摘要
Mishrif组作为伊拉克东南部R油田重要的油气产层之一,储层成因及分布规律认识不清制约着该层系后备油气资源开发利用成效。本文综合岩石薄片、岩心物性、常规及特殊测井数据等资料,分别分析了沉积、成岩要素对Mishrif组储层的控制作用,认为R油田Mishrif组生物礁滩、滩前、滩后、潟湖相皆不同程度发育储层:规模性优质储层发育在生物礁滩环境,强烈溶蚀作用及弱胶结作用是重要成储条件,储集空间以溶孔、粒间溶孔及铸模孔为主;低能相带储层形成于弱胶结作用环境,未被胶结物充填保留的生屑颗粒间溶孔、粒内孔是储层发育的基础。对比不同类型储层岩电响应特征,刻画并描述了Mishrif组优质储层的分布规律:Mishrif组下部(MB段)生物礁滩储层物性优于上部(MA段)同类储层,优质储层位于准层序上部,受大气淡水溶蚀作用改造显著;滩后、潟湖相中等品质储层叠置发育在生物礁滩型储层上部,且由于差异胶结作用的影响使之在横向及垂向上表现出明显的非均质性。
The Mishrif Formation (Upper Cretaceous) is an important carbonate reservoir in Middle East,and the knowledge of formation and distribution of Mishrif carbonate reservoir has important significance for efficient exploration and development of hydrocarbon resources. Based on the comprehensive utilization of thin sections,petrophysical data,conventional logging data and imaging and NMR logging data of Mishrif Formation in R oilfield,southeast Iraq,we comparatively analysed the sedimentary and diagenesis factors of Mishrif carbonate ramp reservoirs,and defined well logging responses and described the distribution of various reservoirs. The reservoirs developed in reef \ bioclastic shoal,back-shoal,fore-shoal and lagoon facie. The high-quality reservoirs are mostly concentrated in high energy reef \ bioclastic shoal settings where strong corrosion and weak cementation are the important diagenetic conditions. The low-energy facies reservoir formed in weak cementation environment, and the retained inter-granular (dissolved) pores and intra-granular pores which had not been filled with cements are the foundation for quality reservoir. The filling of micrite and various cements resulted in inferior reservoir quality with limited pore space. The qualities of reef \ bioclastic shoal reservoir in the lower Mishrif formation (MB) are better than those in the upper Mishrif formation (MA). The high quality reservoir developed in the upper of para-sequence,which was intensively affected by meteoric dissolution. The moderate quality reservoir formed in back-shoal and lagoon facies lies on the top of the reservoir developed in bioclastic/reef facies,which show progradational sequence along with relative sea level continuously declining.Since different degree of cementation, reservoirs with various petrophysical conditions vertically distributed with each other.
引文
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