Modeling Diagenesis of Icehouse Platforms Using CARB3D+
Peter Smart1, Fiona Whitaker1, Gareth Jones2,
Graham Felce1 (1)
A fundamental challenge in carbonate reservoir characterization is predicting the spatial distribution of early diagenesis, which in turn can have a critical control on porosity and permeability heterogeneity. During icehouse times, high-amplitude sea level oscillations cause repeated vertical migration of the water table and underlying hydrological zones, and large variations in vadose zone thickness. The consequent diagenetic overprinting generates a complex pattern of cementation and secondary porosity and permeability in the reservoir, which is difficult to predict from seismic data or interpolation between cored wells.
CARB3D+ is an innovative 3D forward modelling program that can predict the co-evolu-tion of sedimentary facies and early diagenesis in a sequence stratigraphic context. This can improve the accuracy of predictions and yield multiple scenarios of reservoir quality for input to geological models.
Preliminary results from CARB3D+ show complex icehouse overprinting generates spatial and temporal patterns in hydrological zone residence times that can be linked explicitly into the sequence stratigraphic framework. Model output can be tied directly to well-core via exposure surfaces. Results also show the importance of ‘missed beats’ in the creation of major exposure horizons, with different hydrological zone residence time patterns occurring for progressive higher order sea level fluctuations. Because relative sea level is an important control on both sequence stratigraphy and diagenesis, the simulated sequence stratigraphic framework provides a useful constraint on prediction of early diagenetic evolution.
Through a process-based modelling approach, it is now possible to predict complex diagenetic overprint patterns through carbonate platforms, during icehouse times.