Mechanism Of Transporting Natural Gas And Physical Simulation Of Transporting Efficiency On Reverse Fault

This paper researches internal structure of fault zone through field geological exploration to Kuche Depression, there are two zones: one is breakage zone characterized by growing fault rocks, the other is break zone characterized by growing induced fracture. It analyses the difference of structure property and the difference of physical property to different zoning. Base on the evolving process of fault, it describes the evolving property of the dominant transporting passage in different stage. There are three transporting passages in the fault zone during the fault from active period to static period: associated fractures in active period of fault, induced fractures around static period of fault and connectivity pores in static period. The process of transporting natural gas through these transporting passages is continuous occur. By collecting data, it analyses geological conditions and migrating mechanism that the fault transports natural gas by every transporting passage, then it compares efficiency to them, the result shows that the "pump suction"characterized by high speed and high efficiency is main migrating form at the active period of fault. Under this migrating form, the migrating passage is associated fractures of fault, the migrating drive is pressure, so the associated fractures is dominant passage that exists at active period of fault, and under the "earthquake pump"driving, the natural gas migration through associated fractures is the main migrating form. Toward the migrating mechanism of "pump suction", it discusses the migrating model and the accumulating law of natural gas through fault. Through analysis on typical structure in Kuche Depression, it indicates that the fault of different type have different action in the course of natural gas accumulating: the fault of through salt bed that runs through source rock, reservoir and cap formation have action on dissipation and relief to natural gas, the fault of below salt bed that runs through source rock and reservoir have action on injection to natural gas, the fault of destroying trap that runs through reservoir and cap formation have action on dissipation to natural gas and the fault of reservoir interior have action on adjusting horizon to natural gas distribution. There are four transporting modes on fault combination: fault of below salt bed joins to fault of through salt bed by fault or reservoir, fault of below salt bed joins to fault of below salt bed by reservoir, fault of below salt bed joins to fault of through salt bed by reservoir and fault of destroying trap and only one fault of through salt bed. Base on the mode of fault combination, then choosing typical structure of represent, the migrating process of natural gas is occurred by physical simulation. On the basis of this, it analyses accumulating property of natural gas in Kuche Depression, and there are four model of fault transporting systems by summarized: fault transporting systems composed by fault of below salt bed and fault of through salt bed, fault transporting systems composed by fault of below salt bed, fault transporting systems composed by fault of below salt bed, fault of destroying trap and fault of through salt bed and fault transporting systems composed by only fault of through salt bed. In these fault transporting systems, the former two model are effective mode of transporting natural gas in Kuche Depression, natural gas inject trap at highly efficiency, this easy yield accumulation of natural gas at large scale, and can form big gas field, on the contrary, the others transport natural gas at lowly efficiency relatively, this little yield accumulation of natural gas at large scale, and only can form small gas field or gas show. Through discussing the effectiveness of source rock and trap, summarizing highly efficiency mode of fault transporting system, it is effective fault transporting system that runs through effective source rock and effective trap. The mode have important function to leading next exploration in Kuche Depression.