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Isotopic investigation of subsurface rock and fluid interactions: Case studies of CO2 sequestration and gas-bearing shale formations

Gardiner, James B. (2014) Isotopic investigation of subsurface rock and fluid interactions: Case studies of CO2 sequestration and gas-bearing shale formations. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Isotopic studies have been used for decades to gain insight into geochemical reactions and the mixing of subsurface fluids. The three studies presented here focus on the use of strontium (Sr) and neodymium (Nd) isotopes as geochemical tools that can complement geologic and geochemical knowledge and improve our understanding of how chemical reactions can alter subsurface fluids and surrounding geologic formations.
The first study investigates the groundwater in Chimayó, New Mexico, where upwelling CO2 has affected the groundwater for over a century, making it a natural analog for an aquifer above a leaking CO2 reservoir. Sr isotope data for Chimayó groundwaters span a wide range (0.7098-0.7176) over a limited spatial extent (6 km2) and indicate that different strontium sources are present in geochemically similar waters. When combined with geochemical data, Sr and C isotopes identify and quantify CO2 transport processes predicted in previous work (Keating et al., 2010).
The second study is a geochemical and isotopic characterization of produced waters from an oil field prior to CO2 enhanced oil recovery. Fluid samples were taken from the producing reservoir formation, which is currently flooded with water. Samples were also taken from the overlying groundwaters. Differences in Sr isotopic values between the produced waters and the groundwaters indicate that Sr isotopes could be used to monitor CO2 storage permanence. When compared with a conventional field that produces from the same reservoir formation, the water flooded field had distinct TDS and 87Sr/86Sr values. The geochemical isotopic differences between the waters suggest that each field may have a distinct brine migration history.
The third study uses Sr and Nd isotopes to investigate the sediment sources of the Middle Devonian aged Marcellus shale and the rock units surrounding it. For the shale samples, the Nd isotope data was used to constrain a model mantle age of ~1.4-1.6 Ga, indicating a Grenville aged sediment source. The age-corrected Sr isotope data indicate a depositional age of ~390Ma. Together, this isotopic data indicates that these rocks are composed of Grenville aged sediments that experienced minimal post-depositional alteration.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Gardiner, James B.jbg10@pitt.eduJBG10
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairCapo, Rosemaryrcapo@pitt.eduRCAPO
Committee MemberBain, Danieldbain@pitt.eduDBAIN
Committee MemberHakala,
Committee MemberHarbert, Williamharbert@pitt.eduHARBERT
Committee MemberStewart, Brianbstewart@pitt.eduBSTEWART
Date: 30 January 2014
Date Type: Publication
Defense Date: 15 November 2013
Approval Date: 30 January 2014
Submission Date: 6 January 2014
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 153
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Geology and Planetary Science
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: CO2 sequestration, Marcellus shale, Sr isotopes, Nd isotopes, enhanced oil recovery
Date Deposited: 30 Jan 2014 20:48
Last Modified: 30 Jan 2019 06:15


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