Abstract - A key issue in geological model definition for hydrocarbon exploration and 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 hydrocarbon migration and reservoir production flow models of faulted clastic sequences.
The treatment of so-called ‘sealing’ faults in flow modelling for hydrocarbon exploration and development 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, we expect that the application, and refinement, of existing methods will significantly improve our understanding of flow within faulted clastic sequences.
It is not known, for example, the extent to which the very different approaches used in migration and production flow modelling are justified. Whilst production flow modelling takes no account of the two-phase properties of faults, migration modelling is not concerned with the single phase properties (e.g. permeability) of faults. We speculate about the extent to which these end-member approaches can be combined to provide an integrated basis for handling faults in migration and production flow modelling. We also outline several new methods which improve and broaden the scope of fault handling in production simulation of clastic reservoirs. 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 hydrocarbon migration and production. Nevertheless, we recognise that the 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 methods.
Abstract of talk given to:
6th Petroleum Geology Conference (Barbican), London, October 2003, p70.