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Energy the nexus of everything: January 2012 Archives

This weekend I joined a town hall forum in Cuero, TX, (DeWitt County, Texas) on the edge of the very hot Eagle Ford formation in South Texas.  The Eagle Ford is currently a hot bed of activity for hydraulic fracturing for both natural gas and liquids production, depending upon where drilling occurs. As with many regions, local people there are concerned that hydraulic fracturing, and the associated activities surrounding that process (e.g. injection of 'produced' water and waste fluids, trucks on the road, extraction of drinking well water), might cause some deleterious impacts such as depleting or contaminating groundwater supplies.  This town hall was one way of getting information out to landowners and the public.

There is much anecdotal 'evidence' and stories of one water well or another getting contaminated soon after hydraulic fracturing commences in area.  Actually, sometimes water quality has gotten better!  A local water well driller and service provider noted some of the things he thought might be going on, and they made a lot of sense.  Before the actual hydraulic fracturing process commences, the oil and gas companies fill up a man-made pond at the drill site that will hold the 4-8 million gallons of water typically needed for the fracturing.  In the case of much of South Texas, and the Eagle Ford formation, the water comes from the local underground sources of drinking water.  As explained at the Cuero town hall, the rate at which groundwater is being pumped into the holding ponds might be causing much or all of the impacts on local water wells.

Under normal conditions, water flows in a preferred direction in an aquifer, and relatively slowly at that.  This slow flow rate and constant preferred direction settles out sediments and orients them against rock pore surfaces accordingly (like getting sediment build-up at a dam). If a water well begins extracting water at a high enough rate, it can cause pressure changes in the aquifer such that reversal of local water flow can occur.  When this reversed flow occurs, it can dislodge sediments and minerals that will then move with the water flowing in a new direction.  With these sediments now mixed with the aquifer water, they can sometimes be seen in individual water wells when before there were no sediments.  Thus, it would be easy to conclude that hydraulic fracturing IS the cause of water well contamination, at least temporarily.

The reality is that the life cycle impacts of hydraulic fracturing can be larger than the specific process of fracturing itself.  In some cases, which seems likely in DeWitt County, Texas (but more study and cataloging of data would be needed to know for sure), obtaining the fracturing water from local groundwater sources could be the major/only impact of any consequence. More than that, the rate of the well water pumping could be a major factor such that slower pump rates could prevent changes in aquifer flow and stirring of sediments.

While the folks at this town hall meeting are now much more informed, the same cannot be said for most local residents.  The next step for the stakeholders could be (provided funding can be obtained) the collection of data on well water quality, timing for any changes in quality and water level, and timing of hydraulic fracturing activities to understand the likely relationships between fracturing, well water withdrawal rates, and local well water quality.
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