FEATURES OF FLUID MIGRATION AND HYDROCARBON ACCUMULATION IN THE ACTIVE AND INTERMITTENT STAGES OF FAULT EPISODIC ACTIVITIES

Periodical episodic activities of faults lead to the periodical episodic movement of fluid migration along fault zones. One episodic activity of a fault consists of two stages: the active stage and the intermittent stage. During the active stage, fluid in deep formation migrates vertically along fault zones and then flows laterally in reservoirs under the power of superpressure or seismic pump, and the fluid migrates in the mixed phase states of oil, gas and water. In the intermittent stage, when fault zones are still open and pressure in leading systems has not got to balance, fluid flows adjustively in fault zones and bilateral reservoirs until the pressure is balanced. When faults close completely, fluid flow ceases. So the transport ability of fault zones is strong in the active stage but weak in the intermittent stage. In the episodic active stage, complex hydrocarbon-accumulating zones with multiple oil-bearing measures, which contain the same formation with different oil sources or different formations with the same oil source, will form adjacent to fault zones. In the episodic intermittent stage, the redistributed oil and gas pools in leading systems lead to the intact vertical series of undersaturated oil pools, high-saturated oil pools, oil and gas pools and pure gas pools around fault zones.