A Simulation Model for Hydrodynamic Oil/Gas Entrapment

Abstract

Some major gas fields in Canada are trapped by hydrodynamic forces originating from down-flowing water. A thorough understanding of the intimately intertwined forces that determine the shape and volume of hydrocarbons trapped under hydrodynamic conditions will therefore enhance the authors ability to rank (with respect to hydrocarbon potential) an area with hydrodynamically active aquifers. A simulation model has been developed and is used to investigate systematically the response of the hydrocarbon-water interface to changing aquifer conditions. For any given aquifer geometry and water flow velocity, the model allows for permeability variations in order to simulate facies changes, and it also allows for variable density difference between water and hydrocarbons. The model solves the equations for steady state flow. Results from a variety of aquifer geometries and flow conditions will be exhibited and will show how the density difference between water and hydrocarbons, the velocity of flowing water, and varying permeability all influence the amount of hydrocarbons that can be trapped under hydrodynamic conditions in comparison to the amount that can be trapped under hydrostatic conditions. This procedure therefore reveals cases in which hydrodynamic conditions enhance the capacity of a given trap and which need to be allowed for.