| Summary: | YZ gas field group in the Pearl River Mouth Basin is located at the edge of the continental shelf, and the gas reservoir is buried deeper than 3 000 m. Structural research faces multiple problems, such as large changes in water depth, large changes in the thickness of the surface low-velocity mudstone, and small-scale shallow gas. It is difficult to predict the depth of gas reservoirs precisely, which brings risks to the implementation of the overall development plan in the gas fields. Aiming at this problem, a research idea of integration of processing and interpretation is proposed: firstly, dense velocity analysis is carried out along the target layer and its upper seismic reflection layer to improve the accuracy of seismic velocity analysis; secondly, in order to eliminate the systematic error of well-seismic velocity, the macro correction of seismic velocity is carried out by using the calibrated velocity of synthetic seismic records, and the corrected velocity is used to perform time-depth conversion to obtain the initial depth structure; the main source of the residual error at the well point is clarified by the correlation analysis method, and with the correlation trend surface as the constraint, the error grid is edited in combination with the residual error of the well to correct the initial depth structure. Finally, a higher-precision depth structure is obtained by correcting the small error at the well location. The practice of gas field exploitation shows that the error between the structural depth predicted by this method and the actual depth of development wells has been reduced from 10-40 m to less than 10 m, which has successfully improved the accuracy of structural prediction, effectively guided the design and implementation of development wells, and reduced the risk of gas field exploitation. For oil and gas fields under similar geological conditions, the detailed study of the structure is not only based on data-driven velocity analysis and seismic imaging, identifying and eliminating the influencing factors of the structure is also the key.
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