石油与天然气地质2025，Vol.46Issue(5)：1446-1465,20.DOI:10.11743/ogg20250505
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
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
摘要
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.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Key words
sandy debris flow reservoir/diagenetic evolution/gravity flow tight sandstone/Chang 7 oil layer group/Fuxian area/Ordos Basin分类
能源科技引用本文复制引用
张军,白玉彬,张海,赵靖舟,徐宁..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[J].石油与天然气地质,2025,46(5):1446-1465,20.基金项目
国家自然科学基金项目(42372155) （42372155）
陕西省自然科学基础研究计划项目(2025JC-YBQN-437) （2025JC-YBQN-437）
陕西省教育厅专项科研计划项目(24JK0603) （24JK0603）
西安石油大学研究生创新基金项目(YCX2412017). （YCX2412017）
