SHALE ORGANIC HETEROGENEITY EVALUATION METHOD AND ITS APPLICATION IN SOURCE ROCKS GRADING EVALUATION: A Case Study of Mesoproterozoic Jixianianin in Liaoxi Depression

It is difficult to characterize hydrocarbon potential of the whole source rock layer with limited test samples due to the strong heterogeneity in organic matter abundance(TOC) of shale. Taking LLD2 well in Liaoxi Depression as the research object, the paper analyzes the main source rocks of Tieling Formation (Jxt) and Hongshuizhuang Formation(Jxh), and makes the grading evaluation as well as spatial distribution characteristics of source rocks with different abundance grades in terms of TOC through variable coefficient ΔlogR on the basis of organic geochemical study and logging response characteristics of source rocks. The results show that the organic matter abundance of Jxh is generally above 2%, significantly higher than that of Jxt, both dominated by the organic matter type Ⅱ with a little Ⅰ-type kerogen. The source rocks are in the over-mature stage of gas-generation peak period, probably serving as the main Jixianian source rock layer.