鄂尔多斯盆地姬塬油田西部长8段储层成岩作用与致密成因  

DIAGENESIS AND CAUSES OF TIGHT SANDSTONE OF CHANG 8 RESERVOIRS IN THE WEST OF JIYUAN OILFIELD OF ORDOS BASIN

作　　者：姚婷婷[1] 鲍志东[1] 张云龙[1] 魏文风 窦鲁星[1] 韦明洋 管聪 

机构地区：[1]中国石油大学(北京)地球科学学院/油气资源与国家重点实验室,北京102249

出　　处：《矿物岩石》2016年第2期99-111,共13页Mineralogy and Petrology

基　　金：国家科技重大专项(2011ZX05004-004)

摘　　要：通过22口井共计600.02m的岩心观察、125块普通薄片和16块铸体薄片的鉴定,153块普通薄片和235块铸体薄片的鉴定报告,12个扫描电镜观察,结合阴极发光、X射线衍射、荧光等手段,分析姬塬油田西部长8段储层岩性、物性特征,针对该地区成岩作用类型、成岩阶段、成岩演化序列、成岩环境的研究发现:岩石主要类型为长石质岩屑砂岩和岩屑质长石砂岩,结构成熟度中等,成分成熟度差—中等。储层经历了压实作用、压溶作用、胶结作用、交代作用和溶蚀作用等成岩作用,整体处于中成岩A期。典型成岩序列为压实作用-泥晶方解石胶结-石英加大、长石加大-绿泥石膜-长石、岩屑溶蚀、高岭石生成(油浸)-自生石英、自生长石-铁方解石胶结-长石、岩屑、铁方解石溶蚀。成岩过程中碱性和酸性环境交替出现。储集空间以原生粒间孔隙和粒内溶蚀孔隙为主,其中水下分流河道物性最好,孔隙度8%~18%,渗透率0.3×10^(-3)~14×10^(-3);分流间湾物性最差,孔隙度小于6%,渗透率小于0.1×10^(-3)。研究区原始沉积物具有初始孔隙度40.28%~41.55%。压实作用平均减少孔隙度30.53%,对储层影响最大;胶结、交代作用使孔隙度进一步平均降低了4.85%;后期的溶蚀作用新增平均孔隙度3.04%,对储层物性有一定改善作用,局部地区是储层物性改善的主要因素。The lithology,characteristics of physical property are analyzed and the diagenetic types,stages,diagenetic evolution sequence,diagenetic environment are studied on the basis of observation of drilling core,identification of thin sections,combined with the analysis of SEM,CL,X-ray,so as to explore the cause of formation of dense Chang 8 reservoirs in the west of Jiyuan Oilfield.It shows that the reservoir rocks of Chang 8are composed by feldspathic lithic sandstone and lithic feldspathic sandstone,with medium maturity structure and general composition maturity.The reservoir is experienced diagenesis of compaction,pressure solution,cementation,metasomatism and dissolution and so on,in the middle diagenetic A stage.The typical diagenetic sequence in the area is as follows：compaction-micritic calcite cement-qartz,feldspar increase-chlorite film-dissolution of feldspar and debris,formation of kaolinite（oil breakthrough）-autogenyquartz,autogeny-feldspar-iron calcite cement-dissolution of feldspar,debris,iron calcite.Diagenetic process is in the alkaline and acidic diagenetic environments which occur alternately.Reservoir space primarily consists of intergranular porosity and intragranular dissolution pores.Deposition has a fundamental effect on the physical properties of reservoir and diagenesis plays a decisive role in the late stage of the reservoir.The reservoir physical properties of underwater diversion channel are well developed with 8%-18% porosity and 0.3×10^-3-14×10^-3 permeability.On the contrary,the physical properties of shunt bay are poorly developed with porosity less than 6%and permeability less than 0.1×10^-3.The initial porosity of the original sediments in the studied area ranges from 40.28% to 41.55% and the primary porosity is reduced by 30.53%through compaction,which greatly affect the physical properties of the reservoir.Meanwhile,porosity is further reduced by 4.85% through cementation and metasomatism.Dissolution in the later stage produced some secondary pores,which increase porosity b

关 键 词：姬塬 长8 成岩作用 成岩序列 致密成因 

分 类 号：TE122.2[石油与天然气工程—油气勘探]