USING CARBON ISOTOPES TO MONITOR CO2 AT THE CONSOL ENERGY INC. COAL SEQUESTRATION PILOT TEST SITE IN WEST VIRGINIA, USA

The use of carbon isotopes is one of the most effective ways for monitoring, verification and accounting (MVA) of injected CO₂ as carbon forms part of the CO₂ molecule itself. The study focuses on using carbon isotopes to understand CO₂ dissolution, monitoring CO₂ plume migration, and identifying the presence/absence of CO₂ leakage into overlying formations and shallow subsurface at the CONSOL Energy Inc. sequestration test site located in Marshall County, West Virginia along the Pennsylvania Fork of Fish Creek. The CO₂ gas is being injected, for testing both coal bed methane recovery and carbon sequestration, into the Upper Freeport coal bed at ~1200 feet depth. Ongoing CO₂ injection began in 2009, and ongoing geochemical environmental monitoring of shallow ground water, Fish Creek, and vadose zone gas began in 2008. In summer 2012, water and gas sampling began for carbon isotopic analysis at or near the test site; water is being sampled and tested from three groundwater monitoring wells, a few domestic groundwater supplies, and Fish Creek, and gas is being sampled and tested from the CO₂ injection source gas tank, two deep coal bed methane producing wells, one deep monitoring well, and eight shallow vadose zone monitoring wells. The preliminary data indicate that the CO₂ gas used in this sequestration operation has a different isotopic value compared to naturally occurring CO₂ in the geological formations. Initial data indicate that carbon isotopes can be used as an effective “natural built-in tracer” for monitoring the CO₂ plume and/or its leakage into overlying shallow aquifers and upper subsurface.