查干凹陷下白垩统砂岩储层碳酸盐胶结物成岩期次及形成机理  

Carbonate cements in Lower Cretaceous Bayingebi sandstone reservoirs in Chagan Sag, Yin-e Basin: Formation phases and formation mechanisms

作　　者：魏巍[1,2] 朱筱敏[1,2] 国殿斌[1,3] 费李莹 苏惠[3] 蒋飞虎[3] 谈明轩[1,2] 吴陈冰洁 

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249 [2]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [3]中国石化中原油田分公司石油勘探开发研究院,河南濮阳457001 [4]中国石油新疆油田分公司勘探开发研究院勘探所,克拉玛依834000

出　　处：《地球化学》2015年第6期590-599,共10页Geochimica

基　　金：国家科技重大专项(2011ZX05001-002);国家自然科学基金(41272133)

摘　　要：通过矿物学、岩石学和地球化学方法,分析了查干凹陷下白垩统巴音戈壁组碎屑岩储层中多期碳酸盐胶结物的特征及成因机理。结果表明,根据碳酸盐胶结物的组分和结构,从矿物学和成岩序列的角度,可划分出三期胶结物类型,分别是Ⅰ期泥晶方解石、Ⅱ期含铁方解石,以及Ⅲ期的铁方解石、白云石及少量铁白云石。碳氧同位素研究表明,Ⅰ期泥晶方解石胶结物形成于常温常压中,主要从过饱和的碱性湖水介质中析出,形成于早成岩阶段A期,早于压实期,对孔隙的形成起到保存作用;Ⅱ期铁方解石形成于早成岩阶段B期-中成岩阶段A期,受控于埋藏过程中的水岩作用影响,其中的碳酸根来源于有机酸脱羧产生的CO_2,而Ca^(2+)和Fe^(3+)来自长石类颗粒的溶解和黏土矿物的转化,该期胶结物主要充填在残余原生粒间孔和各类次生溶孔中,对储层以破坏作用为主;Ⅲ期碳酸盐胶结物主要形成于中成岩阶段B期,成岩环境由弱酸向弱碱性转化,黏土矿物转化释放Mg^(2+)和Fe^(3+),其中Fe^(3+)被烃类还原成低价铁,为Ⅲ期含亚铁碳酸盐胶结物提供了充足来源,该期胶结物与Ⅱ期胶结物类似,对储层形成也属于"破坏型成岩作用"。By means of mineralogy, petrology and isotopic geochemistry, the geologic characteristics and diagenetic mechanisms of the multiphase carbonate cements in the Lower Cretaceous reservoir were investigated and discussed. Based on the composition, texture and occurrence states of these carbonate cements and their paragenetic sequences, three phases of carbonate cements, including calcite I, ferric calcite II, and dolomite and ankerite III, were recognized. C/O stable isotope characteristics indicate that calcite I is precipitated directly from the oversaturated alkaline water media under normal conditions, and is mainly formed in eogenetic A phase prior to compaction, which helps to protect porosity. Ferric calcite II is formed in eogenetic B phase to mesogenetic A phase, and its carbons are originated from CO2 released by decarboxylation of organic acid while its Ca2＋ and Fe3＋ ions are derived from dissolution of feldspar and clay mineral transformation. Carbonate cements II were distributed in calcite I and feldspar particles and serve to destroy pores of the reservoir rocks. Carbonate cements III are mainly formed in mesogenetic B phase where the diagenetic environment was changed from acidic to alkaline. As a result, Ca2＋, Mg2＋ and Fe2＋ ions were released from clay minerals and provide the sources for carbonate cements III. Furthermore, carbonate cements I show consolidation effect on primary porosity to improve the reservoir compressive resistance and prevent reservoir porosity. In contrast, carbonate cements II and III generally are filled in the remained primary pores and secondary pores to deteriorate the reservoir property.

关 键 词：下白垩统 巴音戈壁组 砂岩储层 碳酸盐胶结物 碳氧同位素 储层成岩 查干凹陷 

分 类 号：P59[天文地球—地球化学] P597.2[天文地球—地质学]