琼东南盆地崖北凹陷崖城组煤系烃源岩发育环境及控制因素

Depositional environment and controlling factors of coal measures source rocks of Yacheng Formation in Yabei depression of Qiongdongnan basin

依据沉积环境控制烃源岩发育理论,研究了琼东南盆地崖北凹陷崖城组煤系烃源岩的发育环境及主控因素,并建立了研究区崖城组煤系烃源岩的发育模式。崖城组煤系烃源岩主要形成于半咸水、还原-弱还原的扇三角洲平原河道间泥炭沼泽环境和半咸水、弱还原-弱氧化的潮坪潮上带-潮间带泥炭沼泽环境。沉积环境、古气候条件、相对海平面变化以及古构造控制煤系烃源岩的发育,其中沉积环境控制着煤系烃源岩中有机质类型、有机质丰度、显微组分及煤层的厚度,古气候条件提供了煤系烃源岩发育的物质基础,相对海平面变化影响着煤系烃源岩的展布及保存条件,古构造则是聚煤盆地形成、演化的主要控制因素。崖城组煤系烃源岩有两种发育模式,一是在扇三角洲平原河道间泥炭沼泽环境中水体的还原性起主导作用,二是在潮坪潮上带-潮间带泥炭沼泽中高生物生产率起主导作用。

The primary hydrocarbon source rocks of Yabei depression in Qiongdongnan basin are coal measures of Yacheng Formation. On the basis of the theory that depositional environment controls the formation of coal measures source rocks, the depositional environments and controlling factors of coal measures source rocks were studied, and the development models of coal measures source rocks were established. The depositional environments of coal measures source rocks were saline-reducing peat swamps of the braided river delta plain and saline-oxidative peat swamps of tidal flat. The controlling factors of coal measures were depositional environments which governed the abundance and types of organic matters, microscopic constituents, and thickness of coal measures, paleo-climate which provided material background for the development of source rocks, sea level which controlled the distributive characteristics of coal measures within the strata and the perversion condition, and paleo-structure which determined formation and evolution of specific basins. There are two development models of coal measures source rocks of Yacheng Formation in Yabei depression： one is peat swamps of tidal flat in which the reduction played the leading role; the other is peat swamps of the braided river delta plain in which the high productivity was the most effective factor.