ENHANCING ANALYTICAL METHODS TOWARDS THE GEOCHEMICAL AND BIOGEOCHEMICAL FINGERPRINTING OF SHALE GAS SYSTEMS
Open Access
- Author:
- Piotrowski, Paulina Karolina
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 22, 2018
- Committee Members:
- Franklin Lewis Dorman Jr., Dissertation Advisor/Co-Advisor
Thomas E Mallouk, Committee Chair/Co-Chair
Squire J Booker, Committee Member
Philip C Bevilacqua, Committee Member
William D Burgos, Outside Member - Keywords:
- Analytical Chemistry
Hydraulic Fracturing
GCxGC - Abstract:
- Hydraulic fracturing is a frequently utilized technique for the extraction of natural gas entrapped in shale formations. However, many have raised concerns about the environmental impacts of this process. Little is known about the organic chemistry of the flowback or produced water resulting from the hydraulic fracturing process. A better understanding of flowback and produced water chemistry and shale chemistry may facilitate environmental fingerprinting and help determine the potential impacts of contamination events from shale gas operations. Utilizing comprehensive two-dimensional gas chromatography (GCxGC) coupled to time-of-flight mass spectrometry (TOFMS) has allowed for a better understanding of hydrocarbon origins in flowback and produced waters. Through the investigation of a series of five injection fluids and five flowback samples from a single unconventional gas well in northeastern PA by GCxGC-TOFMS, chemometric analysis by mass spectral scripting algorithms revealed that specific hydrocarbon composition remains constant during the flowback period and contains very little signature of injected fluids. Additionally, GCxGC with high-resolution time-of-flight mass spectrometry followed by Kendrick mass defect analysis of flowback from four nearby wells indicated a unique hydrocarbon pattern in each case. It was hypothesized that the hydrocarbon chemistry of the shale contributes to hydrocarbon signature of the flowback. To further explore the hydrocarbon signature hypothesis, thermal desorption methodologies were developed as a sample introduction tool for GCxGC-TOFMS analysis of shale rock samples. The method was evaluated against Soxhlet extraction and shown to be reproducible and efficient for the hydrocarbon analysis of shale rock cores. This novel and robust characterization of Marcellus and Utica shales demonstrated the hydrocarbon differences between the two formations and improved the understanding of hydrocarbon speciation within the native rock. Additionally, thermal desorption coupled to GCxGC may provide more detailed analysis of hydrocarbons than what is currently implemented in the industry to pinpoint the most advantageous areas to exploit by hydraulic fracturing. Lastly, biogeochemical fingerprinting of environmental contamination form shale gas operations was also explored through bioaccumulation studies in the freshwater mussel, Elliptio complanata. Mussels were exposed to hydraulic fracturing wastewaters and their fatty tissue was analyzed by for both organic and inorganic components by GCxGC-TOFMS and ICP-MS, respectively, that could be indicators of bioaccumulation of the produced water. Increased accumulation of strontium was observed in mussels dosed with produced water. Chemometric strategies were employed to distinguish the signatures of produced water exposure. Principle Component Analysis was used as an exploratory data analysis method and demonstrated the uptake of cyclic hydrocarbons in the fatty tissues of mussels. This study demonstrated the potential of biogeochemical fingerprinting and impact of possible environmental contamination from shale gas operations.