Study of the thermal history reconstruction for Lower Paleozoic carbonate succession

The palaeothermometry is one of the most in use methods to reconstruct the thermal history of sedimentary basins. However, the reconstruction of thermal history and hydrocarbon generation history of high/over matured carbonate succession in the Lower Paleozoic has long been a difficult problem for lack of suitable and mature index and palaeothermometry, which has obstructed the oil and gas exploration in the marine carbonate areas in China. Some palaeothermometries, such as bitumen reflectance, CAI of conodonts, reflectance of vitrinite-like macerals, are employed to study thermal history of Lower Paleozoic carbonate areas by applying the vitrinite reflectance models, based on the relationship between these indexes and vitrinite reflectance. Since these indexes have some different shortcomings, this paper introduces the application of free radical concentration as paleotemperature index in carbonate area. A series of free radical data are tested based on the thermal modeling of different types of kerogen under different temperature and time, and quantitative models are obtained between free radical concentration of organic matter and time-temperature index (TTI) for three types of kerogen, which may provide a new method to reconstruct the thermal history of carbonate succession.