Contribution of high‐resolution 3D seismic near‐seafloor imaging to reservoir‐scale studies: application to the active North Anatolian Fault, Sea of Marmara

Abstract

High Resolution (HR) marine seismic acquisition contributes to numerous research fields. The vertical resolution is of metric scale in order to study geological processes at a short time scale or to characterise small objects. 3D seismic imaging allows optimal resolution to be reached whereas 2D images are blurred mainly by side effects. Developed for the oil industry decades ago and tailored to the exploration for hydrocarbon reservoirs, 3D seismic, as applied to higher resolution targets, is more recent. Available technological advances in acquisition have allowed research institutes to develop innovative 3D high‐resolution marine seismic systems tailored to these targets. The seismic survey carried out in 2009 on the Western High, Sea of Marmara, illustrates the value of HR3D imaging. Since the destructive İzmit earthquake in 1999, an intensive international research effort has demonstrated that the Western High is one of the key structures for assessing the processes of deformation related to the North Anatolian Fault (NAF). The 30‐km2 HR3D survey centred on the main NAF was acquired using a dual streamers ‐ dual source‐array configuration. In spite of the minimal 3D processing sequence that was applied to the data, the fine imaging of the seabed and of the sedimentary stratigraphy and structures is much better than HR2D seismic. Comparison with an autonomous underwater vehicle (AUV) multi‐beam bathymetric survey carried out at the same location enables the limits of the vertical resolution of the seismic data to be assessed. The lateral resolution is between 13.5 and 25 metres at the seabed. The HR3D seismic data highlight the interplay between tectonic processes and stratigraphy. In particular, differential uplift leads to syntectonic deposition and submarine slides. The widespread occurrence of gas in the sedimentary sequence is clearly shown by anomalously high seismic amplitudes. 3D imaging of these high amplitudes enables the identification of the pathways through faults and permeable units that gas takes as it migrates to the seabed.

Gas and seismicity within the Istanbul seismic gap

“…At shallow levels, the gas migration pathways were mapped down to a few hundred meters beneath the Western High seabed, using 3D, high-resolution seismic data collected in 2009 46 (Fig. 6).…”

“…The data also reveal that gas follows buoyancy-driven, upward migration paths in permeable layers and along faults, controlled by the regional strain field as it is expressed in the seafloor topography, with the primary E-W orientation parallel to the NAF and secondary tectonic orientations oblique to the NAF 47 . Locally, mud volcano-like structures may also offer preferential pathways for the gas to migrate up to the seafloor.

Figure 6Seismic section extracted from the high-resolution 3D seismic box shot in 2009 46 along the thick black line displayed in Fig. 5, with a simplified, tentative interpretation.

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“…Seismic section extracted from the high-resolution 3D seismic box shot in 2009 46 along the thick black line displayed in Fig. 5, with a simplified, tentative interpretation.…”

Ultra-high resolution 3D marine seismic: an overview

“…: [Arthur et al, 2011;Thomas et al, 2012]) сейсмические прие-моизлучающие системы принято классифицировать по разрешающей способности и частотному составу записи:…”

“…В работе [Thomas et al, 2012] приведена класси-фикация существующих систем с учетом частотного состава возбуждаемых колебаний и, соответственно, разрешающей способности и глубинности исследова-ний. Ниже приведена дополненная авторами таблица с учетом всех известных нам на сегодняшний день систем для проведения 3D сейсмоакустических наб-людений на акваториях.…”