oa Monitoring CO2 Migration Using Time-lapse Seismic Data

Time lapse seismic data provides an ability to track the progress of migrating CO2 during the injection process. When supercritical CO2 is injected into a formation, the formation's structure, seal, reservoir mineralisation, temperature and pressure dictates the fluid's migration pattern, and its state-of-phase. Understanding the basic rock physics and interaction of CO2 with the associated PT relationships, mineralisation and seal status is a prerequisite for seismic monitoring, geophysically tracking the CO2 as it moves. This paper uses the conditions of Sleipner in the North Sea. As with any chemical mix, the rock matrix may be change state as a function of the presence of CO2. The result is a dynamic process requiring a seismic methodology for tracking CO2 migration within any reservoir. Consequently while 3-D seismic is widely regarded as the preferred but expensive tool, other tools are emerging which may be more cost effective, but a knowledge of reservoir conditions is still a prerequisite to determining the optimum tool.