石油与天然气地质 ›› 2025, Vol. 46 ›› Issue (5): 1446-1465.doi: 10.11743/ogg20250505

• 油气地质 • 上一篇    

鄂尔多斯盆地富县地区三叠系延长组长7油层组深水重力流致密砂岩成因与分布

张军1,2(), 白玉彬1,2(), 张海3, 赵靖舟1,2, 徐宁4   

  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 717000
    4.延长油田股份有限公司 富县采油厂，陕西 延安 727500
  • 收稿日期:2025-04-27 修回日期:2025-08-19 出版日期:2025-10-30 发布日期:2025-10-29
  • 通讯作者: 白玉彬 E-mail:zj1012311730@126.com;baiyubin@xsyu.edu.cn
  • 第一作者简介:张军（1998—），男，硕士研究生，致密油（页岩油）成藏与地质评价。E-mail： zj1012311730@126.com。
  • 基金项目:
    国家自然科学基金项目(42372155);陕西省自然科学基础研究计划项目(2025JC-YBQN-437);陕西省教育厅专项科研计划项目(24JK0603);西安石油大学研究生创新基金项目(YCX2412017)

Origin and distribution of deep-water gravity-flow tight-sand reservoirs in the oil layer group of the 7th member of the Yanchang Formation， Fuxian area， Ordos Basin

Jun ZHANG1,2(), Yubin BAI1,2(), Hai ZHANG3, Jingzhou ZHAO1,2, Ning XU4   

  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 717000，China
    4.Fuxian Oil Production Plant of Yanchang Oil Field Co. ，Ltd. ，Yan’an，Shaanxi 727500，China
  • Received:2025-04-27 Revised:2025-08-19 Online:2025-10-30 Published:2025-10-29
  • Contact: Yubin BAI E-mail:zj1012311730@126.com;baiyubin@xsyu.edu.cn

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摘要：

鄂尔多斯盆地富县地区三叠系延长组长7油层组广泛发育深水重力流储层，但储层致密化机理尚不明确。综合运用X射线衍射（XRD）、物性分析、粒度分析、铸体薄片、扫描电镜（SEM）、高压压汞和油层解释等测试方法和技术，分析了长7油层组重力流储层的基本特征，并重点探讨了其储层致密化机理和分布规律。结果表明：①长7油层组岩性以细粒长石砂岩和岩屑长石砂岩为主，孔隙度介于0.50% ~ 18.40%，平均值为8.44%，渗透率介于（0.01 ~ 14.10） × 10-3 µm²，平均值为0.36 × 10-3 µm²。砂质碎屑流储层孔隙结构最优，物性最佳，平均孔隙度为8.94%，渗透率为0.39 × 10-3 µm²；滑动-滑塌储层次之，平均孔隙度为8.28%，渗透率为0.40 × 10-3 µm²；浊积岩储层最差，平均孔隙度为6.90%，渗透率为0.28 × 10-3 µm²。②重力流储层粒度细、分选性差、杂基含量高，抗压实能力弱，碳酸盐胶结物含量高，是导致储层致密化的主要原因，后期溶蚀作用较弱，未能改变长7油层组储层整体致密的面貌。③长7油层组整体处于中成岩A期。期间经历1期油气充注，包裹体均一温度主要为110 ~ 120 ℃，油气大规模成藏发生于早白垩世晚期（120 ~ 105 Ma）。④长7油层组砂质碎屑流发育Ⅰ类优质储层，砂质碎屑流 + 浊流区发育Ⅱ类中等储层，而浊流发育Ⅲ类差储层。综合分析认为，长71和长72油层亚组砂质碎屑流发育层段是深水致密砂岩油藏勘探开发的有利区。

关键词: 砂质碎屑流储层, 成岩演化, 重力流致密砂岩, 长7油层组, 富县地区, 鄂尔多斯盆地

Abstract:

Deep-water gravity flow reservoirs are widely distributed in the oil layer group of the 7th member of the Yanchang Formation （also referred to as the Chang 7 oil layer group） in the Fuxian area， Ordos Basin. However， the tightening mechanisms of these reservoirs remain unclear. Using test methods and technologies including X-ray diffraction （XRD）， petrophysical analysis， granulometry， casting thin section observation， scanning electron microscopy （SEM）， high-pressure mercury intrusion porosimetry， and oil layer interpretation， we analyze the fundamental characteristics of gravity flow reservoirs in the Chang 7 oil layer group， highlighting the tightening mechanisms and distribution patterns of the reservoirs. The results indicate that the Chang 7 oil layer group consists primarily of fine-grained feldspathic sandstone and lithic feldspathic sandstone， with a porosity ranging from 0.5% to 18.4% （average： 8.44%） and a permeability from 0.01 × 10-3 µm² to 14.1 × 10-3 µm² （average： 0.36 × 10-3 µm²）. Within this member， sandy debris flow reservoirs exhibit the most favorable pore structures and the best physical properties， with an average porosity of 8.94% and a permeability of 0.39 × 10-3 µm². Slide-slump reservoirs come the second， which have an average porosity of 8.28% and a permeability of 0.40 × 10-3 µm². In contrast， turbidite reservoirs show the poorest physical properties， with an average porosity of 6.90% and a permeability of 0.28 × 10-3 µm². The gravity flow reservoirs are poorly sorted and characterized by fine grain sizes， high matrix content， and weak resistance to compaction. Furthermore， these reservoirs exhibit high carbonate cement content， which is identified as the primary reason for reservoir tightening. Week dissolution in the late stage failed to change the overall tightness of reservoirs in the Chang 7 oil layer group. Diagenetic evolution places the Chang 7 Oil layer group in the meso-diagenetic stage A， having undergone a single-phase hydrocarbon charging， with the homogenization temperatures of inclusions ranging primarily from 110 ℃ to 120 ℃. Large-scale hydrocarbon accumulation in this oil layer group occurred during the late Early Cretaceous （105 ~ 120 Ma）. In the Chang 7 oil layer group， high-quality Class Ⅰ reservoirs occur in sandy debris flow deposits. In contrast， moderate Class Ⅱ reservoirs are found in intervals consisting of sandy debris flow and turbidity current deposits， and poor Class Ⅲ reservoirs appear in turbidity current deposits. The comprehensive analysis suggests that the section with sandy debris flow deposits in the 1st and 2nd oil layer sub-groups represent play fairways for the exploration and exploitation of deep-water tight-sand oil reservoirs.

Key words: sandy debris flow reservoir, diagenetic evolution, gravity flow tight sandstone, Chang 7 oil layer group, Fuxian area, Ordos Basin

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