Integrated Subsurface Evaluation of a Saline Aquifer Selected for CO2 Disposal

As part of an ongoing subsurface evaluation of a saline aquifer for potential CO2 disposal, a seismic polarity reversal, conformant with structural closure, was noted. This amplitude anomaly, in conjunction with petrophysical analysis appears to indicate a transition in reservoir quality associated with post depositional cementation of halite. Reservoir engineering data was used to derive a 1D model that explained a depth control mechanism for the precipitation of salt. This led to a new geological model construction that invoked the concept of influxes of meteoric water into the reservoir. This influx would dilute existing pore waters preventing salt cementation and/or dissolve existing salt cements resulting in the transition in reservoir quality observed. Effective medium theory was used to forward model the seismic response from the new geological model to compare with actual 3D seismic. Comparisons between the synthetic data set and the 3D seismic volume were favourable. The integration of subsurface disciplines lends weight to the plausibility of the conceptual model, however the impact of its validity is significant for the development moving forward. A planned appraisal well on the flanks of the structure will be used to provide further insight as to the substance of the conceptual thinking.