Sylvain Calassou1, Thierry Rives2
(1) Elf Exploration Production, Pau, France
(2) TotalFina Elf, Pau, France
ABSTRACT: Fault Sealing and Cap-Rock Integrity Prediction in Deep Water Turbidites
Present challenges in exploration of deep water turbidites are infilling and cap rock integrity. Their prediction is strategic in order to reduce risk when very high cost wells are concerned.
Using specific attributes from West Africa 3D seismic, we observe major and minor faults, and active gas chimneys and gas bubbles. These indicators are correlated with tructures suggesting fluid migration is associated with active deformation. As soon as, in this geological context, maturation and expulsion are contemporaneous with the last deposits (upper tertiary to present time), analysis of the relative distribution between structural heterogeneities and fluid indicators allow to constrain deformation mechanisms and a new 3D concept of deformation: sedimentary flattening, is proposed. This concept allows to understand complex geometry within channels and to localise unexpected faults and seismic fractures. A characterisation of fault types versus fluids indicators can be established and dynamic fault behaviors are deduced from the migration pathways. Where channels are superposed, complex migration pathways with horizontal and vertical fluid flows can be shown.
Chimneys and bubbles over reservoirs indicate cap rock active gas leakage which implies the presence of overpressured hydrocarbon. Reservoir hydrocarbon infilling can be deduced from the fault typology and from relationships between deformations and fluid indicators. Paradoxically leaking cap rock can evidence of a full hydrocarbon reservoir!
This new understanding and original approach of deformation mechanisms in deep water zones give new insight for exploration in gravity driven deformational context.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado