北部湾盆地涠西南凹陷流一段非构造油气藏

Subtle hydrocarbon reservoirs in Liu-1 Member of the Weixi'nan Sag,Beibuwan Basin,China

在北部湾盆地涠西南凹陷流一段高精度等时层序地层单元划分基础上开展精细沉积相研究,并进一步分析流一段非构造油气藏的油源条件、圈闭条件和非构造圈闭的形成特征。研究表明,流一段油源丰富,油气运移充注充分,储盖组合良好,主要形成断层-岩性(圈闭)油气藏、不整合面遮挡型(圈闭)油气藏、砂岩上倾尖灭型(圈闭)油气藏和砂岩透镜体岩性(圈闭)油气藏4类非构造油气藏,(扇)三角洲砂砾岩体是这些圈闭的主要储集层。断层-岩性圈闭的特征是断层走向与三角洲物源方向垂直或交切;不整合面遮挡型圈闭的特征是三角洲砂体上游被剥蚀;砂岩上倾尖灭型圈闭的特征是三角洲砂体下游发生构造抬升;砂岩透镜体岩性圈闭主要发育在深水区的中深湖,一般为三角洲前方的浊积体。根据以上特征,预测了流一段非构造油气藏的有利钻探目标。

After high-resolution sequence stratigraphy was built,the authors studied the fine sedimentary facies and the oil source,trap conditions and formation of non-structural traps in the Liu-1 Member.The Liu-1 Member has abundant oil source,sufficient migration and charge of oil and gas,and excellent reservoir and cap association.The reservoirs include four types： fault-lithologic reservoir,unconformity reservoir,sandstone updip thinning out reservoir,and sand lens reservoir.The major reservoir layers are fan delta or delta sandy conglomerates.The characteristic of fault-lithologic traps is that fault strikes are normal to or intersect the direction of fan delta sources.The upriver sand bodies are eroded in unconformity traps.The downriver sandbodies uplift in sandstone updip thinning out traps.Sand lens lithologic traps are mainly formed by turbid sand distributed in deep lakes in the front of deltas.According to these characteristics,favorable targets are predicted.