中国前中生代海相烃源岩发育的构造—沉积条件

Tectonic-Sedimentary Conditions for Development of Pre-Mesozoic Marine Source Rocks in China

中国前中生代主要发育海相沉积,发育多层系、多沉积类型的烃源岩,展示了中国海相层系广阔的油气资源前景。但受构造背景和沉积环境的差异性控制,这些烃源岩的品质和分布规律也存在很大差异。震旦纪—早古生代早期(Z-O2),中国主要板块处于洋盆扩张、陆块离散的构造—沉积阶段,围绕华北、扬子、塔里木等主要陆块周围,发育被动大陆边缘斜坡相烃源岩,这类烃源岩具有宽带状分布、范围广、品质优、长期继承性发育的特点。早古生代晚期(O3-S),为洋盆俯冲消减、古中国陆汇聚形成阶段,受板块边缘隆起围限,主要发育台内坳陷烃源岩,这类烃源岩具有面状分布、持续时间较短的特点。晚古生代—中生代早期(D-T),华北以相对的稳定构造背景为主,主要发育海陆过渡相煤系烃源岩,此类烃源岩具有面状分布、分布面积大、以生气为主的特点;南方以离散构造背景为主,华南台地裂解成"盆包台"格局,在深裂陷内部发育深水盆地相烃源岩,此类烃源岩具有窄带状分布、品质优、分布面积较小的特点。

The Pre-Mesozoic in China are dominated by marine deposits with multiple-layer series and multiple-type source rocks,indicating the huge potential for oil/gas exploration in the marine sequences of China.However,the differential control of tectonic setting and sedimentary background results in significant differences in the quality and distribution of source rocks,thus controls the exploration potential of the marine sequences.During Sinian-Early Paleozoic（Z-O2）,the main plates in China were in a tectonic-sedimentary period with ocean basin extending and landmass dispersing.Source rocks of passive continental margin slope facies were developed in the peripheries of main landmasses such as Huabei,Yangtze and Tarim.These source rocks feature in wide zonal distribution,extensive distribution,high quality and long-term inheritance development.In the late of Early Paleozoic（O3-S）,ocean basins subducted and China Ancient Land converged and took shape.Under the constraint of uplifts on plate margin,source rocks were mainly developed in intra-platform sags.They are characterized by planar distribution and small thickness.In Late Paleozoic-early Mesozoic（D-T）,North of China was dominated by cratonic tectonic setting where coal measure source rocks of transitional facies were developed.These source rocks feature in planar distribution,large area and gas predominance.In contrast,South of China was dominated by divergent tectonic setting and the Huanan platform split into a tectonic framework of ＂basin surrounding platform＂.Source rocks were deposited in the interior of deep faulted depression and are characterized by narrow zonal distribution,high quality and small area.