AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Role of Carbon Isotopes in Addressing the Water-Energy Nexus: Example from Powder River Basin Wyoming
(1) Geology and Geography, West Virginia University, Morgantown, WV.
(2) Geology and Geophysics, University of Wyoming, Laramie, WY.
(3) Renewable Resources, University of Wyoming, Laramie, WY.
(4) Wyoming State Geological Survey, University of Wyoming, Laramie, WY.
Understanding the relationship between water and energy takes on new urgency with mounting pressure on limited fresh water resources. In several areas, coalbed natural gas (CBNG) production from coal seams requires large volumes of co-produced water to be pumped out from the subsurface. One of the most difficult issues the CBNG operators and State Regulatory Agencies face in these areas is to devise cost effective monitoring and management practices for the immense quantities of co-produced water.
We explored the potential use of stable carbon isotope signature of dissolved inorganic carbon (δ13CDIC) to track the source and fate of CBNG co-produced water in Powder River Basin of Wyoming. In the study area, the CBNG co-produced waters have positive δ13CDIC values in range of +10‰ to +21‰ V-PDB, distinct from the ambient regional surface and groundwaters, with δ13CDIC values ranging from -10‰ to -15‰ V-PDB. Initial data from our study indicate that these contrasting δ13CDIC signatures can serve as a natural fingerprint to monitor the fate of CBNG co-produced waters in surface streams and shallow aquifers of the region. The δ13CDIC signatures, when used in conjunction with other geochemical proxies can also help in assessing the effect of contribution of CBNG co-produced water on the water quality of the receiving surface/ ground waters. Preliminary results also demonstrate that carbon isotope signatures of produced water samples collected at the well heads can be used to authenticate a) if produced water being withdrawn from the targeted coal seam and b) if the coal seam is hydrologically isolated.
The isotopic tools developed in these studies could potentially be used to devise effective produced water management strategies, decrease costs associated with produced water treatment/disposal, and also help reduce the water footprint of CBNG production.