威林斯頓盆地奥陶系白云岩储层同位素与成岩作用分析

ANALYSIS OF ISOTOPES AND DIAGENESIS OF ORDOVICIAN DOLOMITE RESERVOIR IN THE WILLISTON BASIN

李伟 蒲仁海 卿海若

Li Wei Pu Renhai Qing Hairuo

中国地质大学, 资源学院, 武汉, 430074 2. 中国石化, 中原石油勘探局钻采处, 河南, 濮阳, 457001 3. 西北大学, 地质系, 西安, 710069 4. 里加纳大学地质系, 里加纳, 萨斯克切温省, SKS4S0A2, 加拿大

Faculty of Earth Resources, China University of Geosciences, Wuhan, Hubei 430074, China 2. Drilling and Oil Production Engineering Department, Zhougyuan Petroleum Exploration Bureau, SINOPEC, Puyang, Henan 457001, China 3. Department of Geology, Northwest University, Xi'an, Shaanxi, 710069, China 4. Department of Geology, University of Regina, Regina, Saskatchewan, SK S4S 0A2, Canada,

威林斯顿(Williston)盆地上奥陶统红河群灰岩由于不同期次的白云岩化作用,形成了4种不同产状类型的白云石:纹层状微晶白云石、生物钻孔充填白云石,基质白云石、马鞍状白云石,只有基质白云石因具晶间孔而成为储层。4种白云石的氧、碳、锶同位素组成均与晚奥陶世的海水同位素组成有较大区别。岩石学和地化研究表明,前2种白云石的白云岩化流体应来自晚奥陶世海水,但今天的同位素组成反映了后期的改造或重构;储层白云石形成的温度稍高,时间可能稍晚,白云岩化流体可能来源于志留纪海水、或寒武—早中奥陶世海水、或深部热液;马鞍状白云石的形成应与深部热液有关。白云岩化成层状发生可能与薄的富含有机质的Kukersite页岩有关。

As a result of different stages of dolomitization,four types of dolomite rocks occurred in the Upper Ordovician Red River limestones of Williston Basin.Within the four types of dolomite rocks that are laminated micro-crystalline dolomite,burrow filled dolomite,matrix dolomite and saddle dolomite,only the matrix dolomite serves as reservoir with inter-crystalline pores.The composition of oxygen,carbon,and strontium isotopes of the four dolomites are obviously different from that of the isotopes of Late Ordovician marine water.Petrology and geochemistry study shows that dolomitization fluid flows of the former two dolomite rocks should come from Late Ordovician marine water,but today's their isotope composition reflect lateral rebuilding or modification.Reservoir dolomite rocks formed at a slightly higher temperature,and a rather later stage,and their fluid flows of dolomitization might come from marine water of Silurian or Cambrian-Middle Ordovician epoch or from thermal fluid in depth.The formation of saddle dolomites should be associated with deep thermal fluids.Occurrences of dolomitization along certain horizons are probably related to several thin layers of Kukersite shale that contains substantial organic materials in this area.

https://doi.org/10.11781/sysydz200901087