富油气凹陷“满凹含油”论——内涵与意义

The intension and signification of "Sag-wide Oil-Bearing Theory" in the Hydrocarbon-rich Depression with terrestrial origin

富油气凹陷指陆相沉积盆地中烃源岩质量好、规模大、热演化适度与生烃量和聚集量都位居前列的含油气凹陷。富油气凹陷形成“满凹含油”的条件是 :①烃源岩生烃总量大 ,可保证各类砂体聚油成藏 ;②有效烃源岩面积大 ,为各类砂体与烃源岩提供最大接触机会 ,有利于油气运聚成藏 ;③湖盆振荡变化使砂、泥岩频繁间互 ,为各类岩性 地层圈闭形成创造条件。富油气凹陷呈满凹分布的岩性 地层油气藏的形成主要受最大湖泛面、不整合面与断层面的控制 ,油气在有利沉积相带、岩性或地层尖灭带、沉积阶段古地形坡折带、裂缝带与次生孔隙发育带相对富集 ,“甜点”则位于斜坡背景上发育的主砂体以及有裂缝和鼻状隆起背景参与成藏的各类砂体中。富油气凹陷“满凹含油”论的提出是对“源控论”与“复式油气聚集”理论的发展 ,可使油气勘探跳出二级构造带范围 ,实现满凹勘探 ,大规模拓展勘探范围。图 8表 2参

A hydrocarbon-rich depression means one developed in the terrestrial sedimentary basins, with the source rocks of high TOC, large scale and suitable thermal evolution as well as huge amount of hydrocarbon generation and migration. The conditions of sag-wide oil-bearing formation in such depressions should be: ① massive hydrocarbon generation provides sufficient source for accumulation in all kinds of sand bodies; ② large scale effective source kitchens usually occupy larger portion of the sags, which offer more opportunity for direct contact between source and reservoirs; ③ lake vibration through time causes frequent alternation and variation of sandstone and mudstone in vertical and lateral directions, which provides suitable condition for formation of different kinds of lithostratigraphic traps. The formation of sag-wide distributing lithostrigraphic traps is mainly controlled by max lake flooding surface, unconformities and fault surface. And hydrocarbon accumulations are dominantly located in favorable sedimentary facies zones, lithological or stratigraphic pinch out belts, slope-breaks at syndepositional stages, fracture zones and secondary pore zones, which are usually called 'sweet points'. The 'sweet points' are more likely to occur in the major sand bodies and sandstone noses with structural background. Sag-wide oil-bearing theory could develop the theories of 'Source Control Accumulation' and 'Composite Zones of Hydrocarbon Accumulations', which can expand the plays beyond sub-structure zones and widely enlarge the target scope.