ABSTRACTIn the application of a conventional common‐reflection‐surface (CRS) stack, it is well‐known that only one optimum stacking operator is determined for each zero‐offset sample to be simulated. As a result, the conflicting dip situations are not taken into account and only the most prominent event contributes to any a particular stack sample. In this paper, we name this phenomenon caused by conflicting dip problems as ‘dip discrimination phenomenon’. This phenomenon is not welcome because it not only leads to the loss of weak reflections and tips of diffractions in the final zero‐offset‐CRS stacked section but also to a deteriorated quality in subsequent migration.The common‐reflection‐surface stack with the output imaging scheme (CRS‐OIS) is a novel technique to implement a CRS stack based on a unified Kirchhoff imaging approach. As far as dealing with conflicting dip problems is concerned, the CRS‐OIS is a better option than a conventional CRS stack. However, we think the CRS‐OIS can do more in this aspect. In this paper, we propose a workflow to handle the dip discrimination phenomenon based on a cascaded implementation of prestack time migration, CRS‐OIS and prestack time demigration. Firstly, a common offset prestack time migration is implemented. Then, a CRS‐OIS is applied to the time‐migrated common offset gather. Afterwards, a prestack time demigration is performed to reconstruct each unmigrated common offset gather with its reflections being greatly enhanced and diffractions being well preserved.Compared with existing techniques dealing with conflicting dip problems, the technique presented in this paper preserves most of the diffractions and accounts for reflections from all possible dips properly. More importantly, both the post‐stacked data set and prestacked data set can be of much better quality after the implementation of the presented scheme. It serves as a promising alternative to other techniques except that it cannot provide the typical CRS wavefield attributes. The numerical tests on a synthetic Marmousi data set and a real 2D marine data set demonstrated its effectiveness and robustness.

A detail analysis on common-reflection-surface (CRS) stack method is performed based on a unified Kirchhoff imaging theory from which an output imaging scheme (CRS-OIS) is derived. The CRS-OIS greatly simplify the implementation of traditional CRS stack from which both an enhanced prestack dataset and enhanced ZO image can be achieved. Thus, it can be seen as a significant improvement on CRS stack method. In this paper, the CRS-OIS is applied to the real data acquired in South China Sea for the first time. The general improved image quality and improved interpretability of target events such as the base of Paleozoic and Moho in the ZO image fully demonstrate its effectiveness.

本文基于克希霍夫成像理论,对共反射面元(CRS)叠加方法进行了深入分析,阐述了等旅行时面共反射面元叠加方法(CRS-OIS)原理及其测试效果.指出CRS-OIS是对于传统共反射面元叠加方法的重要改进,它简化了传统CRS叠加方法,可以同时得到信噪比大幅度提高的叠前道集与零炮检距成像剖面.该方法首次被用于南海深水二维地震数据处理,处理结果表明基底与莫霍面的成像品质得到明显改善,提高了剖面的可解释性.

For the serious problem that seismic imagines of middle to deep intervals are influenced by multiple reflections in offshore oilfields,a technique of coherent fitting multiple suppression based on AVO forward models has been developed.In applying this technique,seismic data is divided into the main effective wave and the main multiple components by using AVO forward modeling,and the latter can be eliminated by dip scanning and coherent simulation of the signals.Then the effective signals will be rebuilt using a method of data reconstruction.The application results show that this technique is greatly shorter in calculation time and more satisfactory in multiple suppression effects than the conventional techniques,and can effectively avoid residual multiple reflections due to combination effects when applying the conventional techniques of multiple suppression,ensuring the reliability of seismic relative amplitudes.

The finite difference is an important method of wave-field numerical simulation.In order to solve the problem of numerical dispersion of the conventional finite difference method,we start with frequency-space domain qP wave equation in 3-D transversely isotropy with a vertical axis of symmetry(VTI) media,and present the optimal finite difference operators based on conventional finite difference operators.Then we get the optimal coefficient by the Gauss-Newton method in optimization theory to make the finite-difference equation phase velocity equal to that of wave equation,so the numerical dispersion and numerical anisotropy will be minimum in theory.The results of velocity dispersion analysis and numerical simulation show that the finite-difference method using optimal operators can improve the numerical simulation accuracy,and decrease the numerical dispersion efficiently which can supply the foundation for qP wave simulation in frequency-space domain in 3-D VTI media.

Anisotropic prestack depth migration becomes closer to perfection since after many years of research and development. In seismic processing, however, inaccurate parameters estimation of the media is the main reason for poor imaging quality. When the estimated parameters of VTI media are close to their real values, the residual curvature analysis modeling method of anisotropic migration velocity analysis based on wave equation is applicable to anisotropic and laterally varying media because it is not associated with the complex geological condition. We will obtain a velocity modeling by anisotropic migration velocity analysis with the common imaging gathers extracted from a migration result. Numerical experiments and field data show that this method could improve the quality of migration results and obtain a robust image of VTI.

The problem of amplitude preservation has not been well solved in seismic data processing because of subsurface complexity,and it is still in a stage of groping.In this paper,a set of techniques and a flow of relative amplitude preservation processing with high resolution are summarized for offshore seismic data,according to our processing practice in recent years,which has made good application results in offshore hydrocarbon exploration.

目前对于地表以下构造复杂、地层产状变化大的滩海资料,虽然有很多软件推出一些针对性的处理技术,但由于都建立在一定的理论假设基础上,很难取得令人满意的效果。为此,通过对在缅甸滩海较为特殊的地震资料在处理和解释过程中遇到的各种关键问题,进行较为深刻地剖析和总结,展望目前的各种处理技术,对问题的成因和解决进行了一些非常有现实意义的思考,期望在类似复杂地表滩海地震资料的采集和处理上起到帮助作用。

目前针对构造成像处理的常规处理技术己经比较成熟。相对保幅处理技术由于地下情况的复杂性,一直未能得到很好地解决,目前还处在摸索阶段;国内已有不少处理人员在相对保幅处理方面做了很多有益的尝试,取得了不错的效果;通过近几年处理工作实践,总结了一套相对保幅处理思路和流程,在海上石油勘探中取得了很好的应用效果。