渤海湾盆地及鄂尔多斯盆地上古生界-天然气成藏条件分析

对渤海湾盆地与鄂尔多斯盆地上古生界烃源岩、储层、盖层、圈闭等成藏要素的地质特征分析结果表明,鄂尔多斯盆地和渤海湾盆地均具有完整的生、储、盖组合和基本的自生自储成藏条件。对成藏条件时间配置关系的对比发现,鄂尔多斯盆地以1个沉降—抬升幕、持续生烃、早期成藏为特征,渤海湾盆地则以多个沉降—抬升幕、二次生烃、晚期成藏为特征。成藏条件的空间配置关系对比表明,鄂尔多斯盆地上古生界烃源岩、储层、盖层在时间上及纵横向上具有连续性,天然气保存条件良好,可形成大面积分布的岩性气藏,资源潜力大。渤海湾盆地上古生界烃源岩、储层、盖层时间连续性较差,天然气需要较大幅度的垂向运移才能成藏,二次生烃区与构造高部位成藏区之间的横向重叠区分布局限,以形成中、小规模但丰度较高的构造气藏为主。

Gas pool-forming conditions for Bohai Bay Basin and Ordos Basin in the Upper Paleozoic

Analysis of some important factors for forming gas pool such as source rock, reservoir rock, cap rock and trap in the Upper Paleozoic of Ordos Basin and Bohai Bay Basin shows that the two basins are both favorable to form the self-source and self-reservoir gas pools with a complete combination of source rock, reservoir and cap rock. The timing matching relation between the poolforming factors shows that Ordos Basin is characteristics by single embedding-uplifting episode, continuous hydrocarbon generation and early gas accumulation, while Bohai Bay Basin is characteristics by multiple embedding-uplifting episode, secondary hydrocarbon generation and late gas accumulation. The spatial matching relation of pool-forming factors shows that the Upper Paleozoic in Ordos Basin has timing, vertical and lateral continuity of resource rock, reservoir rock and cap rock. So it has good preserving condition for natural gas and can form big lithologic gas pools distributed in great area. Ordos Basin has a great potential of natural gas resources. Natural gas in Bohai Bay Basin needs vertical migration with a great altitude to become reservoir. Bohai Bay Basin with a limited superposing area of secondary hydrocarbon generating zone and structural accumulation zone in high part can only form structural gas pool with moderate-small size and high gas abundance.