南沙海域构造演化与油气资源前景

TECTONIC EVOLUTION AND HYDROCARBON POTENTIAL OF NANSHA OFFSHORE AREA

运用地质构造活动论和地壳演化阶段论的观点 ,分析、研究了南沙海域区域构造演化的历史及其与盆地形成的关系。研究表明 ,南沙海域为东亚大陆边缘的一个组成部分 ,在其形成、演化过程中具有明显的旋回性和阶段性。依其地球动力学背景及演化过程 ,将南沙海域分为两大演化旋回 ,即盆地形成前演化旋回和盆地形成演化旋回。前者相对单一 ,后者又可分为三个演化阶段 ,即晚白垩世—中始新世裂谷—断陷阶段、晚始新世—中新世断坳反转阶段和晚中新世—第四纪热沉降阶段。与之相对应 ,形成了 13个沉积盆地。在这些盆地中 ,蕴藏着极其丰富的油气资源 。

According to the viewpoints of the theory of geological tectonic activity and the theory of crustal evolution stage; the regional tectonic evolution history and its relation to basin formation in Nansha offshore area are analyzed and studied in the paper. Through an investigation, it was indicated that the Nansha offshore area is of obvious cyclicity and staging character in the process of its formation and evolution, being a component part of the East Asia continental margin. In consideration of the geodynamic background and evolutional process, this area may be divided into tow macrocycles , i. e. basin-preformed cycle and basin-formed cycle. The former is relatively unitary, but the latter may be also divided into three sub-stages. They are the rift stage from Late Cretaceous to Middle Eocene; the fault-sag overturning stage from Late Eocene to Miocene; and the thermal subsidence stage from Late Miocene to Quaternary. 13 sedimentary basins were formed in correspondence with these stages. These basins will be the new fields of offshore oil and gas exploration in China, being rich in hydrocarbon resources.