Articles & Presentations
- 400′ Horizontal Well Radius of Influence
- Horizontal Wells Bring Site Closure
- Directional Technologies assists Samsung Corporation with innovative horizontal remediation well installation for the Yongsan District “Dream Hub” Project in Seoul, South Korea
- Horizontally Drilled Well Screens Solve Subslab Problems
- Horizontal Wells allow Rapid Clean up of R&D Facility Gasoline Release
- First horizontally drilled Electrical Resistance Heating System!
- Horizontal Well – Drilling Fluid – Bentonite vs Bio-Polymers
- Remembering 9/11: Directional Technologies Aided in World Trade Center Rescue Effort
- Horizontal Soil Vapor Extraction
- Benefits Of Horizontal Wells
- Directional Technologies, Inc. conducts unique horizontal remediation well installation in Railroad Yard
- Horizontal Air Sparge Wells Solve Access Limitations Beneath Air Field Tarmac
- Radial Horizontal Well System Targets Specific LNAPL Viscosities in Multiple Product Plume
- DTI Installs 3 Blind Horizontal Remediation Wells in Cobble
- Plume Control under a City Building – Vapor Intrusion Mitigation
- Directional Drilled Horizontal Wells and Engineered Horizontal Remediation Wells Screens Accelerate Site Closure
- Horizontal Wells Used to Remediate Historically Challanged Site
- Site Remediation Using Horizontal Air Sparge (AS)/ Soil Vapor Extraction (SVE), and Multiphase Extraction (MPE) Wells
- Post-Closure Analysis Proves Success of Enhanced Hydrocarbon Bioremediation Using Twelve Horizontal Sparge Wells at Petroleum Products Bulk Terminal
- Installation and Operation of an Air Sparge and SVE System Using Horizontal Directionally Drilled Wells
- Enhanced Delivery of Potassium Permanganate Using Horizontal Wells
- Achieving Delivery Goals with Engineered Screens
- Horizontal Soil Vapor Extraction and Horizontal Air Sparge Well Case Study- Installation to remediated site closure
- Enhanced Delivery of Potassium Permanganate Using Horizontal Wells
Directional Technologies, Inc. was contracted to design and install a horizontal well soil vapor mitigation system.
The horizontal well had to be installed under the slab in the fill material. The decision to place the well in the fill material was made after the horizontal well was designed and fabricated because during a pilot trench it was discovered that clay existed just below the fill material. Directional Technologies was asked if we could install the horizontal well just below the slab. We reviewed the utilities and determined that it was possible.
The preliminary start up for the horizontal well system is showing a 400’ radius of influence on parts of the well. Needless to say, the client is very pleased. This is not a typical radius of influence for a horizontal well which is usually 80’ to 120’ perpendicular to each side of the well screen. This extraordinary radius will allow the client to cover the entire building with only 3 or 4 horizontal wells versus trenching the entire building.
Directional Technologies, Inc. is the nation’s expert horizontal remediation well drilling contractor. We have been designing and installing horizontal remediation well system since 1993. Contact us at 1-877-788-4479 or email@example.com to bring this level of experince to your next project.
BARRIER AIR SPARGING
Why Air Sparging?
Quick Refresher: air sparging (AS) is a proven groundwater remediation technique that removes volatile organic compounds (VOCs) from groundwater by injecting air into water-saturated formations. There are two common approaches to AS. The first involves injecting air through wells into the impacted area to remediate the plume. The second creates a transport barrier by sparging downstream from the impacted zone, VOCs are removed as the groundwater passes through the sparge barrier and aeration enhances natural attenuation.
How are Barrier Air Sparge Systems Usually Installed?
There are three principal methods: vertical wells, horizontal wells and horizontal trenches.
How Do Vertical Wells and Horizontal Trenches Fall Short? One must ensure there is appropriate overlap to account for radius of influence (ROI) limits with a vertical well network to avoid breakthrough. Vertical well networks require interconnecting piping which can be costly to install and cause expensive business interruptions in commercial areas. There are practical limits to the number of vertical wells that can be networked due to piping friction losses and blower sizing requirements. Horizontal trenches involve depth limitations related to readily available excavation equipment and the potential for expensive business interruptions.
Horizontal AS wells typically have 20-40' perpendicular ROI on each side of the well screen.
1,000 foot AS Barrier well
installed at a depth of 23'
to protect Lake Michigan.
HRW directionally drilled by
Directional Technologies, Inc.
How Can Horizontal Wells Enhance The Barrier Sparging Process?
Horizontal wells typically have a robust radius of influence if properly designed. Directional Technologies uses a proprietary screen design methodology to ensure uniform air flow across the screen length. Horizontal wells can be designed to effectively protect extensive areas. For example, Directional Technologies recently installed a 1,000-foot long horizontal well to serve as an AS barrier at a site adjacent to Lake Michigan in Waukegan, IL. Horizontal wells do not involve complicated interconnecting piping networks – connect your surface equipment at one location. In addition, horizontal wells can be “stacked”, if required, to provide a deeper barrier. In other words, two horizontal wells could be installed one on top of the other (appropriately spaced to ensure overlapping ROI) from essentially one drilling location. Finally, horizontal wells can be configured to avoid expensive business disruptions in commercial locations typically associated with vertical technologies.
Directional Technologies Installs Horizontal Wells!
Directional Technologies has been successfully installing horizontal wells since 1984! The companies' experience in the oil field, environmental remediation industry and utility industry allows us to complete projects that were previously considered unfeasible. Give us a call to discuss your next AS system project.
For additional information
contact Kathy Sequino
Air Force Base tarmac is a double-edged sword with respect to environmental remediation. Concrete thicker than at commercial airports virtually eliminates infiltration and limits migration of jet fuel constituents in groundwater, but source material in the vadose zone remains indefinitely, extending the life of the groundwater plume. Horizontal air sparge wells are an effective means of addressing both saturated and unsaturated hydrocarbons beneath airport or air field tarmac, but they cannot be installed unless the drilling contractor can overcome a barrage of challenges, including:
- Flight line traffic and work restrictions,
- Limited site access to work areas, and inability to place and operate drilling equipment on the tarmac,
- Aircraft noise,
- Signal interference to the drill head locating system caused by tarmac concrete and subsurface utility banks, allowing only highly trained and experienced horizontal well drilling specialists to keep the wellbore on target,
- Frequent interruption of the work schedule to accommodate aircraft, and
- Strict adherence to workday schedules.
Directional Technologies, Inc. successfully overcame all of these challenges while installing four horizontal air sparge wells at an Air Force facility in the southeastern United States. The wells fan out over a span of about 120 degrees from a central drilling rig area, so the wells were like spokes of a wheel. Each well placed 150 feet of screen at 25 feet below the tarmac surface. The wells were drilled without exit points, and the tarmac remained free of excavation or any other invasive drilling-related activity. The tarmac was accessible for short periods of time for surveying purposes, and Directional Technologies developed a drilling program that accommodated limited, controlled access along most of the drill path. In spite of these limitations, the client received detailed as-built diagrams of the well paths and profiles.
Local hydrogeology added to the challenges met by the Directional Technologies’ experienced drilling team. Heaving sands along portions of the well paths caused differential sticking of the drill string and well casing during drilling and installation. The drilling team resolved the problem efficiently by adjusting the drilling fluid program and completion method.
All four wells were completed with 3-inch schedule 10s slotted stainless steel screen. The screens were slotted longitudinally, with slots parallel to the axis of the pipe. Longitudinal slots were chosen to maximize pipe strength and air flow distribution. The slots were 0.011 wide, providing filtration control for the fine to medium sand in the target zone.
The wells were completed with 6-inch, schedule 80 PVC pipe, with conventional slots appropriate for LNAPL recovery. Each well was equipped with a down-hole pump that can easily be moved to the optimal location for efficient LNAPL recovery. The ability to adjust the pump location along the horizontal screen allows continuous optimization of recovery in response to changing positions of the multiple LNAPL phases with contrasting viscosities. This flexibility avoids or greatly delays the need for installing new well points that are often required in vertical LNAPL recovery well fields as the LNAPL distribution changes.
Directional Technologies, Inc. (DTI) installed the 6 wells, with over 200 feet total of screen, in less than two weeks. Forklifts moved unimpeded during those two weeks, allowing the shipping department to continue business as usual. Operation and maintenance of the LNAPL recovery system will likewise not impede operations at the paint facility. The centralized location of surface equipment in the underground tank at the center of the “wheel” of horizontal recovery wells will cut the time required for O&M activities to a fraction of what would have been required for an equivalent vertical well LNAPL recovery system dispersed within the building.
A retail gasoline station in Tallahassee Florida with leaking underground storage tanks sits atop a local groundwater divide, causing petroleum hydrocarbon plumes to migrate in opposite directions from the site. In one direction, the plume has migrated under a residential neighborhood on downward sloping terrain, and in the opposite direction, the plume has migrated under a major intersection of two 6-lane US highways and under a fast-food restaurant building and its parking lot and drive-through lanes.
The site is being remediated under a Florida state petroleum cleanup program. The preferred remedy selected under the state program was air sparging accompanied by soil vapor extraction (SVE), but the implementation proved to be difficult or impossible using vertical wells, due to the lack of available ground locations for wellheads and piping.
Directional Technologies, Inc. was retained to design and install four horizontal air sparge wells and four horizontal SVE wells to remediate the multidirectional petroleum hydrocarbon plume. Horizontal air sparge and horizontal SVE wells were installed in pairs, with the horizontal SVE wells extracting air at double the flow rate of the companion horizontal air sparge wells, per the state of Florida’s requirements. Two such pairs were installed in each of the two opposing plumes.
A horizontal well installation program was developed to meet a number of logistical challenges, including:
- A dense network of subsurface utilities, tanks and monitoring wells at the gasoline retail station that required narrow tolerance along the planned wellbore paths
- Drilling and locating through a high-density neighborhood, with many homes and fenced yards
- Drilling and locating across multiple highway lanes, with traffic and strong subsurface interference to the locating system
- Drilling and locating under the gasoline retail facility and fast-food restaurant with drive-through lanes, with zero interruption of the flow of business at either location.
The horizontal wells were 600 to over 900 feet long, with 200 to 440 feet of slotted, 4-inch SDR-11 high density polyethylene (HDPE) well screen. Horizontal air sparge screen depths range from 45 to 50 feet below ground surface (bgs), and horizontal SVE screen depths range from 35 to 40 feet bgs. The changes in screen depth reflect both changes in topography and water table elevation. Over 6,100 feet of horizontal well casing, including almost 2,600 feet of screen, were installed and developed in less than 6 weeks. The well development program was designed to take advantage of the elevation relief between entrance and exit points of the horizontal wells.
The companies' experience in the oil field, environmental remediation industry and utility industry allows us to complete projects that were previously considered unfeasible. The company personnel have been directional drilling horizontal wells since 1984! Please give us a call to further discuss the key elements of successful horizontal remediation systems.
For additional information, contact
Directional Technologies, Inc.
Wells are wells are wells, right? Both conventional vertical wells and directionally drilled horizontal wells have a screened casing that is connected to solid riser casing which leads to the ground surface. Groundwater or soil vapor is drawn through a well screen to remove contaminants. Remediation agents such as air, bioamendmnents or potassium permanganate are injected through a well screen to treat contaminants in situ. This is where the similarities end.
There are some important practical benefits of horizontal wells, independent of the remediation strategy.
- Horizontal wells can be installed in areas with subsurface obstructions such as utilities and under buildings, lagoons, wetlands, railroad tracks, etc. Directional drilling makes it possible to install wells where vertical drill rigs have no access.
- Natural flow patterns in typical soil strata tend to create plumes that are much longer and wider than they are thick. Horizontal wells can therefore be favorably oriented to take advantage of plume geometry and flow direction. This allows horizontal wells to achieve greater efficiency of delivery or recovery than vertical wells in many hydrogeologic settings.
- Accurate installation with respect to elevation and location allows for efficient recovery of LNAPLs, but the well placement must take into account fluctuations in the water table. Installation along the base of aquifer allows efficient recovery of DNAPLs and prevents further downward migration through the confining layers.
- Because of the larger screen area in contact with the impacted media, fewer wells may be needed, and therefore fewer pumps, less piping, and lower operation and maintenance costs. Horizontal wells can be drilled and completed while normal site business continues without interruptions.
- Horizontal wells have a longer screen interval in contact with a larger mass of contaminated media. This results in a greater zone of influence and more efficient remediation. The table below describes the typical zones of influence for common subsurface conditions and this generally results in shorter time of operation and quicker cleanup.
Horizontal well technology can be adapted to many in situ remediation techniques.
Groundwater Pump and Treat
A horizontal well is in contact with a larger area of soil or groundwater and therefore can treat a larger mass of contaminates. Since only one submersible pump is needed in a horizontal well system compared to typically 5 or more pumps in a comparable system of vertical wells, savings can be realized in both up-front capital costs and long-term operation and maintenance costs
See Illustrations Below
This technology injects air, nutrients or other amendments into the contaminated zone, to stimulate microbial growth and promote the degradation of contaminants. The increased surface area provided by horizontal wells allows for more efficient delivery and distribution of amendments as compared to vertical wells. Increased surface area is of particular advantage in diffusion-driven delivery of some bioamendment materials.
Air Sparging and Soil Vapor Extraction (SVE)
In this technology air is introduced below the water table to enhance not only bioremediation but also volatilization of contaminants. It will remove dissolved and adsorbed contaminants from the saturated and vadose zones. Groundwater is not removed to the surface for treatment.
In general, this technology employs two parallel wells—one below the water table to inject air and one above the water table to extract vapors. Due to the long screened interval (increased surface area) and linear configuration horizontal wells more effectively distribute air into and extract vapors from the contaminated area.
Success stories using this approach have been reported for releases at airports impacted with jet fuel, petroleum terminals, refineries and pipelines. In all of these cases the impacted media consisted of soils and groundwater with dissolved and adsorbed constituents, and with free product. This approach can successfully mitigate a plume of contamination flowing off-site, protecting down-gradient neighbors.
In an article entitled “Horizontal Biosparge Wells Treat Petroleum Free Product (Horizontal News Volume 8/Number 1, Fall 2005) Louis B. Fournier, PhD reported that a typical vertical sparge well will have a radius of influence of less than 20’ around the well. Whereas, horizontal sparge wells will typically have a radius of influence of 100’ on each side of the well. For this reason a horizontal well will introduce far more air into the subsurface than a vertical sparge well. Similarly, this results in greater removal of contaminants via SVE.
Additionally, according to Dr. Fournier, if free product is present, the use of vertical sparge wells can “push” the separate phase product away from the wells. EPA guidance suggests that the presence of separate phase petroleum may prevent vertical sparge wells from cleaning up a contaminated site due to the migration of product away from the vertical well. While there is migration of free product away from a horizontal well it must travel much further to get out of the treatment zone due to the much larger zone of influence. Horizontal biosparge wells can be designed to minimize mounding and keep migration under control.
In many cases, the cost of environmental cleanup is lower if the system takes advantage of horizontal well technology, not only because of lower annual operation and maintenance costs, but because cleanup goals are met in less time than with a traditional vertical well system.
In summary horizontal wells have functional differences that result in improved remediation efficiencies. This can result in total project savings of 50% or more.
The company has experience in the oil field, environmental remediation industry and utility industry which allows us to complete projects that were previously considered unfeasible. The company’s personnel have been directional drilling horizontal wells since 1984! Please give us a call to further discuss the key elements of successful horizontal remediation systems.