Omar Abou-Sayed explains the specialist treatment and disposal techniques which should be deployed for the safe management of wastes in the oil and gas industry.
The oil and gas industry has several options for handling the waste materials resulting from exploration, development, and production of crude oil and natural gas. From drilling wastes to production fluids, waste that can be detrimental to the environment needs careful disposal to minimise the impact on the environment.
Burial: During drilling, completion, and production operations, various wastes including muds, cuttings, produced water, tank bottoms, and others are created along the oil and gas. These wastes can be disposed of through a variety of methods, including burial, either onsite or (more commonly) offsite
Onsite burial uses lined or unlined pits dug into the earth. Unlined pits receive mud, drill cuttings, and other materials. Some operators drain the fluids from the pits and then bury the solids. If the pits are not properly lined there is a great risk of groundwater contamination from hazardous materials in the waste leaching into the soil. Moreover, if they are not properly fenced or covered, there is a risk to livestock or wildlife entering the pit and becoming ill or dying from exposure to the waste materials. Moreover, these wastes often contain high proportion of chlorides (salts) which can harm the land’s ability to support crops and vegetation.
In most states pits are required to be lined before waste is dumped into them. Even with a liner, the waste can escape into the ground through ruptures in the liner or by overflowing the pit. Soil and water contamination negatively impacts human life as well as the surrounding ecosystem.
Offsite burial, most often occurs at a landfill, which is an engineered earthen impoundment used for the permanent disposal of a variety of municipal, industrial, and hazardous wastes. The landfill may be lined with clay or synthetic liners as part of a system to capture fluids and leaching from other wastes.
Before you dispose of oil and gas wastes in a landfill, check for a permit to receive oilfield wastes and other substances resulting from E&P operations. An operator with multiple well sites within the area may open and operate a private landfill while commercial operators can receive wastes from multiple operators.
In dry conditions, airborne particulate matter and dust from contaminated soils are kicked into the air. You can control this by using dust suppressants or covering the waste with a layer of clean soil or other inert material.
Landfarming is the controlled and repeated application of wastes to the soil surface, a technique for reducing the concentration of oily, hydrocarbon-rich wastes before they are disposed elsewhere. Landfarms are not typically meant as a permanent disposal sites but rather as spaces to treat waste using naturally occurring or introduced microorganisms in the soil to break down the hydrocarbons
Hydrocarbon breakdown is maximised by creating optimal conditions for microbial activity with the right balance of moisture, nutrients, and soil oxygenation. In some areas, you may need to add water, nutrients, and additional soil to the existing site. Biodegradation can be further enhanced with soil aeration.
Moisture control also helps to minimise dust in extended dry conditions. However, water application should be closely monitored, so no run-off or leaching occurs within the landfarm area. A variety of tillage and composting techniques helps with bioremediation or the recovery of the ecosystem.
Similar to landfarming, land spreading is a one-time application of wastes to an area where they are incorporated into the top 6 to 8 inches of soil to maximise hydrocarbon volatility and biodegrading. Do not use this technique with wastes containing metals, salts, acids, or similar constituents in high enough levels to sterilise or permanently impair the soil system.
High temperatures can evaporate, combust, or breakdown hydrocarbons in waste materials. Some additional treatment may be required to remove metals and salts. Thermal treatment is typically performed at a permanent facility although mobile thermal treatment units have been developed.
There are two types of thermal treatment: incineration and thermal desorption.
- Incineration occurs in rotary or cement kilns; the hydrocarbons are destroyed by high heat in the presence of air.
- Thermal desorption occurs in indirect rotary kilns, by thermal phase separation, or thermal distillation. Heat is applied to the wastes to vaporise volatile and semivolatile hydrocarbons.
Gasses may be combusted to reduce the emission of toxic components, or they may be condensed and separated to recover heavier hydrocarbons.
In slurry injection, solid waste is ground into small particles and mixed with liquid to create the slurry. The waste slurry is then injected underground into rock formations through annular injection or in a dedicated disposal well.
Slurry injection requires higher pressure to induce rock fracturing thereby creating a disposal domain for the waste, but is the only technique which removes waste completely from the biosphere.
Over the decades, regulation of oil and natural gas wastes has increased as the impacts of these materials has grown worldwide. Environmental considerations are typically the basis for regulation, but safety is also a major concern. Many larger E&P operators maintain standards above those required under regulations. Conversely, there is often insufficient oversight from regulatory bodies to assure the compliance of the many participants in the broad industry.
Oil and Gas Waste Regulations in the United States
In 1976, the Resource Conservation and Recovery Act was introduced. RCRA considered all material as either a solid waste or a product. Hazardous waste was considered a subcategory of solid waste regulated under a specific subsection of the act.
Hazardous waste is that which has been specifically listed by the Environmental Protection Agency as hazardous because it has one or more hazardous characteristics, such as high flammability. RCRA created a hazardous waste management system to cover the entire lifecycle of production.
Nonhazardous waste was handled under another subsection of the act.
This concept grew out of the shortcomings of the Solid Waste Disposal Act of 1965, an amendment to the Clean Air Act. Before RCRA, these noncomprehensive regulations were wholly inadequate for defining and controlling storage and disposal of wastes, particularly when recycling was thrown into the mix.
Closely following the implementation of RCRA was a round of exemptions for operators who generated or reclaimed particular materials as outlined by law. Certain relatively benign wastes and materials from crude oil reclamation operations were exempted from RCRA disposal requirements. Service companies may or may not be covered by an exemption, depending on the wastes they deal with.
Most E&P wastes are classified by regulation as non-hazardous. However, they share the same negative effects on health and the environment as they would were they produced by other industrial activities which would have caused them to be classified as hazardous under the regulations. Thus, it is critical to take stewardship of these materials seriously when planning any project. Identify the types of waste you will be handling and determine the safest, most cost-effective method of disposal before you commence operating.
Omar Abou-Sayed received his Bachelor of Science degree in Mechanical Engineering from the University of Texas at Austin and his MBA from the Harvard Business School. Omar’s leadership experience spans the global energy, chemicals, oilfield services, and renewables industries. He is the founder and CEO of Advantek Waste Management Services, an oilfield waste management startup dedicated to preserving the environment for future generations.
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