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Hydrocarbon Episodic Migration in Fault Zones: Insights From Physical Simulation Experiments

Abstract

Hydrocarbon migration is an important aspect of basin modeling and petroleum system, and fault zones as the dominant pathway for vertical hydrocarbon migration has been widely studied. However, recent studies show that a fault zone commonly has a complex internal architecture composed of a fault core and damage zones. And the recognition of such complexity has aroused hot debates about hydrocarbon flow regime within fault zones. In this paper, we established a physical model to explore hydrocarbon flow regime within a fault zone during the active stage by multiple episodic transient hydrocarbon charging. The results show that the internal architectures control pathway and flow regime during hydrocarbon episodic migrating within a fault zone, hydrocarbon saturation also has an influence on the pathway in a certain extent. Fault core is the dominant migration pathway during hydrocarbon episodic migration along a fault zone, and the prospective traps for hydrocarbon accumulating locate on the relative active side of the fault blocks. Moreover, the amount of hydrocarbon migrating along a fault zone has a logarithmic relationship with time during a single episodic hydrocarbon-charging process, implying that the hydrocarbon episodic migration along a fault zone is a Previous HitnonlinearNext Hit process. The velocity of hydrocarbon episodic migration along a fault zone may have a constant range, and the order of magnitudes may be 102∼103 m/yr. The processes of hydrocarbon episodic migration along a fault zone contain 3 different fluid flow regimes: (1) the Previous HitnonlinearTop fluid flow regime with a high speed; (2) the transitional fluid flow regime; and (3) the linear-Darcy fluid flow regime. The shift of fluid flow regime within a fault zone is a complex process which is controlled by the interaction of multi-physics fields. Moreover, a fault zones commonly has considerable volumes and can form fault body reservoirs in some specific circumstances. And the forming condition of fault body reservoirs is the equilibrium between driving forces and resistances during hydrocarbon migration within the fault zone.