沉积盆地下古生界碳酸盐岩地区热历史恢复方法探索

古温标是目前恢复沉积盆地热历史最常用方法之一,但在下古生界高过成熟碳酸盐岩由于没有合适的成熟度标定参数(古温标),对其经受的热历史和成烃史的恢复一直是困扰中国海相碳酸盐岩油气勘探的问题。目前常用的沥青反射率、牙形石色变指数、镜状体反射率等各类古温标,在用于早古生代碳酸盐岩地区的热历史恢复时都是借助于它们各自与镜质体反射率之间的关系,再利用现有的镜质体反射率模拟热历史方法来恢复热历史,因而存在不同的缺陷。重点介绍了利用有机质自由基浓度作为碳酸盐岩地区古温标的可能性。通过不同时间和温度下的热模拟得到的有机质自由基浓度数据,初步建立了三种类型有机质的自由基浓度(N)与时间-温度指数(TTI)的定量模型。这种有机质自由基浓度与TTI的关系式为碳酸盐岩地区古地温的恢复提供了新的方法。

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.