Subbasalt Marchenko imaging with offshore Brazil field data

Abstract

Sub-basalt imaging for hydrocarbon exploration faces challenges with the presence of multiple scattering, attenuation and mode-conversion as seismic waves encounter highly heterogeneous and rugose basalt layers. A combination of modern seismic acquisition that can record densely-sampled data, and advanced imaging techniques make imaging through basalt feasible. Yet, the internal multiples, if not properly handled during seismic processing, can be mapped to reservoir layers by conventional imaging methods, misguiding geological interpretation. Traditional internal multiple elimination methods suffer from the requirement of picking horizons of multiple generators and/or a top-down adaptive subtraction process. Marchenko imaging provides an alternative solution to directly remove the artifacts due to internal multiples, without the need of horizon picking or subtraction. In this paper, we present a successful application of direct Marchenko imaging for sub-basalt de-multiple and imaging with an offshore Brazil field dataset. The internal multiples in this example are generated from the seabed and basalt layers, causing severe artifacts in conventional seismic images. We demonstrate that these artifacts are largely suppressed with Marchenko imaging and propose a general work flow for data pre-processing and regularization of marine streamer datasets. We show that horizontally propagating waves can also be reconstructed by the Marchenko method at far offsets.

Marchenko Green’s Function Retrieval in Layered Elastic Media from Two-Sided Reflection and Transmission Data

“…It is observed that the Green's function matrix G can be eliminated from the reflectionand transmission-based representations by subtracting Equation ( 13) from Equation (10). This leads to…”

“…After taking the inverse Fourier transform (as defined in Equation (A3) and applying operator Z to the second and fourth rows, we obtain Equation (10), presented in the main text.…”

“…Inversion of the Marchenko equation has proven to be an effective tool for the retrieval of Green's functions in an unknown acoustic medium from single-sided reflection data [1,2]. For an introduction to this subject, the numerical implementation of the Marchenko equation, field data applications and recent developments, see [3][4][5][6][7][8][9][10][11], respectively. An equivalent (Marchenko) equation has also been derived for wave propagation in elastic media [12][13][14].…”