Enriched Mechanism of Natural Gas of Lower Jurassic in Dibei Area,Kuqa Depression

Li Feng; Jiang Zhenxue; Li Zhuo; Wang Xihan; Du Zhongming; Luo Xiao; Xin Shiyin

doi:10.3799/dqkx.2015.138

Abstract：Tight sandstone gas of the Lower Jurassic is widely developed in Dibei area in the Kuqa depression.Therefore,the research of its enriched mechanism is of great significance.The data of the cores,rock slice,laser confocal scanning,displace-ment pressure,fluid inclusion petrological observation and microthermometric analysis are utilized to explore the enriched mechanism of the natural gas.Results show that:(1)the gas-source condition of Dibei area is superior and natural gas charged in short time;(2)fracture-pore type reservoir is widely developed and reservoir property is superior;(3)several thick mud-stones and gypsum mantles cover the natural gas reservoirs and the conservation condition of the natural gas is superior;(4) composite fault-sand body pathway system is well developed and the natural gas accumulated with high-efficiency;(5)Dibei ar-ea is characterized by “early-stage accumulation of oil and late-stage accumulation of gas”.The natural gas charged in the period of Kuqa age (5-0 Ma)and reservoir desificated in the period of early Kangcun period (8 Ma),which means that the period of reservoir desification was earlier than the period of bulk natural gas charging.Controlled by tectonic movement,the accumula-ting processes of the natural gas are separated into three phases:charged with oil at the early-middle periods of the Miocence;charged with the superposition of deep basin gas reservoir in Pliocene;charged with adjustment,modification and re-enrichment in Xiyu period.The study of enriched mechanism of the natural gas in Dibei area can facilitate the exploration for potential tight sandstone gas.