Acta Petrolei Sinica ›› 2025, Vol. 46 ›› Issue (8): 1517-1535,1627.DOI: 10.7623/syxb202508006

• PETROLEUM EXPLORATION • Previous Articles     Next Articles

Dolomite genesis of Ordovician Kelimoli Formation in western Ordos Basin

Bai Ying, Gao Jianrong, Zhao Zhenyu   

  1. PetroChina Research Institute of Petroleum Exploration and Development, Beijing 100083, China
  • Received:2024-09-04 Revised:2025-01-06 Published:2025-09-06

鄂尔多斯盆地西缘奥陶系克里摩里组白云岩成因

白莹, 高建荣, 赵振宇   

  1. 中国石油勘探开发研究院 北京 100083
  • 通讯作者: 白莹,女,1990年2月生,2017年获北京大学博士学位,现为中国石油勘探开发研究院高级工程师,主要从事沉积储层与地质勘探研究工作。Email:byshimmer@petrochina.com.cn
  • 作者简介:白莹,女,1990年2月生,2017年获北京大学博士学位,现为中国石油勘探开发研究院高级工程师,主要从事沉积储层与地质勘探研究工作。
  • 基金资助:
    中国石油长庆油田公司科学研究与技术开发项目(2023-KTSY-DO32)资助。

Abstract: This paper focuses on dolomite reservoirs of Ordovician Kelimoli Formation in western Ordos Basin. Through core observation and microscopic identification, combined with comprehensive geochemical analytical methods including isotopes, major and trace elements, fluid inclusion thermometry, and U-Pb isotopic dating, the paper clarifies the petrological characteristics of dolomites, reveals the genesis of dolomites, and establishes dolomitization model. The research results show as follows. (1)Based on the macroscopic distribution characteristics and microscopic grain morphology, the dolomites of Kelimoli Formation can be divided into finely-powder crystalline dolomite, laminated dolomite, residual structure fine grain dolomite, fine-medium grain dolomite A, fine-medium grain dolomite B, and medium-coarse porphyritic dolomite. (2)In the eastern restricted platform of western Ordos Basin, the laminated dolomite of Kelimoli Formation is affected by the quasi-contemporaneous microbial dolomitization, and its dolomitization fluid is from near-surface seawater. The finely-powder crystalline dolomite is originated from the quasi-contemporaneous evaporative pumping dolomitization, and its dolomitization fluid is from low-salinity evaporative seawater. In the central platform margin of western Ordos Basin, the dolomites of Kelimoli Formation are formed by quasi-contemporaneous reflux dolomitization and superimposed by shallow-medium burial-stage porewater dolomitization, where the residual structure fine grain dolomite, euhedral-subhedral fine-medium grain dolomite A, and anhedral fine-medium grain dolomite B are developed. Part of the fine-medium grain dolomite B developed near weathering crust in the east side of the platform margin zone is involved by the incorporation of meteoric water during diagenetic process. The medium-coarse porphyritic dolomite structurally associated with faults are developed on the central platform margin of western Ordos Basin, which corresponds to the medium-deep burial hydrothermal dolomitization involving marine-derived brines in the early period. (3)The dolomitization of Kelimoli Formation are mainly attributed to the quasi-contemporaneous evaporative pumping and reflux-seepage processes, followed by porewater dolomitization in shallow-medium burial period, hydrothermal dolomitization in medium-deep burial period, and early microbial dolomitization.

Key words: western Ordos Basin, Ordovician, Kelimoli Formation, dolomitization, reservoir

摘要: 以鄂尔多斯盆地西缘典型钻井中奥陶系克里摩里组白云岩储层为研究对象,通过岩心观察和岩石薄片鉴定,结合多种地球化学分析成果(同位素、主量/微量元素、流体包裹体测温及U-Pb同位素定年等),明确了白云岩的岩石学特征,揭示了白云岩成因,建立了白云石化模式。研究结果表明:①根据宏观分布特征和微观晶体形态,克里摩里组白云岩可分为粉晶—细晶白云岩、纹层白云岩、残余结构细晶白云岩、细晶—中晶白云岩A、细晶—中晶白云岩B和中晶—粗晶斑状白云岩。②在鄂尔多斯盆地西缘东部局限台地,克里摩里组的纹层白云岩受准同生期微生物白云石化作用影响,其白云石化流体为近地表海水;而粉晶—细晶白云岩形成于准同生期蒸发泵吸白云石化作用,其白云石化流体为低盐度蒸发海水。在盆地西缘中部台缘带,克里摩里组白云岩形成于准同生期的回流渗透作用并叠加了浅层—中层埋藏期孔隙水白云石化作用,对应发育残余结构细晶白云岩、自形—半自形细晶—中晶白云岩A和他形细晶—中晶白云岩B,其中,部分发育在台缘带东侧风化壳附近的细晶—中晶白云岩B在成岩过程中有大气淡水加入。盆地西缘中部台缘带还发育与断裂相关的中晶—粗晶斑状白云岩,该类白云岩形成于早期有海源卤水参与的中层—深层埋藏期热液白云石化作用。③准同生期蒸发泵吸白云石化作用与回流渗透白云石化作用是克里摩里组的主要白云石化模式,浅层—中层埋藏 期孔隙水白云石化作用、中层—深层埋藏期热液白云石化作用以及早期微生物白云石化作用为次要白云石化模式。

关键词: 鄂尔多斯盆地西缘, 奥陶系, 克里摩里组, 白云石化作用, 储层

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