鄂尔多斯盆地西缘冲断带中段奥陶系克里摩里组高能滩隐伏构造成藏潜力

Hydrocarbon accumulation potential of concealed structures in the high-energy shoals of the Ordovician Kelimoli Formation in the central section of the thrust zone along the western margin of the Ordos Basin

时保宏 蔺嘉昊 张涛 王红伟 张雷 魏嘉怡 李涵 刘刚 王蓉

Baohong SHI Jiahao LIN Tao ZHANG Hongwei WANG Lei ZHANG Jiayi WEI Han LI Gang LIU Rong WANG

近年来，少数探井在鄂尔多斯盆地西缘冲断带上古生界石盒子组8段和山西组1段隐伏构造发现了低产天然气。推覆体下盘隐伏构造研究对天然气勘探具有重要的意义。基于最新钻探成果、地震资料、岩石薄片和有机地球化学等资料，研究了西缘中段逆冲推覆构造下盘古生界隐伏构造特征，分析了奥陶系克里摩里组油气成藏地质条件和勘探潜力，提出了隐伏构造带有利勘探方向。研究结果表明：①受侏罗世—白垩世燕山期自西向东强烈推覆应力作用影响，研究区推覆体下盘地层被动挤压褶皱变形，广泛发育南北向呈排状展布的隐伏构造，隐伏构造圈闭规模较大，断层不发育，封闭性较好。②奥陶系克里摩里组发育缓坡高能滩相储层，主要为中-粗晶白云岩，储集空间以晶间孔、晶间溶孔及裂缝为主，储层孔隙度介于3 % ～ 6 %，渗透率在（1 ～ 8）×10 μm。③发育乌拉力克组和克里摩里组2套海相优质烃源岩，干酪根以Ⅰ型和Ⅱ型为主，镜质体反射率（）在1.50 % ～ 1.90 %。④天然气垂向和侧向双向供烃，源-储配置关系良好，隐伏构造圈闭形成与烃源岩主生、排烃期匹配性好。低幅度隐伏构造带与高能滩的叠加区是天然气的富集区。初步预测滩相白云岩与隐伏构造叠合有利面积为300 km。马家滩段烟墩山、惠安堡和马家滩3个隐伏构造带是下一步克里摩里组天然气勘探的有利区域。

In recent years， several exploration wells have revealed low-yield natural gas in the concealed structures of the 8 member of the Upper Paleozoic Shihezi Formation and the 1 member of the Upper Paleozoic Shanxi Formation in the thrust zone along the western margin of the Ordos Basin. Hence， investigating the concealed structures in the footwall of nappes is significant for natural gas exploration in the study area. Using the latest drilling results， seismic data， observations of petrographic thin sections， and organic geochemical data， we explore the characteristics of the Paleozoic concealed structures in the footwall of thrust nappes within the central section of the western margin of the Ordos Basin. Accordingly， the geological conditions for hydrocarbon accumulation and hydrocarbon exploration potential of the Ordovician Kelimoli Formation is analyzed and favorable exploration targets are proposed in the concealed structural zone. The results indicate that， under the influence of intense W-E-oriented stress of nappes during the Yanshanian movement （Jurassic to Cretaceous）， strata in the footwall of nappes in the study area deformed under passive compression and folding， resulting in the extensive development of SN-oriented concealed structures distributed in rows. These concealed structures exhibit large-scale traps and underdeveloped faults， suggesting favorable sealing performance. The Ordovician Kelimoli Formation contains high-energy ramp shoal reservoirs consisting primarily of medium-to-coarse-crystalline dolomites. These reservoirs exhibit storage spaces dominated by intercrystalline pores， intercrystalline dissolution pores， and fractures， with porosity ranging from 3 % to 6 % and permeability from 1 × 10 to 8 × 10 μm. Two suites of high-quality marine source rocks occur in the Wulalike and Kelimoli formations， with kerogen dominated by Types I and II1 and vitrinite reflectance （） ranging from 1.50 % to 1.90 %. The study area exhibits both vertical and lateral hydrocarbon supply， a favorable source rock-reservoir configuration， and the formation of the concealed structure traps is well matched with the main hydrocarbon generation and expulsion period of source rocks. The superimposed areas of low-amplitude concealed structural zones and high-energy shoals serve as natural gas enrichment areas， with the favorable superimposed areas of 300 km from preliminary prediction. Additionally， the Yandunshan， Huianbu， and Majiatan concealed structural zones in the Majiatan section along the western margin of the Ordos Basin are identified as favorable areas for future natural gas exploration in the Kelimoli Formation.

10.11743/ogg20250106