Identification and analysis of bottom simulating reflectors in the Foz do Amazonas Basin, Northern Brazil

This work proposed an additional approach to investigate gas hydrate occurrences in the Foz do Amazonas Basin, in the Brazilian Equatorial Margin. The automatic comparison of seafloor seismic amplitudes with those from the Bottom Simulating Reflectors (BSR) was used to exhibit the reversal of signal polarities among the seafloor (positive) and the BSR (negative), reinforcing the identification of BSR in areas where its visualization was unclear. Additionally, we used the envelope attribute to highlight the BSR in the seismic section. Subsequently, we decomposed the seismic data into different frequency bands, applied a -90 degrees phase rotation to the data and recalculated the envelope attribute for each section decomposed in frequency bands. This technique improved visualization, allowing the identification of intervals where BSR were laterally discontinuous, revealing to be valuable for mapping the gas hydrate distribution in Foz do Amazonas Basin.

KEYWORDS:
gas hydrates; Foz do Amazonas Basin; envelope attribute; seismic amplitudes; spectral decomposition

Authorship

Laisa da Fonseca Aguiar

Exploratory Interpretation and Reservoir Characterization Group, Department of Geology and Geophysics, Universidade Federal Fluminense - Niterói (RJ), Brazil. E-mails: laisafonseca@id.uff.br, fernando_freire@id.uff.br, wagnerlupinacci@id.uff.br, cguizan@id.uff.brUniversidade Federal FluminenseBrazilNiterói, RJ, BrazilExploratory Interpretation and Reservoir Characterization Group, Department of Geology and Geophysics, Universidade Federal Fluminense - Niterói (RJ), Brazil. E-mails: laisafonseca@id.uff.br, fernando_freire@id.uff.br, wagnerlupinacci@id.uff.br, cguizan@id.uff.br

https://orcid.org/0000-0003-4436-1417

Antonio Fernando Menezes Freire ^**Corresponding author.

https://orcid.org/0000-0002-8102-8341

Cleverson Guizan Silva

https://orcid.org/0000-0003-1731-7883

Wagner Moreira Lupinacci

https://orcid.org/0000-0002-5728-7423

*Corresponding author.

L.A. wrote the first draft of the manuscript and prepared all figures; A.F. provided advisorship regarding gas hydrates, regional geology, and seismic interpretation; improved the manuscript through corrections and suggestions; C.S. provided advisorship regarding gas hydrates, regional geology, and seismic interpretation; improved the manuscript through corrections and suggestions; W.L. provided advisorship regarding seismic interpretation and seismic attributes; improved the manuscript through corrections and suggestions.

Competing interests: The authors declare no competing interests.

SCIMAGO INSTITUTIONS RANKINGS

Figures

Figures (13)

Thumbnail

Figure 1.
Location of the 2D seismic lines in the Amazon Deep Sea Fan, Foz do Amazonas Basin.

Thumbnail

Figure 2.
Non-interpreted (top) and interpreted (bottom) seismic line 0270-2004b displaying the two sectors of BSR (white). In sector 1, the BSR cuts across deformed strata of the Amazon Deep-Sea Fan compressional domain.

Thumbnail

Figure 3.
Non-interpreted (top) and interpreted (bottom) seismic line 0239-0034 displaying the two sectors of BSR (white), cutting across deformed strata of the Amazon Deep-Sea Fan compressional domain.

Thumbnail

Figure 4.
Proposed workflow applied for the analysis of BSR.

Thumbnail

Figure 5.
Seismic amplitude plots of section 0270-2004b after extracting the amplitude values for the seafloor (blue) and the BSR (orange) along sectors 1 and 2. BSR values are mostly negative and large; however, there are portions with positive values, implying BSR discontinuity.

Thumbnail

Figure 6.
Seismic amplitude plots of section 0239-0034 after extracting the amplitude values for the seafloor (blue) and the BSR (orange) along sectors 1 and 2. These graphs were considerably smooth but intervals of positive values, especially on sector 2, suggests a lateral discontinuity of the BSR.

Thumbnail

Figure 7.
Seismic section 0270-2004b with the envelope attribute, suggesting the BSR continuity to the southeast of sector 1.

Thumbnail

Figure 8.
Seismic section 0239-0034 with the envelope attribute, suggesting the continuity of the BSRs in between sectors 1 and 2 and further to the SW and NE.

Thumbnail

Figure 9.
Frequency spectra for seismic sections (A) 0270-2004b, and (B) 0239-0034.

Thumbnail

Figure 10.
Seismic section 0239-0034 with the 20 Hz decomposed frequency band (top) and with the -90º phase rotation and the envelope attribute (bottom). The sectors interpreted as BSR are displayed in black. The red arrow indicates a discontinuity of BSR that became more evident after applying spectral decomposition.

Thumbnail

Figure 11.
Seismic section 0239-0034 with the 30 Hz decomposed frequency band (top) and with the -90º phase rotation and the envelope attribute (bottom). The black box (bottom) can indicate a zone within the GHSZ where the saturation of free gas is higher. The orange box (top) reinforces the interpretation of BSR continuity, also observed with the envelope attribute (Fig. 8).

Thumbnail

Figure 12.
Seismic section 0270-2004b with the 20 Hz decomposed frequency band (top) and with the -90º phase rotation and the envelope attribute (bottom). BSR is displayed in black. Lateral discontinuity of BSR can be noticed in the two sectors.

Thumbnail

Figure 13.
Seismic section 0270-2004b with the 40Hz decomposed frequency band (top) and with the -90° phase rotation and the envelope attribute (bottom). The red arrow (bottom) shows the lateral discontinuity of BSR. The orange boxes (top) highlight possible BSR continuity, also noticed with the envelope attribute (Fig. 7).

Figure 1. Location of the 2D seismic lines in the Amazon Deep Sea Fan, Foz do Amazonas Basin.

Figure 2. Non-interpreted (top) and interpreted (bottom) seismic line 0270-2004b displaying the two sectors of BSR (white). In sector 1, the BSR cuts across deformed strata of the Amazon Deep-Sea Fan compressional domain.

Figure 3. Non-interpreted (top) and interpreted (bottom) seismic line 0239-0034 displaying the two sectors of BSR (white), cutting across deformed strata of the Amazon Deep-Sea Fan compressional domain.

Figure 4. Proposed workflow applied for the analysis of BSR.

Figure 5. Seismic amplitude plots of section 0270-2004b after extracting the amplitude values for the seafloor (blue) and the BSR (orange) along sectors 1 and 2. BSR values are mostly negative and large; however, there are portions with positive values, implying BSR discontinuity.

Figure 6. Seismic amplitude plots of section 0239-0034 after extracting the amplitude values for the seafloor (blue) and the BSR (orange) along sectors 1 and 2. These graphs were considerably smooth but intervals of positive values, especially on sector 2, suggests a lateral discontinuity of the BSR.

Figure 7. Seismic section 0270-2004b with the envelope attribute, suggesting the BSR continuity to the southeast of sector 1.

Figure 8. Seismic section 0239-0034 with the envelope attribute, suggesting the continuity of the BSRs in between sectors 1 and 2 and further to the SW and NE.

Figure 9. Frequency spectra for seismic sections (A) 0270-2004b, and (B) 0239-0034.

Figure 10. Seismic section 0239-0034 with the 20 Hz decomposed frequency band (top) and with the -90º phase rotation and the envelope attribute (bottom). The sectors interpreted as BSR are displayed in black. The red arrow indicates a discontinuity of BSR that became more evident after applying spectral decomposition.

Figure 11. Seismic section 0239-0034 with the 30 Hz decomposed frequency band (top) and with the -90º phase rotation and the envelope attribute (bottom). The black box (bottom) can indicate a zone within the GHSZ where the saturation of free gas is higher. The orange box (top) reinforces the interpretation of BSR continuity, also observed with the envelope attribute (Fig. 8).

Figure 12. Seismic section 0270-2004b with the 20 Hz decomposed frequency band (top) and with the -90º phase rotation and the envelope attribute (bottom). BSR is displayed in black. Lateral discontinuity of BSR can be noticed in the two sectors.

Figure 13. Seismic section 0270-2004b with the 40Hz decomposed frequency band (top) and with the -90° phase rotation and the envelope attribute (bottom). The red arrow (bottom) shows the lateral discontinuity of BSR. The orange boxes (top) highlight possible BSR continuity, also noticed with the envelope attribute (Fig. 7).

How to cite

copy

Sociedade Brasileira de Geologia R. do Lago, 562 - Cidade Universitária, 05466-040 São Paulo SP Brasil, Tel.: (55 11) 3459-5940 - São Paulo - SP - Brazil
E-mail: sbgeol@uol.com.br

Acompanhe os números deste periódico no seu leitor de RSS

Versão para download de PDF

PDF

Inglês

Versões e tradução automática

Versão original do texto

English

Tradução automática

Google Translator
Microsoft Translator

Como citar

RIS

BIBTEX

Outros formatos de citação e exportação:

SciELO - Scientific Electronic Library Online
Rua Dr. Diogo de Faria, 1087 – 9º andar – Vila Clementino 04037-003 São Paulo/SP - Brasil
E-mail: scielo@scielo.org

Leia a Declaração de Acesso Aberto

Métricas

Identification and analysis of bottom simulating reflectors in the Foz do Amazonas Basin, Northern Brazil

PlumX

Mensagem

[1] *Corresponding author.