Formation And Evolution Mechanism Of Salt Structures Developed In The Middle Of The South Atlantic

Chinese hydrocarbon exploration is heading for overseas,unconventional deep seated.and deep water environm ents The difference between the salt structures that developed on both sides of the South Atlantic and their forming mechuism are key scientific problems for high efficient hydrocarbon exploration and exploitation about salt structures related hydrocarb on reservoirs.Based on systematic interpretation of seismic pro files in the South Atlantic,different salt structures are recognized and their forming processes are reconstructed and modeled to recognize the main controlling factors.The following conclusions can be drawn:(1)There are 7 typical salt structures consisting of salt raftsalt pillow,salt anticline,salt stock,salt wall,salt canopy and salt sheet on both sides of the South Atlantic.They change in a sequence from salt rafts,salt diapirs,salt walls,and salt sheets from the seashore to the sea,forming different tectonic belts from east to west obviously.(2)The salt structures show strong segmentation from north to south and asymmetrical distribution between the South America,and the West Africa.Their asymmetrical distribution is indicated by arepeated sequence of salt walls and salt diapirs that have been found outside of the salt sheets both in the southern segment of the South America and in the northern segment of the West Africa.While no such repeating in the middle segment,indicating a symmetrical distribution.(3)The deformation of different types of salt structures can be divided into the following 5 stages:forming the bottom morphology before Aptian:precipitation of the Aptian salt province,slight deformation in late Early Cretaceous,strong deformation in Late Cretaceous and tectonic stabilization in Cenozoic(4)It is found that the deforma.tion and evolution of salt structures are mainly controlled by the slope declination.underlying uplift and differential loading from the overlying sediments.Salt structures are prone to develop in those regions with steeper bottom morphology,higher underlying uplift and thicker overlying sediment at ion.(5)The spatial distribution of the salt structures indicates that hydrocarbon exploration should be conducted preferentially in the Santos Basin and the Campos Basin in South America,and in the Kwanza Basin:the Lower Congo Basin and the southern Gabon Basin in West Africa.Research results have not only great theoretical significance for tracing the asymmetric rfting of the South Atlantic,but also practical value for hydrocarbon exploration and exploitation about salt structures related hydrocarbon reservoirs.