From the first day gas and oil wells got drilled, pits have been developed to contain the drilling wastes and fluids. Ground pits are dug holes and they can be on the system ground containment like steel frac tanks.
Uses of Pits
Pits have many significant uses such as:
- for completing and treating wells
- for storing produced water
- for the need of emergency overflow
- for oil temporary storage
- for waste oil burn off
- for fluid’s momentary storage
The controlling of frac fluids inside the pits is the most dangerous element in avoiding surface ground water contamination. The tank’s failure, pit liner, and flow line that carry fluids can end up with the release of impure materials towards the water. Environmental cleaning of these materials is expensive and it requires longer time in doing the job. So it is important to prevent immediately the release of these materials.
Pits created through the excavation of the ground need to have pit lining. It’s important because pit lining helps to avoid fluid infiltration to the ground’s sub-surface. The method will depend on the soil condition, storage period, and the fluids placed within the pit. Pit liners are typically made of synthetic materials and compacted clay such as treated fabric and polyethylene. These two are combined together by using especial equipment.
There are certain rules about pits, surface protection, and ground water, which all depend on a particular state. Aside from liners, other states may have requirements for pits to be used in long-term fluid storage. They will be put in a minimum distance from the water surface reducing the risks of water contamination. This happens if there is unavoidable release coming from the pits. In other locations, pits can be put in places regarded as “drainage natural channels.” There are also states which inhibit the use of pits because they can cross on water table.
Modern systems are now being developed to avoid using pits. One of which is the handling systems for closed fluid loop. This method stops the need for pits by maintaining the fluids inside the series of tanks and pipes all over the fluid storage procedure. Because fluid is not in direct contact with the ground, the possibility of polluting the water is reduced.
Handling of Fluid and Disposition
After hydraulic fracturing, fluids go back to the surface for a definite length of time known as flow back. Flow back is between 3% (the least amount) to 80% (the biggest amount) of the total water and materials used in fracturing. In addition to the used original fluid, flow back has also minerals and fluids found in the designed fracture. Certainly, flow back water needs proper management in a responsible way.
The regulation of wastes in flow back fluid is dependent on the state regulatory agencies. It all depends upon the state’s condition. At least nine states have jurisdiction over the management of waste for gas and oil exploration.
Appropriate flow back disposal of liquid is significant in protecting both ground water and surface. The big amount of flow back fluids is thrown off in the ground beneath the injection wells. Proper removal of flow back fluids to the examined injection wells is the best way to separate the fluids from near-surface surroundings.
The essential geological settings required for wells are not present in every area. Depending on the location, there can be other process of handling frac fluids like discharge and treatment. This can be conducted in centralized facilities treatment. If discharging is allowed in state, it should be made under strict controls that require permit from the state.