琼东南盆地深水区富气凹陷形成控制因素与勘探实践——以陵水凹陷为例

Formation control factor analysis and exploration practice in gas-rich sag in deep-water areas of Qiongdongnan Basin:a case study of Lingshui sag

琼东南盆地深水区陵水凹陷下渐新统崖城组广泛发育潮坪—潟湖沉积体系,其煤系地层在高地温场背景下广泛生气,是主力烃源岩;中新统莺歌海组—黄流组沉积期琼东南盆地发育中央峡谷水道,横穿陵水凹陷,水道砂体是有利的油气聚集场所,水道砂体周围被广泛发育的半深海—深海相泥岩覆盖,封盖条件优越;热流体成因的底辟带为崖城组煤系地层烃源岩生成的油气运移到莺歌海组—黄流组水道砂体中提供了有效通道。上述因素共同控制了陵水凹陷成为琼东南盆地深水区潜在富气凹陷,勘探发现了陵水1-1气田,显示出良好的资源潜力和勘探前景。

In the western deep-water area of Qiongdongnan Basin, northern South China Sea, a tidal fiar -lagoon sedimentary system was developed widely in the early Oligocene Yacheng Formation of Lingshui sag, where coal measure strata generated gases exten- sively in high-temperature geothermal fields and served as the major hydrocarbon source rocks. During the depositional period of Mi- ocene Yinggehai-Huangliu Formation, the central canyon was developed across Lingshui sag, providing river-course sand bodies that are favorable spaces for oil and gas accumulation; the periphery of these sand bodies were covered by hemipelagic-abyssal mud- stone, showing advantageous sealing and capping conditions. Thermal fluid-related diapirs provided an effective pathway for the migration of oil and gas generated by coal measure strata of the Yacheng Formation to sand bodies of the Yinggehai-Huangliu Formation. Under the ioint actions of the above factors, Lingshui sag has evolved into a potential gas-rich sag in the deep-water area of Qiongdongnan Basin. The discovery of Lingshui 1-1 gas field in Lingshui sag demonstrates the source potential and explo- ration prospects of the sag.