Tectonic Evolution And Thermal History Simulation Of The Lower Congo Basin

Lower Congo Basin belongs to typical passive continental marigin basin and located in West Africa coast, which experienced three evolution stages, i.e. the pre-rifting stage, rifting stage, transition stage and the passive continental marigin.In recent years it has become one of the hottest oil and gas exploration region on a global scale.In this paper, combining previous research results, using different methods to carry out the structural evolution, burial history, thermal evolution simulation of the three aspects of research, according to the result of simulation and recovery and different areas of the basin deposition rate and thermal evolution degree of comparative analysis, then provide a scientific and theoretical basis for the discovery of the Lower Congo basin in the field of oil and gas resources exploration.According to the data collection and analysis, this paper mainly discusses the basin tectonic evolution, strata sedimentary characteristics, sedimentary face change relation with ancient water depth, physical properties of rock feature, present geothermal field (ground temperature, geothermal gradient and rock thermal conductivity, heat flux) distribution and other aspects of research, establish the important basic parameters for the burial history and thermal history in the process of basin simulation research.Segmented back stripping technology has been used in the study of the burial history, research found that the thickness of the rift stage strata is 2000-3000m, which has the northwest, central and southwest three sedimentary depression center with a decentralized distribution; and the strata thickness in the depression period is 1000-2000m, sedimentary depression centers concentrated in center and south. The deposition rate of the basin in each period is different, the deposition rate overall discipline is gradually higher in rifting and depression stage and long-term stability with low rate in drift Ⅰ-Ⅱ stage,while it shows a sharp steped increase in early and late Neogene(driftⅢ).Using the combination of the instantaneous shear mode and geochemical dynamics mode to analysis geothermal and thermal evolution history of the basin, the geothermal gradient in the strata of upper Aptain evaporates is 3℃/100m, while the geothermal gradient under the Aptain evaporates reach to 4℃/100m, the reason of the variance is the geothermal gradient and heat conductivity of each strata are different. According to the analysis of measured heat flow data shows that the basin heat flow variance from north to south and east to west, the feature in east and north is high, low in south and west, the average heat flow is 50-70 mW/m2. In the respect of N-S thermal evolution, the general characteristics is high in the central and northern and low in southern. At the same time, the thermal evolution feature of W-E is high in sham and ultradeep water(west region), medium in continental shelf(central region), low in the continental area(east region).