• 主管:

      天津市地质矿产勘查开发局

    • 主办:

      天津地热勘查开发设计院

    • ISSN

      1001-1412  CN 12-1131/P

    青藏高原东北缘敦煌盆地电性结构特征及对油气资源勘探的启示

    Electrical Structure Characteristics of the Dunhuang Basin in the Northeastern Margin of the Tibetan Plateau and Implications for Hydrocarbon Exploration

    • 摘要: 敦煌盆地西部整体油气基础地质工作程度相对东部而言较低,自西参1井、墩1井在五墩凹陷发现中-下侏罗统(J1-2)发育烃源岩并见到良好油气显示后,盆地西部同期凹陷的油气成藏条件和勘探前景也获得了重视。为查明清台凹陷及其邻区的侏罗系分布特征及主要构造格架,通过一条长度100 km的CEMP剖面,获得了敦煌盆地西部5 km以浅的电性结构模型。结合区域重磁资料综合解释表明:研究区整体具有“两坳一隆一斜坡”的构造格局,由南向北依次为阿克塞坳陷、三危山隆起、安敦坳陷和玉门关斜坡;剖面共识别7条断裂,其中F1、F2为三危山隆起南部断裂、北部断裂,F3为矛头山断裂,F4为若羌-红柳园断裂,F6为北阿尔金断裂,F7、F8为推断断裂;清台凹陷具有北断南超的箕状断陷特征,侏罗系低阻电性特征明显,厚度约1 500~2 000 m,沉积中心偏北,元古界结晶基底埋深约2 500~3 500 m。本研究为敦煌盆地西部油气资源评价和下一步勘探部署提供了可靠的地球物理依据,清台凹陷北部沉积中心及F7断裂控制的局部构造为下一步油气重点勘探方向。

       

      Abstract: The overall degree of fundamental petroleum geological work in the western Dunhuang Basin is relatively low compared with the eastern part. Since the discovery of source rocks in the Lower-Middle Jurassic (J1-2) with favorable hydrocarbon shows in the Wudun Sag by Wells Xican-1 and Dun-1, the hydrocarbon accumulation conditions and exploration prospects of the coeval sags in the western basin have also received increasing attention. To investigate the distribution characteristics of the Jurassic and the main tectonic framework in the Qingtai Sag and its adjacent areas, a 100 km-long Continuous Electromagnetic Profiling (CEMP) profile was acquired, yielding an electrical structure model within the upper 5 km beneath the western Dunhuang Basin. Comprehensive interpretation integrated with regional gravity and magnetic data indicates that the study area as a whole exhibits a tectonic framework of “two depressions, one uplift and one slope”, which, from south to north, are the Aksay Depression, Sanweishan Uplift, Andun Depression, and Yumenguan Slope. A total of seven faults were identified along the profile: F1 and F2 are the southern and northern boundary faults of the Sanweishan Uplift, respectively; F3 is the Maotoushan Fault; F4 is the Ruoqiang - Hongliuyuan Fault; F6 is the North Altun Fault; and F7 and F8 are inferred faults. The Qingtai Sag is characterized by a half-graben geometry with a faulted northern margin and an onlapping southern margin. The Jurassic exhibits distinct low-resistivity electrical characteristics, with a thickness of approximately 1 500~2 000 m and a northward-shifted depocenter; the Proterozoic crystalline basement occurs at a burial depth of approximately 2 500~3 500 m. This study provides a reliable geophysical basis for hydrocarbon resource evaluation and future exploration deployment in the western Dunhuang Basin. The northern depocenter of the Qingtai Sag and the local structures controlled by the F7 fault are identified as priority exploration targets for future hydrocarbon exploration.

       

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