东海盆地X凹陷天然气成藏条件与成藏模式

Gas accumulation conditions and mode in X sag of East China Sea Basin

东海盆地X凹陷是中国近海天然气勘探开发主战场之一。天然气成藏条件与富集规律研究表明,“烃源岩、储层、圈闭、运移”四元耦合控制X凹陷天然气汇聚成藏。X凹陷中西部具有两种天然气成藏模式:一种是凹中渐新统花港组挤压背斜-岩性圈闭成藏模式,天然气垂向优势运移、规模性汇聚;另一种是西部斜坡始新统平湖组构造-岩性圈闭成藏模式,天然气超压驱动、近距离侧向运移、“纵向叠置、横向连片”聚集。X凹陷中西部天然气主要富集于凹中渐新统花港组挤压背斜带和西部斜坡始新统平湖组构造-岩性圈闭带中。

The X sag of East China Sea Basin is one of the main areas for offshore gas exploration and development in China.The study result of gas accumulation conditions and enrichment law indicates that the quaternate coupling of“source rock,reservoir,trap and migration”controls the accumulation of gas in X sag.There two gas accumulation modes in the central and western zone of X sag.One is the compression anticline lithologic trap accumulation mode of Oligocene Huagang Formation in the central sag,which is characterized by gas migration mainly in vertical direction and large-scale accumulation;the other is the structural lithologic trap accumulation mode of Eocene Pinghu Formation on the western slope of the sag,which is characterized by overpressure driven short distance lateral migration and“vertically superimposed,horizontally contiguous”gas accumulation.The gas in the central and western zone of X sag is mainly concentrated in the compression anticline zone of Oligocene Huagang Formation of the central sag and the structural lithologic trap zone of Eocene Pinghu Formation in the western slope of the sag.