石油与天然气地质 ›› 2025, Vol. 46 ›› Issue (5): 1367-1391.doi: 10.11743/ogg20250501

• 油气地质 • 上一篇    下一篇

鄂尔多斯盆地陕北地区三叠系延长组长7—长9油层组重力流沉积致密油富集条件与勘探潜力——兼论拗陷型湖盆的石油勘探范式

赵靖舟1,2(), 高振东3, 孟选刚3, 吴伟涛1,2, 白玉彬1,2, 曹磊1,2, 赵子龙1,2   

  1. 1.西安石油大学 地球科学与工程学院，陕西 西安 710065
    2.西安石油大学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:2025-08-01 修回日期:2025-09-16 出版日期:2025-10-30 发布日期:2025-10-29
  • 第一作者简介:赵靖舟（1962—），男，教授，油气成藏与非常规油气地质学。E‑mail： jzzhao@xsyu.edu.cn。
  • 基金项目:
    国家科技重大专项(2016ZX05050)

Geological conditions for tight oil enrichment and its exploration potential of gravity-flow deposits from the 7th to 9th oil groups of the Triassic Yanchang Formation， Ordos Basin： Discussion on the petroleum exploration paradigms of downwarped lacustrine basins

Jingzhou ZHAO1,2(), Zhendong GAO3, Xuangang MENG3, Weitao WU1,2, Yubin BAI1,2, Lei CAO1,2, Zilong ZHAO1,2   

  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 Shiyou University，Xi’an，Shaanxi 710065，China
    3.Yanchang Oil Field Co. ，Ltd. ，Yan’an，Shaanxi 716000，China
  • Received:2025-08-01 Revised:2025-09-16 Online:2025-10-30 Published:2025-10-29

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摘要：

鄂尔多斯盆地陕北定边—吴起—志丹—甘泉—富县一带延长组下组合（长7—长10油层组）是近年来延长油田重点勘探的地区和层系。通过对125口井、共计约2 115 m长的岩心观察，结合400余口井的粒度资料及系统的测井相分析，研究发现：①研究区长7—长9油层组广泛发育重力流沉积，并以砂质碎屑流沉积为主，其次为浊流沉积。②长7—长9油层组重力流沉积储层、烃源岩和封盖条件等均十分优越，致密油勘探潜力大，预测石油地质资源量约25 × 108 t。③源-储-封组合类型是控制研究区长7—长9油层组致密油成藏和富集的主要因素，并将研究区源-储-封组合划分为4类11种，其中源夹储型和源上储下型最为有利。④建立了适用于鄂尔多斯盆地延长组烃源岩特征的烃源岩评价新标准，研究区长7—长9油层组三套烃源岩均为优质烃源岩，以长7油层组为最好，其次为长9油层组和长8油层组烃源岩。⑤提出了基于油井产量分级、富集指数及其地质控制因素分析的甜点评价方法。⑥中国油气勘探范式正在发生重要转变，勘探对象由浅水沉积向深水重力流沉积的转变，是拗陷型湖盆油气勘探的重要趋势之一。⑦拗陷型湖盆重力流沉积成藏条件优越，特别是砂质碎屑流沉积砂体规模大、物性好，含油性优于浊流沉积，且资源潜力大，应作为深水重力流沉积石油勘探开发的主要目标。

关键词: 富集条件, 勘探范式, 重力流, 致密油, 延长组, 拗陷型湖盆, 鄂尔多斯盆地

Abstract:

The lower oil play， namely the 7th to 10th oil groups， of the Yanchang Formation in the Dingbian-Wuqi-Zhidan-Ganquan-Fuxian area of northern Shaanxi within the Ordos Basin， has emerged as a key target for the exploration of the Yanchang oilfield in recent years. In this study， we investigate this oil play by integrating observations of approximately 2 115 meters of cores from 125 wells， grain-size data from more than 400 wells， and a systematic analysis of logging facies. The results indicate that gravity-flow deposits are widely distributed across the 7th to 9th oil groups of the Yanchang Formation （also referred to as the Chang 7‒9 oil groups） in the study area. These deposits are dominated by sandy debris-flow deposits， followed by turbidity-current deposits. The gravity-flow deposits exhibit excellent source rock-reservoir-cap rock conditions and hold great potential for tight oil exploration， with possible petroleum initially-in-place （PIIP） estimated at about 2.5 × 109 t. The type of source rock-reservoir-seal assemblages is identified as a major factor controlling the accumulation and enrichment of tight oil in the Chang 7‒9 oil groups in the study area， and theses assemblages therein can be classified into four categories with a total of 11 specific types. The configurations featuring reservoir interbedded with source rocks and vertically-stacked source and reservoir， among others， represent two most favorable assemblage categories for tight oil accumulation. Moreover， new evaluation criteria for source rocks of the Yanchang Formation in the Ordos Basin are established. These criteria highlight the predominance of excellent source rocks across the Chang 7‒9 oil groups in the study area. Within this interval， the Chang 7 oil group is recognized as containing the most favorable source rocks， followed by the Chang 9 and Chang 8 oil groups. Furthermore， a new sweet spot assessment method is proposed based on the grading of well production， and the analysis of enrichment factor （EF） and associated geological controlling factors. China’s hydrocarbon exploration paradigms are undergoing significant shifts， with a shift from shallow-water deposits to deep-water gravity-flow deposits representing a major trend in the hydrocarbon exploration of downwarped lacustrine basins. Specifically， gravity-flow deposits exhibit favorable hydrocarbon accumulation conditions in downwarped lacustrine basins. Particularly， sandy debris-flow deposits exhibit a larger scale， favorable physical properties， and better oil-bearing properties compared to the turbidity-current deposits， establishing them as a major target for petroleum exploration and exploitation of deep-water gravity-flow deposits.

Key words: enrichment condition, exploration paradigm, gravity flow, tight oil, Yanchang Formation, downwarped lacustrine basin, Ordos Basin

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