南海西缘走滑带中南段的热模拟研究

Thermal Simulation of the Middle-south Section of the Strike-slip Fault Zone in the Western South China Sea

摘要:

南海西缘以走滑断裂系统为特色，是南海各陆缘中结构构造最复杂、研究程度相对欠缺的海陆构造边界。针对南海西缘走滑带的热效应研究程度低、而该走滑带又对周缘含油气盆地的形成和演化意义重大的现状，对西缘走滑带中南段进行了热模拟研究。通过模拟软件Comsol计算西缘走滑带中南段在距今约30Ma时间尺度下因走滑摩擦生热而产生的温度和热流，结果表明，中南段越东-万安断裂在距今30Ma时间尺度下、70km深度范围内，由于走滑摩擦而产生的最高温度约为434℃，产生的最大热流约为55mW/m²，而南段卢帕尔断裂在相同的时间尺度和深度范围内，由于走滑摩擦而产生的最高温度约为300℃，产生的最大热流约为40mW/m²，与实测结果相比，误差控制在15%以内。该热模拟研究结果为研究西缘走滑带周缘新生代盆地中烃源岩的热史及成熟史提供了基础理论依据，对走滑带周缘盆地的油气勘探潜力评价具有一定意义。

Abstract:

The western margin of the South China Sea is characterized by a strike-slip fault system,and it is one of the most complex structures and relatively lack of research at present of the various continental margins in the South China Sea. In this paper thermal simulations of the mid-south section of the western margin strike-slip fault zone were conducted because that the slip zone has significant implications for the formation and evolution of the surrounding petroliferous basins. The simulation software Comsol is used to calculate the temperature and heat flow generated by strike-slip friction in the middle-south section of the western marginal strike-slip fault zone at a time scale of about 30Ma. The results show that the maximum temperature generated by the strike-slip friction in the Yuedong-Wanan fault is about 434℃ and the maximum heat flow generated is about 55mW/m² at the 30Ma and the depth of 70km while the maximum temperature generated in the Lupaer fault is about 300℃ and the maximum heat flow generated is about 40mW/m² at the same time and the same depth. Compared with the measured results,the error is controlled within 15%. Our results provide a basic understanding of the thermal history and maturation history of source rocks in the Cenozoic Basins around the western marginal slip zone,and have important theoretical significance and practical application for the evaluation of the potential hydrocarbon exploration in the strike-slip fault zone.