Prospect Identification and Evaluation Using Fully Integrated Fault and Top Seal Fill-and-Spill Modelling

Stephen R. Freeman, Nicola A. McCabe, Simon D. Harris, and Robert Knipe
Rock Deformation Research, Leeds, United Kingdom

Many of the African hydrocarbon accumulations represent significant challenges for exploration. The complex nature of the structures in conjunction with the presence of multiple stacked reservoirs that are interleaved with impermeable stratigraphy make the identification of prospects and the realistic prediction of accumulations difficult. In this contribution we present a new means of predicting hydrocarbon accumulations by integrating capillary entry pressures of both faults and stratigraphy (including top seals) into full 3D flow models. These are used to model the potential fill levels for different stratigraphic realisations. The method allows for the modelling of hydrocarbon accumulations in a manner that honours the buoyancy forces appropriate for individual hydrocarbon types, the impact of local pressure variations and hydrodynamic drives. In this example we use several African datasets to demonstrate the potential impact of different stratigraphies, structures and fill styles on potential prospect fills.
By conducting a full 3D flow simulation to model the accumulations, complex relationships such as confining top and base seals, stratigraphic pinch-outs and waste zones can be sensibly modelled. The process also allows for the computation of volumes in place based upon fully variable porosity distributions.

The system has numerous advantages over more traditional ball rolling fill-and-spill type analyses, the main one being that it models fully continuous 3D geological volumes rather than just several discrete interfaces. This type of technique therefore has particular advantages in more complex stratigraphic and structural scenarios, such as those present in the African deltas and the fold and thrust belt provinces.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery