吉木萨尔凹陷芦草沟组致密油储层初步研究:岩性与孔隙特征分析
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摘要
通过岩心观察、薄片鉴定、电子探针观测,结合野外剖面及测井和地震等资料,分析吉木萨尔凹陷芦草沟组致密油储层岩性与孔隙特征。结果表明致密储层段由呈韵律互层产出的白云岩类/粉砂岩类与泥岩类构成,一般由3~5个韵律组成,具有一定的非均质性。储层岩石类型主要为白云质粉砂岩/粉砂质白云岩、砂屑白云岩以及泥晶白云岩。其中白云质粉砂岩/粉砂质白云岩分布最广,为芦草沟组上、下储层段("甜点")最主要储集岩,砂屑白云岩只分布于上储层段,泥晶白云岩以薄的夹层形式分布于上、下储层段。电子探针微区观测表明,储集空间以溶蚀型孔隙为主,孔径大小从几μm到30μm,可分为粒间/晶间溶孔、粒内溶孔以及部分裂缝型孔隙,发生溶蚀作用的矿物以钠长石为主,白云石次之。定量分析表明,白云质粉砂岩/粉砂质白云岩主要由钠长石、白云石以及少量钾长石等矿物组成,砂屑白云岩主要由微晶白云石和少量钠长石等矿物组成,泥晶白云岩主要由微晶白云石和少量石英、钠长石等矿物组成。
Petrology and pore characteristics of the tight oil reservoir in the Lucaogou Formation,Jimusar Sag,were carefully studied by core observation,thin section identification,and EMPA analyses,with reference to outcrop profiles,and logging and seismic data.It was found that the reservoir section was heterogeneous and mainly consisted of rhythmically interbedded dolomite/ siltstone and mudstone,with 3~5 rhythms in one section.Rock types identified include dolomitic siltstone,silty dolomite,dolarenite,and dolomicrite,of which the former two were most widely distributed and served as the main reservoir rocks of the upper and lower reservoir segments ‘(sweet points') of the Lucaogou Formation;while dol-arenite was distributed only in the upper segment and dolomicrite occurred as thin interlayers in both segments.Observations of EMPA showed that dissolved pores,which could be subdivided into intragranular pores,intergranular pores and cracks,were the main pore type,and their diameter ranges from several μm to 30μm.The minerals dissolved were mainly albite,followed by dolomite.As to the composition of the rocks,dolomitic siltstone and silty dolomite mainly consisted of albite,dolomite,and some potassium feldspar.Dol-arenite was composed of microcrystalline dolomite and some albite,and dolomicrite mainly consisted of microcrystalline dolomite and some quartz,albite and other minerals.
Petrology and pore characteristics of the tight oil reservoir in the Lucaogou Formation,Jimusar Sag,were carefully studied by core observation,thin section identification,and EMPA analyses,with reference to outcrop profiles,and logging and seismic data.It was found that the reservoir section was heterogeneous and mainly consisted of rhythmically interbedded dolomite/ siltstone and mudstone,with 3~5 rhythms in one section.Rock types identified include dolomitic siltstone,silty dolomite,dolarenite,and dolomicrite,of which the former two were most widely distributed and served as the main reservoir rocks of the upper and lower reservoir segments ‘(sweet points') of the Lucaogou Formation;while dol-arenite was distributed only in the upper segment and dolomicrite occurred as thin interlayers in both segments.Observations of EMPA showed that dissolved pores,which could be subdivided into intragranular pores,intergranular pores and cracks,were the main pore type,and their diameter ranges from several μm to 30μm.The minerals dissolved were mainly albite,followed by dolomite.As to the composition of the rocks,dolomitic siltstone and silty dolomite mainly consisted of albite,dolomite,and some potassium feldspar.Dol-arenite was composed of microcrystalline dolomite and some albite,and dolomicrite mainly consisted of microcrystalline dolomite and some quartz,albite and other minerals.
引文
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张建,刘楼军,黄芸,等.2003.准噶尔盆地吉木萨尔凹陷中-上二叠统沉积相特征[J].新疆地质.21(4):412-414.
彭雪峰,汪立今,姜丽萍.2011.准噶尔盆地东南缘二叠系芦草沟组沉积环境分析[J].新疆大学学报.28(4):395-400.
赵霞飞,赵永胜,邓启予,等.1994.准噶尔盆地南缘上二叠统芦草沟组和红雁池组层序地层学初析[J].成都理工学院学报.21(3):112-120.
高智梁,康永尚,刘人和,等.2011.准噶尔盆地南缘芦草沟组油页岩地质特征及主控因素[J].新疆地质.29(2):189-193.
王东营,汤达祯,苟明福,等.2007.准噶尔南缘阜康地区芦草沟组油页岩地质特征[J].中国石油勘探.6:18-22.
吴绍祖,屈迅,李强.2002.准噶尔芦草沟组与黄山街组的古气候条件[J].新疆地质.20(3):183-186.
Huang Z,Yang S,Chen Z.1997.Mineralogical correlation betweenprimary and replacement dolomites[J].Science in China-Series D,40(1):91-98.
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