A New Characterization Method of Velocity Anomaly and its Application in the Southwest of Bozhong Sag

Drilling of the Bohai Oilfield in the Neogene stratum reveals velocity anomaly in some areas, mainly manifested as contradictions between oil and water, big different between the pattern of time map and depth map, etc. In this study, a method of envelope decompacting of stacked velocity field solves the velocity anomaly, determines the distribution of velocity anomalies accurately and intuitively, quantifies the value of velocity anomaly, and confirms the direct relationship between the velocity anomalies and slip faults. Using variable-velocity structure mapping to effectively avoid velocity traps, construct real structural form, and guide oil and gas exploration of Neogene. At present, the common factors causing velocity anomalies are faults, sand ratio, etc. The reasons for velocity anomalies in the lower part of the Minghuazhen Formation of the Southwest in Bozhong Depression are analyzed in detail, and the influence degree on velocity is in the order of faults, structural amplitude and sand ratio. The fault development zone generally leads to high velocity anomalies, and the closer to the fault zone, the greater the anomaly. Multi-well drilling proves that this method is feasible and effective, and this method has great industrial application and promotion value.