渤海海域深层太古界变质岩潜山大型凝析气田的发现及其地质意义

Large condensate gas field in deep Archean metamorphic buried hill in Bohai sea:discovery and geological significance

渤海湾盆地是我国东部典型的油型盆地,已发现天然气田储量规模较小。近几年渤海油田通过勘探研究思路转变和地质认识创新,在渤中凹陷西南部渤中19-6构造深层太古界变质岩潜山获得天然气勘探重大突破。通过重新认识凹陷生排烃能力,提出渤中凹陷巨大生气潜力是大型凝析气田形成的基础;完善深层优质盖层"被子"封闭模式,提出区域性稳定分布的高压异常泥岩控制大型天然气田的形成;明确变质岩储层成因机理,提出构造-风化作用主导下的裂缝型储层形成机制,运用地球物理多属性融合技术实现了优质裂缝型储层预测;提出渤中19-6构造区具有"优质烃源岩深埋生气、变质岩潜山多期构造运动控储、厚层超压泥岩‘被子’控制油气汇聚运移和保存"的天然气成藏模式。这些创新成果指导了渤中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领域性突破,所取得的理论认识突破和勘探实践经验对于推动渤海湾盆地深层天然气勘探具有重要指导意义。

Bohai Bay basin is a typical oil type basin in eastern China,and the discovered gas reserves are limited.In recent years,through the transformation of the exploration thinking and innovation of geological knowledge,the Bohai oilfield has made a major breakthrough in natural gas exploration in deep Archean metamorphic buried hill of BZ19-6 structure in southwestern Bozhong sag.By reconsidering the ability of hydrocarbon generation and expulsion of the sag,the great potential of gas generation of Bozhong sag is the basis for the formation of large-scale gas field.By improving the＂quilt＂model of the deep high-quality caprock,the stable distribution of regional highpressure mudstone is proposed to control large-scale gas reserves.By clearing the formation mechanism of metamorphic reservoir,the fractured reservoir dominated by tectonic and weathering is putting forward,and the high quality fractured reservoirs are predicted by geophysical multi-attribute fusion technology.The study shows that BZ19-6 structure in the southwestern Bozhong sag has the hydrocarbon accumulation model of＂deep buried high quality source rock generating gas,multi-phase tectonic controlling the reservoir of metamorphic buried hill,‘quilt＇of the thick overpressure mudstone controlling the hydrocarbon convergence,migration and preservation＂.These achievements have led to the discovery of large condensate gas field in BZ19-6 structure and a gas explorato-ry filed breakthrough in Bohai sea.The theoretical understanding breakthrough and exploration practical experience obtained are of great guiding significance for promoting deep gas exploration in Bohai Bay basin.