珠江口盆地惠州凹陷西南部新近系岩性油气藏勘探思路与关键技术

Exploration approach and techniques for the Neogene lithologic reservoirs in the southwestern Huizhou Sag,Pearl River Mouth Basin

地层岩性油气藏是珠江口盆地油气勘探的一个难点领域,其关键问题在于如何准确定位岩性油气藏有利发育区和落实岩性圈闭的有效性。通过对研究区岩性油气藏地质与地球物理方面的研究,形成了"源""相"双控的勘探思路。惠州26洼是惠西南地区经钻探证实的富生烃洼陷,紧邻惠州26洼,且长期相对上隆的惠州21构造带和惠西低凸起,经断裂沟通源岩,具有油气强充注的有利条件;新近系沉积时期,惠州21构造带以独立于三角洲体系之外的陆架砂脊—砂席砂体为主要沉积特征,惠西低凸起以三角洲前缘的河道—河口坝砂体为主要沉积特征,这些砂体都有利于形成多种类型的岩性圈闭。在这2个岩性油气藏发育有利区,运用少井条件下高精度层序地层分析技术、等时成因砂体重构技术、基于地质模式的地震切片分析技术等关键技术,对岩性圈闭砂体沉积边界进行追踪和刻画,有效指导了该地区岩性圈闭的落实。该勘探思路及关键技术在惠西南地区惠州21构造带和惠西低凸起取得了良好的效果。

The exploration of lithologic reservoirs is one of the difficult fields in the Pearl River Mouth Basin.The key problems are how to accurately identify exploration zones and effectively implement lithologic traps.Throughout successive rounds of researches about geology and geophysics of the lithologic reservoirs in this field,an exploration approach double controlled by "source"and "facies"was formed,which effectively guided the exploratory zones' selection of lithologic reservoir.It has been proved by drilling that the Huizhou 26 subsag in the southwestern Huizhou district is rich in hydrocarbon.Next to the Huizhou 26 subsag,the Huizhou 21 structure and the Huixi low uplift,which are relatively higher,are favorable for oil and gas enrichment when connected with source rocks through fractures.During the Neogene sedimentary period in this area,shelf sand ridge and sand sheet isolated from delta system were the major sedimentary features in the Huizhou 21 structure,while the Huixi low uplift was featured by channel and mouth bar sand within delta front.These two kinds of sands pinched out laterally easily,which were both favorable for the formation of lithologic traps.Some key technologies,including high-resolution sequence stratigraphy analysis under rare wells,seismic attribute slice analysis under sedimentary model and reconstitution of isochronic genetic sand bodies,contributed a lot to the depiction of the pinchout boundaries of these target sands,which substantially implemented the lithologic traps in this area.With this exploration approach and these key technologies,the Neogene lithologic reservoir exploration achieved good results in the Huizhou 21 structure and the Huixi low uplift in the southwest Huizhou Sag.