ABSTRACT Effective monitoring of geological CO storage requires selecting optimal tools from the arsenal of geophysical and geochemical techniques. In addition, a critical consideration is to determine how one should monitor the site. We focus on a mathematical model for estimating optimal interval of time-lapse seismic surveys for monitoring sequestration sites.
Time-lapse seismic provides good coverage and resolution for subsurface monitoring of CO2 sequestration (Myer et al., 2002). It is an established technique and initial results from Sleipner demonstrate that time-lapse surveys can effectively track subsurface CO plumes (Arts et al, 2004). However, time-lapse is expensive and may account for over half of total monitoring costs (Benson et al, 2004). While lower than carbon-capture and storage costs, they can be significant when accumulated over the lifetime of a storage project. Using a dynamic programming formulation, we examine trade-offs between survey costs, remediation costs, and the harmful consequences associated with CO seepage to the biosphere. We also perform Monte Carlo sensitivity analyses to understand the effects of critical parameters on the mean optimal interval between surveys. Numerical results from the mathematical model and sensitivity analysis can be useful inputs for designing cost-effective monitoring programs and determining regulations. The results indicate that site-specific monitoring schedules are essential for sequestration policy and planning since the optimal schedule is sensitive to parameters that will vary across different geological storage sites. Quantitative models such as the one presented support qualitative analysis regarding decisions in sequestration monitoring.