Water Journal : Water Journal November 2012-1
my point of view water NOVEMBER 2012 7 Baseline monitoring is increasingly being used because unconventional shale and tight oil reservoirs are often source beds of hydrocarbons for overlying conventional reservoirs. In addition, old, so-called legacy wells, many drilled at the beginning of the last century, may not have been subjected to as rigorous regulation as those drilled in recent times, so it is important to distinguish the impacts of modern wells. Another issue of concern to communities is the substantial volumes of freshwater used as the injection fluid for hydraulic fracturing. During the hydraulic fracturing phase, a shale gas well requires an average of 1.14ML and this can be as high as 2.65ML. While these volumes are relatively small compared to other industrial water uses, impact in local areas where water resources are constrained can be high. However, at the end of production, studies of water depletion from coalbed methane extraction in Wyoming have shown that within a decade or less the recovery is back to about 65 per cent to 80 per cent and we see no long-term impact on the draw-down levels at the watershed area level. The current emphasis on work and directions is on recycling, which not only conserves freshwater, but allows produced flowback waters and some fracturing chemicals to be reused and wastewater disposal impacts to be moderated. Operators are also increasingly using brackish and saline waters and experimenting with alternatives such as liquid carbon dioxide, propane gel, or adding nitrogen gas to substantially reduce the amount of freshwater needed, but without contamination potential. Meeting the Challenge of Expanded Production In summary, the principal impacts from shale gas and oil production are from phases of the production cycle unrelated to the specific hydraulic fracturing process. These are the same kinds of impacts long noted and long regulated in conventional oil and gas development and production. In the US, state and federal government agencies are gearing up to meet the challenge of much expanded unconventional gas and oil production. The hope is that regulations are appropriate and diligently enforced so that the environment can be protected and the nation can enjoy the economic and security benefits of greater domestic production of energy. A well drilling rig works in the eastern plains of Colorado.
Water Journal December 2012
Water Journal September 2012-1