通化盆地三棵榆树断陷油气成藏条件分析

Hydrocarbon accumulation condition analysis of Sankeyushu fault depression in Tonghua Basin

针对通化盆地三棵榆树断陷油气勘探程度低及成藏前景不清的问题,对研究区下白垩统的生、储、盖及其组合特征开展了系统评价。认为三棵榆树断陷下白垩统鹰嘴砬子组、林子头组两套湖相地层发育厚层暗色泥岩,具备较强的生烃能力,是一个"小而肥"的富烃断陷,勘探潜力较大。该断陷不仅发育巨厚、高成熟度烃源岩,并发育叠加连片的扇三角洲前缘砂体,加之断陷内早期断裂晚期活动较少及烃源岩与储层近距离互层式接触,构成了有利的"自生自储式"生储盖组合,具备断层-岩性圈闭、火山岩遮挡圈闭以及致密裂缝型岩性圈闭成藏的有利条件。其中三棵榆树断陷中南部的通地2-通地4-通地18井区为有利勘探区带。通地17更井钻探获得工业气流,初步证实了三棵榆树断陷的勘探潜力。

To understand the oil and gas potential of the under-explored Sankeyushu fault depression of Tonghua Basin,the characteristics of source rock,reservoir,caprock and their assemblage in the Lower Cretaceous of the study area were systematically evaluated.It shows that the Sankeyushu fault depression contains thick dark mudstones with strong hydrocarbon generating capacity in two sets of lacustrine successions of the Lower Cretaceous Yingzuilazi and Linzitou formations,and is a"small and fertile"hydrocarbon-rich fault depression with great exploration potential.The fault depression is not only with thick and mature source rocks,but also overlapping fan delta front sand bodies.In addition,the early faults in the fault depression are less active,and the source rocks and reservoirs are closely interbedded,forming a favorable "self-generating and self-storing"source-reservoir-caprock assemblage,which is favorable for the formation of fault-lithologic traps,volcanic barrier traps and tight fractured lithologic traps.Among them,Tongdi 2-Tongdi 4-Tongdi 18 well area in the central-south part of Sankeyushu fault depression is a favorable exploration zone.Industrial gas flow was obtained from the well Tongdi 17 geng,which preliminarily confirmed the exploration potential of Sankeyushu fault depression.