川东地区海相高演化层系的成熟度指标研究

结合川东地区地质条件和沉积演化史,对普光5井等4口井中-古生界岩心(岩屑)样品的伊利石结晶度及热史进行了系统研究。结果表明,伊利石结晶度是海相高演化层系成熟度的重要指标。在川东地区,中生代陆相地层的伊利石结晶度多大于0.42°(Δ2θ),镜质体或沥青反射率小于3%,地层尚处于晚成岩后期阶段;中、古生代海相地层伊利石结晶度多为0.42~0.25°(Δ2)θ,镜质体或沥青反射率为3%~6.5%,地层处于极低变质阶段。川东北地区伊利石结晶度与晚期包裹体均一温度及由镜质体反射率推算的古地温有较好的线性关系,当伊利石结晶度为0.42°(Δ2θ)时,晚期包裹体均一温度及由镜质体反射率推算的古地温约为180℃,地层已进入有机质过成熟和晚成岩后期阶段。

Research on maturity indicators of high-maturity marine strata in the eastern Sichuan Basin

In combination with the geological background and sedimentary evolution in the eastern Sichuan Basin,the data of illite crystallinity,vitrinite reflectance(VR_o),bitumen reflectance（BR_o）and homogenization temperature of fluid inclusions of Mesozoic-Paleozoic core (debris) samples show that Mesozoic continental strata in eastern Sichuan Basin are characterized with illite crystallinity values over 0.42°（Δ2θ），the VRo and BRo less than 3%，and lies in late diagenetic stage.Mesozoic-Paleozoic marine strata are characterized with illite crystallinity values from 0.25 to 0.42°（Δ2θ），the VR_o and BR_o from 3% to 6.5%，and lies in very low-grade metamorphic stage.The value of illite crystallinity has a good linear relation with homogenization temperature of fluid inclusions and the paleotemperature deduced from VR_o.While the value of illite crystallinity is equal to 0.42°（Δ2θ）,the paleotemperature and homogenization temperature of inclusions are about 180℃.The illite crystallinity value is an indicator of important thermal maturity and paleotemperature at the digenetic-metamorphic and high-over mature stages.