摘要
针对古城地区奥陶系主力产气层鹰山组下段的白云岩储层,通过系统岩心、薄片鉴定和取样测试,研究储层段岩石学特征和地球化学特征,恢复其原岩结构和沉积相带;研究区内成岩流体的性质、期次、活动范围、储集空间的结构差异性和成岩演化路径的差异性。薄片鉴定揭示鹰山组三段白云岩主体为细晶白云岩、粉晶白云岩和中晶白云岩;不同层段的白云岩基岩和灰岩的稀土元素总量ΣREE总体较低,二者稀土元素分配模式相似,具有LREE相对富集、HREE相对亏损,Ce负异常,La正异常的特征,少量的细晶白云岩基岩Eu轻微正异常;鹰三段白云岩、灰岩和蓬莱坝组粉晶白云岩δ^(18) O值主体区间为-8‰^-3.5‰,δ^(13) C值主体区间为-2‰~0‰,显示出鹰三段白云岩成岩环境主体是中温环境,蓬莱坝组细晶白云岩和鹰山组四段(鹰四段)灰岩8个样品所测得的δ^(18) O值区间为-9.1‰^-8‰,显示出其成岩环境经受过较高温影响。研究区至少有5类流体对储层发育有影响,依次为:早期淡水、有机质、硅质流体、晚期白云石化流体和含Ca流体。台地边缘的灰岩浅滩相沉积物是鹰下段(鹰三段和鹰四段)储层发育的物质基础,中等程度的白云石化作用形成早期的晶间孔,残留的灰质成分在晚期埋藏条件下进一步被溶蚀,此过程是孔隙型储层的发育机制;研究区NE向走滑断裂是硅质流体运移的主要通道,埋藏环境下,从深部上涌的富Si热液通过循环增热本地流体,形成中等温度范围的热液,其溶蚀作用大于充填作用,沿断裂和高孔渗地层溶蚀白云岩基岩形成孔洞,随后的富Mg热流体活动对孔洞形成也有积极作用,此过程是裂缝—孔洞型储层的发育机制。
Based on cores and slices examination after systematic sampling,rock petrological and geochemical characteristics of the carbonate reservoir of the Lower Ordovician Yingshan Group in Gucheng area,Tarim Basin are studied.Thin section analysis reveals the third segment dolomites of Yingshan Group mainly consist of silty dolomites,fine dolomites and medium dolomites.The original rock textures of some dolomites are recovered and Yingshan Group is interpreted as platform edge shallow facies.Matrix dolomites and limestones of the different segments within the Yingshan Group have similar REE compositions and REE distribution patterns：theirΣREE is generally low,with relative enrichment in LREE,relative depletion in HREE,negative Ce anomalies and positive La anomalies.Additionally several fine dolomite samples have slightly positive Eu anomalies.The δ^18 O values of dolomites and limestones in the Yingshan Group and silty dolomites in the Penglaiba Group mainly range from-8‰ to-3.5‰,and δ^13 C values mainly range from-2‰ to 0‰.Integration of all data indicates that diagenetic environment of dolomites in Yingshan Group mainly belong to moderate temperature.However,theδ^18 O values of 2 Penglaiba Group dolomite samples and 5 limestone samples in the fourth segment of Yingshan Group range from-9.1‰ to-8‰,which indicates rock within these two groups once was altered by hydrothermal fluids during the late diagenetic process.Diagenetic fluid properties,phase and range of motion are identified in the area.There were at least 5 types of fluids which could affect reservoir development.They are early fresh water,organic matter,siliceous fluid,late dolomitization fluid and late calcium fluid orderly.On the basis of platform edge shallow facies,moderate dolomitization provided intercrystalline space of reservoir during early diagenesis,and calcareous residues were dissolved furtherly in the late burial conditions.This process is the development mechanism of porosity reservoir.On the other hand,the upwelling Si-rich hydrothermal fluid heated the local fluid circularly along the NE trending strike slip faults and porous formations,such moderately hydrothermal fluids could dissolve the matrix dolomites.Subsequently magniferous fluids impacted the matrix dolomites in the same way.This process is the development mechanism of fracture vug reservoir.
作者
周波
曹颖辉
齐井顺
黄世伟
刘策
贾进华
陈秀艳
Zhou Bo;Cao Ying-hui;Qi Jing-shun;Huang Shi-wei;Liu Ce;Jia Jin-hua;Chen Xiu-yan(PetroChina Research Institute of Petroleum Exploration ＆ Development,Beijing 100083,China;Exploration Department,Daqing Oil field Company Ltd.,PetroChina,Daqing 163000,China)
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2018年第6期773-783,共11页
Natural Gas Geoscience
基金
国家科技重大专项"下古生界-前寒武系碳酸盐岩油气成藏规律
关键技术及目标评价"(编号:2016ZX05004)资助
关键词
塔里木盆地
古城地区
下奥陶统
白云岩储层
发育机制
Tarim Basin
Gucheng area
Lower Ordovician
Dolomite reservoir
Development mechanism
