Application of First Break Tomography to Shallow Water Gas Cloud Area——A Case Study in Bohai Bay
Velocity modeling is a key step in seismic imaging.The current mainstream reflec-tion tomography technique faces challenges in obtaining accurate velocity models due to strong absorption and scattering effects from shallow gas.In this paper,we successfully ap-plied the first break tomography technique to the velocity model building of a large oil and gas field in Bohai Bay,taking advantage of the characteristics of first break that are less af-fected by gas clouds,easy identification and easy picking up.The results show that first break tomography can establish a high-precision medium-to-shallow velocity model.Com-pared with the conventional reflection wave tomography,this method can accurately describe the low-velocity anomalies in the gas cloud area,significantly improve imaging quality of the gas cloud area and eliminate the structural twist.It also proves that the first break tomo-graphy technique can obtain reliable velocity models in the middle and shallow layers under the condition of weak amplitude and low SNR in the gas cloud area,which provides a good solution for the velocity model building of the area with significant velocity anomaly in the shallow layer.
gas cloud areavelocity modelingfirst break tomography
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