西沙海区碳酸盐台地地震反射特征及沉积模式

Seismic reflection characteristics and depositional model of carbonate platforms in Xisha sea area

随着南海海盆的持续扩张,西沙海区整体沉降,从早中新世起西沙碳酸盐台地开始发育,而且在台地之上生长了不同类型的生物礁。通过地震识别认为,西沙海区生物礁在地震剖面上表现为顶底强振幅的丘形连续反射、内部弱振幅杂乱反射;碳酸盐台地表现为顶部强振幅连续平行反射、底部界面局部模糊、内部强弱相间亚平行连续反射。通过对西沙海区地层层序的分析以及大量地震资料的解释认为,在西沙碳酸盐台地的发育早期它受基底构造的控制,而在后期主要受多期海平面变化的影响,其发育演化经历了初始生长—加积—出露—二次生长—淹没等一系列阶段,复杂的演化过程也使西沙碳酸盐岩具有较好的储集条件和油气远景。

Xisha area subsided along with the seafloor spreading of the South China Sea,carbonate platform and different types of reef began developed from Early Miocene in this area.Based on the seismic analysis,reefs in Xisha area show high-amplitude moundy continuous reflection at the top and the bottom,chaotic reflection inside the reef,carbonate platform shows high-amplitude continuous sub-parallel reflection at the top and a partly obscure bottom boundary,the internal reflection shows high-amplitude reflection interbedded with weak-amplitude reflection.Based on the stratigraphic sequence analysis in Xisha area and the seismic interpretation,the development of Xisha carbonate platforms was mainly controlled by the basement structure at the early stage and then mainly controlled by the relative sea-level fluctuation,so Xisha carbonate platforms experienced several development stages such as initial establishment stage,aggradation stage,exposure stage and flooding stage.The complicated development process makes the carbonate reservoir to have favorable reservoir properties and hydrocarbon potential.