Fundamental Approaches to Dolomitisation and Carbonate Diagenesis in Different Hydrogeological Systems and the Impact on Reservoir Quality Distribution

The accurate prediction of the geometry of subsurface dolomite geobodies, their connectivity, and the distribution of reservoir properties is a fundamental challenge in carbonate reservoir characterization. Reactive Transport Models (RTM) couple geochemical reactions with fluid flow to facilitate both 2D and 3D quantitative, process-based investigations of dolomitization and related carbonate diagenetic reactions. The paper will highlight new results and key conclusions from simulations of dolomitization mechanisms in four different hydro-geological systems: 1) Brine reflux, 2) Mixing zone and sub mixing zone, 3) Geothermal circulation and 4) Fault controlled hydrothermal circulation. Simulations provide new insights on the spatial distribution and dynamic behavior of:

•Geometry and distribution of dolomite bodies generated by different styles of subsurface fluid flow and their dynamic interactions; •Regional versus local controls on dolomite occurrence and connectivity; •Sensitivity and hierarchy of geological controlling parameters; •Spatial and temporal relationships between dolomitization and associated diagenetic minerals including anhydrite cements and Mississippi Valley Type (MVT) mineralization; •Effect of hydrothermal fluid induced dolomite recrystallization and anhydrite dissolution; •Criteria to help identify the distribution of reservoir quality including high permeability dolomite "sweet spots".

When integrated with conventional subsurface data and stratigraphic, geochemical, and structural framework, Reactive Transport Models of dolomitization 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 3D visualization of dolomite body 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. Copyright © 2013 International Petroleum Technology Conference.