Modeling intrasalt layers when building velocity models for depth migration: Examples of the Santos Basins,  Brazilian offshore

Maul, Alexandre; Fonseca, Josué; Teixeira, Leonardo; Barros, P.; Boechat, João Batista; Nunes, J.P. Pereira; Yamamoto, T.; González, María; González, Gaspar

doi:10.1190/segam2018-2996209.1

Cited by 7 publications

(17 citation statements)

References 9 publications

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“…The representation of geological features decreases the computational effort as it reduces the numbers of iterations in order to obtain good gather alignments prior to the final migration process (Maul et al, 2018a).…”

Section: Discussionmentioning

confidence: 99%

“…In this study, the wells were labeled with capital letters from A to N, and the official names can be found in Table 1. Maul et al (2018aMaul et al ( & 2018c demonstrate, using 182 wells of different 9 projects/fields in the Santos Basin, that the evaporitic section of these studied fields has many features in common, such as mineral percentages of occurrence, mineral percentages x thickness relation and velocity ranges per mineral groups.…”

Section: Study Area and Available Datamentioning

confidence: 99%

“…During the methodology development, several applications have taken advantage of using this strategy of modeling evaporitic stratifications. The more promising applications are related to uncertainties Jardim et al, 2015), geomechanics (Toríbio et al, 2017;Teixeira et al, 2018), Kirchhoff migration and Reverse Time Migration -RTM (Gobatto et al, 2016;Fonseca et al, 2018;Maul et al, 2018a) and the initial model for Least-Square Migration (Dias et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

“…Observe the better imaging when using the model with the stratification insertion: better continuity of the reflector Bx over Ax and By over Ay, and the more coherent positioning in Bz than Az (notice the evaporitic behavior above the analyzed point). Adapted fromMaul et al (2018a).…”

mentioning

confidence: 99%

“…Observe the better focusing of the image when using the model with the stratification insertion: positions Bx over Ax, and better imaging building (continuity in geology) in By than Ay. Adapted fromMaul et al (2018a).…”

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confidence: 99%

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Improving Pre-Salt Reservoirs Seismic Images When Considering the Stratified Evaporites Insertion in the Initial Model for the Velocity Updating Processes Prior to the Seismic Migration

Maul¹,

Santos²,

Silva³

et al. 2019

Braz J Geophys

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ABSTRACT. Structurally complex areas, such as the pre-salt section in the offshore Santos Basin, SE Brazil, is a challenge to represent the geology using seismic images. One of the main causes of the observed imaging problems is the evaporitic section and its considerations about velocities used for seismic migration purposes. Some authors consider set to this section an almost constant value (close to 4,500 m/s) which approximately represents the halite velocity, the most abundant mineral in this salt formation. Others, over these models, apply the tomographic inversion or FWI schemes giving to the velocity model the mathematical support to build confident seismic images. We believe in the importance to build starting velocity models reflecting the existing geological features prior to applying the tomographic/FWI updating. In this sense, we propose the insertion of the so-called stratifications within the evaporitic section using an adaptation of the model-based seismic inversion technique. Following this new velocity model including the stratification, we suggest tomographic iterations update, or FWI, to add to the geological constrains of the model the needed mathematical convergence. Finally, in this work, we performed the seismic migration with and without inserting these geological features in the initial velocity model and compared the results.Keywords: evaporitic section, stratifications, velocity model, seismic migration, seismic image.RESUMO. Em áreas estruturalmente complexas, como na seção pré-sal da Bacia offshore de Santos, região SE do Brasil, é um desafio representar a geologia utilizando imagens sísmicas. Uma das principais causas dos problemas observados está nas considerações sobre a seção evaporítica e suas velocidades com propósito de migração sísmica. Alguns autores consideram esta seção como tendo velocidades aproximadamente constantes (próximas de 4.500 m/s), o que representa aproximadamente o comportamento da halita, o mineral mais abundante nesta seção. Outros, sobre este modelo aplicam a atualização por inversão tomográfica ou FWI para dar ao modelo de velocidades o suporte matemático necessário para construir imagens sísmicas confiáveis. Nós acreditamos na importância de construir modelos iniciais de velocidades que reflitam as características geológicas existentes antes de aplicar esta atualização tomográfica/FWI mencionada. Neste sentido, propomos a inserção das denominadas estratificações dentro da seção evaporítica, utilizando uma adaptação da técnica de inversão sísmica model-based. Seguindo este novo modelo incluindo as estratificações, sugerimos a atualização por iterações tomográficas, ou FWI, para adicionar ao controle geológico do modelo a convergência matemática necessária. Finalmente, neste trabalho, nós realizamos a migração com e sem a inserção destas características geológicas no modelo inicial de velocidades e comparamos os resultados.Palavras-chave: seção evaporítica, estratificações, modelo de velocidade, migração sísmica, imagem sísmica.

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Section: Discussionmentioning

confidence: 99%

Section: Study Area and Available Datamentioning

confidence: 99%