关键词: 走时层析, 全波形反演, 偏移成像, 涠洲油田

Abstract:

The Weizhou Oilfield in Beibu Bay, South China Sea, has a complex structure, developed faults and fractured strata, resulting in a non-uniform velocity structure. To meet production requirements, this area has undergone multi-round traveltime tomography velocity modeling, including velocity modeling of dual-azimuth streamer seismic data. However, imaging quality remains poor. Full waveform inversion (FWI) builds a more accurate velocity model by making full use of the amplitude and traveltime information of the seismic wavefield. However, this process usually requires that the seismic data contain long offset components. Given the limited offset of streamer seismic data in the Weixi exploration area, this paper develops a high-precision velocity modeling technique process that combines FWI and traveltime tomography. Firstly, multi-scale FWI from low to high frequency is used to invert shallow and intermediate layer velocity models derived from high-SNR turning and refracted wave signals. Reflection traveltime tomography is then used to update the deep-layer velocity model. Compared to conventional reflection traveltime tomography modeling, the accuracy of the velocity model is improved, which in turn improves the structural imaging of the target area, making the fault structure more discernible. This work lays a solid data foundation for the oilfield to increase storage and expand production and realize benefit exploitation.

Key words: traveltime tomography, full waveform inversion, seismic migration, Weizhou Oilfield