PRODUCERS across all shale gas plays are keenly aware of their water usage and the need for sustainability, both for their own operations and for society at large. In particular, producers are working to reduce the volume of freshwater used in hydraulic fracturing by recycling and reusing frac flow-back water.
A typical well in the Marcellus requires 3 million-5 million gallons of water to fracture stimulate, according to Range Resources, which, the company notes, represents 0.003 per cent of the daily consumptive water demand in Pennsylvania. By comparison, according to US Geological Surveystatistics, power generation consumes almost 100 times as many gallons a day, while public water systems and other industrial uses each consume more than 25 times that of shale gas operations.
A comparison of water usage per MMBtu of energy output also shows natural gas ranging from 0.6 to 5.8 gallons. This compares with nuclear power at 8-14 gallons an MMBtu, crude oil at 8-20, coal-powered electric generation at 13-32, and biodiesel from soy at 14,000-75,000 gallons an MMBtu, according to a US Federal Reserve report cited by Range. Recycling and reusing flow back further improves this relative efficiency, the company points out.
Water Recycling Pioneer
Range Resources pioneered flow-back water recycling in 2009, and today uses recycled water in most of its completion operations, says Dennis Degner, director of operations for Range's Southern Marcellus Shale Division. "Reusing flow back and produced water accounts for 30 to 40 per cent of Range's overall water usage in Pennsylvania," he reports.
When additional freshwater sourcing is needed, Degner says the company uses approved surface water withdrawals as well as municipal water sources. Typically, these are rivers and reservoirs that are resistant to drought.
The majority of Range's core operating area is serviced largely by withdrawing and recycling water from the Ohio River, states Degner. The company transports the water through its own infrastructure to well sites throughout its core operating area in southwestern Pennsylvania.
"The infrastructure from the Ohio River is sized so that we can push enough water from the river at the flow rate needed for the frac job, and have essentially no impact on the river," he says.
Range's full flow rate from the Ohio River to a frac job is less than 0.001 per cent of the river's seven-day, 10-year low flow, Degner elaborates. Water is transported mainly in trucks or pipeline, through municipal infrastructure, or temporary aboveground pipes. "We prefer a pipeline because it minimizes truck traffic and is a more cost-efficient way to transport the water," he remarks.
Range is one of a few companies with high volume access to super sources, such as the Ohio River in Pennsylvania, Degner says. "The infrastructure to the Ohio River enables us to utilise a large-volume, drought-resistant source, and allows us to move away from smaller seasonal sources that may be restricted because of seasonal low flows," he points out. "After fracture stimulation, water returned from the well is collected in a closed-loop system at the surface."
Freshwater Use By Oil And Gas In Texas
Despite increasing drilling activity, a study conducted in 2011 by theBureau of Economic Geology at the University of Texas and updated in February this year projects increased use of brackish and produced water in place of freshwater along with flat-to-declining freshwater consumption by oil and gas operators.
Degner says flow-back treatment depends on the type of completion, geologic formation, and water quality required for the frac design. In most cases, he says, the flow-back water must be settled and filtered to remove total dissolved solids and then treated for bacteria. In some cases, advanced treatment technologies such as evaporation and distillation are needed to fully remove remaining salts.
SOURCE: Range Resources Corp