下扬子地区重建型海相烃源油气领域评价及勘探对策

Evaluation and Exploration Strategy for Reconstructed Petroleum System of Marine Hydrocarbon Source in the Lower Yangzi Region

下扬子及邻区的岩石圈演化经历了五个阶段:太古宙古陆核形成期;元古宙下扬子板块形成期;古生代南方古陆形成期;中生代南、北陆拼贴期;中—晚燕山运动以来的大陆边缘离裂期。其中的第三个阶段即古生代南方古陆形成期是下扬子地区海相油气领域的形成期,海相中—古生界厚度可达上万米,含三套生烃岩系,厚度大,叠合连片,原始生烃条件属于一流,且有两大套区域性盖层,形成下古和上古两套成油气组合。在中生代南、北陆拼贴期,上述原生海相油气领域遭受重创,但主要是对当时已形成的油气系统的破坏,对烃源岩的破坏不是太严重,大部分生烃潜力得以保存,这为喜马拉雅期重建型海相烃源油气领域的形成保存了基础,这也是下扬子地区海相油气勘探的前提。对下扬子地区重建型海相油气领域可划分出五种类型:陆相中一新生界覆盖型:火山岩覆盖型;推覆体上盘覆盖型;龙潭煤系致密砂岩含油层领域;龙潭煤系煤层气领域。下扬子地区重建型海相烃源油气领域属于大盆地的范畴,其中最主要的是陆相中一新生界覆盖型,但这是一个极为复杂的油气领域。文中对勘探思路、勘探部署、综合研究、方法攻关及老资料利用等多个方面提出了具体的意见和建议。

The lithosphere evolution in the Lower Yangzi region and its peripheral areas has experienced five stages during the whole geological history from the Archaean to Cenozoic Eons.During the third one,the formation stage of Paleozoic South China Pa- leocontinent,over 10 000m-thick Mesozoic-Paleozoic marine sequence deposited in the Lower Yangzi region,which is also the formation stage of marine petroleum system.There are three thick sets of source rock systems with excellent hydro- carbon-generating condition and two large sets of regional caps,which well constitute the Lower and the Upper Paleozoic petroleum systems.During the fourth stage,the one of the South China plate collided with the North China plate during Mesozoic era,the primary marine petroleum system was re- constructed.Although the preexisting petroleum system was destroyed,most hydrocarbon potential is preserved since most of source rock did not disturbed seriously,which lays a foun- dation for the reconstruction and formation of Himalayan marine petroleum system.The reconstructed marine petroleum system can be subdivided into five types: the Mesozoic-Cenozoic con- tinental rock-capping petroleum system,the volcanic rock-cap- ping one,upper nappe wall-capping petroleum system,the tight Longtan coal-measures sandstone oil system and the Longtan coal-measures coal-related gas system.The first one is the most significant but is also a basin-extent and quite com- plex one.Some feasible suggests are brought forward on ex- ploration policy and deployment,research methods and so on.