试论中国近海两个坳陷带油气地质差异性

中国近海辽阔的海域蕴藏了丰富的油气资源,历经40年的勘探取得了丰硕的成果。限于技术、资料和研究深度,多年来人们一直认为中国近海诸盆地的类型、油气地质条件相似,属于大陆边缘的新生代断陷(裂谷)盆地。但是,对大量地震、钻井资料的分析表明,中国近海存在两个坳陷带,这两个坳陷带的构造位置、地温梯度、盆地类型、形成时期、沉积环境、油气地质条件、油气性质等明显不同。第一坳陷带包括渤海湾盆地、南黄海盆地、台北坳陷、珠一坳陷、珠三坳陷和北部湾盆地,是位于陆壳上的湖相断陷(裂谷)盆地,以生油为主。第二坳陷带包括浙东坳陷、珠二坳陷、琼东南盆地和莺歌海盆地,是陆—洋过渡壳上的海相坳陷盆地,以生气为主。第一坳陷带已经成为重要的产油区,预测第二坳陷带将会成为中国海上的大气区。

Analysis on differences of petroleum type and geological conditions between two depression belts in China offshore

The broad offshore is very rich in oil-gas resources in China. Amounts of oil and gas were discovered in this area during 40 years of exploration. However, owing to the limitation of technology, information and research extent, it has always been considered that all the basins in China offshore are similar in types and geologic conditions and classified as the Cenozoic rift basins on the continental margin. The analysis on a massive amount of seismic and drilling data shows that there are two depression belts in China offshore. The two depression belts are evidently different from each other in their tectonic situations, geothermal gradients, basin types, forming periods, sedimentary environments, petroleum geologic conditions and petroleum properties. The first depression belt containing Bohai Bay Basin, South Yellow Sea Basin, Taibei Depression, ZhuⅠ Depression, Zhu Ⅲ Depression and Beibuwan Basin is the lacustrine rift basin located on the continental crust and mainly generates oil. The second depression belt containing Zhedong Depression, Zhu Ⅱ Depression, Qiongdongnan Basin and Yinggehai Basin belongs to the marine depression basin located on the continent to ocean transitional crust and mainly generates gas. The first depression belt has already become a very important oil producing area, and the second depression belt is expected to be a large gas producing area in China offshore.