松辽盆地岩石热导率柱及古地温场分布特征

Thermal conductivity column of rocks and distribution characteristics of paleo-geothermal field in the Songliao Basin

  • 摘要: 盆地古温度场与地热、油气资源的形成演化密不可分。为明确松辽盆地关键时期的古地温场特征,以实测的269块样品热导率和汇编的前人数据为基础建立热导率柱,并以镜质体反射率Rran为约束进行多口单井的埋藏史−热史模拟。结果显示,松辽盆地平均热导率为1.79 W/(m·K),热导率随深度增加而增大,在上部地层中增大的速率大于下部。热导率随地层年龄增大而增大。松辽盆地北部Rran主要在0.8%~1.6%,齐家古龙凹陷Rran最大。埋藏史−热史表明,白垩系青山口组地层在明水组末期达到最大古地温,然后至今呈逐渐降低的趋势。古地温场平面分布显示松辽盆地北部青山口组地层在大部分地区的最大古地温达到120℃以上,显著高于现今地温场。青山口组从沉积后进入盆地热沉降发育阶段,随着古埋深的增加,古地温逐渐增至最大。此时较高的古地温条件能够促进页岩油气的成熟。明水组末期受古太平洋板块运动影响,发生了显著的抬升冷却事件,在冷却过程中温度梯度降低幅度较小的地区形成了地热温度条件有利区。研究成果可为松辽盆地地热、油气资源的形成机理研究提供理论参考。

     

    Abstract: The paleo-geothermal field of a basin is closely related to the formation and evolution of geothermal, oil, and gas resources. To ascertain the characteristics of the paleo-geothermal field in the Songliao Basin during some critical periods, this study established the thermal conductivity column of rocks in the basin using measurements from 269 samples and compiled previous data. Then, it simulated the burial and thermal histories of multiple wells under the constraint of vitrinite reflectance (Rran). The results indicate that the thermal conductivity of the Songliao Basin increases with the depth, with increasing rates higher in the upper strata than in the lower strata and an average of 1.79 W/(m·K). Furthermore, the thermal conductivity also increases with the age of strata. The Rran of the northern Songliao Basin primarily ranges from 0.8% to 1.6%, peaking in the Qijiagulong sag. The burial and thermal histories reveal that the paleo-geotemperature of the Cretaceous Qingshankou Formation peaked in the late stage of the Mingshui Formation deposition, followed by a gradual decrease until the present. The planar distribution of the paleo-geothermal field indicates that the Qingshankou Formation in the northern Songliao Basin exhibited a maximum paleo-geotemperature of above 120°C in most areas, which is significantly higher than the present level. The basin entered the thermal subsidence stage after the deposition of the Qingshankou Formation, and its paleo-geotemperature gradually peaked with an increase in the paleo-burial depth. In this stage, the high paleo-geotemperature was favorable for the maturation of shale oil and gas. In the late stage of the Mingshui Formation, the Songliao Basin underwent a notable uplifting and cooling event under the influence of the movement of the Paleo-Pacific Plate. In the cooling process, areas with a small decreasing amplitude of the geothermal gradient became favorable areas of geothermal conditions. The results of this study will provide a theoretical reference for research on the formation mechanisms of geothermal, oil, and gas resources in the Songliao Basin.

     

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