Abstract - A key issue in geological model definition for hydrocarbon production evaluations is the accurate definition and modelling of both the geometry and the flow properties of faults. Concentrating on issues relating to the flow properties of faults, this talk considers the principal constraints and methods used for their inclusion in reservoir production flow models of faulted clastic sequences.
The treatment of so-called ‘sealing’ faults in flow modelling for hydrocarbon production has become more geologically-driven and more quantitative in recent years. Methods for the prediction of fault properties are now more refined, though still relatively immature, and methods for their inclusion in flow models have, as a consequence, also improved. Although further research is required on the formation, geometry and properties of fault zones and fault rocks, the application and refinement of existing methods can significantly improve our understanding of flow within faulted clastic sequences.
Reservoir production flow models are now capable of including geologically derived fault properties which offer the best means of achieving robust history matches and of improving production forecasting and planning. We present a selection of case studies illustrating the strengths of existing approaches, such as their ease of use and flexibility, their expanding geological content and the improved geological know-how derived from their application. One of the allied benefits of these innovations is the definition of improved links between geoscience and engineering workflows, in which geologists can define, or even generate, fault properties for inclusion in reservoir flow models and can examine, with engineers, the impact of faults on flow. Whilst the flow response can be expressed in conventional terms, i.e. production curves, 3-D visualisations of flow through reservoirs, including across-fault flow rates, represents a very useful means of identifying key structural controls on flow. We also outline several new methods which improve and broaden the scope of fault handling in production simulation models. These methods additionally allow inclusion, at the resolution of a conventional faulted simulation model, of two-phase fault rock properties, of more accurate across-fault transmissibility and of complex sub-resolution fault zone structure (e.g. relay zones).
Whatever the shortcomings of existing methods they represent a much improved, geologically-driven, basis for modelling reservoir production. Nevertheless, we recognise that one of the most significant hurdles to advancing our understanding of hydrocarbon flow could be the changes in work practice required for the adoption of these new approaches.
Abstract of talk given to:
Future of Geological Modelling in Hydrocarbon Development, Geological Society of London, March 2005.