Sub-salt imaging on VSP multi-component data: A case study in DB1 well-site, Tarim Basin, China

摘要

PP, PSV and SS reflection data with high S/N ratio were extracted from a 3-C offset VSP data set at DB1 well-site in Tarim basin by means of wavefields i-dentification, 3C orientation and wavefield separation. On the basis of accurate velocity estimation, imagings of the three types of wavefields have been performed in depth domain. Therefore, the sub-salt structure imaging distortion induced by salt velocity and the difficulty in stratigraphy correlation of PP, PSV and SS imgings in time domain were reduced. Integrating the common features of these imagings, we got the analysis described as follows: (1) A regional continuous mark horizon E_(2-3)s can be identified reliable at depth of 5450 m in DB1. The identification of E_(2-3)s can improve the imaging of target zone E_(2-3)s and enhance the reliability of data interpretation. (2) Main sub-salt horizons below E_(2-3)s dip to the north, adverse to the former interpretation of dipping to the south. (3) Converted wave has higher resolution than P wave and its imaging indicates geological character of target zone more clearly.