Flowback and produced fluid (FP) chemistry and isotopic compositions provide “windows” into the kinds of rock-water interactions occurring during and after hydraulic fracturing. In turn, quantifying these interactions allow us to estimate the extent of elemental and isotopic exchange leading to estimates of the stimulated reservoir volumes (SRV) affected by frac fluids.   Flowback/Produced fluid samples from several wells were collected from two Utica-Point Pleasant (UPP) sites (UPPW and UPPS) in Ohio, and one site in West Virginia Marcellus (Marcellus Shale Energy and Environment Laboratory (MSEEL)) over a period of approximately two years. <br/>     The results of the water analysis show that the FP fluid compositions are remarkably similar in spite of the different lithologies between the UPP and Marcellus formations.  Flowback fluid composition are distinctly different from the composition of input fluids.  The strong correlations among most of the major constituents in the brines with conservative species such as Cl or Br, which suggests that in situ brine composition in these formations diluted by the relatively fresh input fluids used in hydraulic fracturing is dominating flowback brine composition, and the large-scale temporal changes can be described by diffusion of these brines in micropores to the larger fracture network generated by hydraulic fracturing. The Na-Cl-Br relationships suggest the brines from both the UPP and Marcellus formation are derived from evaporated paleoseawater.  However, the small but systematic decrease in the Cl/Br ratio over time suggests a potential contribution from halite dissolution early on during flowback, an encroachment of a brine with a different composition during the later stages of flowback, and/or a change in the mechanism of Cl/Br release from the micropores.<br/>    There are distinct differences in the geochemistry of the brines that reflect geochemical paleoprocesses including dolomitization, sulfate reduction and ion exchange reactions as well as contemporaneous brine-rock interaction, either from the dissolution of primary rock, oxidation of reduced species or adsorption-desorption reactions in the subsurface.  These differences are most apparent in the geochemistry of sulfur species and alkaline earth elements.<br/>

Geochemical and isotopic trends in flowback and produced waters from the Utica and Marcellus formations

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.