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中东地区白垩系Mishrif组主要由富含生物碎屑的颗粒泥晶灰岩及泥晶颗粒灰岩组成。基于薄片研究了伊拉克鲁迈拉油田Mishrif组碳酸盐岩中生物碎屑特征及其成岩作用的相异性特点,并总结了生屑成岩作用差异性特征对储层的影响。该区Mishrif组重要的生物碎屑有三大类,即双壳类、棘皮类和有孔虫类。这些生物碎屑主要经历了同生阶段的泥晶化和大气淡水溶蚀作用,中-浅埋藏期的压实压溶、充填胶结、新生变形等多期成岩作用。泥晶化作用主要发生在有孔虫壳体外壁;溶蚀作用更易发生在双壳类和有孔虫壳体中。胶结作用在不同类别生物碎屑上的表现形式不同,且对储层中早期孔隙的破坏强烈。不同类别生物碎屑的结构、大小、成分的差异造成了成岩作用的差异并进而影响储层物性。
The Cretaceous Mishrif Formation in the Middle East consists mainly of particulate clastic-rich dolomitic limestone and marlite limestone. The characteristics of bioclastic features and the diagenesis of the Mishrif Formation in the Rumaila oilfield of Iraq are analyzed based on the characteristics of the dissimilarities. The differences of bioclastic diagenesis on the reservoir are also summarized. There are three major classes of biological debris in the Mishrif Formation in this area, namely bivalves, echinoderms, and foraminifera. These biological clasts mainly experienced the stages of syngenetic stage of the mud crystallization and atmospheric freshwater dissolution, medium-shallow burial compaction pressure solution, filling cementation, new deformation and other multi-stage diagenesis. Mud-crystallization mainly occurs on the outer wall of foraminifera shell; dissolution is more likely to occur in bivalves and foraminifera shells. The cementation has different manifestations on different types of biological clasts and strongly destroys the early pores in the reservoir. The differences in structure, size and composition of different types of biological clays cause diagenetic differences and thus affect reservoir physical properties.