The Laurabada UltracubeTM project entailed the reprocessing of two open-file 3D datasets with a modern broadband de-ghosting and pre-stack depth migration sequence over what is highly sought-after acreage. The UltracubeTM is split into two cubes: The Eastern cube is near-shore, shallow water whilst the Western cube is deep-water in the Gulf of Papua.
There has been a significant data quality uplift from the reprocessing of the legacy data which has revealed exciting new potential in the Gulf of Papua.
Source and receiver deghosting was applied in the reprocessing which significantly improves the low frequency content. For Laurabada East, this helps with the imaging below the fold belt as that is quite dispersive and attenuative with the seismic source. Similarly, on Laurabada West, there is multiple large carbonate bodies that are highly absorptive which is only penetrated by the low frequency signal.
The legacy processing only applied 2D SRME for the demultiple, whereas the reprocessing has used 3D GSMP/SRME from Western Geco. In the fold belt on Laurabada East this in particular helped with the complex diffracted multiples from the seabed that were contaminating the pre-Tertiary grabens. On Laurabada West there were complex peg leg multiples from the top carbonates which were modelled and subtracted effectively.
The legacy processing only used an isotropic PSTM workflow, whereas the reprocessing used an anisotropic TTI pre-stack depth migration. In Laurabada East, the PSDM workflow allowed for high resolution velocity modelling in the fold belt which improved the pre-Tertiary graben imaging and depthing. In Laurabada West, there was detailed carbonate velocity modelling which combined with the deghosting allowed for much improved resolution on the flanks and base of the carbonate pinnacles.
The Laurabada West UltracubeTM 3D Reprocessing Survey comprises of ~770km2 whilst the Laurabada East UltracubeTM 3D Reprocessing Survey covers ~1,020 km2.
|Key Processing Parameters||
Source and receiver broadband deghosting
5 iterations of anisotropic tomography for velocity model building
Kirchhoff Pre-Stack Depth Migration
Kirchhoff PSDM Full stack and 4 angle stacks
Kirchhoff PSDM final CDP gathers
Velocity and anisotropy products
What does it mean when Bottom Simulators are Black Swans
Author: Karyna Rodriguez, Neil Hodgson, Julia Davies (Discover Geoscience)
GEO ExPro – June 2021
Determining the geothermal gradient in an undrilled region has direct implications for basin modelling and remains one the largest areas of uncertainty in frontier basin exploration today. Bottom Simulating Reflectors (BSRs) occur at the base of a shallow gas hydrate layer in many of the worlds deep water basins and by calculating the geothermal gradient from the sea floor to base hydrate, quantitative and qualitative inference of the deeper heat flow can assist basin modellers in their work. However, BSRs do not always simulate the seabed and such deviant behaviour can lead them to be interpreted as ‘anything but’ the base of the gas hydrate. Yet such black swans suggest BSRs may be even more useful in mapping variations in heat flow and geotherm than we had previously recognised.