The Research Of Fluid Inclusions Of Northeast Sichuan Maoba Gas Reservoir And Its Geological Significance

Maoba gas reservoir is a medium gas reservoir where located in carbonate rocks of Lower Triassic Feixianguan formation under reservoir. This article is carry out a system study of fluid inclusions by the reservoir of Lower Triassic Feixianguan formation in Northeast Sichuan Maoba gas reservoir, thereby calculate reservoir formation Physico-chemical condition, divided the oil and gas charging period and determining the accumulation of the times, discusses accumulation evolution and accumulation model. The results show that:The fluid inclusions of Maoba gas reservoir occur in Calcite and gypsum where are filling in the holes of limestone of Lower Triassic Feixianguan formation. The types of inclusion in the study area can be divided into H2 O inclusion,hydrocarbon-H2 O inclusion and hydrocarbon inclusion three broad categories. The fluid inclusions of Maoba gas reservoir are divided into four periods: The first(I)phase inclusions formed in the early diagenesis and consist mostly of liquid H2 O inclusions and gas-liquid H2 O inclusions, the homogenization temperatures of the gas-liquid H2 O inclusions vary within the range of 85~89?;The second(II) phase inclusions formed in the early stage of late diagenesis, mainly liquid H2 O inclusions and gas-liquid H2 O inclusions, and see a small amount of liquid hydrocarbon inclusions and gas-liquid hydrocarbon inclusions, the gas-liquid H2 O inclusions homogenization temperature ranges from 113~150?,;The third(III) phase inclusions formed in the late stage of late diagenesis and consist mostly of H2 O inclusions, gas hydrocarbon inclusions, hydrocarbon-H2 O inclusions,bitumen inclusions,the homogenization temperatures of the gas-liquid H2 O inclusions vary within the range of 155~206?,;The fourth(IV) phase the gas-liquid H2 O inclusions homogenization temperature changes in 100~152 ?, the inclusions combination include liquid H2 O inclusions, gas-liquid H2 O inclusions, and containing native sulfur gas-liquid water inclusions and gas hydrocarbon inclusions, occasionally liquid hydrocarbon inclusions and gas-liquid hydrocarbon inclusion. The salinity(wt% Na Cl) of the oil bearing reservoir fluid varies from 0.35~17.29%(wt% Na Cl),the density of the oil bearing reservoir fluid is 0.91~1.08g/cm3, the salinity of thefluid and the density decreases gradually from the II phase to the IV phase; The homogenization pressure of the fluid inclusions in the reservoir is1843~2025×105Pa,it is buried between 7091~7791m.It is show that Composition analysis of a single fluid inclusion, The gaseous composion of the CH4 inclusions and hydrocarbon-H2 O inclusions is mainly CH4 in The Maoba gas reservoir,Secondly, it also contains some H2 S gas and a small amount of CO2,The platform fringing Oolitic beach reservoir of Feixianguan group formation in the Maoba was found a kind of gas-liquid H2 O inclusions for involving native sulfur.The Maoba gas reservoirs experienced two periods of oil and gas charging: The first stage of hydrocarbon-charging is later early Jurassic and Middle Jurassic(178~164Ma),Second oil-gas filling is the late Jurassic to Eocene(154~55Ma).After Eocene, the gas reservoir went into the stage of destruction and evolution of epigenetic transformation. According to periods, combinations and homogenization temperature of fluid inclusions in Maoba gas reservoirs, indicating Maoba gas reservoirs of oil and gas through the beginning stages of oil generation, generating a large number of oil and gas condensate- wet phase, dry gas phase, the transformation of epigenetic damage stage four stages. It is experienced three stages of the hydrocarbon accumulation process of Maoba gas reservoirs: oil reservoir formation stage, the gas reservoir formation stage, the oil-gas reservoir damage stage.