebrae Well System is installed and used to determine ROI prior to the installation of the full remediation system. Detailed site assessment data is critical to the Vertebrae design. In most cases it is easy to allow for complete ROI overlap and excellent coverage based on the efficiency and number of segments possible in a single Vertebrae Well System.
How is the size of the wells determined?
- Well diameter is determined based on treatment function (i.e. injection vs. air sparging vs. vapor extraction) and the total length of the well system. The size may be adjusted to account for pressure/friction loss along the well system. Typical sizes range from ½-inch to 2-inch with “protective” conduit sizes ranging from 2-inch to 6-inch. Additional customizable capabilities are available based on specific project requirements. In general, a multipurpose size tubing is often the outcome of our installations.
What type of flow rates can be achieved with the Vertebrae Well System?
- Our Vertebrae Well Systems can accommodate most flow rates. We balance the desire to have higher flow rates with the need for control. Since our Vertebrae Well System designs are fully customizable, we can build a system based on the specific site design requirements. Flows will be dependent on the site lithology and conveyance tubing size.
- Currently, we have always outperformed the requirements provided by our clients for flow. A few examples include:
- A project site where the client wanted a sparge curtain with well segments that produce 30 cfm of air in 7 segments. Our well segments produced 40 to 50 cfm each.
- A site in Colorado where a client designed an SVE system for 30 cfm per point, and our Vertebrae well segments each performed at 35 cfm.
- A pump and treat site where the client designed a system for 1.5 gpm, and our well segments produced 2.3 gpm.
- Keep in mind, the total flow rates of the system can be extensive and robust, for instance, the air sparge curtain above was supplying 290 cfm in a 140 ft curtain. Even a small well system design using 1/2” tubing over 700 ft long was able to use 18 wells to inject 13 gpm.
How many well segments can be put in one bore?
- The number of well segments in a single bore is dependent on the type and size of the wells being installed and is completely customizable based on the design specifications. Currently our design information indicates as many as 30 may be practical.
- To date, the largest number of well segments that we have installed in one bore has been 18 independent well segments and we have installed as few as two.
Are there any limitations on the drilling location?
- The options for horizontal drilling are unique as the plume can be approached from many different directions. Several factors come into play to find the best drilling location:
- The footprint of the typical drilling equipment requires approximately 400 square feet of space. If a larger drill rig is required to reach the desired depth/length or geologic formation, more set-up space will be necessary.
- The typical setback to reach the desired depth is generally a 3:1 slope, which is where the drill rig is set up. This is unique in comparison to other operations that can require a 5:1 or greater slope.
- Surrounding utilities play a significant role in the feasibility of the proposed drilling location and must be marked for type, size, location, and depth.
How are Vertebrae Well Systems developed?
- Vertebrae Well Systems are developed by surging and pumping the well segments until clear (for wells below the water table). However, with independent control, we can develop all well screens simultaneously with a manifold. Due to the high performance of the Vertebrae well screens, the development process only takes a fraction of the time when compared to traditional horizontal well installations.
Can Vertebrae Well Systems be installed blind?
- Yes, Vertebrae Well Systems can be installed blind. In 2019, 63% of our Vertebrae Well Systems were installed blind.
What is the size of the entrance and exit pits associated with the typical entrance/exit horizontal borehole installation?
- This is highly variable, dependent on the size of the borehole and how many boreholes are used in the same pit. Typically, the entrance pits are usually 1 to 2-feet deep and 2 feet x 3-feet but can be larger. The exit area in general is as small as 1-foot x 1- foot.
How long does it take to install a single Vertebrae Well System?
- This is highly variable and is dependent on total bore length, depth, site lithology and conduit size. On average, a common exit/entrance bore with a Vertebrae Well System installation takes three days. The first day is typically used for equipment delivery, set-up, layout, site preparation and staging, the second day to drill and install the Vertebrae Well System and the third day is used to grout and develop the well segments. The time it takes to install a well system is dependent on the above referenced variables.
- A proprietary expansive grout seal is injected in discrete intervals between the well segments to seal the borehole pathway and isolate the independent well segments.
- The isolation has been verified on several sites using pressure and vacuum testing.
- In addition, the contaminant isocontours developed from sampling the individual well segments indicates true separation. Information presented to us from our clients shows that the users control of the systems has been remarkable and led to better treatment of their project sites.
- We also obtained visual proof of grout integrity via an examination by Aestus’ GeoTrax system that is designed to effect subsurface imaging.
How much Investigation Derived Waste (IDW) is generated?
- This is highly variable and is dependent upon the lithology, bore size, bore total length, and bore type. An estimate of the volume of IDW is provided based on bore hole diameter and total length which can be used for planning purposes. The borehole diameter is minimized to reduce waste.
How are the Vertebrae Well Systems maintained?
- Typically, the Vertebrae Well Systems have not required extensive maintenance routines. If necessary, the wells can be surged with air, water, or the appropriate chemical to alleviate any clogging that may have occurred. The extensive scrubbing or surging associated with the initial well development of a typical single, monolithic horizontal well installation is not required with the Vertebrae Well System. This is a result of the cleaner installation process using a sleeve, and the larger open area that allows better communication with the lithology and easier development.
How accurate is the HDD bore on depth?
- The available walk-over tracking technology is highly sophisticated and is precise to within inches. There are several variables that can affect this including total depth, surrounding ground interference, and the ability to walk over the bore path.
Currently there is no certification for PFAS-free wells in the industry. However, EN Rx is the first to address this issue. We now can provide a Certified PFAS-Free Well System for the cost of the laboratory verification. We test what we sell before we ship and will provide a copy of the lab analysis.
What are the longest Vertebrae Well Systems installed in a single borehole?
- To date the longest Vertebrae Well System is built with 18 independent well segments and is 875 feet long with a borehole length of 972 feet. The total build length was 1030 feet.
- Longer Vertebrae Well Systems are possible, there are many benefits to dividing very long plumes into parts or making transects. First is cost, two 700 foot bores using smaller rigs are less expensive than one 1,200 foot bore. Frictional losses also come into play as well as the ability for more control. In addition, site space and ease of installation are factors considered to make this judgement. However, we know there will continue to be situations that require long wells and longer blind wells so stay tuned to see how this develops over time.
What is the deepest a horizontal well can be installed?
- This is highly dependent on geologic factors, but depths over 100 ft are possible and worth considering.
Can you drill deeper than the suction limit of the water, i.e. beyond 30 ft bgs?
- Yes, if development is not required for injection or air sparging, this is completed like our typical installation.
- If sampling and water collection is required where the water table is greater than 30 ft bgs we can use special double valve pumps to develop and purge the wells. This is slower than normal development but just as productive.
- A blind bore requires a ‘trip in’ / ‘trip out’ installation doubling the drilling. This results in a third pass to reem out the initial pilot bore prior to installation. .It also requires a larger bore to accommodate the circumference of the drill rods and conduit. This requires time and thus cost more.
Can we sample as we go?
- Soil sampling during drilling has been a ‘trip in’ / ‘trip out’ based technology for a long time. It has been cost prohibitive in many cases. We are working on a sampling technology to allow several samples to be collected as we drill to provide lithologic and quantitative data.
What are the injections limitations for reagents?
- Our well segments outperform other typical wells used for injection. Vertebrae Well Systems essentially can push any liquid, emulsion or particulate suspension, but there are limits regarding gels and other very high viscosity materials or those with large solid loads or particulates.
Are Vertebrae Well Systems nested wells?
- Yes, fundamentally they are multiple well screens each with individual risers and individual well seals between each screen providing a multiplicity of well zones. However, there are a few major differences between vertical nested wells and Vertebrae Well Systems.
- First are dimensions. There can be a significantly greater distance between well zones, offering excellent seals and more coverage. This discreteness is adjustable but, in most cases, there are 2 to 10 times more distance between screens as typical nested wells.
- The second major difference is hydraulic in nature. The well systems are generally installed in a single stratigraphic horizon. This means there is no concern of transporting the contaminant to a different zone. This concern is minimized by the distance of travel and the competent seals set in place.
- The third is the quantity of wells. When installing one Vertebrae Well System in place of 10 or even 20 vertical wells, we have significantly reduced the risk of creating a contaminant pathway. Furthermore, the drilling location is typically placed away from possible sources. These factors effectively reduce the risk by orders of magnitude.
- In addition, there is no contaminant drawdown when installing the wells in the same manner.
Why use Vertebrae Well Systems?
- Vertebrae Well Systems offer multiple advantages to traditional vertical wells, they can be installed in difficult to access areas as itemized above. They can be placed on the most effective horizontal plane for a chosen remediation strategy, creating more efficient well segment design. With one bore location per Vertebrae Well System, all the individual well segments are separately plumbed to the surface and located in one discreet area, so disturbance is minimal during on-site activities and eliminates the need for additional trenching.
ENVIRONMENTAL INNOVATION LIKE NO OTHER
Our expertise is in filling data gaps and delivering treatment reagents with nested, segmented well systems. We take site assessment and treatment to a new level by overcoming access issues, transforming Site Conceptual Models and facilitating paths to site resolution or closure.
EN Rx SUPPORT PLATFORM™
SP is a self-contained, solar-powered, remotely operating and communications-ready device that facilitates site assessment and remediation. It is programmable for pulling gas/water samples for analysis or, used in reverse can inject reagents to effect treatment.
EN Rx REAGENT™
A unique ISCO product that is a mixture of a proprietary inorganic reagent and hydrogen peroxide. EN Rx Reagent simultaneously activates the peroxide and stabilizes the exotherm– literally it is a unique, slow release free radical generator with a longevity several months.