Published September 15, 2021 | Version v1
Conference paper Open

Case Study from N.W. Carnarvon using WEB-AVO Inversion to Map Low Saturation Gas & Unravel Geology Using 'Noisy' Seismic

  • 1. Delft Inversion, Paardenmarkt 1, 2611PA Delft,, The Netherlands, coffin@delft-inversion.com
  • 2. Delft Inversion, Paardenmarkt 1, 2611PA Delft,, The Netherlands, kelsay@delft-inversion.com
  • 3. Chevron Australia Pty Ltd, 250 St Georges Terrace, Perth, WA 6000, Australia, srehman@chevron.com

Description

This case study applies the next generation of seismic AVO inversion technology to a project in the NW Carnarvon Basin offshore Western Australia. The technology is called WEB-AVO (Wave Equation Based - AVO Inversion) and no longer considers the earth as a series of layers with interfaces that create primary only reflections. The difference is that WEB-AVO does not use the reflectivity and convolution model. Instead, it applies the wave equation that considers the total wavefield in the reservoir interval. This includes primaries, interbed multiples, mode-conversions and transmission effects. The area studied considers the Main Barrow Sand for a blind test and then looks at the Mungaroo which is known to have a complex wavefield in this area. The Mungaroo has significant overburden challenges, and it is not obvious if these are creating AVO false positives. The results show a robust match to a blind well in the Barrow Sands which confirms the stability of the algorithm. In the Mungaroo we used a technique called Interbed Multiple Investigation (WEB-IMI) to explore the source of the complex wavefield. We studied the progression of the wavefield over the interval and see the compounding effects from the non-primary energy. In the inversion we contrast the results using a conventional inversion (where primaries only are considered) and contrast this with the WEB-AVO results on both 'raw' and 'conditioned' gathers. We see the greatest uplift between the primaries only and the WEB-AVO results and discuss the conditioning. Finally, using the inversion products; compressibility () and shear compliance (M), we were able to separate the different reservoir sands present within the Mungaroo. We identify unique characteristics in this domain, and this then allowed us to resolve the confusion caused that was caused by the AVO false positive.

Notes

Open-Access Online Publication: March 01, 2023

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