ISSN 1000-3665 CN 11-2202/P

    济阳坳陷地层放射性生热率及其对深部地热场的影响

    Radiogenic heat production rate and its impacts on the deep geothermal field in Jiyang Depression

    • 摘要: 济阳坳陷作为渤海湾盆地的次级构造单元,在岩石圈伸展构造背景下形成了高热流背景,深部具备干热岩资源潜力。沉积地层的放射性生热是地表热流的关键构成,对深部地热场分布及地热资源产出具有重要影响,但目前济阳坳陷放射性生热率数据覆盖不全,其对深部地热场的贡献仍未明确。文章系统采集46件跨地层层位、多岩性的岩芯样品进行放射性生热率测试分析,结合自然伽马(GR)测井资料,建立了适用于该区域的GR-A 经验转换关系式,构建了区域地层生热率柱,量化模拟了沉积层放射性生热的热贡献。研究表明:济阳坳陷沉积层的平均放射性生热率1.40 μW/m3,标准差为±1.25 μW/m3,其空间分布受地层岩性组合与成岩作用的控制,即碎屑岩的放射性生热率随泥质含量增加及压实程度的增强而升高,而碳酸盐岩因放射性元素贫化导致生热率普遍偏低(平均<0.5 μW/m3),但其热导率高;太古宙地层因富含花岗岩、混合花岗岩等酸性岩浆岩,兼具最高生热率(平均2.31 μW/m3)和较高热导率(2.78 W/(m·℃)),形成“高生热-强导热”的优势组合,成为干热岩开发的优势目标层位。通过热流贡献的量化模拟分析,隆起区沉积地层的放射性生热量达30.5 mW/m2,占地表热流的37.2%,显著影响了深部地温场。研究揭示了济阳坳陷地层生热率的控制因素及热贡献,对渤海湾盆地其它次级构造单元的地热资源勘探开发具有重要意义。

       

      Abstract: As a secondary tectonic unit of the Bohai Bay Basin, the Jiyang Depression has formed a high heat flow background under the context of lithospheric extensional tectonics, with potential for hot dry rock (HDR) resources in the deep subsurface. Radiogenic heat production of sedimentary strata is a key component of surface heat flow and exerts a significant impact on the distribution of deep geothermal fields and the output of geothermal resources. However, currently, the coverage of radiogenic heat production rate data in the Jiyang Depression is incomplete, and its contribution to the deep geothermal field remains unclear. In this study, 46 core samples across different stratigraphic horizons and with multiple lithologies were systematically collected for testing and analysis of radiogenic heat production rates. Combined with natural gamma ray (GR) logging data, a regional empirical GR-A conversion relationship was established, a regional stratigraphic heat production column was constructed, and the thermal contribution of radiogenic heat production in sedimentary layers was quantitatively simulated. The study shows that the average radiogenic heat production rate of sedimentary layers in the Jiyang Depression is 1.40 μW·m−3, with a standard deviation of ±1.25 μW·m−3. Its spatial distribution is controlled by stratigraphic lithological associations and diagenesis: the radiogenic heat production rate of clastic rocks increases with the increase in argillaceous content and compaction degree; carbonate rocks generally have low heat production rates (average < 0.5 μW·m−3) due to the depletion of radioactive elements but high thermal conductivity; Archean strata, rich in acidic magmatic rocks such as granite and migmatitic granite, have both the highest heat production rate (average 2.31 μW·m−3) and relatively high thermal conductivity (2.78 W/(m·℃)), forming a “high heat production - strong thermal conductivity” advantageous combination and thus becoming the preferential target horizon for HDR development. Through quantitative simulation analysis of heat flow contribution, the radiogenic heat production of sedimentary strata in the uplift area reaches 30.5 mW·m−2, accounting for 37.2% of the surface heat flow, which significantly affects the deep geothermal field. This study reveals the controlling factors and thermal contributions of stratigraphic heat production rates in the Jiyang Depression, providing basic data on lithology-thermophysical property coupling for deep resource exploration, and is of great significance for geothermal resource exploration and development in other secondary tectonic units of the Bohai Bay Basin.

       

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