Can I Use A Class II Well to Inject Industrial Wastewater?
If your project involves injecting industrial wastewater, you may be wondering what the laws are surrounding this practice. What is allowed, and what is regulated? Here is some information about Class II injection wells.
Types of Underground Injection Wells
The U.S. Environmental Protection Agency (EPA) has defined six classes of underground injection wells, based on their uses. Class II wells are associated with oil and gas production and Class I injection wells are used to manage liquid wastes derived from industrial sources.
Class II injection wells contain three subcategories:
- Enhanced recovery wells: This is the most common type of Class II wells, accounting for about 80 percent of all Class II wells. These are used to help recover oil and natural gas by injecting fluids into oil-bearing formations.
- Disposal wells: As the name suggests, these are used in the disposal of wastewater, including produced waters extracted with flowback waters associated with fracking. This type of wells accounts for about 20 percent of all Class II wells.
- Hydrocarbon storage wells: These are used to store oil, primarily as part of the U.S. strategic petroleum reserve. These are less common.
Using Class II Wells to Inject Industrial Wastewater
The determination of whether any waste stream can be legally injected into any particular Class of injection well is based almost entirely on the source that generates the waste stream. Waste streams may be identical in physical and chemical makeup, but the source of generation is key in determining the waste classification and subsequent allowable method of disposal.
Here is a common question or scenario for your consideration. The waste stream considered for injection is described as a calcium chloride (CaCl2) brine waste stream and it is generated from cooling tower blowdown water at an industrial facility. This waste stream has low total dissolved solids (TDS) content and it is non-hazardous. This waste stream is derived from an “industrial” source and is labeled as Class I non-hazardous wastewater.
For our second scenario, the waste stream considered for injection is described as a calcium chloride (CaCl2) brine waste stream and it is generated from upstream oil and gas processing facility at natural gas compressor station. This waste stream has low total dissolved solids (TDS) content and it is non-hazardous. This waste stream is derived from an “oil and gas processing” source and is labeled as Class II wastewater.
Clearly, both waste streams have the same chemical and physical makeup and the only difference is the source from which they are derived. So, can I use a Class II injection well to inject industrial wastewater? The answer is NO. Industrial wastewater cannot be injected into a Class II injection well. There have been a few instances where a limited quantity of Class I non-hazardous waste has been allowed for disposal in a Class II injection well, but these activities required special permission. Can I injection Class II wastes derived from “oil and gas” processing in my Class I injection well? The answer is YES…….as long your approved permit lists Class II oil and gas wastes as one of the possible waste streams for injection, it can be injected into a Class I injection well.
Addition Class II Injection Well Information
In addition to oil and gas, brines are also brought to the surface during the production of hydrocarbons. Once on the surface, these brines are separated from the hydrocarbons and reinjected back into underground formations. This is a very common use for Class II disposal wells, which, as mentioned above, make up about 20 percent of all Class II wells.
In enhanced oil recovery (EOR) wells, fluids made up of fresh water, brine, steam, carbon dioxide (CO2) or polymers are injected into the underground formation to reduce the viscosity of oil and gas and make it available for recovery. Typically, this is done with a single injection well surrounded by many other production wells that bring the oil and gas to the surface.
Hydraulic fracking is a similar process used in enhance hydrocarbon production in low permeability formations. Fracking involves injecting a fluid along with a proppant (usually sand) under high pressure. As the formation fractions, the fluid enters to void space and carries the proppant. When the pressure is released, the proppant holds the fractures open so the fluid can return to the well. According to the EPA, wastewater from hydraulic fracking can also be injected into Class II wells.
Since 1992, Terra Dynamics Incorporated has provided integrated project management, engineering, field operations supervision, geological evaluation, reservoir studies and other services, with a specialization in injection well services for industrial and refinery applications. When your project involves using Class I or Class II injection wells, reach out to the experienced professionals located at our Round Rock, TX office. We look forward to working with you!