伊朗西南部上白垩统Sarvak组成岩作用及有利储集层形成模式

Model for the Genesis of Favorable Reservoir and Diagenesis of the Upper Cretaceous Sarvak Formation in SW Iran

基于中东地区中生代碳酸盐岩储集层和中国碳酸盐岩储集层特征差异大,国内相关研究较少现状,本文以伊朗西南部A油田上白垩统Sarvak组作为对象,以取心薄片分析资料为基础,结合沉积地质背景和储集层特征,重点对储集层成岩作用类型和成岩序列进行研究,并建立了优质储集层发育成岩模式。研究表明,研究区储集层成岩作用主要包括泥晶化作用、压实（压溶）作用、胶结作用、溶蚀作用、新生变形作用、白云岩化作用和岩石破裂作用。决定优质储集层形成的主要时期为同生-准同生成岩阶段,主导成岩作用为溶蚀作用。有利储集层类型为富含厚壳蛤碎屑的礁滩体储集层,成岩模式为受不同级别层序界面控制形成的同生-准同生连续岩溶。高频层序界面引发的同生岩溶使得储集层内形成大量生物铸模孔,三级层序界面引发的准同生岩溶（局部岩溶）导致孔隙在空间进行再分配,使得最有利储集层集中分布于紧邻三级层序界面之下20～30m储集层内。层序内部受控高频层序界面影响形成的以铸模孔和灰泥溶蚀孔群为主的上白垩统储集层,在后期构造微裂缝配合下也可形成相对较好储集层。

As the Mesozoic carbonate reservoir in the Middle East,which is obviously different to the carbonate reservoir in China,has been studied limitedly by Chinese scholars at present,the Cretaceous Sarvak Formation in the A oilfield in SW Iran has been selected in this paper for studying its reservoir diagenesis,diagenetic sequences and for building diagenetic model of the high quality reservoir based on the analyses of drilling cores and the comprehensive analysis of geological background and reservoir characteristics. Research results show that the reservoir diagenesis mainly includes micritization,compaction（ pressolution）,cementation,dissolution,neomorphism,dolomitization and fracturing. The high quality reservoirs was mainly formed in the syngenetic-penesyngentic diagenetic stage through the dominant dissolution. The favourable reservoir is the reef-shoal reservoir containing abundant fragments of rudist bivalve. It wasformed through the typical syngeneticpenesyngentic continuous karstification under the control of various stratigraphic boundariesat different levels. The syngenetic karstification,in the high frequency stratigraphic boundaries,resulted in the formation of a large amount of Rudist moldic pores in the reservoir. The penesyngenetic karstification（ local karstification）,caused by the 3rd order stratigraphic boundaries,resulted in the redistribution of pores and fissures in reservoir and made the most favourable reservoir concentrated inthe zone where is generally 20 ～ 30meters below the 3rd order stratigraphic boundaries. The Upper Cretaceous reservoir,which is dominated by moldic pores and matrix dissolution pores formed under the influence of the high frequency stratigraphic boundaries in the strata,can also form the relatively good reservoir with the overprint of the late fissures.