基于储层结构的厚壳蛤建隆沉积模式——以伊朗SA油田Sarvak油藏为例

The Rudist-buildup Depositional Model Based on Reservoir Architecture:A case from the Sarvak reservoir of the SA oil field,Iran

针对伊朗SA油田上白垩统Sarvak油藏富含厚壳蛤碎屑Sar-3层开发所遇问题,运用岩芯,薄片,XRD,三维地震等资料,对厚壳蛤建隆沉积模式及对应形成储层结构进行研究。研究表明Sar-3沉积期主要发育属于碳酸盐缓坡沉积体系内障壁岛—滩亚相内的厚壳蛤丘和伴生潮坪两类微相,结合区域构造沉积背景建立沉积模式,该模式强调以下要点:1受构造运动影响形成的古地层隆起为影响厚壳蛤生物礁建隆分布主控因素;2受海平面下降和古地层隆起向上抬升影响,厚壳蛤建隆在生长早期受强水流作用破坏,搬运再沉积形成缓丘状礁滩混合体;3Sar-3层上部广泛发育潮坪环境致密泥晶灰岩沉积,受古地貌控制,边部构造低部位区垂向可叠置发育多期潮坪沉积;4旋回末形成局部短暂水上暴露环境,大气水所造成的淡水淋滤作用为影响储层性质及结构主要因素。Sar-3层垂向结构可表征为二元结构,下部为厚壳蛤灰岩储层,上部为潮坪致密灰岩隔层,两者厚度受控于古地貌,古地貌高点为储层有利发育区。以此为依据提出相应水平井开发对策:古地貌高部位区力争轨迹保持在油层中部钻进,低部位区前段以微倾角钻穿油层,后段确保在储层底部钻进。

This paper studies on the lithofacies,sedimentary facies,depositional models and reservoir architecture of the rudist-bearing zone of Creatures Sarvak Formation in South Azadegan oilfield of Iran by utilizing the coring,thin section,XRD data of 5 coring wells. Firstly,identified the lithofacies by the Dunham classification. Secondly,clarified the rudist-mound and tidal flat are the main microfacies in Sar-3 depositional time. Based on the regional depositional setting,we built the depositional model of Sar-3,which highlight four key points： 1 The rudist-buildup forming was controlled by the paleo-high; 2The build-up without the landward colonize by the regression and formation uplift,and they reach the wave-base and eroded by the high energy current,the rudist fragments were dispersed and re-deposited,forming the moundy allochthonous deposition; 3The tidal flat exists widely in the upper Sar-3 and the duration time depends on the paleo-structure,in the lower part could develop tidal deposit of several stages vertically;4The exposure within the leaching effect by the meteoric water occurred in the late cycle,which is the main controlling factor to the reservoir architecture. From the model,we can obtain the following findings： the Sar-3 featured as the dualistic architecture layer,the lower is the rudist bearing limestone of reservoir and the upper is the tidal dense limestone of interlayer,and the thickness of each is controlled by the paleo-geomorphology,and the paleo-high is the preferential exploitable area. According to this,we proposed the horizontal well development strategy that keeping the trajectory in the middle of the oil-zone in the pale-high,in the paleo-low,assure the forepart trajectory crossing the oil-zone and then keep it in the lower part.