Natural gas wells in the booming Eagle Ford Shale in South Texas will use significantly less amounts of water for hydraulic fracturing (fracking) compared to municipalities and farmers in the region, a water expert said.

Darrell Brownlow -- a principal with Intercoastal Inland Services LLC and Carrizo Consulting LP and a board member of the San Antonio River Authority -- told NGI's Shale Daily that fears the Carrizo-Wilcox Aquifer would be depleted by oil and gas activities in the Eagle Ford were unfounded.

"The drought that has been experienced across so much of Texas over the last year certainly heightened everybody's interest and concerns regarding water use," Brownlow said Wednesday. "But the concern is about equivalent to the lack of concern there seemed to be a year and a half ago when we were in a heavy rainfall period. We live in Texas and we seem to go from droughts to floods. However, it's natural and important that people are conscious of our water supplies."

Brownlow used his 28-page report from June on water usage in the Eagle Ford as the background for a speech at the Developing Unconventional Gas Eagle Ford Conference & Exhibition last week in San Antonio.

Using calculations based on gallons and acres per foot (ac/ft) -- where 1 ac/ft equals 325,000 gallons -- Brownlow estimates that every well in the Eagle Ford will require about 4.9 million gallons (15 ac/ft) of water, which includes 4.7 million gallons (14.5 ac/ft) for hydraulic fracturing and 162,500 gallons (0.5 ac/ft) for drilling.

Based on an estimate that between 20,000 and 25,000 wells could be drilled in the Eagle Ford over the next 20 years, Brownlow said estimated water use for wells over the next 20 years, excluding recycling, could total between 300,000 and 375,000 ac/ft. At that rate, Eagle Ford wells could use an average 15,000 ac/ft per year.

That's significantly lower than water used across the region. By comparison, the South Texas water management region that includes Bexar County, TX, uses 1.1 million ac/ft per year. Brownlow said that means Eagle Ford wells use about 1.3% of the region's water.

Brownlow added by the year 2060, municipalities would use about 50% (637,236 ac/ft) of the water in south central Texas, while irrigation would take up another 23.7% (301,679 ac/ft).

"I think most people really have no idea that we're using this much water for all of these other things," Brownlow said.

The report went on to conclude that 83 wells in the Eagle Ford would use the same amount of water -- 1,250 ac/ft -- as 625 acres of corn. Assuming each well produced 300Mboe over its lifetime at prices of $100/bbl, the economic gain from oil and gas would be $2.49 billion, compared to the $187,500 that could be made if corn annually fetched $300/acre.

"I wasn't trying to send any message any direction one way or the other, it's just that the comparative economics are pretty stark," Brownlow said. "This was an attempt to provide some perspective on the economic comparison between utilizing water that we use for agriculture compared to what we use for oil and gas. I think most people will find that fascinating."

Brownlow said operators in the western portion of the Eagle Ford would need to have water trucked in because there are no local high-capacity freshwater wells in the area, but they are available in the northern and central portions of the play. He added that the Carrizo is too deep in the eastern portion of the play, so operators will need to tap the Evangeline Aquifer or other shallow aquifers along the Gulf Coast for water. He said recycling would also play a major role throughout the play.

Reservoir and aquifer managers kept a close eye on the state's water levels in the wake of a devastating drought, but did not enact any water restrictions in the Carrizo-Wilcox Aquifer (see Shale Daily, Aug. 11; June 15).

"The state has a very active water planning effort," Brownlow said. "The entire state is able to accommodate this level of usage [by natural gas wells] into its plan, and to make sure that we have ample water for all other needs. The horse is not out of the barn. While we're certainly experiencing a boom in the Eagle Ford, there's ample time for the planning bodies to take these things into consideration."