Abstract:

Petroleum systems of block A in Lower Congo Basin were divided into two salt layers such as pre-salt and pos-salt, and hydrocarbon of this two systems migrated in different ways. Based on seismic and basin modeling data, temperature and pressure fields were employed to calculate density of oil and gas in order to find out the characteristics of fluid potential and its implication to hydrocarbon migration and accumulation in block A of Lower Congo Basin. The fluid potential of post-salt petroleum system was controlled by depth and sedimentary facies. Hydrocarbon migration dynamics exhibited fluid potential driving difference, with the most important controlling factors being buoyancy and capillary pressure. The key factor of hydrocarbon accumulation is the good match between effective tensional fault, marine oil-gas source rock and turbidite stone. The fluid potential of pre-salt petroleum system was characterized by depth-controlled and hydraulic pressure-controlled while buoyancy and overpressure allowed hydrocarbons to migrate. The key factor of hydrocarbon accumulation is the coupling between burial depth of strata underlying salt layer and salt thickness. Overall, fluid potential is better matched with hydrocarbon discovery in the study area, and the coinciding lower regions of oil, gas and water potential are the major next-term exploration area.

Key words:  tight sandstone, ground stress , resistivity , horizontal principal stress