珠江口盆地开平凹陷油气地质新认识与勘探突破

New understanding and exploration breakthrough of petroleum geology in Kaiping sag, Pearl River Mouth basin

珠江口盆地开平凹陷历经40年勘探,长期未能实现勘探突破。针对成盆机制及洼陷结构、烃源发育层段和分布范围、成藏规律这3方面,通过精细地震解释、烃源岩评价、成藏综合分析等研究,取得了新认识。研究认为:(1)开平凹陷具有“拆离-核杂岩”型成盆机制及“早断陷—中拆离—晚断坳转换”演化特征;(2)文三段和文四段是主力烃源岩发育层段,优质烃源岩主要分布在开平主洼、开平西洼以及开平东洼;(3)开平主洼缓坡带具有“源-断-储”三元耦合成藏模式,是油气勘探有利区带。认识指导勘探,2022年获得了开平11-4油田重要发现,实现了开平南部斜坡带勘探突破。

After 40 years of exploration, the Kaiping sag in the Pearl River Mouth basin has failed to achieve exploration breakthroughs for a long time. Aiming at three geological aspects of basin-forming mechanism and sag structure, hydrocarbon source development intervals and distribution range, and accumulation laws, new understandings have been obtained through researches of fine seismic interpretation, source rocks evaluation, and comprehensive analysis of hydrocarbon accumulation. The results show that:(1)Kaiping sag has a basin-forming mechanism of “detachment-core complex” type and the evolution characteristics of “fault depression in early period-detachment in middle period-fault sag transformation in late period”.(2)The 3rd and 4th members of Wenchang Formation are the main source rocks, and high-quality source rocks are mainly distributed in the main Kaiping sag, the western Kaiping sag and the eastern Kaiping sag.(3)The gentle slope belt of the main Kaiping sag has a three-element coupling accumulation model of “source-fault-reservoir”, which is a favorable area for oil and gas exploration. Guided by these understandings, an important discovery of the KP11-4 oilfield was made in 2022, achieving an exploration breakthrough in the southern slope belt of Kaiping sag.