伊朗西南部上白垩统Sarvak组储层特征及主控因素

运用取芯,薄片,电镜扫描及三维地震等资料,对位于扎格罗斯盆地盆缘当前热点开发区的伊朗A油田上白垩统Sarvak组储层特征及主控因素进行研究。研究表明:Sarvak组储层岩性以富含厚壳蛤、有孔虫、钙化藻和浮游有孔虫等生屑颗粒的灰岩和白垩灰岩为主。储层受岩溶作用影响明显,储集空间以生屑铸模孔,灰泥溶蚀孔群,溶孔,溶洞为主。结合压汞,孔渗关系,岩性等因素在层内综合划分出孔洞-孔隙型,裂缝-孔隙型,孔隙型和致密非储层四类。最有利储层为孔洞-孔隙型,岩性主要为富厚壳蛤碎屑灰岩,次有利储层为裂缝-孔隙型和孔隙型,岩性主要为富有孔虫碎屑白垩灰岩。储层主控因素为层内三级层序边界,古地貌隆起和岩石破裂作用。三级层序边界控制有利储层垂向位置,古地貌隆起控制储层性质平面分布,岩石破裂作用影响储层整体含油性。基于以上认识提出勘探开发建议:对层内三级界面的识别和明确原沉积期古隆起位置为确定油田垂向优先开发层位及平面有利开发区域的关键。距层序界面较远,厚度较大的白垩储层受岩石破裂作用影响较大,纵横向分布发育不稳定,储量计算应考虑对纵向不同类别储层进行分类评价。

Characteristics and Main Controlling Factor of the Upper Cretaceous Sarvak Reservoir,SouthWest Iran

This paper studys on the characteristics and main controlling factors of the upper Cretaceous Sarvak reservoir by the coring, section, SEM, well logging and 3D seismic data. The study area is the Azadegan oilfield of the SouthWest, Iran and which situated in the "hot zone" of the Zagros foreland basin nowadays. The main lithology of the Sarvak is the limestone and chalk limestone which is abundant of the rudist, foraminifer debris. The reservoir is influenced by the multi-stage of the karstification effect and the effect reservoir space is the moldic pore, cavern, vug, and mud matrix dissolved pore. According to the MISC, por-per relationship and lithology, we divided the reservoir into four types that are vug-pore, fracture-pore, matrix pore and non-reservoir. The optimum is the vug-pore and the mainly is the rudist bearing reservoir, and the secondary reservoir is the fracture-pore and the matrix pore reservoir, and mainly is the foraminifer bearing chalk limestone. The reservoir main controlling factor are the 3rd Squence boundary, palaeogeomorphology of the depositional time and rock fracturing by the multi-stage tectonic activities. The Squence boundary control the vertical position of optimum reservoir, the palaeogeomorphology control the lateral reservoir quality distribution, and the rock fracturing control the oiliness property of the chalky limestone. According to these findings, we propose the development suggestions as below: Clearing the 3rd sequence boundary of inner formation and the paleo-high of depositional time is the critical factors to select the favorable vertical develop zone and lateral develop area. The reservoir quality and oiliness of the thick chalk limestone is influenced by the rock fracturing, and is more unstable compare with the reservoir zone near the sequence boundary. So, at the early stage of the field development, we should consider the grading evaluation criteria in the reserves calculation.