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海相沉积盆地广为发育盐岩,盆内油气藏多与盐岩有关.塔里木盆地是中国最大的海相沉积盆地,该区以往的盐构造研究主要集中于其作为良好盖层的封堵性能和作为构造圈闭的盐相关构造.实测表明,盐岩热导率远大于普通沉积岩(约2~3倍),盐岩这一强烈的热物性差异必然会对盆地地层温度分布及烃源岩热演化产生显著影响,但该问题尚未引起重视.本文基于系列理论模型和库车前陆盆地盐构造地震解释剖面,采用二维有限元数值模拟实验,定量探讨了盐构造的热效应及其对烃源岩热演化的影响.研究表明,盐体会造成盐上地层显著增温(3%~13%)和盐下地层降温(11%~35%),进而分别加速盐上烃源岩和抑制盐下烃源岩的热演化过程.盐体的热导率、几何形态、厚度和埋深是控制地热异常幅度的主要因素.异常范围与盐体尺寸有关,横向上可达盐体宽度的2倍、垂向上为盐体厚度的2~3倍.盐构造使得库车前陆盆地盐下地层温度显著降低,造成盐下侏罗系烃源岩镜质体反射率(Ro)降低约18%,从而有利于盐下深层油气的保存.库车前陆盆地东、西部的盐构造在埋深、厚度、成分和构造变形样式等方面均存差异,这可能是造成该区中生界烃源岩有机质成熟度时空差异分布的原因.上述盐构造的热效应对中国海相沉积盆地深层油气资源潜力评价与勘探具有重要意义.
The marine sedimentary basins are widely developed of salt rocks, and the basin oil-gas reservoirs are mostly related to salt rocks. The Tarim Basin is the largest marine sedimentary basin in China. Previous salt structure studies in the area mainly focus on its sealing performance as a good caprock And the tectono-tectonic traps.The measured results show that the thermal conductivity of salt rocks is far greater than that of normal sedimentary rocks (about 2 to 3 times). The strong difference of thermal properties of salt rocks will inevitably affect the temperature distribution of the strata and the source rock However, this issue has not yet drawn much attention.Based on the series of theoretical models and the seismic interpretation profiles of the salt tectonics in the Kuqa foreland basin, a two-dimensional finite element numerical simulation experiment was conducted to quantitatively investigate the thermal effects of salt tectonics and their effects on hydrocarbon The results show that salt can cause significant temperature increase (3% -13%) in salt formations and cooling (11% -35%) in salt formations, and then accelerate the growth of source rocks and salt Thermal evolution of hydrocarbon source rocks The thermal conductivity, geometry, thickness and depth of salt bodies are the main factors controlling the magnitude of geothermal anomalies.The range of anomalies is related to the size of salt bodies and can be up to twice , Vertical salt thickness 2 to 3 times.The salt structure makes the Kuqa foreland basin significantly lower the temperature of the salt formation, resulting in the salt sub-Jurassic source rock vitrinite reflectance (Ro) decreased by about 18%, which is conducive to the deep sub-salt oil and gas The salt structures in the eastern and western parts of the Kuqa foreland basin are different in depth, thickness, composition and tectonic deformation pattern, which may be the reason for the spatiotemporal variation of the maturity of organic matter in the Mesozoic source rocks in the area The thermal effects of the above salt tectonics are of great importance for the evaluation and exploration of the potential for deep hydrocarbon resources in the marine sedimentary basins of China.