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Data Integration from Side Wall Cores to Image Log to Seismic Architecture of Deepwater Cretaceous Section: An Example from Sierra Leone

Gerard, Jean *1; Painuly, Promod 1; Franquès, Jordi 1; Herrá, Adela 1; Mansary, Abdul 1; Franco, Alejandro 1; Net, Laura 1; Pallottini, Fabio 1
(1) Repsol, Madrid, Spain.

Exploration of Cretaceous deepwater sediments in West Africa provided information on reservoir potential that can be assesed at different scales. The understanding of depositional processes and architecture of the reservoirs relied on integration of the entire dataset including up-scaling with iterations between steps. An example of data integration from an exploration well is provided here.

As full conventional cores in wildcat is uncommon, several runs of side wall cores provide key information on the texture of the sediments, shale content, pore network, reservoir properties, and depositional facies. Close inspection of the SWC provided information on deepwater sedimentation as each facies was identified and interpreted in an updated facies classification based upon Mutti (1992 and 1999).

Discreet information provided by SWC was used for a close calibration of the image logs and to a lesser degree the set of conventional wireline logs in order to produce a continuous sedimentological log of the entire Cretaceous section.

Stacking pattern was analysed and compared with a detailed biostratigraphical study. Stratigraphical breakdowns and taxon events were used to validate the sequence analysis performed at different orders. A three-fold stratigraphic hierarchy was performed at 3rd order system, 4th order complex and 5th order storey, the later being the flow unit. Stacking pattern and facies succession led to a prediction of the architecture near the well bore.

The hierarchy of the stratigraphy and stacking pattern were used to calibrate various 3D seismic cubes (PSDM: Full stack, angle stacks) in order to get a better understanding of the different flow units in both map view and 3D as numerous incisions between channel storeys supply communicating points within lower order channel complexes.

Finally, an attempt to tie the stacking pattern, architecture and biostratigraphical breakdowns with eustatic sea level curve was done and checked against results from other exploration wells using random seismic lines tying these wells.
 

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California