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Global QI Manager
A new, high-quality regional dataset covering 22 469 sq. km is enabling the identification of important petroleum system elements in the underexplored Orphan Basin. Block evaluations for the upcoming license rounds can be performed with confidence with this multisensor broadband seismic data and its reliable prestack attributes. The most recently acquired part of this regional dataset is the North Tablelands survey acquired in 2019 as an extension of the Tablelands and Long Range surveys, which were acquired in 2017-2018 by PGS and TGS.
Stratigraphic complexity in the Tertiary reservoir section has traditionally been difficult to resolve on 2D data. East Canada requires deep structural resolution and high-fidelity data over deep and shallow targets. Strong lateral velocity variations between the Jurassic structural highs and the adjacent section add to the complexity. Wells drilled have been on the highs and not located accurately.
Depth migration techniques have been widely used in areas with strong lateral velocity variation. Least-squares migration is an emerging new imaging technique that compensates for acquisition limitations and variable illumination, and provides more reliable amplitude information particularly in areas of high structural complexity. In Tablelands, a data-domain LSM approach was selected to improve the vertical seismic image resolution and enhance the fault definition, especially in the syn-rift section.
Full waveform inversion (FWI) and least-squares migration (LSM) use the extra broad frequency range recorded in the GeoStreamer data to better estimate a detailed velocity field and produce a robust image of the subsurface. FWI addresses the key challenge of rapid lateral velocity variation while LSM increases the resolution in the reservoir sections.The FWI velocity model and LSM depth slice show the structural conformability of the estimated high-resolution seismic velocity field.
60 Hz one-way wave equation migration compared with PGS LSM. Least squares migration delivers a higher resolution image with significantly improved fault definition. Blue and orange markers indicate improvements in the Tertiary and Jurassic respectively. Blue arrows indicate improvements in the Cretaceous and Jurassic.
A final QI analysis including lithology and fluid prediction through a three-term AVO inversion was performed on the full integrity data from the Tablelands survey using all the available information including well log data. Three wells are present in the region of Long Range, Tablelands and North Tablelands; the Great Barasway F-66 well (drilled in 2006), Lona O-55 (drilled in 2010), and the Margaree A-49 well (drilled in 2013). These three wells drilled the main reservoir and source rock in the area. The Tithonian to Kimmeridgian interval was used to build a regional rock physics model. The Great Barasway well was modeled and has a good tie to the source rock and high-quality siliciclastic reservoirs.
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Global QI Manager
Senior Account Manager, NSA