--> Long Offset AVO in an Integrated Approach for Optimized Field Development Planning on the AKPO Field, Nigeria, by Annie Durand, Laurent Guy, Rosnes Rune Hope, Henri Houllevigue, Severine Lalande, Frederic Merlet, and M. Rowlands; #90037 (2005)
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Long Offset AVO in an Integrated Approach for Optimized Field Development Planning on the AKPO Field, Nigeria

Annie Durand1, Laurent Guy2, Rosnes Rune Hope2, Henri Houllevigue3, Severine Lalande1, Frederic Merlet3, M. Rowlands2
1 Total, Paris la Defense, France
2 Total,
3 Total, Port Harcourt, South Africa

The AKPO Field is a Giant discovery made in April 2000 and situated in 1350m of water some 140km offshore Nigeria in OPL 246. The License is operated by South Atlantic Petroleum (60%) with Total Upstream Nigeria Ltd as Technical Adviser (24%) and Brasoil (16%). The Miocene reservoirs are deposited in a turbiditic environment representing an alternation of channels and lobes between 2500-4000 mSS. Five wells have been drilled to date. Reprocessing of the original 3D seismic data acquired in 1998/99 was initiated in 2003 with the objective of using long offset Previous HitAVANext Hit (Amplitude Previous HitVariationNext Hit with Previous HitAngleTop) attributes to ensure the best possible reservoir characterisation and future drilling trajectories. Long offset AVO has been proven to be a useful exploration tool for Deep-Offshore Africa. In recent years, TOTAL has attempted to make better use of AVO data and its related attributes to optimise the field reservoir model, implementation of complex wells and the Field Development Plan. This requires:

  • Several wells with accurate Vp, Vs, Density and Walkaway VSP for a calibrated petroelastic model.
  • High quality borehole guided reprocessing including definition of adequate AVO sub-stacks.
  • Elastic simultaneous inversion of sub-stacks Definition of relations between seismic attributes and geology.
  • Integration of seismic derived attributes in the reservoir model and well trajectories design.
  • 2D or 3D synthetic elastic modelling of 40 seismic effects expected in the reservoir.

An integrated approach in the interpretation and synthesis of the results is crucial and requires team work by the geoscientists all the way to development. Integrated reservoir characterisation using reprocessed AVO data leads to improved seismic resolution and inversion results; improvements in the sedimentological and reservoir modelling; more accurate reserves estimation; optimised drilling trajectories and also provides a guideline for future seismic monitoring of the field.