北海盆地形成演化对大油气田的控制作用

分析了北海盆地的形成演化对大油气田形成的控制作用。研究认为,北海盆地经历了8个构造演化期,加里东运动期形成了主要变质岩基底;海西运动导致古特提斯洋关闭,形成联合古陆,同时沉积了盆地南部重要的煤系烃源岩;陆内克拉通期盆地南、北部持续沉降,前期干旱,后期大范围海侵,形成了盆地南部有利的储、盖配置;裂谷期区域拉张环境,产生了以维京、中央和默里湾为典型的地堑系与海槽;热隆起期中部区域隆起,伴随大量火山活动,为盆地北部储集层的发育提供大量物源;主要裂谷期中部穹窿沉降并被海水淹没,盆地北部发育优质烃源岩;晚裂谷期沉积环境相对稳定,盆地中部发育大量白垩,北部沉积泥灰岩,形成了盆地北部区域性的盖层;后裂谷期挪威—格林兰海陆壳分离,在之前的构造格架下持续稳定地接受沉积,为油气保存提供有利环境。最终形成南部为大气田、北部以大油田为主的分布格局,同时在维京和中央地堑内分别形成了上生下储与下生上储2种不同的成藏特征。

Control Effect of Evolution of North Sea Basin on Formation of Giant Oil-Gas Fields

The North Sea basin underwent eight orogenic stages and gave rise to the frameworks that the metamorphic basement was formed in Caledonian stage;Pangaea following Paleo-Tethys closure shaped in Hercynian,and the coal-measure source rock deposited in the southern North Sea basin;southern and northern North Sea basin continued subsidence in intra-craton stage,with early arid climate and late large-scale marine transgression,forming favorable reservoir-cap rocks assemblage in south of it;regional extension environment gave rise to Viking,Central and Moray Firth grabens and troughs in rifting stage;uplifting of central North Sea basin companied with many a volcanic activity in thermal uplift stage,providing large amount of provenances for development of the northern reservoir rocks;central dome subsidence in major rifting stage followed by being submerged,causing premium source rocks development in northern of it;relatively stable sedimentary environment in late rifting state allowed large amount of chalks to develop in the central and deposit marls in the northern,shaping regional cap rocks in the northern of this basin;and in post-rifting stage,Norway-Greenland Sea separation occurred,and sustained and stable deposition under previous structural framework provided favorable environment for oil and gas preservation.Finally,these resulted in framework as giant gas fields dominantly distributed in the southern and giant oil fields in the northern,and contemporarily,upper source-lower reservoir and lower source-upper reservoir characteristics were found in Viking graben and Central graben,respectively.