库车前陆盆地中生界烃源岩有机质成熟度演化及影响因素

Evolution of Mesozoic source rock's organic maturation in Kuqa foreland basin and its influence factors

杨树春 卢庆治 宋传真 袁玉松 王红军 胡圣标

Yang Shuchun Lu Qingzhi Song Chuanzhen Yuan Yusong Wang Hongjun Hu Shengbiao

库车前陆盆地侏罗系烃源岩值为0.55%～1.88%,均值为0.93%,主体处于生油高峰期;三叠系烃源岩值的分布范围为0.60%～2.59%,均值为1.1%,主体处于生油晚期。现有钻井测温资料表明,库车前陆盆地2 000 m深度实测温度变化范围为40～60℃,4 000 m深度实测温度变化范围为60～90℃,6 000 m深度实测温度变化范围为100～150℃。经热史恢复,库车前陆盆地自三叠纪以来,始终处于较低热流状态,表现为中生代相对较热(50～55 mW/m),新生代以来,地表热流处于持续缓慢降低过程,最终降至现今的40～50 mW/m。三叠系、侏罗系烃源岩分别于160～170 Ma及100 Ma进入低成熟阶段,进入生气阶段的时间是145 Ma及75 Ma,最早进入低成熟阶段的区域在克拉苏地区,其次为秋里塔格构造带,最晚进入低成熟阶段的地区在拜城凹陷。自23 Ma后有机质成熟度开始显著增高,三叠系、侏罗系现今均处于生气阶段。烃源岩成熟度状态主要由盆地沉积埋藏史及热史所决定。逆冲推覆和含膏岩层对烃源岩的成熟度也有一定的影响,其影响幅度取决于逆冲的断距、含膏岩层的厚度及其侧向变化幅度。

The main body of Jurassic source rock in Kuqa foreland basin is in its peak of oil generation,with value in the range of 0.55%-1.88% and average value of 0.93%.While that of Triassic source rock is in its late period of oil generation,with value in the range of 0.60%-2.59% and average value of 1.1%.The(available)borehole temperature measurements indicate that the temperatures at 2 000,4 000 and 6 000 m in Kuqa foreland basin vary in the range of 40-60℃,60-90℃,and 100-150℃,respectively.Thermal history restoration shows that Kuqa foreland basin has always been in relatively low heat flow conditions since Triassic. The surface heat flow was relatively high in Mesozoic(50-55 mW/m)and has been continuously and slowly lowering since Cenozoic and finally to the contemporary 40-50 mW/m.The Triassic and Jurassic source rocks entered into low maturity stage in 160-170 Ma and 100 Ma respectively,and entered into gas generation stage in 145 Ma and 75 Ma respectively.The earliest area that entered into low maturity stage is Kelasu,followed by Qiulitage structural zone,and Baicheng sag was the last one.The maturity of organic matter began to increase remarkably since 23 Ma,and both the Triassic and Jurassic source rocks are in their gas generation stage now.The maturity of source rock is mainly controlled by sedimentary and burial history and thermal history of the basin.Overthrusting and gypsiferous rock have also certain influences on maturity of source rock,the intensity of which depends on the displacement of overthrust fault and the thickness and lateral variation of gypsiferous rock.

10.11743/ogg20050613