石油与天然气地质 ›› 2025, Vol. 46 ›› Issue (5): 1466-1484.doi: 10.11743/ogg20250506

• 油气地质 • 上一篇    

鄂尔多斯盆地志丹地区延长组长7—长9油层组深水重力流沉积特征及含油性

陈伟涛1,2(), 赵靖舟1,2(), 高振东3, 李哲1,2, 孟选刚3, 闫新智3, 董旭3   

  1. 1.西安石油大学 地球科学与工程学院,陕西 西安 710065
    2.陕西省油气成藏地质学重点实验室,陕西 西安 710065
    3.延长油田股份有限公司,陕西 延安 716000
  • 收稿日期:2025-06-11 修回日期:2025-08-06 出版日期:2025-10-30 发布日期:2025-10-29
  • 通讯作者: 赵靖舟 E-mail:3218828010@qq.com;jzzhao@xsyu.edu.cn
  • 第一作者简介:陈伟涛(2002—),男,硕士研究生,地质资源与地质工程。E‑mail: 3218828010@qq.com
  • 基金项目:
    国家科技重大专项(2016ZX05050)

Characteristics and oil-bearing properties of deep-water gravity-flow deposits in the 7th-9th oil groups of the Yanchang Formation, Zhidan area, Ordos Basin

Weitao CHEN1,2(), Jingzhou ZHAO1,2(), Zhendong GAO3, Zhe LI1,2, Xuangang MENG3, Xinzhi YAN3, Xu Dong3   

  1. 1.School of Earth Sciences and Engineering,Xi’an Shiyou University,Xi’an,Shaanxi 710065,China
    2.Shaanxi Key Laboratory of Petroleum Accumulation Geology,Xi’an,Shaanxi 710065,China
    3.Yanchang Oil Field Co. ,Ltd. ,Yan’an,Shaanxi 716000,China
  • Received:2025-06-11 Revised:2025-08-06 Online:2025-10-30 Published:2025-10-29
  • Contact: Jingzhou ZHAO E-mail:3218828010@qq.com;jzzhao@xsyu.edu.cn

摘要:

基于鄂尔多斯盆地志丹地区15口取心井的厘米级岩心精细描述、117口取样井的粒度分析数据、11口井的薄片鉴定结果以及23口试油井的日产油资料,系统论证了该地区三叠系延长组长7—长9油层组(长7—长9)的深水重力流沉积特征及其对油气分布的控制作用。研究结果表明:①研究区主要发育砂质碎屑流、浊流和滑动-滑塌3种深水重力流沉积类型,并以砂质碎屑流沉积为主。②砂质碎屑流沉积发育厚层块状砂岩,可见泥岩撕裂屑和泥包砾构造,分选与磨圆较好,粒度累积概率曲线表现为偏粗态的短尾两段式或一段式,粒径略粗于浊流沉积砂岩;浊流沉积发育不完整的鲍马序列,可见火焰状构造和底模构造,单砂层厚度小,砂岩粒度累积概率曲线主要为偏细的一段式;滑动-滑塌沉积以包卷层理、变形构造和同沉积阶梯状断层为典型特征。③储层物性与含油性分析表明,砂质碎屑流沉积砂体的物性总体优于浊流沉积,含油级别以油斑-油浸为主,含油饱和度较高,试油井日产油量也更大;而浊流沉积砂体含油性相对较差,以油斑-油迹为主,表明砂质碎屑流沉积砂体比浊流沉积砂体更有利于油气富集和产出。综合认为,鄂尔多斯盆地志丹地区三叠系延长组长7—长9普遍发育的砂质碎屑流沉积是研究区最有利的含油砂体沉积类型,应作为下一步油气勘探的重要靶区。

关键词: 砂质碎屑流沉积, 浊流沉积, 深水重力流沉积, 控油性, 沉积砂体, 延长组, 志丹地区, 鄂尔多斯盆地

Abstract:

Based on the centimeter-scale characterization of cores from 15 cored wells, grain size analyses of 117 sampled wells, observations of thin sections from 11 wells, and production test data from 23 wells, we systematically investigate the characteristics of deep-water gravity-flow deposits in the 7th‒9th oil groups of the Triassic Yanchang Formation (also referred to as the Chang 7‒9 oil groups) in the Zhidan area, Ordos Basin, as well as their controlling effects on hydrocarbon distribution. The results indicate that the study area primarily exhibits three types of deep-water gravity-flow deposits: sandy debris-flow deposits, turbidity current deposits, and slide-slump deposits, with the first type predominating. The sandy debris-flow deposits contain thick-bedded massive sandstones, with rip-up clasts and mud-coated intraclasts observed. They are generally well sorted and rounded, and their grain-size cumulative probability curves show short-tailed two-segment or one-segment patterns with a coarse-skewed distribution, exhibiting slightly coarser grains than those observed in the turbiditic sandstones. The turbidity current deposits feature incomplete Bouma sequences, displaying flame structures, sole marks, and small single-layer sand thicknesses. Their grain-size cumulative probability curves primarily show a fine-skewed one-segment pattern. The slide-slump deposits are typically characterized by the presence of convolute beddings, deformation structures, and synsedimentary stepped faults. Analyses of reservoir properties reveal that the sandy debris-flow deposits generally possess better physical properties than the turbidity current deposits. Furthermore, the oil-bearing grades of the sandy debris-flow deposits are dominated by oil stains to oil immersion, resulting in relatively high oil saturation and high daily oil production during production tests. In contrast, the turbidity current deposits exhibit poorer oil-bearing properties, primarily limited to oil stains to oil traces. These findings suggest that the sandy debris-flow deposits are more favorable to hydrocarbon enrichment and production than the turbidite-flow counterparts. Overall, the comprehensive analysis indicates that within the Chang 7‒9 oil groups, Zhidan area, Ordos Basin, the widely distributed sandy debris-flow deposits represent the most favorable oil-bearing sand body type and should therefore be prioritized as significant targets for future hydrocarbon exploration.

Key words: sandy debris-flow deposits, turbidity current deposits, deep-water gravity-flow deposits, control on oil-bearing property, Sedimentary Sandbody, Yanchang Formation, Zhidan area, Ordos Basin

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