湖相碳酸盐岩去白云石化作用及其与储集性的关系——以济阳坳陷东营凹陷沙四段为例  

Dedolomitization of lacustrine carbonate rock and influence on reservoir property,Sha Ⅳ member of Dongying sag

作　　者：石砥石[1] 姜秀芳[2] 王全柱[3] 

机构地区：[1]中国石油大学(北京)资源与信息学院,北京102249 [2]中国科学院广州地球化学研究所,广东广州510640 [3]中国石化股份胜利油田分公司河口采油厂,山东东营257200

出　　处：《油气地质与采收率》2010年第6期16-19,共4页Petroleum Geology and Recovery Efficiency

基　　金：国家重大科技专项"渤海湾盆地精细勘探关键技术"(2008ZX05006)

摘　　要：湖相碳酸盐岩以层薄、分布面积广、局部富集高产为显著特点。对其成岩作用，特别是去白云石化作用机理进行研究，对认识该类储层、指导下步勘探开发部署具有重要意义。通过对方解石脉与白云石化的关系、锶同位素特征和流体包裹体特征等研究，认为在有机质成熟、烃类开始形成时产生大量的有机酸，满足了去白云石化所需要的酸性环境，在该环境中去白云石化流体与砂屑颗粒进行水一岩作用后，Ca^2＋取代Mg^2＋形成方解石。由于去白云石化作用，在砂屑间的残余粒间孔内沉淀形成微晶或巨晶状方解石，从而使储层内原生粒间孔堵塞、面孔率降低、孔隙类型由原生粒间孔转为以晶间微孔为主。通过多口井大量薄片观察和统计，去自云石化作用可使原生粒间孔隙降低15％～36％，对储层的形成起破坏作用。Lacustrine carbonate is characterized remarkably by thin layer,widely distribution,locally concentration and high-yielding.It is of great significance to study the mechanism of its diagenesis,especially its dedolomitization,for the understanding of this type of res-ervoir and the deployment on subsequent exploration and exploitation.Based on the analysis of relationship between calcite veins and dolomitization,Sr isotopic characteristics and fluid inclusion characteristics,it was concluded that,large amount of organic acid was generated when organic matter became mature and hydrocarbon began to generate accordingly,moreover,the acidic environment which is crucial for dedolomitization is formed as well,in which,calcite was generated as Ca2+ substituting Mg2+ due to water-rock interaction between dedolomitization fluid and psammitic grains.Due to the dedolomitization,microcrystal or macrocrystal calcite was precipitated within the residual intergranular pores between psammitic grains,and the primary intergranular pores in the reser-voir are blocked and sealed,resulting in the decreasing of surface porosity and intercrystalline micropores turning into the predomi-nant pore type instead of primary intergranular pores.According to the observation and statistics of large amount of rock thin section of several wells,the primary intergranular pores can be decreased by 15%-36% due to dedolomitization,which exerts great unfa-vorable effects on the reservoir.

关 键 词：去白云石化作用 锶同位素特征 流体包裹体特征 储集性 孔隙丢失 湖相碳酸盐岩 

分 类 号：TE112.221[石油与天然气工程—油气勘探]