Geochemical Analysis of Surface and Shallow Gas Flux and Composition Over wa Proposed Carbon Sequestration Site in Eastern Kentucky

Grants and Contracts Details


Geochemical Analyses of Surface and Shallow Gas Flux and Composition Over a Proposed Carbon Sequestration Site in Eastern Kentucky Fractured organic-rich Devonian shale in mature gas fields in eastern Kentucky is being evaluated as a possible reservoir for carbon sequestration. Injection of C02 into the shale reservoir will produce free C02 and CH4 gases. Buoyancy forces and reservoir pressurization will provide driving forces for migration of these gases. Monitoring thus becomes a critical and necessary task in evaluating the fate of C02 and assessing the efficacy and safety of the sequestration project. The importance of monitoring is the motivation for this proposal. Specifically we propose to measure and document rates of surface gas flux and the composition of surface and shallow soil gases in areas overlying possible carbon sequestration sites in eastern Kentucky. The documentation provides: (1) a database for interpreting the atmospheric, biologic, and geologic (microseepage) contributions to gas flux pre-injection, (2) a screening tool for selecting possible sequestration sites, and (3) a background database for monitoring changes in surface and shallow gas flux and composition that might occur during a sequestration project. The project will be implemented in three sequential and partly overlapping phases. GIS databases will be constructed for three previously selected possible sequestration sites during Phase I. The databases will include GPS coordinates for gas wells in the field, gas monitoring locations (Phase II) and wells (Phase III), water well and spring locations, gas production histories with an emphasis on gas composition, and water chemistry data. The GIS databases will be used to spatially analyze the gas production and water chemistry data, and data generated from monitoring activities in this project. Phase II work will measure: (1) surface flux of C02 and CH4 using closed chamber methods, (2) concentration of C02 and CH4 in the shallow soil zone « 1 meter) using gas chromatograph methods (GC), and the stable isotope (carbon and oxygen) composition of C02 in the soil using mass spectrometer methods. In an effort to analyze a range of soil gas character, measurements will be performed in a reconnaissance manner among the three possible sequestration sites. Measurements will be performed in the summer and winter. Because of reduced biologic input to soil gas flux, winter measurements will be critical for detecting the subtle geochemical signature of microseepage. Data from the first year of measurements will be used with other geologic, engineering, and geochemical data, and cultural considerations in selecting a "best available" sequestration site. Surface and shallow gas measurements will continue over the "best available" site during the second year of work. Phase III work be performed in area of the "best available" site during the second year. This work will examine changes in gas character over a significant vertical soil profile in five wells drilled to 10 meters. Based on Phase II analysis, the wells will be located in areas that likely do and do not have microseepage. The goal of Phase III work is to more definitively evaluate the presence of microseepage. As with the shallow gas work, measurements will be done seasonally and include measuring the concentration of C02 and CH4 and the stable isotope composition of C02. In addition, the concentration of light alkanes (C2H6, C3H8) will be measured using GC methods. Light alkanes are often associated with thermogenic gases and their presence would thus be strong evidence for microseepage. The stable carbon isotopic composition of CH4 will be measured to look for shifts in gas isotopic composition, which might signify microseepage. Radiocarbon (14C) measurements of C02 will be conducted on samples collected during the last sampling. Radiocarbon measurements, expressed in percent modern carbon (PMC), provide a measure of the degree to which carbon in C02 is young (Le. radiogenically rich) versus old (Le. radiogenically dead). C02 derived from older geologic sources (Le. microseepage) would be expected to have low PMC values, whereas C02 derived from soil biologic activity would be expected to have high PMC values.
Effective start/end date7/15/0512/13/08


  • Department of Energy: $277,989.00


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