Abstract: In 2025, PetroChina Tuha Oilfield Company proposed the exploration strategy of "exploring both deep and shallow layers for three-dimensional breakthroughs". Well Fukang2 was deployed on the eastern slope of Fukang sag in Junggar Basin. During well testing, the Upper Permian Shangwuerhe Formation and the Lower Triassic Jiucaiyuan Formation produced high-yield industrial oil flows of 25.44 m³/d and 56.16 m³/d, respectively. This opened up a new phase of three-dimensional exploration characterized by vertical multi-strata and planar multi-fields in the study area. Based on outcrop, drilling and logging, seismic, and various analytical test data, a comprehensive study was performed on hydrocarbon sources, reservoirs, and accumulation of oil reservoir in the Shangwuerhe and Jiucaiyuan formations on the eastern slope of Fukang sag. The research results indicate that the study area primarily develops two sets of source rocks, i.e. the Permian Lucaogou Formation and the Upper Member of Carboniferous Songkaersu Formation. Their organic matters are dominated by Type Ⅱ₁-Ⅱ₂ and Type Ⅱ₂-Ⅲ kerogens, exhibiting good to excellent and fair to good organic richness, respectively. Both suites of source rocks are predominantly in the mature stage. The crude oil from Well Fukang2 is characterized with relatively light carbon isotopes and predominant algal-derived organic matters, whose biological precursors are formed in a saline reducing environment, consistent with the depositional conditions of the Lucaogou Formation source rocks. This suite of source rocks exhibits high hydrocarbon generation intensity, generally exceeding 200×10⁴t/km². The Shangwuerhe Formation and Jiucaiyuan Formation mainly developed the braided river delta to lacustrine sedimentary systems, where the reservoirs demonstrate low porosity and ultra-low permeability. The Shangwuerhe Formation is dominated by secondary dissolution pores, residual intergranular pores, and microfractures, whereas the Jiucaiyuan Formation is primarily characterized by residual intergranular pores. Both the Shangwuerhe Formation and Jiucaiyuan Formation exhibit lithologic sandstone reservoirs. On the eastern slope of Fukang sag, under the control of large-scale sand bodies, nose-shaped structural settings, and overpressure-fracture systems, three favorable exploration areas, i.e., Fuzhong, Kangtan1, and Fu47 structures with a total area of approximately 310 km², were identified in the Shangwuerhe Formation. Moreover, under the control of hydrocarbon migration pathways and high-quality reservoirs, two favorable exploration areas, i.e., Fubei and Sha’nan with a total area of approximately 317 km², were identified in Jiucaiyuan Formation. This study not only provides a geological basis for the efficient hydrocarbon exploration in the Fukang sag of Junggar Basin, but also offers valuable insights for lithologic reservoir exploration in similar regions both domestically and internationally.

Key words: Junggar Basin, Fukang sag, Upper Permian Shangwuerhe Formation, Lower Triassic Jiucaiyuan Formation, petroleum geological conditions, accumulation elements, exploration domains

摘要： 2025年,中国石油吐哈油田公司提出"深浅兼探、立体突破"的勘探思路,在准噶尔盆地阜康凹陷东斜坡部署了阜康2井,于上二叠统上乌尔禾组和下三叠统韭菜园组试油,分别获得25.44 m³/d和56.16 m³/d的高产工业油流,开启了该地区纵向多层系、平面多领域的立体勘探新局面。基于露头、钻井、测井、地震及各类分析测试资料,针对阜康凹陷东斜坡上乌尔禾组和韭菜园组油藏的烃源岩、储层和成藏开展了综合研究。研究结果表明:阜康凹陷东斜坡主要发育二叠系芦草沟组和石炭系松喀尔苏组上段2套烃源岩,其有机质类型分别为Ⅱ₁型—Ⅱ₂型和Ⅱ₂型—Ⅲ型,有机质丰度分别为好—优质和中等—好,烃源岩主体均已进入成熟阶段。阜康2井原油具有碳同位素偏轻、藻类生源为主的特征,指示其来源于咸水还原环境中形成的生物先质,原油特征与芦草沟组烃源岩高度吻合;芦草沟组烃源岩在研究区的生烃强度整体较高,普遍大于200×10⁴t/km²。上乌尔禾组和韭菜园组主要发育辫状河三角洲—湖泊沉积体系,均属低孔、特低渗储层,前者的储集空间以次生溶孔、剩余粒间孔和微裂缝为主,后者则以剩余粒间孔为主。阜康2井的上乌尔禾组和韭菜园组油藏均为砂岩岩性油藏。在阜康凹陷东斜坡,受规模砂体、鼻凸构造背景和超压-裂缝系统控制,上乌尔禾组发育阜中有利区、康探1鼻凸有利区和阜47鼻凸有利区3个勘探有利区,总面积约为310 km²;受输导体系和优质储层控制,韭菜园组发育阜北有利区和沙南有利区2个勘探有利区,总面积约为317 km²。该研究不仅为阜康凹陷下一步的高效勘探提供了地质依据,也为国内外类似岩性油气藏的勘探实践提供了借鉴。

关键词: 准噶尔盆地, 阜康凹陷, 上二叠统上乌尔禾组, 下三叠统韭菜园组, 石油地质条件, 成藏要素, 勘探领域