镜质组反射率梯度与古地温梯度间的关系研究——以陕北榆神矿区5^-2富油煤层为例

Relationship between Vitrinite Reflectance Gradient and Paleogeothermal Gradient—Taking 5^-2 Oil Rich Coal Seam in Yushen Mining Area in Northern Shaanxi as an Example

摘要: 利用吴氏煤变质热动力学方程计算5-2富油煤层的变质温度为54.2℃~76.6℃，并画出古地质时间、镜质组反射率和变质温度三者之间的关系图。为了解释极大的埋深或地温梯度差距，利用不超过深成变质的镜质组反射率梯度值 < 0.06%/百米重新计算古地温梯度。根据已知5^-2富油煤层的地质数据，计算得到在R₀ = 0.53%，ΔR₀= 0.06%/百米，t = 193百万年时产生的地温梯度是9.14℃/百米为最大值，计算得到在R₀ = 0.53%，ΔR₀= 0.01%/百米，t = 205百万年时产生的地温梯度是1.55℃/百米为最小值。即使是在相同的地质条件范围内(古地质时间、镜质组反射率、埋深)，也能够满足转化为不同煤化阶段所需的温度。

Abstract: A coal metamorphic thermal dynamics equation has been used to calculate the paleo-geo temperature of 5^-2 oil-rich coal seam, and the results are 54.2˚C~76.6˚C, and shown in a three dimensional drawing of paleo-geo time, vitrinite reflectance and metamorphic temperature. In order to account for the great buried depth or paleo-geo temperature gradient gaps, the paleo-geo temperature gradient was recalculated using a vitrinite reflectance gradient of <0.06%/100 m. Based on the known geological data of the 5^-2 oil-rich coal seam, the paleo-geo temperature gradient generated at R₀ = 0.53%, ΔR₀= 0.06%/100 m, t = 193 million years is 9.14˚C/100 m, and the paleo-geo temperature gradient generated at R₀ = 0.53%, ΔR₀= 0.01%/100 m, t = 205 million years is 1.55˚C/100 m which is the minimum. Even within the same geological conditions (paleo-geo time, vitrinite reflectance, buried depth), it can meet the temperature required for conversion into different metamorphism stages.