Hydraulic Fracturing and Produced Water Management
The need for cheap and readily available energy and chemical feedstocks, and the desire for energy independence have spurred worldwide interest in development of unconventional oil and gas resources; in particular, the production of oil and gas from deep, shale formations. This deep subsurface fossil energy resource is accessed using hydraulic fracturing, a process that results in large volumes of high-salinity waste that can be challenging to manage. Our research has been addressing the microbial ecology and biogeochemistry of produced water from hydraulic fracturing. A fundamental understanding of how microbial ecology evolves during water management and how those ecological changes impact geochemistry will lead to more economically and environmentally sustainable management strategies for hydraulic fracturing.
Microbial Ecology of Geologic Carbon Sequestration
Geologic carbon storage (GCS) is likely to be part of a mitigation strategy to reduce the anthropogenic CO2 emissions to the atmosphere. During this process, CO2 is injected as super critical carbon dioxide (SC-CO2) in confined deep subsurface storage units, such as saline aquifers and depleted oil reservoirs. The deposition of vast amounts of CO2 in subsurface geologic formations may ultimately lead to CO2 leakage into overlying freshwater aquifers. Introduction of CO2 into these subsurface environments will greatly increase the CO2 concentration and will create CO2 gradients that drive changes in microbial communities. While it is expected that altering microbial communities will impact the biogeochemistry of the subsurface, there is no information available on how CO2 gradients will impact these communities. The overarching goal of this work is to improve the understanding of how CO2exposure will impact subsurface microbial communities at temperature and pressure that are relevant to GCS and CO2 leakage scenarios.
Bromide removal from Produced Water
Selective bromide removal (i.e., extraction of bromide) is of interest for several reasons. Bromide extraction has both economic value (e.g., the marketability of the extracted bromide) and the potential for a positive public health impact at downstream drinking water treatment plants (e.g., reducing brominated disinfection byproduct formation in drinking water).
Brines generated from hydraulic fracturing of shale gas (i.e., flowback water and produced water) and coal-fired power plant flue gas desulfurization (FGD) wastewater may contain high levels of bromide, among many other constituents. Current treatment practices for hydraulic fracturing brines and FGD wastewater do little to remove bromide and other dissolved solids.
Treatment for bromide removal is often prohibitively expensive at drinking water treatment plants, where the concentration is quite low. Thus, removing bromide from wastewater, where its concentration is higher, is of interest.