Abstract: The estimation of erosion thickness is a foundation for studying palaeostructural characteristic, modeling source rock thermal evolution history and analyzing palaeo-fluid potential. Based on the geologic feature and available data of Yanqi basin, 27 exploratory wells are chosen in Bohu depression, for which strata erosion thickness of well is estimated by using mud interval transit time method, and then taking these data as the constraining points, 10 seismic profiles are selected, finally, the whole erosion thickness of Jurassic in Bohu depression is estimated by using seismic profile tracing technique. The result shows that vertically, each formation of Jurassic undergoes erosions to a certain extent, the most eroded series is Upper Jurassic, the second is Toutunhe formation and Xishanyao formation of Middle Jurassic, Sangonghe formation and Badaowan formation of Lower Jurassic are well preserved relatively. Laterally, the different areas in Bohu depression are dissimilarly eroded, the most eroded area is Zhongmachang low swell, the second is the area nearby Yannan fault in the northern Bohu depression, while Sishilicheng sub-sag, Qilipu sub-sag in the north sag and Baotouhu sub-sag in the south sag are eroded slightly.

Key words: Yanqi, Bohu, Jurassic, erosion thickness, interval transit time, seismic profile, depression