歧口凹陷歧北斜坡岩性油气藏及其勘探方法

Theory and Methods of Lithological Reservoir Exploration in Qibei Slope of Qikou Sag

歧口凹陷作为渤海湾盆地一个富油气凹陷,油气资源丰富。具有凹多、凸少、斜坡类型多的特点。随着勘探程度不断提高,斜坡区是今后勘探的重点领域。以歧北斜坡为例,通过强化斜坡成因演化及控砂、控藏机制研究,明确"基底差异沉降控制斜坡构造的形成,基底断裂控制斜坡构造的发育样式"斜坡构造成因机制、"内外物源供砂、调节沟槽输砂、陡缓坡折控砂"斜坡区多元控砂机制、"复式输导、2期充注、高油低气、差异聚集、优势相富集"斜坡区岩性地层控藏机制。创新发展了斜坡区油气成藏理论,探索形成了"选斜坡—建模式—求突破—描砂体—优方案"富油气凹陷斜坡区岩性地层油气藏勘探工作方法。有效指导了歧口凹陷斜坡区岩性地层油气藏预探实践,发现规模储量区。

Qikou Sag is one of the most important hydrocarbon rich sags in the Bohai Bay Basin with landscape of more depression and few uplift,and various kinds of slopes.With the constant improvement of exploration,the slope area is an important object of exploration.Taking Qibei slope as an example,the controlling mechanisms of regional tectonic framework,distribution of sandbodies and reservoir have been discussed intensively by the study of Qibei slope.Three points can be generalized as following：（1）The difference on basement subsidence controls the formation of the slope and the fractured bedrock controls the development style of the slope.（2）The within and outside sources supply sand,regulation of the groove conveys sand and the steep or gentle slope controls sand.（3）The duplicate migration,two recharging,oil higher than gas,the differential accumulation and concentration of favorable facies control the formation of oil and gas reservoir.Then we innovate and develop the hydrocarbon accumulation theory and establish the exploration techniques of the lithostratigraphy reservoir in the sag enriched in oil and gas：Choosing slope-establishing model-seeking breakthrough-tracing sand body-optimizing schemas.The result has effectively directed the pre-exploration of the lithostratigraphy reservoir in the slope area of the Dagang Oilfield and discovered sizable reserves.