对渤海海域隐蔽油气藏勘探的思考——以427构造带为例

Thinking about the subtle reservoir exploration in Bohai sea: a case of 427 structure belt

对于高成本的海上油气勘探来说,规模是制约隐蔽油气藏勘探的关键因素之一。对渤海海域而言,要寻找的不仅仅是隐蔽油气藏,而是有一定规模的隐蔽油气藏。储层特征是影响富生烃凹陷隐蔽油气藏规模的一个关键因素,因此储层特征,即砂体特征就应该成为渤海隐蔽油气藏勘探研究的一个核心,而要研究这个核心,必须要有地质和地球物理技术两方面的结合,而且结合过程中对层序地层、沉积体系、构造三因素进行耦合分析所形成的地质模型至关重要,这就是“一核心、两结合、三因素”的研究思路。与此研究思路相配套的是三项技术包括地质与地球物理相结合的储层预测技术、隐蔽圈闭识别技术和“三因素”框架下的成藏分析技术。以上述研究思路和技术对427构造带进行分析认为,区内已发现的小规模油藏为岩性油藏,不具商业开采价值,原因是其储集体为湖泛期扇三角洲,砂体分散、孤立、连通性差;而下坡寻找具一定规模且连通性好的低位域油气藏和下凹寻找高位域早期大型浊积扇岩性油气藏是在427构造带寻找规模型油气藏的必由之路。

For offshore hydrocarbon exploration with a high cost, reservoir size is one of the key factors to constrain-the exploration of subtle hydrocarbon pools. What needs to be discovered in Bohai sea is subtle pools with a certain size. The characteristics of sand body, as a core of research work are a key factor to control subtle reservoir size in a petroliferous depreesion, and it is required to investigate sand body characteristics by combining geological methods with geophysical techniques. During this combination, it is very important to build a geological model by an integrated analysis of 3 elements, i.e. stratigraphic sequence, sedimentary system and structure. All these have constituted a new research idea of ＂one core, two disciplines ＇ combination and three elements＂ There are also 3 techniques matched with the idea, including reservoir prediction technique, subtle trap identification technique and hydrocarbon accu- mulation analysis technique. Based on an analysis of 427 structure belt by using this idea and the 3 techniques, the small oil discoveries in the belt are considered lithologic pools with no commercial value because their reservoir rocks are deltaic fan sandbodies that are formed during lake flooding and are separated and lack of connectivity. To find sizable hydrocarbon pools in 427 structure belt, it is necessary to look for larger connective reservoirs of low system tracts in the lower slope, and large lithologic reservoirs of turbidite fans within high system tracts in the lower sag.