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高校地质学报 ›› 2021, Vol. 27 ›› Issue (5): 526-535.DOI: 10.16108/j.issn1006-7493.2020084

• 渤海海域中深层油气精细勘探开发理论技术专栏 • 上一篇    下一篇

莱州湾凹陷北洼沙三段砂岩碳酸盐胶结物特征及地质意义

王 彤1,2,朱筱敏1,2*,刘 宇1,2,3,郭 诚4   

  1. 1. 中国石油大学(北京)地球科学学院,北京 102249;
    2. 油气资源与探测国家重点实验室,北京 102249;
    3. 中国石油 新疆油田分公司勘探开发研究院,克拉玛依 834000;
    4. 中海石油(中国)有限公司 天津分公司,天津 300459

  • 出版日期:2021-10-20 发布日期:2021-10-27

Characteristics and Significance of Carbonate Cements in Member 3 of Shahejie Formation in the Northern Subsag of Laizhouwan Sag

WANG Tong1,2,ZHU Xiaomin1,2*,LIU Yu1,2,3,GUO Cheng4   

  1. 1. College of Geoscience, China University of Petroleum, Beijing 102249, China;
    2. State Key Laboratory of Petroleum Resources and Prospecting, Beijing 102249, China;
    3. Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Karamay 834000, China;
    4. Tianjin Branch of CNOOC Ltd., Tianjin 300459, China
  • Online:2021-10-20 Published:2021-10-27

摘要: 碳酸盐胶结特征不仅反映了成岩环境,而且可表明成岩阶段及其对储层质量的影响。综合运用岩石学、矿物学和地球化学等方法,对莱州湾凹陷北洼古近系沙三段砂岩中碳酸盐胶结物的分布规律、形成环境、物质来源、沉淀温度以及其对储层物性的影响进行了系统研究。结果表明:沙三段发育两期碳酸盐胶结物,分别为形成于埋藏早期的菱铁矿和隐晶方解石,以及成岩作用中后期形成的方解石、白云石、铁方解石和铁白云石,其中方解石是最主要的胶结物类型。碳酸盐胶结物形成于埋藏作用中后期的高盐度流体环境,与有机质脱羧作用相关,有机碳是最主要的碳来源,Ca2+是长石的溶蚀和粘土矿物转化的产物。包裹体均一温度研究结果表明,碳酸盐胶结物在油气充注的同时或之后形成。形成于成岩作用早期的碳酸盐胶结物在一定程度上增强了岩石骨架颗粒固结和抗压实能力,同时也是后期有机酸溶蚀的主要对象,对储层物性起到促进作用;溶蚀作用之后形成的碳酸盐胶结物占据粒间孔隙和部分溶蚀孔隙,对储层物性起到破坏作用。

关键词: 碳酸盐胶结物, 碳、氧同位素, 胶结物形成机理, 古近系, 沙三段, 莱州湾凹陷

Abstract: Based on the analyses of petrology, mineralogy, and geochemistry, this paper has studied the distribution, forming environment, material sources, precipitation temperature, and their impacts on the reservoir physical properties for Member 3 of Shahejie Formation sandstones in the northern subsag of Laizhowan sag. Results show that two periods of the cements are developed in the member: the carbonate cements in the early period are siderite and cryptocrystalline calcite, and the carbonate cements in late period are calcite, dolomite, ferrocalcite and ferrodolomite. Calcite is the main type of carbonate cements. The carbonate cements are formed in the high salinity environment in the middle and late stage of diagenesis, resulted from decarboxylation of organic acid. Organic carbon is the main carbon source. Feldspar dissolution and clay mineral transformation  provide abundant calcium for the carbonate development. The study of homogenization temperature of fluid inclusions indicates that carbonated cements are formed at or after the hydrocarbon filling. The carbonate cements formed in the early diagenesis can enhance the consolidation and compaction resistance ability for the rock skeleton particles to a certain degree; meanwhile they can also become the main corroded objects for the late organic acids and possess positive and improving effects on the physical properties of the reservoirs. The cements formed after dissolution often occupy the intergranular partially dissolved pores, so they are destructive to the physical properties of the reservoirs.

Key words: carbonate cement, carbon and oxygen isotopes, formation mechanism, Paleogene, Member 3 of Shahejie Formation;
Laizhouwan sag

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