南海裂陷盆地中斜向伸展及其油气勘探意义

OBLIQUE EXTENSION DEFORMATION WITHIN A RIFT BASIN AND ITS SIGNIFICANCE OF HYDROCARBON EXPLORATION

利用海上钻井、地震等资料,重新认识南海珠江口盆地文昌B凹陷控凹边界南断裂构造变形史及动力学机制,探讨油气勘探意义。研究表明,渐新世—中新世,南断裂具有斜向伸展性质,在倾向剖面,断裂带发育挤压褶皱和破碎主位移带的构造样式;在走向剖面,相关地层呈"厚薄相间"分布。平面上,发育雁列式背斜与洼地共生、"马尾状"断裂体系和右阶斜列阶步断裂体系。斜向伸展动力学机制受控于区域伸展构造应力场与先存南断裂走向。南断裂渐新世—中新世斜向伸展变形,控制和影响了油气成藏要素、流体相态。

Based on drilling well and 3D seismic data of the Wenchang B Sag in the Pearl River Mouth Basin,the tectonic deformation history and dynamic mechanism of the South Fault were reanalysized. The study shows that the South Fault was characterized by oblique extension during Oligocene and Miocene. On the dip of seismic sections, the South Fault are associated with some specific structural styles,such as squeezed fold and fractural displacement zone. On the strike of seismic sections, the re- lated strata show wavelike lateral extension with thin sediments on ＂wave peak＂ and thick sediments in ＂wave valley＂. In a plane view, there exist echelon anticlines and depressions, horsetail faults and right diagonal step faults in the Oligocene. The deformation of oblique extension is supposed to be controlled by a regional extension tectonic stress field and the existing early boundary fault. The ob- lique extension deformation of the South Fault has important effects on the hydrocarbon pools and hy- drocarbon phases.