摘要
白云岩化是影响储层发育是否的重要沉积-成岩过程。作者通过在对川西地区的中三叠统雷口坡组的雷三至雷四段的岩相学,碳、氧、锶、镁同位素以及元素地球化学等综合研究,划分出含膏的泥晶云岩AD0、泥晶云岩D0、泥粉晶云岩D1、粉细晶云岩D2、微生物云岩MD、含灰质藻云岩CD(交代结构)以及去云化的泥粉晶云岩(CD0CD1)等七类白云岩。白云石有序度及铁、锰含量较低。阴极发光以暗紫、暗紫红、蓝紫为主;次为玫瑰红、橙红及橙黄红色。δ^(13)CPDB=1. 95‰～2. 46‰,δ^(18)OPDB=-4. 05‰～2. 70‰;^(87)Sr/^(86)Sr=0. 70778～0. 70807,δ^(26)Mg=-1. 872‰～-2. 124‰,其中δ^(13)C_(PDB)、^(87)Sr/^(86)Sr的平均值与中三叠世全球海水相似;δ^(18)O_(PDB)为弱负漂及正偏移。从D2、D1至D0、AD0,Sr、Na和大部分微量元素含量及比值和δ^(18)O_(PDB)逐渐增加; AD0、少量D0或MD相对富含硅、铝,并与高(低镁)方解石、黏土、有机质等共生。离子组成反映出白云石的前驱物以方解石型为主,少量为文石、原白云石结构。存在广盐、稍咸和超盐度的碱性等沉积环境。白云岩形成主要受向上变浅米级旋回序列,干燥、炎热为主、偶夹潮湿古气候以及古地貌-古水文条件等因素影响。存在浅潟湖的萨勃哈(AD0或D0)、环潮缘至局限台地(D0-D1、微生物诱导MD)、潮间-潮下的微生物礁(席)构成的障壁的台缘带(MD-CD1-CD)、潮坪-开阔台地(D0-D2-CD1、MD)等环境,以萨勃哈和受蒸发泵-密度差驱动的"渗透-回流白云石化"模式为主。
Dolomitization is an important depositional and diagenesis process greatly affecting the reservoir quality.Based on the studies with regard to petrography,carbon,oxygen,strontium and magnesium isotopes as well as the data of major and minor elements composition and ratios of bulk dolomites,seven types of dolomites has been systematic classified,i.e.(1)micritic dolomite with gypsum or anhydrite co-exist AD0;(2)micritic dolomite D0;(3)micritic and microcrystalline dolomite D1;(4)microcrystalline and finely crystalline dolomite D2;(5)fully dolomitized microbialite MD;(6)calcium bearing dolomite CD;and(7)calcitized micritic and microcrystalline dolomite(de-dolomite)CD0,CD1.The average sequentiality(δ)for different dolomites is lower compared with typical dolomite in reflux dolomitization model,and the concentration of Mn and Fe are also rather lower with predominantly dark purple,purplish red,and blue purple,less common by rose-red,orange red and yellow-red(CL).The stable isotope for values for seven different type dolomites areδ13CPDB(1.95‰~2.46‰)andδ18OPDB(-4.05‰~2.70‰),while for 87Sr/86Sr(0.70778~0.70807)andδ26Mg(-1.872‰^-2.124‰),indicating that theδ13CPDB and 87Sr/86Sr of dolomites within the range of globe seawater change and minor negative offset or positive forδ18OPDB in the Middle Triassic.A few D0 and MD as well as AD0 are rich in the concentration of silicon,aluminum with present by a few low or high magnesium calcite,clay minerals and organic matters.Except for the concentration(Sr2++Ba2+)of few samples is large than the(Mn2++Fe2++Zn2+),which most of them assumed as predominantly calcite and subordinate aragonite structure for proto-dolomites.From the type of D2 to D1,or D0 and AD0,the concentration Sr and Na,most of minor-elements and ratios of bulk various dolomites,as well asδ18O shows an increasing tendency,imply that would been in an euryhaline,penesaline and alkaline,hyperhaline sedimentary environment.Heterogeneous geochemical data prevailing in same type dolomite reveals that mul
作者
钱一雄
武恒志
周凌方
黄康俊
邓美洲
李勇
董少峰
王琼仙
QIAN YiXiong;WU HengZhi;ZHOU LingFang;HUANG KangJian;DENG MeiZhou;LI Yong;DONG ShaoFeng;WANG QiongXian(Wuxi Institute,Exploration&Production Research Institute,SINOPEC,Wuxi214151,China;International Exploration and Development Company,SINOPEC,Beijing100083,China;Geology department,Northwestern University,Xi’an710069,China;Exploration&Production Research Institute,Southwest Oil&Gas Company,SINOPEC,Chengdu610081,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第4期1161-1180,共20页
Acta Petrologica Sinica
基金
深地项目(2017YFC0603103)
中国科学院A类战略性先导科技专项(XDAXX010201-3)
国家自然科学联合基金(U1663209)
中国石化西南油气分公司项目(3445000-14-ZC0607-0025)联合资助
关键词
白云岩类型
岩相学
地球化学
白云岩化模式
雷口坡组
川西
Dolomite type
Petrography
Geochemistry
Dolomitization model
Leikoupo Formation
NW Sichuan Basin
