Special Considerations & Topics
Risks of Vertical Wells
Clearly, the advent of groundwater science is structured around vertical wells, but that does not make them immune to a variety of flaws as assessment tools. Among other things, unwanted communication can occur between contaminated and uncontaminated strata by drilling through both.
On the reagent injection side, the risks of installing vertical wells, other than the inefficiencies inherent in those processes. Is largely characterized by daylighting, which is significantly more problematic with chemical oxidants.
Depending on site specific conditions, there are significant benefits in installing horizontal well systems as an alternative to vertical wells. Then, within the scope of options for horizontal wells themselves, the advantages of nested, segmented systems are well characterized in detail on this Website.
Make no mistake about it though, vertical wells or less invasive profiling tools, are very much a part of the overall process, because they guide horizontal installations. It is like needing a tugboat to guide cargo ship into port. In some circumstances, the assessment of site conditions in the vertical dimension will facilitate the horizontal well installation process.
High Resolution Contaminant Distribution (HRCD)
High Resolution Site Characterization (HRSC) is in a sense “old wine in new bottles, because the art of profiling an aquifer is nothing new. Even the more advanced techniques, that offer a very valuable greater “granularity” in defining the matrix, are themselves 20 years in development.
Of course, that is all done with vertical wells, but what happens when site characterization is done in the horizontal plane? In essence, one can create what we are calling High Resolution Contaminant Distribution or HRCD.
In HRCD dynamics we go up “the spine of the plume”, and that relates to naming our product Vertebrae™. The result is a new expression of the all-important Site Conceptual Model (CSM), that makes site assessment and treatment more dynamic and accurate.
Clearly, the way nested, segmented wells can be used for surgical placement of reagents, creates a situation whereby less material is needed to for remediation. This is also facilitated by the collateral use of the EN Rx Support Platform (SP). This translates to relevant achievements in sustainability metrics, which are oftentimes required in competitive bidding as part of Corporate Social Responsibility (CSR) requirements.
Permeable Reactive Barriers (PRBs)
PRBs or Permeable Reactive Barriers, are a long-standing solution to addressing dissolved phase plumes, by intersecting and treating them.
Vertebrae™ Well Systems can be factored into PRB designs as a potential superior treatment option. Diagnostically, they can be used to explore the best transect for placement of a source area treatment, by helping better define the connection between a source and dissolved phase plume.
Permeable Reactive Barriers (PRBs) For Flux Metrics
This is an expansion of the previous application. This year, SERDP/ESTCP awarded Arcadis, The Guelph 360 Consortium and EN Rx a project to advance this engineering concept. The plan involves using Vertebrae PRBs to measure flux by some creative means. First, the wells are placed perpendicular to groundwater flow. Then one strategy will involve the injection and withdrawal of tracers, such that the loss of said tracers can be converted mathematically into expressions of mass flux. Similarly, by using conductive salts as tracers, and with sensors in place, continuous real time data sets can be generated.
Vertebrae Well Systems, in certain cases, including but not limited to sites where there are access issues, can serve to improve assessment at treatment operations over conventional methods.
Leak Detection and Other Sensor-Mediated Processes
A long-standing environmental issue in the oil and gas industry involves leaks from tank-stored hydrocarbon products, and associated infrastructure, as well as the brine-laden produced water from exploration. Vertebrae Well Systems have a role here, when enabled with sensors, to serve as a detection and management process.
Reimagining Recirculation Wells
The traditional installation of recirculation wells for treatment, a strategy that is gaining in popularity, has been to use vertical wells to inject and extract reagents across a horizontal transect. The use of horizontal wells, in the same regard, makes this operation more robust because injections can be made “up the spine of the plume”, and drawn back down in the horizontal plane, to obvious advantage.
Natural Source Zone Depletion (NSZD)
NSZD has been advanced in many quarters to deal with larger industrial impacts – most notably with LNAPLs that can naturally attenuate. The central tenet of NSZD is that, in many complex settings, this variant of natural attenuation (for palpable mass versus dissolved phase impacts), is the only sensible approach. In fact, the science has shown that rates of NSZD can be far greater than what can be achieved when approaching a point of diminishing returns with standard pump and treat operations. Data sets to make a case for NSZD rely on temperature measurements (given a correlation between that and microbial activity) and/or gas evolution (methane for anaerobic processes and carbon dioxide for aerobic processes). Clearly there is a role for Vertebrae systems in collecting relevant data to make the case in a more surgical and accurate manner.
Controlled Vadose Zone Saturation and Remediation
In some cases, when dealing with a contaminated vadose zone that is aerobic, one solution is to flood it with electron acceptors and create an anaerobic environment to drive remediation. To do this, the flooding must be controlled, to prevent leaching contaminates to the groundwater. There are methods to do this effectively with modeling and monitoring (moisture sensors, wells, etc.) and to optimize control of the process, Vertebrae is ideal for this in many respects – especially in concert with the Support Platform (SP). Not only is control a hallmark of this approach, but wells can be emplaced to evaluate and treat the contamination with precision and with multiple layers as needed. At present, the established protocol is surface infiltration which can be inferior to using Vertebrae.
In Situ Thermal Treatment
There is one aspect where Vertebrae can factor into these complex operations, where one must collect the vapors that are generated by the heating process. While there are solutions to this aspect of treatment, there are instances where access is an issue. In those cases, working with Vertebrae is a sensible solution. In the future, subject to working with thermally stable materials, we are evaluating the roll of Vertebrae systems to also deliver the thermal treatment in a surgical manner.
Vertebrae nested, segmented horizontal wells can be applied to sediment management needs several ways. In many settings, the installation of vertical wells is problematic or impossible, but not for horizontal emplacement approaches. This is particularly apparent in identifying the heterogeneity in flow and transport of contaminants at the groundwater – surface water interface due to lithologic changes; a very important metric. Further, there is a roll for Vertebrae systems to assess contaminants beneath a surficial cap to monitor progress, and where necessary, perform treatments with minimal disturbances at lower cost.