Gravity Modelling in Ultradeep Lower Congo Basin - An insight to Non Volcanic margin

Abstract

The West African salt basin is one of the world’s major petroleum provinces and came into existence as a result of Early Cretaceous rifting during the breakup of West Gondwana. Conjugate margins experienced similar tectonic and sedimentary basin evolution during rifting. The rifting lasted for about 20 million years, and subsequently the Atlantic Ocean began to open. Evaporite deposition in the basin followed next during the Aptian to Early Albian periods. During the Albian, the Carbonate platform began to develop in the basin margin. Increased terrigenous influx from the Congo River during Tertiary resulted in the formation of salt withdrawal minibasins and complex salt diapirs. The ultradeep Lower Congo is the northern most basin of Angolan salt province. Our study area in the ultradeep Lower Congo basin includes Blocks 49, 50 and ultradeep North West. In order to understand the prospectivity in the ultradeepwater blocks, seven major events were interpreted, namely the basement, base salt, top salt, Albian, Top Cretaceous, Miocene-Pliocene boundary, and water bottom. One of the biggest challenges encountered during the study was interpreting the basement due to the poor seismic reflectivity beneath the salt diapirs. The basin contains Barremian to Early Aptian organic-rich source rock deposited in deep early-rift lakes under anoxic conditions. Therefore the gravity modelling was performed to understand the basement configuration. This abstract presents the main findings of an integrated modeling project in the ultradeepwater offshore Angola. The main objective of the project was to derive a top-crystalline basement structural horizon. A secondary objective was to refine the initial salt model.