Argentina has the second world reserve of shale gas behind China and the fourth shale oil behind Russia, the US and China. At the same time the country faces a significant structural energy deficit estimated at 3% of GDP which represents a restriction on the growth estimated for the upcoming years. Thus, these non-conventional energy sources seem a viable and strategic alternative for the country to explore. However, what potential environmental impacts related to water and climate change does this methodology imply?
A USGS study shows that the demand for water for fracking grew more than 28 times in the last 15 years in the US, coincidently with the increased production of oil and gas from these unconventional reserves. In Figure 1 you can appreciate the main reservoirs in the US and the demand of water in m3 per well expected, that can exceed 36,000 m3 /well.
Figure 1. Use of water for fracking in the US (Source: USGS).
Environmental concerns related to the exploitation of unconventional hydrocarbons is mainly linked to the use of water, a scarce resource in the region, and the consequences that such technology may have on the pollution of aquifers and the surrounding soil, among others. Figure 2 illustrates the previously mentioned statements.
One question relies in the fact that drilling could contaminate aquifers which populations use to draw water for their consumption. According RAE (Royal Academy of Engineering, UK) the risk of fractures generated by fracking from spreading and contaminating aquifers is minimal, but great part of the success of such process is that the well is designed, built and finally dismantled following the best practices and techniques available. Among these is the obligation to make comprehensive measurements of contaminants in the groundwater in each site and in intermediate points. It is noteworthy that in the case of Argentina the deposits are at a greater depth (deeper than 1000/1500 m) than in USA (less than 500 m). This means less impact on surface water, but also higher costs of development and operation.
Furthermore, as to the volumes of water used for fractures, lies another major conflict regarding the extraction technique of unconventional hydrocarbons. While Neuquén Mining Corporation, based statistical hydrographic information, states that the 25000 to 35000 m3 are required for each drilling is not significant in the eventual involvement that such action may have on the availability of water for human consumption (accounting for about 0.2% of surface water resources, although the full impact will depend on the number of developed wells). However, it should be noted that the values mentioned previously correspond to the volume required per well along their useful life, and consequently the impact will be proportional to the number of wells to be explored. In the case of Vaca Muerta in full operation, this may imply reaching a value in the order of the 300 m3/s of water demand, equivalent to the average flow of the Limay River.
On the other side, the World Resources Institute (WRI) states that Argentina has a medium level of water stress in that region. Although this would not be alarming in the present, it is important to notice that countries like the US, pioneers in shale gas have increased the use of water in their wells by almost 3000%, and consequently the originally favorable situation of Argentina in this aspect could change dramatically, and therefore it should be considered when exploring these alternative fuels. This should be a relevant aspect to assess properly and monitored effectively and continuously.
Figure 2. Water stress linked to the exploitation of hydrocarbons in Argentina (Source: World Resources Institute).
A third aspect related to water and fracking: wastewaters. As mentioned, when making the horizontal perforations around 30000m3 average water are required by each perforation. These contain certain chemical additives which are recovered by up to 70% when the water returns to the surface. In addition, this water is obtained within a mixture of other substances such as dirt and inorganic compounds of the drilled rock. That is why it is vital to treat the recovered liquids before they are return to a superficial circulation. Although there is legislation, in national and provincial level concerning water contamination, in order to prevent disasters such as those in the Riachuelo, where the lack of management and control over the domestic and industrial wastewaters led to the complete deterioration and of the channel, it is necessary to develop specific regulations to control functioning and abandoned perforations. Thus, the constant monitoring and sanction against any non-compliance should be mandatory; a model for the managing of the monitoring process, as well as the approval of actions, should be put in practice. Faced with a scenario of water scarcity, as climate change scenarios predictions state for the coming years in the region where Vaca Muerta is located, the greatest degree of reuse of treated water must be guaranteed and implemented.
The combination of higher costs, high water requirement, the low levels in the recycling wastewater process, implies additional costs and environmental risks that must be considered prior to the proper development of the perforations, and then monitored and managed comprehensively throughout the life of the exploration. In any future scenario facing the likely decrease in water availability it is necessary to consider the opportunity cost of such resource over other uses downstream or upstream of this development, such as the use for human consumption, agriculture and fishing, power generation, industrial uses and demands in order to guarantee an ecological flow for proper behavior of river ecosystems.
The issues discussed, along with other social concerns, are detailed in depth in a recent study by the National Academy of Engineering of Argentina, which has been used for this work.
In any case the relationship between investments required to increase the supply of energy in Argentina and its ecosystem is key to ensure environmental, economic and social sustainability in the medium and long term. With more than 65% of its territory with arid or semi-arid climate, water becomes a key resource for the country and its future. In BerecoLabs we are studying the possibilities that technology begins to offer in order to monitor the impacts using new techniques and also to achieve viable alternative energy sources, leading to a diversified and balanced energy matrix in the medium term.