摘要
采用岩心观察、薄片鉴定、扫描电镜和X射线衍射分析对四川盆地元坝地区下侏罗统大安寨段湖相细粒岩岩性及成岩作用特征进行了描述,探讨了有利岩石类型及成因。本段发育泥岩类(泥岩与页岩)、粉砂岩和灰岩3大类岩石,具体为泥岩与页岩、灰质泥岩,以及介壳页岩和介壳灰岩;矿物组分主要为石英、粘土矿物、方解石、长石和黄铁矿;粘土矿物包括伊蒙混层、伊利石、高岭石和绿泥石;发育介壳页岩和泥岩夹介壳灰岩的岩石组合类型为主。本段细粒岩经历压实作用、胶结作用、溶蚀作用、交代作用、粘土矿物的转化作用及有机质的生烃演化作用,目前处于中成岩阶段B亚期,压实作用和胶结作用是控制页岩和灰岩物性变化的主要因素。受沉积及成岩的控制,富有机质页岩和介壳页岩是最有利的储集岩。成岩影响导致常规储层的介壳灰岩与灰岩致密而没有储集油气,反而使相对致密的细粒介壳页岩成为页岩气藏的有利储层,导致了测试时介壳页岩大量出气而相邻的介壳灰岩无气泡。纹层与微纹层(显微镜下显示纹层)发育及硅质与灰质组分显微定向排列有利于优质储层形成。
Core observation,thin section identification,scanning electron microscopy(SEM)and X-ray diffraction analysis were used to finely describe the petrological characteristics and diagenesis of fine-grained sedimentary rocks as well as to discuss rock types with hydrocarbon potential and their genesis in the Lower Jurassic Da’anzhai Member of Yuanba area in the Sichuan Basin.The results show that there are three types of rocks,namely mudstone(mudstone,conchoidal shale and calcareous mudstone),siltstone and limestone(conchoidal limestone).The main mineral components are quartz,clay minerals(dominated by illite/smectitem(I/S)mixed layer,illite,kaolinite and chlorite),calcite,feldspar and pyrite;the rock assemblages are mainly conchoidal shale and mudstone interbedded with conchoidal limestone.The fine-grained rocks,currently at the B sub-stage of the mesodiagenesis,experienced compaction,cementation,dissolution,metasomasis,recrystallization of clay minerals and hydrocarbon generation from organic matters,of which,compaction and cementation were the major factors controlling the physical properties of shale and limestone.It also shows that,controlled by sedimentation and diagenesis,the organic-rich shale and the conchoidal shale are two most promising rock types for hydrocarbon reservoirs.Also as a result of diagenesis processes,the conventional reservoirs of conchoidal limestone and limestone are too tight to hold any oil or gas,but the fine-grained sedimentary rock and conchoidal shale of less tight are wonderful unconventional shale gas reservoirs.This assumption was verified in field tests during which large volume of gas flew out of conchoidal shale,but none from the adjacent conchoidal limestone.The result also suggests that rocks with well-developed laminae and micro-laminae(observed under microscope)or with siliceous and calcareous compositions of directional arrangement are potentially high-quality reservoir rocks.
作者
朱毅秀
金振奎
金科
郭芪恒
王欢
吕品
王昕尧
师源
Zhu Yixiu;Jin Zhenkui;Jin Ke;Guo Qiheng;Wang Huan;Lyu Pin;Wang Xinyao;Shi Yuan(College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;State Key Laboratory of Petroleum Resources and Prospecting,Beijing 102249,China;Research Institute of Exploration and Development under Liaohe Oilfield Company,PetroChina,Panjin,Liaoning 124010,China)
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2021年第2期494-508,共15页
Oil & Gas Geology
基金
国家科技重大专项(2017ZX05036-004-002)。
关键词
成岩演化
岩石学特征
细粒沉积岩
大安寨段
元坝地区
四川盆地
diagenetic evolution
petrologic feature
fine-grained sedimentary rock
Da’anzhai Member
Yuanba area
Sichuan Basin
