渤中凹陷深层渤中19-6构造大型凝析气田的发现及勘探意义

Discovery and exploration significance of large condensate gas fields in BZ19-6 structure in deep Bozhong sag

渤海海域渤中凹陷深层具有大型天然气田形成的良好地质条件,渤中19-6大型凝析气田是渤海湾盆地迄今发现的最大的天然气田,储量超千亿立方米。利用大量岩心、薄片、测井及地球化学资料,对渤中19-6构造深层天然气成藏条件进行了系统分析。研究表明,渤中凹陷深层具有巨大的生气潜力,是大型凝析气田形成的物质基础;区域性稳定分布的东营组和沙河街组巨厚超压泥岩为大型凝析气田的保存提供了良好的封盖条件;首次在渤海湾盆地古近系孔店组发现巨厚裂缝—孔隙型砂砾岩储层,突破了在凹陷区深部寻找厚层砂砾岩储层的禁区,大大拓展了古近系油气勘探领域;通过对太古宇深埋变质岩潜山优质储层形成机制进行分析,提出多期次动力破碎作用使潜山内幕发育大规模裂缝体系和动力破碎带,是变质岩优质储层形成的关键。这些认识指导了渤中19-6构造大型凝析气田的发现,实现了渤海海域天然气勘探的突破,对渤海湾盆地深层天然气勘探具有重要指导意义。

The deep formation of Bozhong sag in the Bohai sea area has favorable geological conditions for the formation of natural gas fields. BZ19-6 large-scale condensate gas field is the largest natural gas field discovered so far in Bohai Bay Basin, with reserves exceeding100 billion cubic meters. Based on a large number of core, thin section, well logging and geochemical data, the deep gas reservoir-forming conditions in Bozhong 19-6 structure are systematically analyzed. It is proved that the deep layer of Bozhong sag has great potential for generation of natural gas and is the basis for the formation of large-scale condensate gas fields. The extremely thick overpressure mudstones of Dongying Formation and Shahejie Formation with stable regional distribution provide good sealing conditions for the preservation of large condensate gas fields. It is the first time to discover huge thick fractured-porous sandy conglomerate reservoir in Kongdian Formation of Paleogene in Bohai Bay Basin, which breaks through the forbidden area of searching for thick sandy conglomerate reservoir in depression area and greatly expands the exploration field of Paleogene oil and gas. Based on the analysis of the formation mechanism of high quality reservoirs in Archean deep buried metamorphic rock buried hills, it is proposed that the key to the formation of high quality reservoirs in metamorphic rocks is the development of large-scale fracture systems and dynamic fracture zones in buried hills caused by multi-stage dynamic fragmentation. These results have guided the discovery of large-scale condensate gas fields in Bozhong 19-6 structure, contributed to the breakthrough in natural gas exploration in Bohai Sea, and have important guiding significance for deep gas exploration in Bohai Bay Basin.