自然伽马能谱测井在塔河奥陶系地层划分中的应用

Application of GR spectroscopy log in stratigraphic classification of the Ordovician formation in Tahe oilfield

（石油大学资源与信息学院，北京 102200）

(Institute of Resource and Information; Petroleum of University; Beijing 102200; China)

沉积环境的差异使得沉积物具有不同的地球物理和地球化学特征；反过来，根据沉积物特征可以分析沉积物当时的沉积环境。自然伽马能谱测井是沉积岩自然放射性的反映，通过对自然伽马能谱测井资料的进一步分析，可以得到铀比值曲线（PU）和钍比值曲线（PTh）。钍比值曲线反映了地层的沉积环境，铀比值曲线对底层组段界线和风化壳敏感，因此，应用铀比值曲线和钍比值曲线以及铀钍比值交会图可以快速直观地进行风化壳的识别和地层组段划分。将这种方法应用于塔河油田奥陶系碳酸盐岩地层的组段划分中，取得了很好的效果。

Sediments have different geophysical and geo-chemical characteristics under different sedimentary conditions. Vice versa, one can infer sedimentary conditions from the characteristics of sediments. GR spectroscopy log measures the natural radioactivity of sediments. Uranium ratio curve(PU) and thorium ratio curve(PTh) were calculated. PTh depicts the sedimentary conditions of formation. PU is sensitive to the boundary of formation segments and weathering crust. In this paper, we used PU, PTh, and the crossplotting of PU and PTh to identify weathering crust and classify different formations. This method has been applied in the classification of the Ordovician carbonate formation in Tahe oilfield.