A frac tank is a mobile steel storage tank mainly used in the oil and gas industries. The word “frac” comes from hydraulic fracturing, a process that allows natural gas to flow from shale into a production well. A mixture of water, sand and other additives is pumped at high pressure down a wellbore. The pressure creates fractures through which the natural gas escapes. A frac job for one well usually needs two to three million gallons of water and about one million pounds of sand. When multiple wells are located at the same site, the amounts of water, sand and other ingredients increase proportionately. Frac tanks are used for both the frac fluid mixture that is pumped into the wells and for capturing the flow-back water afterward.
Types of Frac Tanks
Frac tanks are generally rectangular and hold four to six hundred barrels of fluid. Some frac tanks are carried on flatbed trucks, while others are self-contained semi-trailers with their own wheels. These have integrated ladders and rails for the safety of workers and can easily be hauled from well site to well site. Many service and rental companies use standardized models so that many frac tanks can be connected and used together. Flow-back storage tanks are modified to handle higher pressures. A new variation, the gas buster tank, prevents explosions by venting built-up gas. Because some frac tanks are used in northern Canada and other extremely cold areas, they have been designed for cold weather. Some have heaters, while others have spray-on insulation that maintains water temperature above freezing. In addition, though warm-weather frac tanks have external manifolds, those in colder climates have internal manifolds to limit exposure to the cold.
Procuring and Maintaining Frac Tanks
Generally, contractors rent frac tanks from service companies that provide fleets of equipment for use in drilling operations. A standard frac tank lasts eight to twelve years, but with the application of chemically resistant interior coating and high-quality paint, damage is reduced and the unit can last longer. Many rental companies equip frac tanks with GPS tracking to prevent theft and facilitate relocation according to demand from customers.
Drawbacks of Frac Tank Use
When multiple frac tanks are needed at a site and the tank sizes do not exactly match, the tanks must be leveled manually with forklifts. The same hoses must be fitted securely to prevent leaks. To check fluid levels on mismatched tanks, operators must continually climb up and down stairs, losing time in the process. Most drawbacks to the hydraulic fracturing process involve not the frac tanks but the overall procedure itself. Hydraulic fracturing uses tremendous amounts of water. Though flow-back fluids have been known to leak and contaminate drinking water, the leakage has not been from frac tanks but rather from containment pits the fluids are stored in on a permanent basis. For this reason, in many locations pits dug into the earth are being phased out and replaced with aboveground storage facilities.
Though the vast majority of frac tanks are used in the oil and gas industry, they are also used for other purposes. Paper mills, refineries and chemical plants use frac tanks. In addition, municipal treatment plants temporarily store sewage waste in frac tanks while the plants are being overhauled.
Marty Colton is a freelance home improvement, environmental science, construction, energy conservation and renovation blogger based in Seattle, WA. Those who may need a frac tank in the near future may want to look at the used models from Dragon Products.