Regional Hydrocarbon Charge Risk in Offshore Nigeria — New Insights from Charge Modeling and Structural Geology
Gary P. Muscio, Carlos Rivero, Richard Eisenberg, and Betty Johnson
Chevron, Houston, TX
A regional evaluation of hydrocarbon charge was undertaken in the offshore Niger Delta integrating petroleum geochemistry, numerical charge modeling, structural geology and potential fields in order to improve the prediction of charge fairways and distribution of oil and gas.
A comprehensive geochemical database consisting of rocks and crude oils, complimented by suitable piston core data was integrated with maturity and fluid flow modeling and potential fields data in order to assess the relative importance of drilled and undrilled source rock candidates as contributors to charge.
In addition to these more traditional hydrocarbon charge analyses we have investigated the impact of structural evolution on timing of oil and gas generation, focus of migration, as well as fluid type. This was achieved using new techniques that numerically integrate structural restorations and classical charge modeling of selected regional transects spanning extensional and contractional provinces in the deepwater and on the shelf.
This new approach has the potential to improve pre-drill risk assessment of hydrocarbon charge in tectonically active plays compared to a classical charge modeling approach. Our results illustrate that the prediction of source rock maturation and petroleum migration in footwalls of thrust terrains can be improved by integrating structurally restored sections. Furthermore, charge modeling without the benefit of using structural restorations can potentially misrepresent timing relationships between hydrocarbon generation and trap formation. This misrepresentation can have significant impact on predicted fluid type and volumes. Structural analysis also provides controls on timing of fault activation, enabling improved modeling of fluid flow where faults can act as migration conduits or as permeability barriers.
AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery