鄂尔多斯盆地天环拗陷中—上三叠统延长组油气资源丰富,勘探潜力巨大,但由于地处盆地西缘,构造活动复杂,断裂分布规律及控藏机制不明。基于岩芯、成像测井、裂缝面方解石C—O同位素及U-Pb同位素定年实验,对洪德地区长6~长8油层组断裂的...鄂尔多斯盆地天环拗陷中—上三叠统延长组油气资源丰富,勘探潜力巨大,但由于地处盆地西缘,构造活动复杂,断裂分布规律及控藏机制不明。基于岩芯、成像测井、裂缝面方解石C—O同位素及U-Pb同位素定年实验,对洪德地区长6~长8油层组断裂的发育特征、形成期次进行研究,并探讨了断裂对油气成藏的控制作用。研究表明:①洪德地区裂缝多集中在延长组下组合,以垂直和高角度的剪切缝为主,裂缝部分充填方解石与石英,可见明显过油痕迹;②裂缝走向以北东东—南西西向占绝对优势,近东西向次之,主要形成于早白垩世中期、早白垩世末期以及晚白垩世早期3期,对应的O同位素换算温度分别为115.39℃、139.83℃和153.55℃;③缝面方解石U-Pb同位素年龄表现为170.6±6.1 Ma、143±12 Ma、104±32 Ma 3期,北东东向主断裂的活动时期为中晚侏罗世—早白垩世,对应于燕山运动期二幕至三幕,与长8油藏的成藏期相吻合。综上分析认为,天环拗陷延长组断裂改善了低渗透储层的物性,起到沟通油源和运移通道的作用,促进了油气在远源砂体中运聚成藏。展开更多
To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D sei...To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D seismic and drilling data,and reservoir sections are thoroughly investigated.Guided by the theory of sequence stratigraphy,the progradational sequence stratigraphic framework of the Yanchang Formation is systematically constructed to elucidate new deposition mechanisms in the depressed lacustrine basin,and it has been successfully applied to the exploration and development practices in the Qingcheng Oilfield.Key findings are obtained in three aspects.First,the seismic progradational reflections,marker tuff beds,and condensed sections of flooding surfaces in the Yanchang Formation are consistent and isochronous.Using flooding surface markers as a reference,a progradational sequence stratigraphic architecture is reconstructed for the middle-upper part of Yanchang Formation,and divided into seven clinoform units(CF1-CF7).Second,progradation predominantly occurs in semi-deep to deep lake environments,with the depositional center not always coinciding with the thickest strata.The lacustrine basin underwent an evolution of“oscillatory regression-progradational infilling-multi-phase superimposition”.Third,the case study of Qingcheng Oilfield reveals that the major pay zones consist of“isochronous but heterochronous”gravity-flow sandstone complexes.Guided by the progradational sequence stratigraphic architecture,horizontal well oil-layer penetration rates remain above 82%.The progradational sequence stratigraphic architecture and associated geological insights are more consistent with the sedimentary infilling mechanisms of large-scale continental depressed lacustrine basins and actual drilling results.The research results provide crucial theoretical and technical support for subsequent refined exploration and development of the Yanchang Formation,and are expected to offer a reference for research and production practice in similar continental lacustrine basins.展开更多
文摘鄂尔多斯盆地天环拗陷中—上三叠统延长组油气资源丰富,勘探潜力巨大,但由于地处盆地西缘,构造活动复杂,断裂分布规律及控藏机制不明。基于岩芯、成像测井、裂缝面方解石C—O同位素及U-Pb同位素定年实验,对洪德地区长6~长8油层组断裂的发育特征、形成期次进行研究,并探讨了断裂对油气成藏的控制作用。研究表明:①洪德地区裂缝多集中在延长组下组合,以垂直和高角度的剪切缝为主,裂缝部分充填方解石与石英,可见明显过油痕迹;②裂缝走向以北东东—南西西向占绝对优势,近东西向次之,主要形成于早白垩世中期、早白垩世末期以及晚白垩世早期3期,对应的O同位素换算温度分别为115.39℃、139.83℃和153.55℃;③缝面方解石U-Pb同位素年龄表现为170.6±6.1 Ma、143±12 Ma、104±32 Ma 3期,北东东向主断裂的活动时期为中晚侏罗世—早白垩世,对应于燕山运动期二幕至三幕,与长8油藏的成藏期相吻合。综上分析认为,天环拗陷延长组断裂改善了低渗透储层的物性,起到沟通油源和运移通道的作用,促进了油气在远源砂体中运聚成藏。
基金Supported by the National Science and Technology Major Project(2017ZX05001)CNPC Technology Project(2023YQX20111).
文摘To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D seismic and drilling data,and reservoir sections are thoroughly investigated.Guided by the theory of sequence stratigraphy,the progradational sequence stratigraphic framework of the Yanchang Formation is systematically constructed to elucidate new deposition mechanisms in the depressed lacustrine basin,and it has been successfully applied to the exploration and development practices in the Qingcheng Oilfield.Key findings are obtained in three aspects.First,the seismic progradational reflections,marker tuff beds,and condensed sections of flooding surfaces in the Yanchang Formation are consistent and isochronous.Using flooding surface markers as a reference,a progradational sequence stratigraphic architecture is reconstructed for the middle-upper part of Yanchang Formation,and divided into seven clinoform units(CF1-CF7).Second,progradation predominantly occurs in semi-deep to deep lake environments,with the depositional center not always coinciding with the thickest strata.The lacustrine basin underwent an evolution of“oscillatory regression-progradational infilling-multi-phase superimposition”.Third,the case study of Qingcheng Oilfield reveals that the major pay zones consist of“isochronous but heterochronous”gravity-flow sandstone complexes.Guided by the progradational sequence stratigraphic architecture,horizontal well oil-layer penetration rates remain above 82%.The progradational sequence stratigraphic architecture and associated geological insights are more consistent with the sedimentary infilling mechanisms of large-scale continental depressed lacustrine basins and actual drilling results.The research results provide crucial theoretical and technical support for subsequent refined exploration and development of the Yanchang Formation,and are expected to offer a reference for research and production practice in similar continental lacustrine basins.
