Method for quickly establishing three-dimensional near-seafloor speed model in shallow sea area

By correcting the shot point to the seafloor in the shallow sea area and directly solving the equations, the impact of various excitation and reception methods on the inversion in the existing technology is solved, and a three-dimensional near-seafloor velocity model is quickly established, which significantly reduces the calculation time and Improved imaging accuracy.

CN109188527AActive Publication Date: 2019-01-11CHINA PETROLEUM & CHEMICAL CORP +1
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
CHINA PETROLEUM & CHEMICAL CORP
Filing Date
2018-10-31
Publication Date
2019-01-11

AI Technical Summary

Technical Problem

In shallow sea areas, the existing first arrival travel time tomography velocity modeling method cannot be directly applied to various excitation and reception methods, resulting in the need for a large number of ray tracing forward simulations during the inversion process, which greatly increases the calculation time.

Method used

By extracting the first arrival information, calculating the velocity and depth of the ray at the reversal point, using linear interpolation method to establish a one-dimensional velocity model, correcting the shot point from seawater to the seafloor, and directly solving the equations to invert the thickness of the underground medium velocity layer , avoiding multiple ray tracing forward simulations.

Benefits of technology

This method is suitable for a variety of excitation and reception methods, significantly reducing the calculation time, which is less than 2% of the conventional first arrival travel time method, simplifying the calculation process, and improving calculation efficiency and imaging accuracy.

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Abstract

The invention provides a method for quickly establishing a three-dimensional near-seafloor speed model in a shallow sea area; the method comprises the following steps of extracting initial informationand extracting a common-center-point gather; calculating the slope of the initial travel time in the common-center-point gather; judging whether a shot point is located in the seawater layer or not,and if yes, correcting the shot point to the seafloor; calculating the speed and the depth of inflection points corresponding to respective offset distances; performing linear interpolation on the speed at each depth to obtain a one-dimensional speed model of the common center point; after all the common-center point domain gathers are processed, adopting the linear interpolation method, calculating the speed values of the rest grid points by utilizing the one-dimensional speed model of all common center points, and a speed model is output. By adoption of the method for quickly establishing the three-dimensional near-seafloor speed model in the shallow sea area, the influence of the seawater layer on ray propagation is overcome, and the influence of multiple excitation receiving modes on an inversion result is eliminated, and the problem that the conventional method needs to carry out multi-ray tracing forward modeling is avoided.
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