西湖凹陷地质认识创新与油气勘探领域突破

Geological understanding and innovation in Xihu sag and breakthroughs in oil and gas exploration

西湖凹陷具有优越的油气地质条件,已发现多个油气田,但多以低渗致密油气藏为主,面临着经济有效开发及常规油气藏勘探方向不明的两大挑战,迫切需要转变勘探思路与拓展勘探领域。2017年以来,通过对西湖凹陷石油地质条件的重新认识和系统研究,明确了以煤系烃源岩为主的物质基础和通源断裂晚期活化的控制因素,基于这两大地质认识创新提出了多层系立体勘探思路,确定了西湖凹陷油气勘探领域及突破方向:斜坡带下层系(始新统平湖组)复合岩性领域与中央洼陷反转带中、上层系(新近系龙井组以上)浅层领域,取得了平湖斜坡带WY中型油气田的发现及中央带CX油气田浅部层系的突破,拉开了西湖凹陷新的勘探序幕,拓宽了西湖凹陷勘探战场,为东海盆地落实“七年行动计划”开辟了新的储量增长点,对西湖凹陷寻找具有经济价值的优质油气指明了方向。

The Xihu sag owns superior oil and gas geological conditions,several oil and gas fields have been discovered there,but most of them are low-permeability tight oil and gas reservoirs.Because of two major challenges of economical and effective development,and unclear exploration direction of conventional reservoirs,it is urgently needed to change the exploration strategy and expanded potential field.Since 2017,through re-understanding and systematic research on the petroleum geological conditions of the Xihu sag,the material foundation dominated by coal-bearing source rocks and the controlling factors of late activation of source-communicated faults have been clarified.Based on the two geological innovations,a multi-strata three-dimensional exploration thought is put forward and the oil and gas exploration areas and breakthrough directions in the Xihu sag are determined:the composite lithological area of the lower strata on the slope belt(Eocene Pinghu Formation)and the shallow area of the middle-upper strata on the inversion zone of central subsag(above the Neogene Longjing Formation),which leads to the discovery of WY medium-sized oil and gas field in the Pinghu slope zone and the exploration breakthrough of shallow CX oil and gas field in the central zone.Those achievements raise the new exploration curtain,expand the exploration battlefield in the Xihu sag and broadened the exploration battlefield in the Xihu sag.They also fulfill the new increment of reserves for“Seven-year Action Plans”of the East China Sea Basin and point out the direction for finding high-quality hydrocarbons with economic value in the Xihu sag.