关键词: 珠二坳陷, 珠四坳陷, 构造演化, 烃源岩, 储层, 成藏组合

Abstract: Seven sags in the deep water area of the Pearl River Mouth Basin reside in two first-order structural units, i.e. Zhu Ⅱ depression and Zhu IV depression. The two depressions commonly underwent five tectonic evolution stages, including initial rifting, sustained rifting, early post-rifting subsidence, late post-rifting subsidence, and neotectonic movement. They are significantly different in tectonic characteristics and sedimentary filling in different stages or during the same stage, thereby leading to different hydrocarbon geological conditions and exploration potentials. Three types of source rocks (i.e. lacustrine mudstone, coal-measure and terrigenous marine mudstone) are mainly developed in the Zhu Ⅱ depression. Two types of source rocks (i.e. coal-measure and terrigenous marine mudstone) are mainly developed in the Zhu IV depression, revealing hydrocarbon accumulation conditions inferior to the Zhu Ⅱ depression. During the first three stages (i.e. initial rifting, sustained rifting, early post-rifting subsidence, and late post-rifting subsidence), multi-stage delta and channel-deep water fan sand bodies were developed; the sand bodies in the Zhu Ⅱ depression are diverse and wide, showing better accumulation capacity. Two sets of plays of late postrifting subsidence and sustained rifting are developed in both depressions. By comparing the play elements, it is concluded that the exploration potential of the Zhu Ⅱ depression is better than that of the Zhu IV depression.

Key words: Zhu II depression, Zhu IV depression, structural evolution, resource rock, reservoir, play