Analysis of 3-D Seismic Data from Block 3 in the Lower Congo Basin, Offshore Angola

Abstract

The Lower Congo Basin (LCB) is a rift basin located in the passive margin of Angola that resulted from the rifting of Gondwanaland, which led to the separation of the Angolan plateau with the South American plate during the Early Cretaceous 144-140 MA. The basin extends over 600 km between 5°S and 8°30’S of latitudes, and it is constrained by Casa Maria Arch to the north and Ambrizete Arch to the south. The basin has undergone pre-rift, rift, and post-rift tectonic phases associated with subsalt, salt, and supersalt units driven by thermal subsidence, extensional updip complex systems, and Aptian compressional salt downdip systems. The area of study is located in the southern part of the LCB, offshore Angola. It has a complex geologic context with a petroleum system comprised of shales, carbonates, and turbidites deposited into marine and deltaic environments. Moreover, regional anticlines and half grabens containing syn-deformational strata have been associated with the LCB. However, the area of study lacks detailed structural and petroleum system analysis. The main focus of this research is to provide a general structural and petroleum system characterization of the area of study based on 3-D seismic reflection and well data provided by the Angolan oil company Sonangol EP. The well data was used to assess possible areas of interest as well as to create a synthetic seismogram that was used to tie the well to real seismic data; meanwhile, the seismic reflection data was used to track reflections of interest, map faults, create surface and isopach maps, extract seismic attributes, and evaluate seismic facies. In addition, the 3-D seismic data was also used to map unconformities and a large anticline bounded by half grabens and listric and planar normal faults.