Application of LithoScanner logging in recognition and evaluation of coaly source rocks

In the Kuqa Depression, the Triassic and Jurassic periods feature five sets of source rock sequences that developed as alternating lake and swamp facies. These sequences can be classified into coal, carbonaceous mudstone, and dark mudstone based on lithology. The source rocks are characterized by high TOC abundance, significant thickness, and wide distribution. However, due to the vertical distribution of multiple source rock layers and the strong heterogeneity in lithological distribution, conventional methods such as the ΔlgR method perform poorly in TOC logging quantification. Objective and MethodsTo better understand the hydrocarbon resource potential and assess reserves in the Kuqa Depression, this study first identified the lithological characteristics of the source rocks through core analysis. Further geological characterization was achieved using geochemical analysis data. The ΔlgR method was initially applied for quantitative TOC logging evaluation, followed by the application of LithoScanner logging for lithological identification of the source rocks. Subsequently, LithoScanner logging was utilized for quantitative TOC evaluation. ResultsOverall, the Triassic and Jurassic source rocks are primarily composed of type Ⅱ1, Ⅱ2, and Ⅲ organic matter, with medium to high maturity. The quality of these source rocks ranges from medium to good. The method of using LithoScanner logging to identify different lithological source rocks and quantitatively evaluate TOC demonstrated a significantly higher accuracy compared to the ΔlgR method.ConclusionThe findings provide valuable guidance for assessing the hydrocarbon resource potential in the Kuqa Depression and expand the application scope of LithoScanner logging data.