Thin-reservoir CO2-plume detection in Farnsworth Field, Texas, using fluid-substitution models

We explore whether fluid-substitution models can be used to quantify the change in seismic wave velocity that occurs as a result of CO₂ injection into a thin sandstone reservoir at 8000 ft. CO₂ is injected into the Morrow B in Farnsworth Field, TX, as part of an ongoing carbon sequestration research and monitoring project. The field area is located on the northwestern flank of the Anadarko Basin, where the thin Morrow B reservoir makes direct seismic observations challenging. Gassmann's equations are used to calculate seismic velocity changes because of changing fluid saturations in the reservoir. Model predictions are compared with time-lapse 3D seismic surveys (pre-injection, and several times after the onset of injection), with cross-well data, and with VSP surveys. The predicted P-velocity variations around the injection wellbore are discernable but small (< 2%) and patterns change with time. This makes comparison with time-lapse data complex. Funding for this project is provided by the U.S. Department of Energy's (DOE) National Energy Technology Laboratory (NETL) through the Southwest Partnership on Carbon Sequestration (SWP) under Award No. DE-FC26-05NT42591.