(M.S. Dissertation)

Shuqian Dong, University of Utah

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Reverse time migration (RTM) is more accurate than traditional migration methods such as Kirchhoff and one-way wave equation methods because it computes numerical solutions to the complete wave equation. However, three-dimensional (3-D) RTM is limited in practice because of its high computational costs. I present a 3-D target-oriented reverse time datuming (RTD) method which can economically generate redatumed data in user-selected areas, such as beneath salt domes. Redatuming bypasses the complex velocity areas by solving the two-way wave equation using an accurate finite-difference strategy. The novel approach is a bottom-up strategy for calculating the Green's functions, which can significantly reduce the computational time compared to conventional datuming. After redatuming, less computationally intensive migration methods such as the Kirchhoff method can be used to image the local target zone that typically contains less complex structures. The chief merit of RTD is that it can provide targeted subsurface images with full wave imaging technology at affordable computational costs. The target-oriented RTD is tested on both 2-D and 3-D SEG/EAGE synthetic data sets and a 3-D field data set from the Gulf of Mexico. The results show that target-oriented RTD can reveal deep structures below complex structures with much less calculation effort than full volume RTM. The only requirement is that the area over the target zone is smaller than that of the acquisition survey.