PGS has launched a quantitative interpretation of its large MegaSurveyPlus dataset offshore Congo.
PGS has launched a quantitative interpretation of its large MegaSurveyPlus dataset offshore Congo.
The geology of the region is revealed beyond block boundaries, enabling new insights into the petroleum systems, play fairways, and analogous discoveries. Opportunities can now be analysed in prestack detail down to prospect level.
Offshore Congo’s proven pre and postsalt petroleum systems have been generating oil and gas for more than 50 years and the area has been extensively covered with 3D seismic data. However, the data was acquired piecemeal, with a focus on specific targets, said PGS.
Congo’s national oil company SNPC partnered with PGS to match and merge final full-stack data from many legacy volumes to create 22,415 km2 of 3D data, 5331 km of matched 2D seismic data. They then added regional interpretation with key horizons tied to released well data.
In 2019, that coverage was enhanced by MegaSurveyPlus reprocessing of 3D data across nearly 9000 km of open and held acreage.
The Congo MegaSurveyPlus was constructed by reprocessing field data from the Congo MegaSurvey, using modern broadband imaging methodologies, including the elimination of multiples and depth velocity model building.
Large lateral variations in velocity introduced by the carbonates and complex salt bodies are handled correctly, on a regional basis, allowing a clear 3D image under the salt for the first time while accurate salt geometry improves understanding of its role in sealing, hydrocarbon migration and trap development, said PGS.
PGS set out to demonstrate the feasibility of using the clear structural image and consistently reprocessed prestack data provided by the Congo MegaSurveyPlus to generate reliable attributes for lead identification across a portion of the shelf.
The team took an integrated approach, treating the angle stacks with reservoir-orientated prestack conditioning (ResOP) to enhance the prestack seismic data. This data was used as input to PGS’ prospect scanner workflow, to estimate relative P-impedance, S-impedance, and Vp/Vs, allowing regional lithology and fluid screening, said PGS.
Finally, applying the available well data to understand the rock-physics relationships in the area, a correlation was made from petrophysical properties to seismic responses found in hydrocarbon reservoirs, which typically display a low relative acoustic impedance and Vp/Vs compared to brine-filled reservoirs.
