EAGER: Effects of Thermodynamic Phase Changes at Reservoir Conditions on the Interfacial Properties of Chemicals Used in Hydraulic Fracturing

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

1252249 Harwell The combination of hydraulic fracturing and horizontal drilling has dramatically affected energy production in the United States and is poised to have a similar impact across the rest of the world. Increased natural gas production from previously uneconomical shale gas reservoir has already led to plummeting natural gas prices, economic booms in several states, and dramatic investments in new manufacturing facilities. The potential is so large that there is already discussion of the possibility of the US becoming energy independent and even becoming a net energy exporter. The growth in hydraulic fracturing operations has, however, led to fears of environmental impacts. One potential impact which causes perhaps the most concern is ground water contamination by the chemicals used in the fracking fluid. Extensive fate and transport studies over the past four decades provide a deep resource for understanding and predicting the migration of typical fracking fluid chemicals should they reach ground water aquifers, but conditions in a typical shale gas reservoir differ dramatically from those in an aquifer. This EAGER project stems from the hypothesis that thermodynamic phase changes in the aqueous solutions which are the carrier fluids in hydraulic fracturing will lead to greatly increased adsorption of fracturing fluid chemicals by both the shale gas minerals and the sand used as a proppant. This increased adsorption implies a greatly reduced potential for the chemicals to find any kind of path by which they might migrate to a ground water aquifer. Understanding these potential phase changes is made more difficult by the high concentrations of dissolved salts (total dissolved solids, TDS) found in hydraulic fracturing operation ?flowback? water. The investigators propose experiments to study the phase changes induced in fracturing fluids by the high temperatures and electrolyte concentrations that develop when the fluids are injected into a shale gas reservoir. They will also measure the interfacial properties of fracking chemicals at the rock/brine and proppant/brine interfaces at gas reservoir conditions of temperature, pressure and TDS. Experiments will include both batch and flow-through reactors and measurements. The intellectual merit of the proposal arises from the contribution to better understanding the effect of reservoir conditions on the thermodynamic activity of fracturing fluid chemicals in a reservoir. The results will provide another key element in understanding the true potential of hydraulic fracturing operations to produce long term environmental damage in the form of chemical contamination of ground water. The broader impact of the proposal arises from the educational benefits to the graduate and undergraduate students who will be supported while conducting the experiments described in the proposal. The results will also make a significant contribution to the debate about fracking?s potential for ground water contamination. The investigators also expect the results to lead to a discussion of design of better fracking chemicals to improve the performance of the fracking fluids under the extreme conditions found in gas shale reservoirs.