Application of inversion to support exploration and development growth opportunity maturation across the North West Shelf asset, Australia
Matthew Docherty A * and John Coffin BA
B
Matthew Docherty graduated with a BSc in Geology from the University of Birmingham (1993) and a PhD from the University of Manchester (1998). He has worked internationally for Hess, Maersk Oil and Woodside Energy on a range of Exploration, Development and Production related assets and projects in the North Sea, West Africa, Gulf of Mexico and the Middle East. He joined Woodside Energy in 2015 and is presently a Geological Advisor for Australia Operations, working in the North West Shelf Asset Team. An active member of PESA, he is currently Secretary and Committee member for the WA branch. |
John Coffin is the Business Manager Asia-Pacific for Delft Inversion. He is a graduate in Geophysics from the University of Leicester (1989) and has been employed in the energy industry for over 30 years. He has worked for Digicon, SSL, Schlumberger, Hampson-Russell, Veritas and CGG. In 1993, he started the London office for Hampson-Russell and has been directly involved in AVO and inversion ever since. In 2004, he moved to Perth, Australia, growing the business in the Asia-Pacific region. In 2020, he joined Delft Inversion and has been establishing a place for WEB-AVO technology in Asia-Pacific. Today, his focus is to see WEB-AVO deliver on its promises as the next generation of AVO inversion. John is an active member of PESA, ASEG, EAGE, SEG and SEAPEX. |
Abstract
The Woodside Energy operated North West Shelf asset covers over 5200 km2, with 15 gas fields producing across multiple Triassic to Jurassic aged reservoirs. To support further exploration and infill opportunity maturation, several seismic wave-equation-based amplitude variation with offset (WEB-AVO) studies have been completed, utilising newly reprocessed 3D seismic data. These studies are targeting specific risks, such as reservoir or gas presence, and uncertainties associated with gas-water-contact (GWC) depth and initially in place (GIIP) volume estimates. The WEB-AVO inversion solves directly for the reciprocals of bulk and shear moduli, compressibility (κ) and shear compliance (M), together with density (ρ). Compressibility is very sensitive to porosity, saturation, shale volume and lithology changes when compared to traditional elastic attributes and can be highly effective for addressing GWC uncertainty. A phased approach was employed in each study, initially building a regional rock physics understanding before focussing on specific targets. With WEB-AVO inversion a key initial step is 1D inversion at well control to ensure the robust recovery of the compressibility and shear compliance information required from the seismic data. A 2D arbitrary line WEB-AVO pilot intersecting offset well control was the next stage to characterise the reservoir(s) away from the 1D inversion tests and then optimise inversion parameters spatially. In the final stage a complete 3D inversion for the whole area was completed and this used the parameterisation optimised from the earlier 1D and 2D inversion testing. These products have significantly improved understanding of exploration and infill opportunity risks and volume uncertainties.
Keywords: exploration and development, seismic inversion, uncertainty and risk reduction, wave-equation-based amplitude variation with offset.
Matthew Docherty graduated with a BSc in Geology from the University of Birmingham (1993) and a PhD from the University of Manchester (1998). He has worked internationally for Hess, Maersk Oil and Woodside Energy on a range of Exploration, Development and Production related assets and projects in the North Sea, West Africa, Gulf of Mexico and the Middle East. He joined Woodside Energy in 2015 and is presently a Geological Advisor for Australia Operations, working in the North West Shelf Asset Team. An active member of PESA, he is currently Secretary and Committee member for the WA branch. |
John Coffin is the Business Manager Asia-Pacific for Delft Inversion. He is a graduate in Geophysics from the University of Leicester (1989) and has been employed in the energy industry for over 30 years. He has worked for Digicon, SSL, Schlumberger, Hampson-Russell, Veritas and CGG. In 1993, he started the London office for Hampson-Russell and has been directly involved in AVO and inversion ever since. In 2004, he moved to Perth, Australia, growing the business in the Asia-Pacific region. In 2020, he joined Delft Inversion and has been establishing a place for WEB-AVO technology in Asia-Pacific. Today, his focus is to see WEB-AVO deliver on its promises as the next generation of AVO inversion. John is an active member of PESA, ASEG, EAGE, SEG and SEAPEX. |
