珠江口盆地白云-荔湾深水区珠江组大型水道体系的发现与勘探意义

Discovery and exploratory significance of a deep-water channel system in Zhujiang Formation,Baiyun-Liwan sag,Pearl River Mouth Basin

综合利用大量二维、三维地震及钻井资料，首次在珠江口盆地白云一荔湾凹陷东侧珠江组中部发现了大型深水水道体系，呈“S”型近SN向展布，北起白云凹陷东北部，经南部隆起，往南延伸进入荔湾凹陷，总长约152km，宽3．0～7．5km。受物源远近及古地形影响，该水道在不同区段具不同的形态与沉积充填特征：北段形态相对较顺直，剖面上呈“V”型或“u”型，以垂向叠置的多期水道充填为主，钻井揭示为正旋回叠加的细砂岩；中段充填了下窄上宽的“U”型复合水道，内部可见天然堤一溢岸、水道及滑塌体；南段演化为形态弯曲的分支水道，加积充填为主，天然堤一溢岸沉积较发育，水道末端沉积了席状朵叶体。水道体系内发育优质储盖组合，经断层及底辟作用与下伏源岩沟通，油气成藏条件优越。中下部水道、天然堤一溢岸中的岩性、地层等非构造圈闭及上部水道、朵叶体中发育的构造岩性复合圈闭为有利勘探目标。珠江组大型水道的发现，将进一步拓宽珠江组深水沉积的勘探领域，有力椎动深水区油气勘探的深入。

Based on the analysis of substantial 2D/3D seismic data and drilling data, a deep-water channel system was discovered for the first time in the central part of Zhujiang Formation, east of Baiyun-Liwan sag in Pearl River Mouth Basin. This channel system is NS-trending in an S pattern, with a total length of 152 km and a width of 3 to 7.5 km. It starts from the northeast of Baiyun sag, traverses the uplift zone southward, and extends into Liwan sag in the south. As influenced by the provenance distance and the palaeogeomorphology, the channel system obtains segmented morphological features and depositional fillings. The northern segment of the channel system is relatively straight with a V or U pattern in the profile, mainly filled with vertically superimposed multiple- phase channels consisting of fine sandstone superimposed upon positive cycles. The middle segment is filled with U-type channel complexes of levee overbank, channels, and slumps with narrow bottom and broad top. The southern segment evolves into sinuous aggradationaI channels with levee-overbank in the flank and sheet-like lobes in the frontal side. Quality assemblage of reservoir and seal are developed in connection to the underlying source rocks through faults and diapirs, providing superior accumulation conditions in the channel system. Profitable exploration targets include nonstructural traps （e. g. , lithologic and stratigraphic traps） in the low middle channels and levee overbank as well as structural and lithologic traps in the upper channels and lobes. Discovery of the deep water channel system in Zhujiang Formation will broaden the exploration scope of the deep-water deposition and promote oil and gas exploration in deep-water areas.