Deep well disposal of selected commercial/industrial wastes is a technically sound process which involves injecting liquid wastes into a deep underground formation (injection zone) using a well specifically constructed for that purpose. Typically injection zones are at depths of one quarter to one mile below the surface and are separated from sources of drinking water by impermeable over-lying rock formations (confining layers) that are hundreds of feet thick.
Injection zones used for commercial/industrial waste disposal characteristically contain saltwater and no potentially usable resources such as drinking water. The wastes are pumped into, and occupy, pore space within the injection zone. Properly located, constructed, operated, and monitored deep wells are designed to permanently isolate and contain injected waste within this zone.
CLASS V Agricultural Drainage Well
Class II EOR Well
CLASS I INDUSTRIAL DISPOSAL WELL
Class III Uranium Solution Mining
Mineralized Ore Body Exempt Aquifer
Base of the lower-most USDW
Class IV wells related to Hazardous and Radioactive Wastewater are banned and a threat to human health and environment requiring immediate closure and remediation if found. Source: USEPA, Underground Injection Practices Council (UIPC)
Download our Class 1 Injection Well Technology Guide
At the Mid-Way Commercial NHIW Processing and Class I Disposal Well facility, liquid wastes are analyzed and undergo an approval process before they can be sent to the facility. Once approved, liquid wastes received from clients are analyzed again on-site, accepted and stored in a combination of above-ground tanks, in-ground tanks or a geomembrane lined basin. All tanks at this facility are within a secondary containment system to prevent release to the environment in the event of a catastrophic failure. After analysis, processing and filtering, solid removed from the liquids are dewatered and disposed at a permitted landfill facility while the liquid wastes are disposed through the on-site permitted Class I injection well. The liquid wastes are injected over 1 mile below the ground level into the Arbuckle Formation. The Arbuckle Formation is a porous sandstone formation that is overlain by numerous major impermeable confining layers which prevent migration of wastes towards the surface thereby posing an extremely low risk to people, animals, plants and drinking water aquifers.
The Mid-Way facility implements the latest technologies to provide liquid storage, transfer and underground injection. Components of the processing facility and the injection well are continuously monitored by computer systems and facility personnel to ensure the safest operation and compliance with the facility permits and all local, state and federal USEPA requirements. In the event that the system components deviate from the established safety protocols or permit requirements, automatic shutdown procedures are initiated until the situation can be accessed. In addition to these automatic safeguards and routine inspections, the facility performs regular groundwater monitoring to ensure that drinking water sources are not contaminated and annual testing is performed to confirm the mechanical integrity of the well and formation conditions.
Safe Design: A Well Within a Well
Protection of drinking water is the primary concern in the construction of a disposal well and is achieved by assuring permanent containment of the waste.
A Well is constructed in stages. First a hole is drilled to a level below all drinking water. A steel surface casing or pipe is installed the full length of this borehole and cement is placed …
… outside of the casing from the bottom to the top to seal the casing into the hole. This provides a barrier of steel and cement to protect drinking water zones.
The next step is to continue drilling below the surface casing into the injection zone. Samples and instrument measurements are routinely taken to evaluate the type and thickness of the formations. Another protective steel casing is installed from the surface to the injection zone and again cemented …
… the entire depth to seal the space outside the casing. This provides two cement and two steel barriers to protect the drinking water zone.
A small pipe, called injection tubing, is installed inside of this protective casing…
Waste will be injected through this inside tubing. It is secured and sealed at the top …
and sealed at the bottom …
and the space between the tubing and the casing, called the annulus, is filled with a non-corrosive fluid under pressure.
The fluid in the annulus is maintained at a different pressure than the waste within the injection tubing. The annulus and injection tubing pressures are continuously monitored and recorded. Any leak which occurs either in the injection tubing or protective casing will result in a change in pressure and the well will be shut down and repaired. This insures that all wastes reach injection zone. Thus, this well within a well provides multiple layers of protection.
Sources: Chemical Manufacturers Association, 2501 M Street, Washington, DC 20037
Petroleum Geology, Exploration, Drilling, and Production, 2nd Edition, by Norman J. Hyne, Ph.D., PennWell Corporation, Tulsa, OK, 2001
Geophysical tool: “Cement Bond” logs (sonic log) after installation of surface casing (2) and injection tubing (5) established for quality control to ensure proper seal integrity from top to bottom.
Injection well and ground water monitoring
Mid-Way Environmental ground water monitoring program monitors ground water monthly to ensure that any adverse impact to groundwater is quickly identified and reported to the Oklahoma department of environmental quality (ODEQ). Reports are published on a quarterly basis originating from (5) 120’ deep wells on-site. In addition, The 260’ deep monitoring well is monitored on a monthly basis.
The Groundwater sampling and analysis plan (gsap) includes a statistical analysis plan for the facility.
Injection well is monitored during well operations for injection fluid quality, injection pressure, injection temperature, annulus pressure and flow rate. Mechanical integrity testing is performed every year and reported to ODEQ.
Deep well monitoring well for the lowermost Underground source of drinking water aquifer (260’).
Deep monitoring well for the uppermost groundwater aquifer (120’).
Not all injection wells are of the same design and purpose.
Seismic activity reporting required within a 10 mile radius of the injection well
Historical data reveals no seismic activity or active fault lines in the immediate area of Mid-Way Environmental’s Class 1 well in the Davenport, OK, area.
The MES class I injection well injects at no more than 1200 psi max and 170 bbl. per minute, normal injection pressure will average between 350 and 570psi. Surface pressure depending on the density of the water which is a much lower PSI and GPM than other injection wells for oil well fracking at 3500 surface PSI and 1600 to 2700 bbl. per minute or 40,000 to 65,000 bbl. per day.
Bottom hole pressure is roughly 3x surface pressure equaling approx. 1500 psi for the mes class I well as opposed to 11,000 psi for the typical oil company fracking well.
Class II Injection Well
Purpose: Regulate and manage safe injection (1) of fluid brought to the surface in connection with oil and gas production and some natural gas storage operations, (2) for enhanced recovery of oil or natural gas, or (3) for hydrocarbon storage operations. Prohibit movement of fluids into USDWs.
Examples of Fluids:
Produced high salinity brine
Crude oil (for storage)
Polymers and vicosifiers for enhanced recovery wells
Drilling fluids and muds
Construction and siting
Cased and cemented to prevent movement of fluids into USDWs
Construction and design of well (casing, tubing and packer) varies
Monitoring and Reporting
Plan for safe plugging and abandoning of wells, including demonstration of financial responsibility
40 CFR 144 Subparts A – E
40 CFR 146 Subparts A and C
Source: EPA Protecting Drinking Water Through Underground Injection Control: UIC Pocket Guide