Reservoir Geophysics: CO2 Sequestration
1. Would it remain feasible to capture the variations and discontinuities in the elastic properties of a deep saline aquifer – following CO2 sequestration (which essentially includes a high-pressure CO2 injection that in effect induces stress changes in aquifer geologic structures) - by using seismic imaging methods - through measuring reflectivity and seismic wave speed?
2. To what extent, monitoring the spatial and temporal distribution of induced seismicity (micro-seismic event) – following CO2 sequestration - would really help us in capturing the least resistive pathways through which CO2 could get escaped?
3. For deep saline aquifers with CO2 sequestration, whether ‘surface monitoring’ (although, surface-recorded micro-seismic data exhibit lower signal-to-noise ratio due to anthropogenic noise generated @ surface and increased location from the actual CO2 sequestration location) would remain to be sufficient;
OR
Should we go for borehole scenarios – towards capturing an improved receiver coverage?
4. In the absence of ‘arrival-time picking’ and with relatively ‘low-quality data’; to what extent, Kirchhoff-based and wave-equation seismic migration approaches would remain to be useful towards capturing the migration of ‘CO2-brine front’ following ‘CO2 sequestration’?
OR
With a relatively accurate velocity model, whether, Time-reverse imaging (TRI) would be able to track the migration of ‘CO2-brine front’ by propagating micro-seismic waveforms in reverse time using an adjoint wave equation, and subsequently, evaluating an imaging condition in order to ideally produce a well-focused ‘CO2-brine interface image’ as a function of space?
5. With a possible ‘highly noisy data’ associated with a deep saline aquifer, whether travel time tomography (TTT) or full wave-form inversion (FWI) would be able to do justice in capturing relatively rough scenarios such as CO2 storage and migration in deep saline aquifers; OR, should we follow migration velocity analysis (MVA) based on stacked image metrics?
6. To what extent, an active-source vertical seismic profiling (VSP) coupled with distributed acoustic sensing (DAS) optical fibers installed in injection wells would be able to do justice in down-hole acquisition following CO2 sequestration?
Whether the coupled DAS-VSP data sets would be able to precisely capture the formation of CO2-brine front in the vicinity of the injection well – as, such data contain higher-frequency information due to shorter travel paths and decreased seismic attenuation relative to conventional surface geophone data?
7. Feasible to capture (i) spatial and temporal distribution of CO2 concentration; (ii) CO2-brine front; & (iii) CO2 leakage path – by developing an image-domain elastic wave-field tomography framework – that could essentially restructure P- and S-wave models that enhance the quality of the above 3 locations from surface-recorded micro-seismic and active-source DAS 3D VSP data?