Fault Leakage Rates Estimated In-Situ: Implications For Fault Seal Evaluation

Summary This presentation examines the main controls on Darcian leakage through fault seals and investigates the evaluation of hydrocarbon column heights in such cases. Firstly, case studies are used to illustrate how fault seal permeability may be estimated in-situ from aquifer compartmentalisation data, improving on existing algorithms currently based mainly on empiric relationships. Secondly the quantitative estimation of hydrocarbon column heights is investigated from the dynamic interplay between charge rates into the trap versus seal leakage rates. A particular consideration is placed on the geometric and petrophysical properties of the leak paths, such as across-fault flow through a fault zone barrier or up-fault conduit leakage. Finally, a consideration is made of the relative importance of aquifer hydrodynamics and dynamic hydrocarbon flow on controlling hydrocarbon contacts. It is concluded that both hydrodynamic flow in the aquifer, and dynamic charging and leaking of hydrocarbons in an active petroleum system, can control hydrocarbon column heights trapped against a seal. Whilst an understanding of the pressure distribution is critical to prospect evaluation in such settings, sensitivity to the geometric parameters of the trap and charge / leak pathways such as fault conduits remains a key uncertainty in the quantitative analysis.