The oilfield is technically just the deposit of oil itself and the land or water above it. This means that oilfields can take many forms, and most include various combinations of pits, ponds, basins, trenches, and other in-ground features designed for storing liquids and sludges. Regardless of their specific design and intended use, all of these features common to the oilfield need proper lining. Understanding the differences in the various pits, and other in-ground features used around oilfields, will ensure you choose the right liner for each installation. While the federal government may exempt these kinds of pits from regulation under the Clean Water Act, each state is still allowed to set plenty of restrictions and requirements on their use.
Reserve Pits
Almost all of the pits on an oilfield will be a reserve pit of one type or another. Reserve pits include all of the various ponds and basins used to hold the oilfield liquids until they’re finished with processing and sealed safely in a disposal well or another container. A reserve pit might contain a freshly pumped mud slurry that still needs skimming to capture the last of the oil, or it might be used to hold drilling fluids after use or when they’re planned for reuse. In general, reserve pits are separate from freshwater holding ponds and other containers for storing unused fluids. They’re primarily used for waste products in the various stages of use and treatment, making them slightly more hazardous to the environment when not properly lined.
Remediation Ponds
Any pits or ponds used for remediation of oilfield waste products will definitely need thorough lining to ensure there’s no contamination of the surrounding soil and groundwater. Since waste products going through active or passive remediation processes will stay in the ponds or pits for months at a time, they’re at a higher risk for leaking or leaching out than liquids only held for a few weeks. The addition of extra equipment like pumps, aerators, filters, and skimmers also complicates both the design and operation of the remediation pond or pit. Yet these features are essential for improving the quality of wastewater and sludge until it’s safe to discharge or ready for disposal in a sealed well.
Frac Pits
Frac pits are a sub-type of reserve pits used particularly on the oilfield for hydraulic fracturing procedures. These retention or reserve ponds can be used for holding flow back and produced water out of an active well, treating water and sludge after a well is shut down, or fresh water that’s waiting for use in a future fracturing process. This means that a single oilfield project site may include a dozen or more different frac pits with different uses or one big basin designed for all of these uses at different stages of the process. Either way, frac pits on the oilfield must be properly lined.
Disposal Pits
Wastewater from oil drilling and hydraulic fracturing is generally injected into old wells and other drilled deposits to keep the hazardous fluids trapped safely underground. However, processed solid wastes like silt, dirt, and sand from the production may be able to be safely buried near the surface instead. Pumping this material deep underground, if it’s not required, is a waste of space that could be holding more risky liquids. Disposal pits for sand, dried mud, and tailings from various drilling operations should be lined to ensure that any runoff and surface water that drips through the material won’t spread any residues.
Wastewater Lagoons
On large oilfield operations, with workers living on-site for 24-hour production, it may be necessary to set up temporary toilet and shower facilities. There are often few options for dealing with the wastewater generated by these activities other than to dig and set up a surface lagoon for treatment. For basic sewage from residential units, open air treatment, with basic aeration for a few weeks, is often sufficient to treat the water enough to make it safe for discharge or reuse. These wastewater lagoons should be lined just as well as any oilfield pit for holding drilling byproducts, since they can still cause health or environmental issues if the water is allowed to leach out.
Drilling Pad Liners
One of the most important uses for reserve pits in the oilfield is as a drilling pad. This is the basin excavated directly around the drilling rig itself to capture all the direct overflow and flow back that occurs during the process. Both drilling and pumping can generate a lot of splashing and spilling, so a well-lined drilling pad captures all that wastewater and liquid to keep it controlled and out of the environment. Valuable oil can also be reclaimed from these pad basins, but the process is much easier if they’re lined to keep ground water and dirt from mixing into the wastewater.
Storage and Transfer Basins
Short-term storage and transfer basins and trenches are used in some oilfield designs to help move raw or processed wastewater between stations. These trenches can stretch between other pits or processing areas and rely on gravity to transfer liquids, or they may take the form of pits and basins that are actively pumped into other areas. Even the most basic trench or basin, designed for temporary transfer or storage, should be lined to ensure there’s no loss of valuable material.
Fire and Stormwater Retention Ponds
Finally, most oilfields feature at least one fire retention pond, to provide enough fresh water for dealing with any fires that might start or move towards the flammable liquids stored on-site. Without a pond or pit full of a few thousand gallons of water hand, it can be practically impossible to transport enough water in time to control the flames. Stormwater retention ponds, to keep water from flowing into other pits that don’t need to be diluted by runoff, often double as these fire retention ponds. Lining isn’t always strictly necessary for these kinds of pits, but it is recommended to prevent the loss of valuable water.
All of these pits tend to hold chemicals and compounds that break down many liner materials. Don’t choose a liner that can’t handle the challenges of the oilfield environment. Turn to BTL Liners for flexible products that won’t break down under constant exposure to petroleum products.
