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热演化史研究是盆地模拟中的重要环节,可以为烃源岩成熟度史、生烃史、排烃史模拟提供必要的参数,以便准确地评价盆地的油气资源。本文根据局部均衡回剥技术所获得的万安盆地的构造沉降曲线,用现今地壳厚度作为条件限制,采用综合反演法将构造沉降曲线与岩石圈均匀拉张模式的理论构造沉降进行拟合,并且考虑地壳和沉积物中的放射性物质的生热量,研究了盆地的热演化史。此外,本文根据上述热演化史,采用David A.Wood法计算烃源岩的R_0值,研究烃源岩的热成熟度史。研究结果表明:自从晚始新世以来,除局部地区地幔热流逐渐增温外,万安盆地地幔热流和基底热流具逐渐减小的趋势,并有北高南低的特征。渐新统烃源岩在盆地中部与北部地区处于过成熟阶段、盆地南部则刚刚成熟,下中新统烃源岩在盆地的北部和中部地区处于成熟阶段和高成熟阶段。
The study of thermal evolution history is an important part of the basin simulation and can provide the necessary parameters for the maturity history, hydrocarbon generation history and hydrocarbon expulsion history simulation of source rocks in order to accurately evaluate the oil and gas resources of the basin. In this paper, according to the structural subsidence curve of Wan’an basin obtained from the local equilibrium back-stripping technique, the present crustal thickness is used as a condition to limit the structural subsidence curve and the theoretical structural subsidence of uniform lithospheric extension model using the integrated inversion method, Considering the heat generation of radioactive materials in the crust and sediments, the thermal history of the basin was studied. In addition, according to the above thermal evolution history, the David A. Wood method is used to calculate the R_0 value of source rocks and to study the history of thermal maturation of source rocks. The results show that, since the late Eocene, the mantle heat flow and base heat flux in Wan’an basin have a tendency of decreasing gradually with the increase of mantle temperature in some areas and the features of low north and high south. Oligocene source rocks are overmatched in the central and northern parts of the basin while the southern part of the basin is just mature. Lower Miocene source rocks are in the mature and mature stages in the northern and middle parts of the basin.