Hydrodynamics and hydrocarbon trapping: Concepts, pitfalls and insights from case studies

Abstract

Abstract Tilted contacts are observed in many oil and gas fields. They are generally attributed to the effect of hydrodynamics. Hydrodynamic flow exists in almost all geological basin types of the Wilson cycle, from passive margins to foreland basins to mountain chains. There are various geological processes driving regional hydrodynamics. Flow is regulated by permeability variations which are given by the geological framework. The role of faults as partial permeability barriers may be a significant regulator for flow. Hydrodynamics is best recognized by using the principles of hydraulic head. However, hydraulic data must be carefully interpreted to avoid pitfalls such as transition zones where variable oil saturation may be falsely interpreted as tilted contacts. In sedimentary basins, we distinguish two different hydrodynamic settings where flow is either mainly gravity-driven (or centripetal), or mainly compaction-driven (or centrifugal). In both cases, hydrodynamics can enhance hydrocarbon trapping. Gravity driven processes are particularly important in the Arabian Shield and North Africa. Centrifugal and centripetal phenomena can co-exist in the same basin, e.g. Mahakam delta or Douala Basin. Turbidites occur typically in centrifugal settings. Hydrodynamic concepts applied to petroleum exploration are not frequently used in industry despite being known for a long time. They may however become increasingly important in conventional exploration as static plays are rapidly being drilled up and the remaining exploration potential of sedimentary basins is increasingly affected by stratigraphic and hydrodynamic trapping components.