Modelling how Faults Influence the Trapping of Oil & Gas

Summary Faults are known to have a significant role in the migration and trapping of hydrocarbons, either offering conduits for, or barriers to, fluid flow. Faults may also influence fluid phase trapping and hence potentially phase fractionation in the subsurface. A Monte Carlo approach is used to model these effects for trap analysis. The aim its to show how varying both fault seal capacity, the fault orientation, the regional stress tensor, and the trap geometry can all affect how oil and gas are retained within a trap. The model reduces the problem to a 1D analysis with a structural description depth-referenced to the crest of the prospect. Both juxtaposition and membrane fault seal are included, together with hydrodynamic effects and fault reactivation risk. A trap scenario is modelled using input parameter distributions and governing equations. The potential of a prospect to trap hydrocarbons is then evaluated in a roll-up of results with the outputs including a predicted hydrocarbon column height distribution and column height control statistics. The technique also offers an insight into potential fluid phase partitioning that may occur dependant on the active leakage mechanism and spill control, enabling gas versus oil columns to be predicted in certain charge scenarios.