Abstract: Some abnormal gas logging displays, which indicate specific hydrocarbon composition, have been found during the drilling process in the Bohai sea. They consist of incomplete gas components with extremely high methane. We described and summarized in this paper the logging characters of the specific layers. Suffering from biodegradation, the oil in shallow layers shows great difference from the normal in geochemistry in gas chromatography. For interpretation and evaluation of the specific reservoir, traditional interpretation methods, which use the charts based on hydrocarbon component ratios, are limited. Using the data of well logging interpretation, sampling and oil testing from the samples with specific hydrocarbon components in the Penglai area, we established a Tg abnormal amplitude-geochemical highlight chart with both the gas data and the geochemical data. Combined with the shape of Tg curve, we developed an interpretation method suitable for the reservoir of the kind with specific hydrocarbon component and extremely high methane. The application of the method is proved efficient in the study area..