Comparison of groundwater above two Permian Basin oil fields (SACROC Unit and
Claytonville Field) near Snyder, Texas should allow us to assess potential impacts of 30 years of
CO2-injection. CO2-flooding for enhanced oil recovery (EOR) has been active at SACROC in
Scurry County since 1972. Approximately 13.5 million tons per year (MtCO2/yr) are injected
with withdrawal/recycling amounting to ~7MtCO2/yr. It is estimated that the site has accumulated
more than 55MtCO2; however, no rigorous investigation of overlying groundwater has
demonstrated that CO2 is trapped in the subsurface. Mineralogy of reservoir rocks at the
Claytonville field in southwestern Fisher County is similar to SACROC. CO2-EOR is scheduled
to begin at Claytonville Field in Fisher County in early 2007. Here we have the opportunity to
characterize groundwater prior to CO2-injection and establish baseline conditions at Claytonville.
Methods of this study will include: (1) examination of existing analyses of saline to fresh
water samples collected within an eight-county area encompassing SACROC and Claytonville,
(2) additional groundwater sampling for analysis of general chemistry plus field-measured pH,
alkalinity, and temperature, stable isotopic ratios of hydrogen (D/H), oxygen (18O/16O), and
carbon (13C/12C), and (3) geochemical equilibrium and flowpath modeling. Existing groundwater
data are available from previous BEG studies, Texas Water Development Board, Kinder Morgan
CO2 Company, and the U. S. Geological Survey. By examining these data we will identify
regional groundwater variability and focus additional sampling efforts. The objective of this study
is to look for potential impacts to shallow groundwater from deep CO2-injection. In the absence
of conduit flow from depth, we don’t expect to see impacts to shallow groundwater, but
methodology to demonstrate this to regulators needs to be established.
This work is a subset of the Southwest Regional Partnership on Carbon Sequestration
Phase 2studies funded by the Department of Energy (DOE) in cooperation with industry and
government partners.Bureau of Economic Geolog