Historical and 2006–2025 estimation of ground water use for gas production in the Barnett Shale, North Texas

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2006

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The Barnett Shale play, currently the most prolific onshore gas play in the country, has seen a quick growth in the past decade with the development of new "frac" (a.k.a. fracture stimulation) technologies needed to create pathways to produce gas in the very low permeability mudstones. This technology uses large amounts of water in a short period of time to develop a gas well. There are currently over 5,600 wells producing gas from the Barnett Shale, with thousands more likely to be drilled in the next couple of decades as the play expands out of its core area. A typical vertical completion consumes approximately 1.2 million gallons, and a typical horizontal well completion 3.0 to 3.5 million gallons of fresh water. Almost 8,000 acre-feet of water (from all sources) was used in 2005, mostly in an area equivalent to a Texas county. This usage has raised some concerns among local communities and other groundwater stakeholders, especially in the footprint of the Trinity aquifer.

In this study, we present projections of groundwater use by the oil and gas industry through 2025. Total water use is highly uncertain, being dependent on the price of gas above all. We approach this uncertainty by developing high, medium, and low scenarios that can be somewhat understood as cases with decreasing gas prices. Other important factors include geologic risk factors in the Barnett (maturity of the shale, thickness of the formation, presence of features limiting or hampering well completion), technological factors (horizontal vs. vertical wells, water recycling), operational factors (number of well completions that can be done in a year, proximity of a fresh-water source), and regulatory factors. The high scenario cumulates most of the high-end water use of the previous parameters, whereas the low scenario uses the low values of their range.

The low scenario utilizes 29,000 AF of groundwater to the 2025 horizon (1,500 AF/yr on average), a clear retreat from the current annual rate of water use by the industry, corresponding to a large drop in gas price. The high scenario calls for a total water use between 2007 and 2025 of 417,000 AF of groundwater (~22,000 AF/yr on average). It corresponds to sustained high gas prices allowing operators to expand to all economically viable areas and produce most of the accessible resource but also includes the assumption that water use is not limiting. All scenarios assume that operators continue using water at a per-well rate similar to that of today and that no technological breakthrough will bring it down. The medium scenario assumes a groundwater use of 183,000 AF (~10,000 AF/yr on average).

In the high scenario, groundwater use steadily climbs from ~5,000 AF/yr in 2005 to 20,000 AF/yr in 2010 and then slowly increases to a maximum of ~25,000 AF/yr in 2025. The medium scenario follows a similar path, climbing to a maximum of ~13,000 AF/yr in 2010 and then slowly decreasing to ~7,500 AF/yr in 2025. The medium case is not necessarily the most likely. Because the Barnett Shale play is dependent on gas prices, a more accurate statement would be to formulate that the medium case is the most likely under the condition that gas prices stay at their current level.

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