石油与天然气地质 ›› 2019, Vol. 40 ›› Issue (6): 1270-1280.doi: 10.11743/ogg20190611

• 油气地质 • 上一篇    下一篇

碳酸盐胶结物形成机制及其对渤海海域C12和Q17构造中生界碎屑岩储层的影响

卢欢, 徐长贵, 王清斌, 杜晓峰, 刘晓健   

  1. 中海石油(中国)有限公司 天津分公司, 天津 300450
  • 收稿日期:2018-03-21 修回日期:2019-07-23 出版日期:2019-12-28 发布日期:2019-10-15
  • 通讯作者: 徐长贵(1971-),男,博士、教授级高级工程师,石油地质。E-mail:xuchg@cnooc.com.cn。 E-mail:xuchg@cnooc.com.cn
  • 作者简介:卢欢(1988-),女,硕士、工程师,沉积储层。E-mail:luhuan@cnooc.com.cn。
  • 基金资助:
    中国海洋石油总公司科技重大项目(CNOOC-KJ125ZDXM07LTD-TJ-02);国家科技重大专项(2011ZX05023-001-004)。

Genetic mechanism of carbonate cements and its impact on the Mesozoic clastic reservoir quality of the C12 and Q17 structures,Bohai Sea Area

Lu Huan, Xu Changgui, Wang Qingbin, Du Xiaofeng, Liu Xiaojian   

  1. Tianjin Branch of CNOOC, Tianjin 300450, China
  • Received:2018-03-21 Revised:2019-07-23 Online:2019-12-28 Published:2019-10-15

摘要: 采用薄片鉴定、X-衍射、扫描电镜、元素分析、盆模软件和激光微区碳氧同位素等分析手段,对C12和Q17构造碳酸盐胶结类型、赋存状态、不同期次碳酸盐胶结物形成机理及其对储层物性的影响进行了对比研究。结果表明,碳酸盐胶结物的差异导致了储层物性的差异,而碳酸盐胶结物的成因和分布主要受埋藏条件、淋滤作用、构造条件和成岩环境差异4个因素的影响。C12构造碳酸盐胶结物含量高,早期和晚期胶结物充填孔隙,且早期胶结物后期未发生溶蚀,仅在中生界顶部不整合面附近发育次生孔隙。这是由于C12构造受反复深埋藏、封闭成岩环境、辫状河的强烈蒸发环境以及早期断层活动的构造条件影响,导致本区碳酸盐胶结强烈,储层致密。Q17构造碳酸盐胶结也较为普遍,但仅在局部细粒砂岩段存在早期胶结物富集段,而在原始沉积条件好的厚层粗砂岩段碳酸盐本身含量低,或发生早期碳酸盐溶蚀,并出现零星铁白云石胶结,物性相对较好。这是由于Q17构造为浅埋藏、开放的成岩环境和断层持续活动的构造条件,淋滤作用影响的范围广、深度大。而晚期铁白云石的出现,与地层水流体活动、油气侵位有关。根据这一现象,提出了差异成岩作用的观点,并从宏观构造和微观成岩的角度进行了探讨。

关键词: 淋滤作用, 成岩作用, 埋藏条件, 差异成岩, 碳酸盐胶结, 构造环境, 中生界, 渤海海域

Abstract: Carbonate cements were pervasively developed in deep clastic strata of the Mesozoic formations in the Bohai Bay Basin.Based on results through thin section identification,X-ray diffraction,Scanning Electron Microscopy (SEM),elements analysis,and numerical basin modeling and laser micro-sampling analysis for carbon and oxygen isotopes,we made a comparative study on the types,occurrences,and genetic mechanisms of carbonate cements of various periods,and their impacts on reservoir physical properties in the C12 and Q17 structures.The results show that the differences of carbonate cements of the two structures have led to different reservoir physical properties,and the generation and distribution of carbonate cements were mostly under the control of burial period,leaching,tectonic conditions,and diagenetic settings.The C12 structure features high content of carbonate cements,and its reservoir pores are filled with both early and later generated carbonate cements.Furthermore,the cements of early generation experienced no dissolution at later stages,while secondary pores developed only near the top Mesozoic unconformity.The reason lies in the impact of repeated deep burial processes,sealing diagenetic conditions,and intensive evaporation of the braided rivers,as well as the early faulting,which resulted in the intense carbonate cementation and then the initiation of reservoir tightening in the C12 structure.In comparison,the Q17 structure is relatively good in reservoir physical properties.Although the carbonate cementation is also intensive in the structure,characterized by early-stage carbonate cement concentration in local intervals of fine-grained sandstones,the thick-bedded coarse-grained sandstone intervals of better original sediment facies have usually low carbonate content or experienced carbonate dissolution at early stages,resulting in sporadic cements of ferron dolomite.This is due to its shallow burial history,open diagenetic settings,continuous fault activities,and wide-spread leaching.The occurrence of ferron dolomite was associated with formation water flows and hydrocarbon charging on the sandstones.Based on these observations,we proposed a concept of differential diagenesis,and discussed its mechanism from both the macro-structure and micro-diagenesis perspectives.

Key words: leaching, diagenesis, burial condition, differential diagenesis, carbonate cementation, tectonic environment, Mesozoic, Bohai Sea

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