石油与天然气地质 ›› 2025, Vol. 46 ›› Issue (5): 1392-1409.doi: 10.11743/ogg20250502

• 油气地质 • 上一篇    

鄂尔多斯盆地定边—富县地区延长组长8油层组致密油富集因素与富集模式

吴伟涛1,2,3(), 李天宇1, 闫新智4, 周凯4, 殷露1, 曹磊1,2,3   

  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.西安石油大学 油气资源智能地球物理探测陕西省高等学校重点实验室,陕西 西安 710065
    4.延长油田股份有限公司 勘探部,陕西 延安 716000
  • 收稿日期:2025-07-05 修回日期:2025-08-29 出版日期:2025-10-30 发布日期:2025-10-29
  • 第一作者简介:吴伟涛(1983—),男,博士、副教授、硕士研究生导师,油气成藏地质学、非常规油气地质与勘探。E-mail: wtwu@xsyu.edu.cn
  • 基金项目:
    延长油田股份有限公司科技攻关项目(YT11153FW0069)

Enrichment factors and patterns of tight oil in the 8th oil group of the Yanchang Formation, Dingbian-Fuxian area, Ordos Basin

Weitao WU1,2,3(), Tianyu LI1, Xinzhi YAN4, Kai ZHOU4, Lu YIN1, Lei CAO1,2,3   

  1. 1.School of Earth Sciences and Engineering,Xi’an Shiyou University,Xi’an 710065,China
    2.Key Laboratory of Hydrocarbon Accumulation of Shaanxi Province,Xi’an Shiyou University,Xi’an 710065,China
    3.Key Laboratory of Intelligent Geophysical Exploration for Oil and Gas Resources of Shaanxi Higher Education Institutions,Xi’an Shiyou University,Xi’an 710065,China
    4.Exploration Department of Yanchang Oilfield Co. ,Ltd. ,Yan’an Shaanxi 716000,China
  • Received:2025-07-05 Revised:2025-08-29 Online:2025-10-30 Published:2025-10-29

摘要:

多源供烃条件下的致密油富集规律研究是油气富集理论的重要内容。以鄂尔多斯盆地定边—富县地区延长组长8油层组(长8)致密油藏为研究对象,综合运用钻井、测井、岩心、薄片、地球化学、试油及试采等资料,系统评价了长7油层组(长7)张家滩页岩、长9油层组(长9)李家畔页岩以及长8泥页岩的烃源岩生烃潜力,明确了致密油藏的基本特征,探讨了不同成藏组合下的致密油富集因素,并建立了相应的富集模式。研究结果表明:①定边—富县地区发育长7、长9和长8等3套好-优质烃源岩,以长7底部张家滩页岩生烃潜力最优,总有机碳含量(TOC)平均值为6.1%,呈大面积分布;长9顶部李家畔页岩和长8泥页岩次之,TOC平均值分别为5.3%和3.9%,分布在甘泉—富县—志丹地区。②长8储层岩性为细砂岩和粉砂岩,其实测孔隙度主峰为4.0% ~ 12.0%,平均值为7.9%,实测渗透率主体为(0.10 ~ 0.40) × 10-3 μm2,中值为0.26 × 10-3 μm2,属于致密储层。该区致密砂岩油藏多呈透镜状、成带成群分布,表现出准连续聚集特征。③长81油层亚组(长81)的致密油油藏富集主要受长73油层亚组(长73)烃源岩供烃能力、源-储之间的薄泥岩厚度和强底板的封堵作用控制,成藏组合以“源上储下”类长73单源直接型最优,其次为“源夹储”类长73+长82油层亚组(长82)双源型组合,而“源夹储”类长73+长91油层亚组(长91)双源型组合较差。长82油藏的致密油富集则主要依赖于长91烃源岩、优质储层条件和盖层的封堵作用控制,其成藏组合以“源下储上”类长91单源直接型最好,其次为“源夹储”类长91+长82双源型组合。④长8油藏发育3种致密油富集模式,分别为定边—吴起地区的长81“强源-强封”高效型富集模式、甘泉—富县地区的长82“优源-优储-优盖”互补型富集模式和志丹地区的长8“多源-优储”协同型富集模式。旨在深化致密油富集理论的同时,有助于长8致密油的高效勘探与开发。

关键词: 富集因素, 富集模式, 致密油, 长8油层组, 延长组, 鄂尔多斯盆地

Abstract:

Research on tight oil enrichment patterns under the condition of multi-source hydrocarbon supply is a key component of hydrocarbon enrichment theory. This study examines tight oil reservoirs in the 8th oil group of the Yanchang Formation (also referred to as the Chang 8 oil group) in the Dingbian-Fuxian area, Ordos Basin. By integrating data from drilling, well logging, core observations, thin-section observations, geochemical analysis, well tests, and production tests, we systematically evaluate the hydrocarbon generation potential of source rocks including the Zhangjiatan shales of the Chang 7 oil group, Lijiapan shales of the Chang 9 oil group, and the shales of the Chang 8 oil group. Accordingly, the general characteristics of tight oil reservoirs are clarified, the factors for tight oil enrichment in different oil plays are discussed, and thereby corresponding tight oil enrichment patterns are built. The results indicate that the Dingbian-Fuxian area contains three suites of good to excellent source rocks: the Chang 7, Chang 8, and Chang 9 oil groups. The widespread Zhangjiatan shales at the bottom of the Chang 7 oil group, among others, exhibit the greatest hydrocarbon generation potential, with an average total organic carbon (TOC) content of 6.1%. They are followed by the Lijiapan shales at the top of the Chang 9 oil group and shales in the Chang 8 oil group, which have average TOC contents of 5.3% and 3.9%, respectively and are distributed in the Ganquan-Fuxian-Zhidan area. Reservoirs in the Chang 8 oil group are dominated by fine-grained sandstones and siltstones, with measured peak porosity ranging from 4% to 12% (average: 7.9%) and measured permeability from 0.10 × 10⁻³ μm² to 0.40 × 10⁻³ μm² (median: 0.26 × 10⁻³ μm²), establishing them as tight reservoirs. The tight-sandstone oil reservoirs in the area mostly show lenticular, zonal, and clustered distributions and are characterized by quasi-continuous accumulation. Shale tight oil enrichment in oil reservoirs in the 1st oil sub-group of the Chang 8 oil group (also referred to as the Chang 81 oil sub-group) is primarily controlled by the properties of the Chang 73 oil sub-group, including the hydrocarbon supply capacity of source rocks, the thickness of the thin mudstones between source rocks and reservoirs, and the sealing performance of the strong floor. In the Chang 81 oil sub-group, the single-source direct oil play in the Chang 73 oil sub-group, characterized by the configuration of upper source rocks and lower reservoirs, proves the most favorable, followed by the dual-source oil plays in the Chang 73 and 82 oil sub-groups, where reservoirs are sandwiched between source rocks. In contrast, the dual-source oil plays in the Chang 73 and 91 oil sub-groups, also characterized by reservoirs sandwiched between source rocks, represents the least favorable oil plays. Shale tight oil enrichment in the Chang 82 oil sub-group largely relies on the properties of the Chang 91 oil sub-group, including the hydrocarbon supply of source rocks, high-quality reservoir conditions, and the sealing performance of cap rocks. Within this oil sub-group, the single-source direct oil play in the Chang 91 oil sub-group, characterized by the configuration of upper reservoirs and lower source rocks, proves the most favorable. It is followed by the dual-source oil plays in the Chang 91 and 82 oil sub-groups, where reservoirs are again sandwiched between source rocks. Three distinct tight oil enrichment patterns are identified in the oil reservoirs of the Chang 8 oil group: (1) efficient enrichment pattern in the Chang 81 oil sub-group in the Dingbian-Wuqi area, driven by strong hydrocarbon supply from source rocks and high sealing performance; (2) complementary enrichment pattern in the Chang 82 oil sub-group in the Ganquan-Fuxian area, marked by the combination of excellent source rocks, high-quality reservoirs and cap rocks; and (3) synergistic enrichment pattern in the Chang 8 oil group in the Zhidan area, characterized by multiple hydrocarbon sources and high-quality reservoirs. This study aims to facilitate the efficient development and exploitation of tight oil in the Chang 8 oil group while advancing the tight oil enrichment theory.

Key words: enrichment factor, enrichment pattern, tight oil, Chang 8 oil group, Yanchang Formation, Ordos Basin

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