格金干馏试验下的焦油产率作为评价富油煤的唯一指标受制于前期较少的勘探资料无法满足富油煤规模化精细评价要求。

基于二分类法提出利用真密度(ρ)和自然伽马(GR)判识富油煤的最佳阈值，并阐释富油煤具有显著岩石物理参数响应的内在机理。

研究表明：不同变质程度煤不具有统一的判识阈值，其中长焰煤类富油煤最佳判识阈值为，原煤真密度小于1.41 g/cm³、GR<80 API，判识正确率达81.82%。上述富油煤的地球物理测井参数响应受控于无机和有机组分条件，其中与焦油产率呈负相关性的灰分产率是影响煤体真密度的主要因素，灰成分(Al₂O₃+SiO₂)所指示的黏土矿物含量对GR值影响显著；而对焦油产率起决定作用的显微组分则同样对原煤真密度变化具有一定影响。从分子尺度，干燥无灰基状态下的真密度(ρ_daf)越小，煤脂肪结构越丰富、越有利于热解产生焦油；反之则芳香结构含量越高、越不利于热解形成焦油。总体而言，多种因素耦合作用使得煤体真密度与焦油产率呈现良好的负相关性。上述认识为基于地球物理测井参数评价富油煤提供了理论指导。

Tar yield, derived from the Gray-King assay, serves as the sole metric for evaluating tar-rich coal. However, insufficient exploration data hinder its effective application in the fine-scale evaluation of extensive tar-rich coal.

Based on binary classification, this study proposed the optimal thresholds for tar-rich coal identification using true density (ρ) and natural gamma-ray (GR) log. Moreover, this study elucidated the intrinsic mechanisms behind the significant petrophysical parameter responses of tar-rich coal.

Key findings are as follows: (1) Coals with various metamorphic grades differ in identification threshold. For instance, long-flame tar-rich coal, the optimal identification thresholds consist of raw coal’s true density of < 1.41 g/cm³ and GR responses < 80 API units, corresponding to identification accuracy of up to 81.82%. (2) The geophysical log parameter responses of the aforementioned tar-rich coal are affected by inorganic and organic components. The ash content, correlating negatively with the tar yield, acts as the dominant factor influencing the true density of coals, and the clay mineral content indicated by the ash composition (Al₂O₃+SiO₂) significantly influences the GR responses of coals. Additionally, macerals, determining the tar yield, produce a certain impact on raw coal’s true density. (3) On a molecular scale, a lower true density under a dry ash-free basis (ρ_daf) corresponds to richer aliphatic structures in coals, creating more favorable pyrolysis conditions for tar production. Conversely, a higher true density corresponds to higher aromatic structure content, which is more unfavorable for tar production through pyrolysis. Overall, the coupling effects of multiple factors contribute to a strongly negative correlation between the true density and tar yield of coals. These findings can serve as a theoretical guide for evaluating tar-rich coal based on geophysical log parameters.