Fine division of logging lithologic section in Ordovician Yingshan Formation, Yubei area, Tarim Basin

The Ordovician Yingshan Formation (over 500 m thick) is the focus for petroleum exploration in Yubei area of the Tarim Basin. Fractures are well developed. Regional tectonic uplift and stratigraphic erosion have made it difficult for formation division and reservoir correlation. Natural gamma curve increases in the study area, and is featured by “horizontal evenness and vertical randomness”. Based on natural gamma ray spectrometry logging and geochemical element logging, the increasing feature of natural gamma ray spectrometry curve is analyzed. Combined with the changes of lithology and logging curve, the Ordovician Yingshan Formation is divided into 4 sections from top to bottom. The 4 sections have good comparability horizontally, providing good foundation for further fine analysis and potential target optimization.