鄂尔多斯盆地马岭地区长8储层成岩作用与有利成岩相带

Diagenesis and favorable diagenetic facies of the eighth member of Yanchang Formation in Maling area,the Ordos Basin

运用常规薄片、铸体薄片、X射线衍射、阴极发光及扫描电镜等实验手段,研究鄂尔多斯盆地马岭地区延长组长8砂岩储集层成岩作用类型及其对储层的影响,划分成岩相并预测有利成岩相带。研究结果表明,研究区长8储层经历了压实、胶结、溶解及交代等多种成岩作用,压实作用和晚期含铁碳酸盐胶结作用使砂岩孔隙大量减少,显著降低储层物性,而溶解作用产生了较多次生孔隙,使储层物性得到明显改善。根据储层物性的主控成岩作用,结合孔隙类型,该区砂岩储集层划分为强溶蚀剩余粒间孔+溶蚀孔相、弱胶结剩余粒间孔相、黏土矿物胶结相、碳酸盐胶结相和强压实相5种成岩相,其中强溶蚀剩余粒间孔+溶蚀孔相和弱胶结剩余粒间孔相储层物性较好,是储层发育的有利成岩相带。

Conventional section,cast section,X-ray analysis,cathode luminescence and SEM samples were used to study the diagenesis of the eighth member of Yanchang Formation（ Chang8） in Maling area of the Ordos Basin,analyze its effects on reservoirs,divide diagenetic facies,and to forecast favorable diagenetic facies. The Chang8 reservoir in the study area has experienced various diagenetic effects such as compaction,cementation,dissolution and metasomatism. Compaction and ferruginous carbonate cementation in the late diagenetic phase reduced the sandstone porosity and the permeability of the reservoir,while dissolution produced a lot of secondary dissolved pores and improved permeablility. According to diagenetic functions and pore types,the sandstone reservoirs in the study area were divided into five diagenetic facies including strongly-dissolved residual inter-granular pores ＋ dissolution pores,weakly-cemented residual inter-granular pores,clay mineral cementation,carbonate cementation,and strong compaction,among which the first two facies are favorable for reservoir development.