珠江口盆地白云东区古近纪挤压-伸展变形模式及勘探意义

Characteristics of Paleogene compression-extension deformation and exploration significance in the Baiyun East area, Pearl River Mouth Basin

珠江口盆地白云东区是白云凹陷2个有利成藏区之一,目前勘探正面临转向古近系深层的阶段,急需重新认识深层洼陷结构构造。为了解决珠江口盆地白云东区古近系深层缓坡带砂岩变少,与伸展型半地堑储层发育模式矛盾的问题,利用改善深层成像的重处理三维深度域地震资料及钻井数据进行综合解释,开展了白云东区古近系及基底之下滑脱面全三维构造解析。研究结果表明:按动力学机制对盆地演化阶段进行了重新划分,构造层序由一个被动裂陷旋回,修改为被动裂陷-主动裂陷-被动裂陷3个旋回;构造幕由3分细化为6个幕次,即由断陷幕-断坳转换幕-坳陷幕细化为裂陷两幕-褶皱两幕-裂陷萎缩幕-漂移幕,细分方案更好地反映了地层变形规律。地层变形方式表现为基底呈东西向挤压构造,盖层为南北向伸展构造。伸展构造发育过程中,主动裂陷旋回参与的基底盖层脱耦变形的新模式协调了白云东区古近纪构造-沉积响应,补充了主动裂陷阶段盆地充填富泥旋回的认识,挤压-伸展同步变形模式丰富了南海盆地空间演化模式,支持了白云凹陷深层新领域的勘探。

The Baiyun East area is one of the two favorable reservoir-forming areas in the Baiyun Sag in the Pearl River Mouth Basin. At present, exploration is facing the stage of turning to the deep strata of the Paleogene. In recent years, drilling has found that the sandstone in the deep gentle slope zone becomes less abundant, which contradicts the development model of extensional half-graben reservoirs. Based on the comprehensive interpretation of deep reprocessing 3-D seismic data and drilling data, a full 3-D structural analysis of the Paleogene and subbasement detachment surface in the Baiyun East area is carried out. The basin evolution stages are reclassified according to the dynamic mechanism. The tectonic sequence has been modified from a passive rift cycle to three cycles of passive rift-active rift-passive rift.The tectonic episode is subdivided into six curtains from three stage cycles: fault episode-fault depression conversion episode-depression episode is subdivided into rift two subepisodes-fold two subepisodes-rift shrinking episode-drift episode, and the subdivision scheme better reflects the law of strata deformation.A new model of compression-extension deformation of the Paleogene basin has been established in the eastern Baiyun area. In the development process of the extensional structure, the new model coordinates the Paleogene structure-sedimentary response of the eastern Baiyun area. This model enriches the evolutionary model of the South China Sea Basin and provides support for the exploration of new deep areas in the Baiyun Sag.