Surface-based Internal Multiple Elimination in the CMP Domain — Theory and Application Strategies on Land Seismic Data

Acta Geophysica, Dec 2016

The data-driven internal multiple elimination (IME) method based on feedback model, which includes CFP-based, surface-based and inversion- based methods, are successfully applied to marine datasets. However, these methods are computationally expensive and not always straightforward on land datasets. In this paper, we first proved that the surface-based IME method, which is the most computationally efficient method among the three methods, can be derived from the CFP theory. Then we extend it to CMP domain under the assumption of locally lateral invariance of the earth, which makes it more computationally efficient. In addition, we proposed applying a time-variant taper based on the first Fresnel zone to predict the multiples more percisely. Besides, the improved S/N ratio and dense offset distribution can be obtained by using the CMP supergather, which makes the CMP-oriented method more suitable for land data. Some practical processing strategies are proposed via case study. The effectiveness of the proposed method is demonstrated with the application to synthetic and field data.

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Surface-based Internal Multiple Elimination in the CMP Domain — Theory and Application Strategies on Land Seismic Data

Surface-based Internal Multiple Elimination in the CMP Domain Theory and Application Strategies on Land Seismic Data Shiguang DENG 0 Wenjin ZHAO 0 Zhiwei LIU 0 0 Chinese Academy of Geological Sciences , Beijing, People's Repulic of China A b s t r a c t The data-driven internal multiple elimination (IME) method based on feedback model, which includes CFP-based, surface-based and inversion-based methods, are successfully applied to marine datasets. However, these methods are computationally expensive and not always straightforward on land datasets. In this paper, we first proved that the surface-based IME method, which is the most computationally efficient method among the three methods, can be derived from the CFP theory. Then we extend it to CMP domain under the assumption of locally lateral invariance of the earth, which makes it more computationally efficient. In addition, we proposed applying a time-variant taper based on the first Fresnel zone to predict the multiples more percisely. Besides, the improved S/N ratio and dense offset distribution can be obtained by using the CMP supergather, which makes the CMP-oriented method more suitable for land data. Some practical processing strategies are proposed via case study. The effectiveness of the proposed method is demonstrated with the application to synthetic and field data. internal multiple; feedback model; surface-based; CMPoriented; land seismic data 1. INTRODUCTION Multiple reflections affect seismic imaging quality, especially when strong subsurface reflectors exist. The interference of multiple energy with primary events could result in interpretation uncertainties. It is necessary to remove multiples before subsequent processing. In general, multiples consist of freesurface multiples and internal multiples. Free-surface multiples are multiples that have experienced at least one downward reflection at the air-water “freesurface”; internal multiples are multiples that have all of their downward reflections below the free surface. Land seismic data is mainly affected by internal multiples. Internal multiples have experienced reflectors that are in general more remote and harder to precisely define (in comparison with freesurface multiples); hence, internal multiples are more difficult to predict and attenuate (Weglein 1999). Two major internal multiple elimination (IME) methods, based on wave theory, are the inverse-scattering series (ISS) and feedback methods. The inverse scattering series (ISS) method for internal multiple elimination is discussed specifically by Araujo et al. (1994), Coates and Weglein (1996), Weglein et al. (1997). The ISS method is fully data-driven and does not require any subsurface information. However, the cost of the ISS approach is considerably greater than the feedback method (Verschuur and Prein 1999). In practice, the feedback method would be a more effective choice. Berkhout and Verschuur firstly proposed the feedback method for the surface-related multiple elimination (SRME) (Berkhout 1982, Verschuur 1991, Verschuur et al. 1992, Berkhout and Verschuur 1997, Verschuur and Berkhout 1997). Berkhout and Verschuur (1997) extended the algorithm from surface to internal multiples by replacing shot records with common-focus-point (CFP) gathers (Berkhout 1997, Thorbecke 1997). Berkhout and Verschuur (2005) illustrated the internal-multiple-removal algorithm with numerical examples. This algorithm can be formulated in terms of boundary-related and layerrelated versions. Verschuur and Berkhout (2005) demonstrated the strategy for applying the two versions of internal-multiple-removal algorithm on physical-model and field data. The boundary-related approach requires the construction of CFP gathers, using focusing operators with correct traveltimes, while the layer-related approach allows traveltime errors. From a cost perspective, the layer-related method costs twice as much computation time as the boundary-related method, even though the boundary-related method involves more user interactions. Despite the extra calculation cost, the ease of use and the robustness of the layer-related approach make it preferable to the boundary-related approach in most situations. Jakubowicz (1998) proposed the surface-based IME method, in which the need for CFP gathers in the boundary-related method is avoided, and internal multiples can be estimated directly from the data measured on the surface. In van Borselen (2002), an extension of this procedure is illustrated to remove internal multiples that have crossed a pseudo-boundary that is chosen to lie between two internal reflectors. Thus, the data-driven internal multiple elimination based on surface data can be applied either in boundary-related version or layerrelated version. Recently, Ypma and Verschuur (2013) redefined internal multiple elimination as a full waveform inversion process, following the principles of estimating primaries by sparse inversion (EPSI) (van Groenestijn an (...truncated)


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Shiguang Deng, Wenjin Zhao, Zhiwei Liu. Surface-based Internal Multiple Elimination in the CMP Domain — Theory and Application Strategies on Land Seismic Data, Acta Geophysica, 2016, pp. 2114-2135, Volume 64, Issue 6, DOI: 10.1515/acgeo-2016-0107