摘要
Wallace G.Dow 1977年提出在半对数直角座标系下,利用实测的镜质体反射率(R_0％)与其对应深度(H)的线性相关关系回归直线即称成熟度剖面估算地层剥蚀厚度的方法。本文根据镜体反射率主要受热力,其次受有效加热时间的影响且具不可逆性,对Dow的方法从理论到应用上作了进一步的探讨,并给出了通过镜质体反射率与深度的线性关系恢复地层剥蚀厚度的三种方法。
In the evaluation of oil and gas resources, it is extremely important in the study of the history of hydrogen source rock burial and thermometamorphic pro- cess to reconstruct the eroded thickness of a stratigraphic section with a big erosional hiatus.
The sudden change in the value of vitrinite reflectance (R_0％) at an unconformity surface indicates the existence of a stratigraphic erosional hiatus under the normal geologic condition. The eroded thickness may be evaluated by measuring the vitrinite reflectance maturation section, that is, a regressive linear graph expressing a good linear correlation between the arithmetic coordinate of depth(H) for a drill hole and a logarithmic one of vitrinite reflectance(R_0％).
It has been reported that the eroded thickness is reconstructed by the section of vitrinite reflectance maturity disrupted horizontally at the unconformity surface (Wallace G. Dow, 1977). In this paper, the method is further studied in terms of the theory and application according to the unreversible character of the vitrinite reflectance due to the influence of thermodynamics and effective heating time. Then, three methods for the construction of the eroded thickness are given: (1)the eroded thickness is directly obtained by direct extrapolation of R_0％ to the lowest value at the ground surface using the horizontally disrupted unconformity surface or the slope below the unconformity surface without changing the branch maturation section: (2) the eroded thickness may be indirectly obtained by calculating the average palaeogeothermal gradient at the maturation section below the unconformity; (3) the eroded thickness may be also reconstructed by the correlative linear graph (H-LogR_0％) on the same bedding plane.
There may be some errrors in measuring vitrinite reflectance, establishing the regression line (H-LogR_0％) and reconstructing the eroded thickness and finding average palaeogeothermal gradient.
出处
《地质论评》
CAS
CSCD
北大核心
1989年第2期119-126,共8页
Geological Review
