REACTIVE TRANSPORT MODELING OF CARBONATE AND SILICICLASTIC DIAGENESIS AND RESERVOIR QUALITY PREDICTION

The accurate prediction of the geometry of subsurface geobodies, their connectivity, and the distribution of reservoir properties is a fundamental challenge in reservoir characterization. Reactive Transport Models (RTMs) couple geochemical reactions with fluid flow, and can be used to facilitate both 2D and 3D quantitative, process-based investigations of carbonate and siliciclastic diagenetic reactions and their impact on reservoir quality. The paper will highlight results and key conclusions from RTMs that have been used to investigate several styles of diagenesis in both carbonate and siliciclastic rocks:

• Dolomitization and anhydrite cementation in different hydrogeological systems;
• Early diagenesis in a freshwater lens and associated hydrological zones in an isolated carbonate platform;
• Geothermal convection and burial diagenesis in a salt buried isolated platform;
• Fault induced hydrothermal fluid flow and illitization in a sandstone reservoir;
• Formation alteration associated with acid stimulation and artificial diagenesis,
• CO₂ Sequestration in Siliciclastic and Carbonate Reservoirs.

Adopting a sensitivity analysis approach, we examined how key natural variables, such as climate, temperature, salinity, fluid composition and porosity/permeability heterogeneity impact different styles of diagenesis and reservoir quality evolution. We also examined how reservoir quality altered by artificial diagenesis associated with acid gas and steam injections can be predicted using RTMs. When integrated with conventional subsurface data and stratigraphic, geochemical, and structural framework, RTMs provide fundamental and robust predictive concepts and reservoir quality models for exploration and new / mature field developments. In particular, the state-of-the-art simulations allow the analysis and 2D/3D visualization of diagenetic geobody spatial and temporal evolution that can translate into alternative “process-based” well correlation methods and strategies for populating diagenetic bodies and their petrophysical properties in geological models for reservoir flow simulations.