Oil pits play an important role in storing waste liquids. The major task of hydrocarbon extraction and usage, after safety, is to keep everything clean – things can get messy bringing oil out of the ground. Fluids of various kinds are involved in both the exploration process and the production process, and a variety of containment pits, basins, ponds, tanks and strategies are employed to keep the environment safe from contamination throughout the entire supply chain.
Unlike surface-water management, which can often be handled in ways that are open to the sky and perhaps even permeable to the underlying soil, oil and the chemical fluids used to handle it must be kept separate from the natural environment. And for this, adequate synthetic geomembranes are crucial – oil pit liners are prevalent, and even enclosed tanks may often be lined, to preserve the structures from decay.
Here are the various ways in which containment and management strategies are deployed in the oilfield.
Oilfield Exploration: Pits on Drilling Sites
- Reserve Pit. Stores drilling fluids (mud) and cuttings during drilling operations. It temporarily holds waste fluids until proper disposal.
- Mud Pit. Contains the drilling mud that is circulated down the wellbore. Includes the active mud pit and reserve mud pits for extra capacity.
- Shaker Pit. Receives drilling mud and cuttings from the wellbore. Equipped with vibratory “shale shakers” to separate cuttings from reusable mud.
- Settling Pit. Allows solids to settle out of the drilling mud. The cleaned mud is then reused in the drilling process.
- Flare Pit. Used to burn off excess natural gas that cannot be captured or processed during drilling, providing a safe area for flaring operations.
- Sump Pit. Collects and stores various types of waste fluids, including rainwater and spills from the drilling site.
- Frac Pit. Stores large volumes of water, sand, and chemicals used in hydraulic fracturing (fracking) operations.
- Disposal Pit. Used for the disposal of non-hazardous drilling waste materials that cannot be recycled or reused.
- Storage and Transfer Basin. Holds fluids temporarily during the transfer from one location to another, ensuring a continuous supply for drilling operations.
Oilfield Production: Pits at Pump Stations
- Produced Water Pit. Stores water brought to the surface along with oil and gas during production. Often saline and may contain hydrocarbons.
- Skim Pit. Separates oil from produced water, allowing oil to float to the top for further processing or disposal.
- Evaporation Pit. Used to evaporate excess water from produced fluids, reducing the volume of water that needs to be disposed of.
- Salt Pit. Stores salt and other solid by-products separated from produced water.
- Fire Pit. Provides a safe area for burning off any flammable waste fluids or hydrocarbons in emergency situations.
- Waste Oil Pit. Temporarily holds waste oil and other hydrocarbons that need to be disposed of or recycled.
- Remediation Pond. Used for the treatment and remediation of contaminated water or soil from drilling and production activities.
- Fire and Stormwater Retention Pond. Collects stormwater runoff and provides a reservoir for firefighting water in case of emergencies.
Hazards to Wildlife and the Environment
Spills and leaks from oilfield pits can contaminate surrounding soil and groundwater with hydrocarbons, heavy metals and other toxins. Volatile organic compounds (VOCs) and other pollutants can also evaporate from pits, contributing to air quality issues and health problems for nearby wildlife and humans. And more explosive risks can come from the simple presence of flammable materials in pits.
Animals may be attracted to pits, mistaking them for natural water sources. This can lead to poisoning, entrapment or death. Birds, amphibians and mammals are particularly at risk. Contamination from pits can affect entire ecosystems, disrupting food chains and harming various species of plants and animals. High salinity and chemical content in produced water pits can be lethal to plants and animals, leading to habitat degradation.
Regulatory Improvements in the USA
Regulation has tightened over the years, including with design and construction standards that now often require double liners, as well as leak detection systems and secure covers for pits. Plans are created for sites to follow mandating the safe closure and remediation of pits to ensure that they do not pose long-term environmental hazards.
The frequency of inspections and the continuous monitoring of pits have both helped to detect and address potential issues before they become significant problems. Waste management, too, has advanced over the years, offering better management and disposal of oilfield waste.
Water and air quality standards have both tightened to protect groundwater and eliminate toxins from the atmosphere. Mandatory environmental impact assessments for new drilling projects help capture potential risks, and wildlife protection now often requires fencing and netting around pits. The world runs on oil and gas, and there would be no modern life without hydrocarbons. Fortunately, the practices for keeping these combustible toxins separated from the living natural world continue to improve.
