凸起及其倾没端——琼东南盆地深水区大中型油气田有利勘探方向

Rises and their plunges:favorable exploration directions for major fields in the deepwater area,Qiongdongnan basin

琼东南盆地深水区存在陵南低凸起、松南低凸起和北礁凸起,其上及其倾没端圈闭非常发育,这些(低)凸起被长昌凹陷、松南-宝岛凹陷、乐东-陵水凹陷、华光凹陷和北礁凹陷包围,呈典型的凹间凸构造格局。深水区烃源岩主要是下渐新统崖城组,其次是上渐新统陵水组和始新统,沉积相-岩性类型主要是潮坪和泻湖相暗色泥岩、煤层、碳质泥岩,中深湖相和浅海相泥岩,具"早期生油、晚期生气"特征。深水区北部的长昌凹陷、松南-宝岛凹陷和乐东-陵水凹陷南侧缓坡带古近系输导体发育好,其上覆新近系岩性以半深海相泥岩为主,断裂不发育且地层超压,凹陷内生成的油气主要沿古近系输导层侧向向松南低凸起、陵南低凸起聚集;深水区南部的华光凹陷和北礁凹陷结构均呈南断北超,凹陷内生成的油气也主要向松南低凸起、陵南低凸起运移。因此,松南低凸起、陵南低凸起及其倾没端为周缘凹陷所生成油气汇聚的主要方向,是深水区寻找大中型油气田最有利的成藏单元和勘探领域。

In the deepwater area,Qiongdongnan basin,there are three rises,i.e.Lingnan lower rise,Songnan lower rise and Beijiao rise,which are surrounded by Changchang sag,Songnan-Baodao sag,Ledong-Lingshui sag,Huaguang sag and Beijiao sag,forming a typical structural framework of ＂rise among sags＂.On the rises and in their plunges have developed multiple traps.The main source rocks in the deepwater area are in Lower Oligocene Yacheng formation,Upper Oligocene Lingshui formation and Eocene,occur as tidal-flat and lagoonal dark shales,coal measures,carbonaceous shales and semi-deep lacustrine/shallow marine shales,and are characterized by ＂early oil generation and late gas generation＂.There are well-developed Paleogene carrier beds along the south gentle slopes of Changchang sag,Songnan-Baodao sag and Ledong-Lingshui sag in the northern deepwater area,which are overlain by the bathyal-shale-predominated Neogene with overpressure but few faults,therefore making the sag-generated oil and gas migrate through the Paleocene carrier beds and accumulate in Songnan and Lingnan lower rises.In the southern deepwater area,Huaguang sag and Beijiao sag are faulted south and overlapped north,and the sag-generated oil and gas may also migrate towards Songnan and Lingnan lower rises.Consequently,Songnan and Lingnan lower rises and their plunges are the main directions towards which the hydrocarbon generated in the surrounding sags migrate and accumulate,becaming the favorable accumulation units and exploration plays for major fields in the deepwater area,Qiongdongnan basin.