摘要
为了厘清成岩作用对页岩气储层的影响,以川南及邻区下志留统龙马溪组黑色岩系为主要研究对象,通过偏光显微镜、背散射和X-射线衍射分析等手段,对其成岩作用进行了研究,结合有机质的镜质体反射率(Ro)、岩石热解、伊利石结晶度等分析,划分出成岩阶段,明确了成岩演化特征。在埋藏成岩过程中,页岩气地层经历了无机和有机成岩作用的共同改造,无机作用主要为压实作用、胶结作用、溶蚀作用和交代作用,有机成岩为有机质的生烃演化作用,二者密不可分、相互影响。成岩演化已达到晚成岩阶段,主要经历了4个阶段:1快速压实阶段;2弱溶蚀-压实阶段;3弱溶蚀、胶结阶段;4弱胶结、交代阶段。受成岩作用的影响,孔隙演化可分为早期原生孔隙大量、快速丧失阶段和中晚期次生微孔隙、微裂缝形成阶段。中成岩A期的弱溶蚀、胶结阶段中的黏土矿物转化和有机质生烃的协同作用是页岩气储层发育的主要原因。
To analyze the impacts of diagenesis on shale gas reservoirs,the black shale in Lower Silurian Longmaxi Formation,together with the southern Sichuan Basin and its periphery are taken as the research object.The polarizing microscope,back scattering,X-ray diffraction analysis and other means were used for diagenesis research.Then diagenetic stages were divided in combination with analyses on vitrinite reflectance(Ro),rock pyrolysis and illite crystallinity of organic matters.Meanwhile,the diagenetic evolution characteristics were also determined.In the burial diagenetic process,shale gas strata are transformed under inorganic-organic diagenesis;inorganic diagenesis mainly includes compaction,cementation,dissolution and metasomatism,while organic diagenesis is primarily the hydrocarbongeneration evolution of organic matters.Both diagenetic types were inseparable with mutual impacts.This evolution has entered the late diagenetic stage,including four main stages,i.e.:1)rapid compaction stage;2)weak dissolution-compaction stage;3)weak dissolution-cementation stage;4)weak cementation and metasomatism stage.As a result of diagenesis,pore evolution can be divided into the early stage for the massive and rapid loss of primary pores and middle-late stage for the formation of secondary micro-pores and microcracks.The main reason for the development of shale gas reservoirs is the synergy between the transformation of clay minerals and hydrocarbon generation of organic matters in the weak dissolution-cementation stage during phase A of the mid-diagenetic stage.
出处
《石油学报》
EI
CAS
CSCD
北大核心
2015年第9期1035-1047,共13页
Acta Petrolei Sinica
基金
中国岩相古地理编图项目(No.1212010916060)资助
关键词
成岩作用
成岩演化
页岩气
龙马溪组
下志留统
川南及邻区
diagenesis
diagenetic evolution
shale gas
Longmaxi Formation
Lower Silurian
southern Sichuan Basin and its periphery
