Articles & Presentations
- 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
- How much does a Horizontal Remediation Well cost
- DTI Installs Horizontal Wells Under Busy Intersection
Symposium Presentations
- 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
Articles & Presentations
Radial Horizontal Well System Targets Specific LNAPL Viscosities in Multiple Product Plume
Directional drilling rig tucked in corner while normal business activities continue
Since the wells were drilled blind, there was no need to exit at ground surface at the far end of the wells. Instead, each well terminated in the target zone at the distal endpoint of the well screen, eliminating unnecessary drilling and surface construction.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.
DTI Installs 3 Blind Horizontal Remediation Wells in Cobble
The Issue
An active retail gas station next to a wetland area has benzene and trimethylbenzene plumes in a water table aquifer containing sand, gravel and cobbles. Rock fragments and boulders several feet in diameter lie in the vadose zone, between the ground surface and the water table. Business at the gas station would slow down or stop for an extended period of time if a vertical air sparge and soil vapor extraction wells had to be drilled through the rock because the wells would surround the pump island, block the driveways, and even interfere with access to the store itself. The vertical wells would have to be closely spaced because of their limited zone of influence.
The Solution
As a national directional driller based in New England, Directional Technologies, Inc. has the experience to complete projects that may confound other companies. New England is known for its tough subsurface conditions and the company has been installing conduits and horizontal wells in gravel, cobbles and rock since 1992. Directional Technologies installed three blind wells—two air sparge wells and one soil vapor extraction well under the pump island, driveways, and even under the retail store—within a week. Blind wells have only one wellhead, avoiding the need to exit through the wetland area, and limiting the amount of drilling through boulders in the vadose zone to three riser sections (one for each well). Cars pumped gas while the directional wellbore was advancing beneath the pump island and driveways. 
Customers roamed the store aisles and paid at the cash register even as the drillers were locating the advancing drill bit 20 feet beneath the floor. The project was completed on time and without a change order request, despite the need to adjust well entry points, paths, screen depths, and completion details.
The Technology
Directional Technologies brought a variety of excavation and drilling equipment to the site to be prepared for any obstacles to drilling. Limited excavation around the wellheads allowed the driller to coax the drill rod through the rock-strewn vadose zone layers. The well screens were drilled beneath the layer of boulders, and the specialized drill bit navigated through cobbles and rock fragments in the target zone. Placement accuracy was achieved with the use of a walkover locating device which allowed the experienced operators to narrow down the location of the drill bit in the midst of interfering subsurface utilities, tanks, and the foundations and flooring of the retail store. Directional Technologies customizes the drilling fluid for subsurface conditions at every job site. The wellbore remained stable during drilling and reaming through the cobbles and rock fragments, and Directional Technologies successfully installed up to 230 feet of completion pipe in each of the three blind horizontal wells.
Plume Control under a City Building – Vapor Intrusion Mitigation
Subsurface remediation in a big city setting is complicated. Limited work space, heavy traffic, noise restrictions, and a dense network of utilities are just some of the factors that conspire to make the installation of any in situ plume control or plume reduction system a seemingly unsolvable logistical puzzle. Horizontal wells placed directly beneath a building can provide protection from soil and groundwater sources of vapor intrusion, and are more effective for plume remediation than wells that are placed down-gradient or up-gradient of the plume just to avoid having to drill wells inside the building.
Directional Technologies, Inc. has mastered this puzzle over many years’ experience working in big cities in the northeast and throughout the USA. An example of this is in New York City, near the boundary between Yonkers and the Bronx, where a former paint plant leaked mineral spirits into soil beneath a building that is currently used by ExtraSpace for public storage. Besides being under a large portion of the building, the groundwater plume extended outside, under a railroad track, and entered a nearby stream.
A combined SVE and groundwater extraction system was installed using three horizontal wells: one SVE well and one groundwater extraction well under the building, and one groundwater extraction well outside the building, along the railroad track. Directional Technologies, Inc. completed all three wells with four-inch stainless steel wire-wrapped
screen. The wells under the building have 50-foot long screens, and the well along the railroad track has a 100-foot long screen. All three are “blind” wells, with riser extending from only one end of the screen section, while the other end of the screen terminates under ground.
Directional Technologies, Inc., is an industry leader in the installation of blind wells. The soil vapor and groundwater extraction wells under the building are 5 and 22 feet deep, respectively. The wells have 50-foot long risers, demonstrating Directional Technology, Inc.’s expertise in minimizing riser length, which was crucial at this site because the wellheads needed to be inside the building. The outside well has a 170-foot long riser in order to accommodate both screen placement and wellhead location requirements.
The wells have performed to the satisfaction of the site owner and New York State Department of Environmental Conservation. The SVE well developed a symmetrical zone of influence extending at least 50 feet away from the well. The groundwater extraction well under the building depressed the water table beneath the building, creating a trough of depression that increased the distance between the water table and the building slab. The well outside the building provides hydraulic control, preventing impact to the nearby stream.
Directional Technologies, Inc.
203-294-9200
ksequino@directionaltech.com
www.directionaltech.com
How much does a Horizontal Remediation Well cost
In the early days of horizontal remediation wells, the estimated costs made many projects completely unfeasible. However, with the advance of technology in directional drilling and innovative solutions within the environmental industry, this technology is becoming affordable and practical.
Like most environmental projects, the cost of a Horizontal Remediation Well will depend on the size and scope of the project. Outlined below are three hypothetical, but yet typical horizontal well projects.
A typical small Horizontal Remediation Well project
A hypothetical dry cleaner sitting on a quarter acre lot.
Contamination and Objective: Removal of separate phase hydrocarbon, remediation of dissolved hydrocarbons and control/prevent offsite migration
Number of horizontal wells: Two 2” PVC Soil Vapor Extraction Wells
Horizontal Well depth: 7 feet below ground surface
Horizontal Well length: 70 feet
Screen Design: Well designed at 3.5 inches of mercury
Lump Sum well installation estimated costs: $25,000 to $35,000
A typical medium Horizontal Remediation Well project
Hypothetical gas station project, < 1 acre in size
Contamination and Objective: Prevent offsite migration of separate and dissolved phase hydrocarbons, recovery of separate phase and remediation of dissolved hydrocarbons
Number of horizontal wells: Three 3” fiberglass wells
Horizontal Well depth: 10 feet and 22 feet
Horizontal Well length: 250 feet each
Screen Design: Two Air Sparge operating at 1 scm per foot and One Soil Vapor operating at 2 sfm per foot.
Lump Sum well installation estimated costs: $150,000 to $200,000
A typical large Horizontal Remediation Well project
Hypothetical manufacturing facility approximately 10 acre size property
Contamination and Objective: Removal of separate phase hydrocarbons, prevention of off-site migration and remediation dissolved hydrocarbon
Number of wells: 12 wells
Horizontal Well depth: 15 to 30 feet in depth
Horizontal Well length: Each well averages 500 feet in length
Screen Design: Eight Air Sparge operating at 1 scm per foot and Four Soil Vapor operating at 2 sfm per foot.
Lump Sum well installation estimated costs: 900,000 to 1,200,000
DTI Installs Horizontal Wells Under Busy Intersection
The Issue
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.
The Solution
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 Technology
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.
Mike Sequino
203-294-9200
msequino@directionaltech.com
Time-Tested Advantages of Horizontal Wells
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
Figure 1. Plan view of drawdown contours around a horizontal well extracting groundwater from a fractured aquifer.
Figure 2. Cross section of drawdown contours around a horiztonal well extracting groundwater from a fractured aquifer.
Figure 3. Plan view of drawdown contours around four vertical wells extracting groundwater from a fractured aquifer.
Figure 4. Cross section of drawdown contours around four vertical wells extracting groundwater from a fractured aquifer.
Enhanced Bioremediation
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.