莺歌海盆地的构造反转作用及其油气勘探意义

Structural inversion and its significance for oil & gas exploration in Yinggehai Basin,NW South China Sea

莺歌海盆地是北西走向红河断裂带末端在第三纪走滑运动形成的扭张性断陷盆地,控制盆地形成演化的构造动力在早—晚渐新世和中—晚中新世发生了改变,导致盆地内部发生了两期性质不同的构造反转作用。晚渐新世—中中新世期间的构造反转表现为轴向近南北的褶皱变形和沉降中心向东南方向的迁移,晚中新世至今的构造反转使盆地西北边缘的北东走向断裂发生反转逆冲。晚渐新世—中中新世构造反转作用导致盆地西北部和中南部的油气聚集特征存在明显差异。

The Yinggehai Basin is a transtensional rift basin formed by a strike-slip movement of the NWtrending Red River Fault Zone during the Tertiary. The controlling stress field of the basin changed during the periods from the Early to Late Oligocene and from the Middle to Late Miocene, which led to two stages of different structural inversion. The inversion from the Late Oligocene to the Early Miocene was characterized by the folds with roughly NS-trending axes and the depocenters immigrating toward SE, while the structural inversion from the Late Miocene till now led to inversion and thrust of the NE-trending boundary faults northwest of the basin. The inversion from the Late Oligocene to the Middle Miocene led to obvious discrepancy of oil ＆ gas accumulation between the northwestern and the central-southern parts of the basin.