歧口凹陷岩性地层油气藏特征及勘探潜力

Characteristics and exploration potential of lithologic-stratigraphic hydrocarbon reservoirs in Qikou Sag of Dagang Oilfield

渤海湾盆地黄骅坳陷歧口凹陷(大港探区)岩性地层油气藏分布广、类型多。形成规模储量的主要为储集层上倾尖灭和构造-岩性复合地层两大类油气藏。决定其圈闭分布的主要因素是古构造背景与沉积物源体系的匹配,成藏机理为“三元耦合控藏”。该工区有5个领域值得重视:①古隆起围斜、倾没端、构造坡折带之反向碎屑物源区;②沉积频繁相变区;③古隆起缓坡带;④(半)封闭湖湾区;⑤湖盆陡坡坡折带及凹陷之中卸载区。根据“宏观岩性地层油气藏”勘探原理,将构造带当作岩性变化带,在复式油气藏勘探方法基础上,采用以岩性油气藏勘探与精细勘探相结合的勘探方法。同构造油气藏相比,该工区岩性地层油气藏分布空间范围广,体系域全,压力场宽,储量也占优势,是油气勘探的重点目标之一。

There are various and abundant lithologic-stratigraphic hydrocarbon reservoirs in Dagang prospecting area of Qikou Sag in Huanghua Depression of Bohai Bay Basin. The primary reservoirs in reserves are the updip pinch out reservoir and structural-lithologic composite reservoir. Those non-structural traps rely on matching between palaeostructure background and sedimentary system. According to palaeostructure cosmetics of Qikou Sag in Dagang prospecting area and distribution characteristics of sedimentary system, there are five important domains for petroleum exploration, including ①enclosed slope of palaeohigh, pitching end, and reversal clastic source area of slope breakl ② frequent facies change area; ③ break in gentle slope of palaeohigh; ④ semi-close lacustrine bay area; ⑤ break in abrupt slope and low-lying offloading areas in depression. According to the exploration principle of ＂macroscopic lithologic-stratigraphic hydrocarbon reservoirs＂, a special exploration strategy was adopted in Dagang Oilfield. The sedimentary system superposition research method was combined with palaeostructure background. The structural zone was emphasized as the lithologic change zone, and the exploration of lithologic-stratigraphic hydrocarbon reservoirs was combined with subtle techniques and procedures. Comparing with the structural reservoir, the lithologic-stratigraphic reservoirs in Dagang prospecting area have more abundant types, more wide distribution areas and more reserves, as well as all system tracts and whole pressure fields. So, these reservoirs are the most important exploration targets.