台南凹陷构造演化与成藏规律

台南凹陷历经觉罗塔格前陆坳陷(C₂-P₁)和博格达前陆坳陷(P₂-J)两个阶段。晚二叠世以来,台南凹陷为吐哈盆地北倾斜坡上的次一级凹陷。由于早二叠世南部觉罗塔格前陆盆地向北部博格达前陆盆地演变,桃东沟群沉积末抬升剥蚀,印支末早燕山的构造反转、裸露剥蚀、块断掀斜、构造肢解等三次较大的改造,决定了台南凹陷烃源岩的分布局限、热演化程度低、资源潜力小,以低熟稠油为主。因此,鲁克沁巨大稠油油藏的油应主要来自台北凹陷。鲁克沁圈闭形成期为印支晚期,成藏期为印支末燕山早期,油气运聚成藏后遭受进一步稠化、调整运移及破坏,使鲁克沁构造带形成众多的断块稠油油藏和沥青封堵油藏。

TECTONIC EVOLUTION AND POOL-FORMING REGULARITY IN TAINAN SAG

Tainan Sag underwent Jratak and Bogda foreland two depression stages.The sag has been a secondary sag on the north dip slop of Turpan-Harmi Basin since Late Permian.The study area underwent three big transformation:(1)the northward transformation from Jratak foreland basin to Bogda foreland basin in Early Permian;(2)uplifting and denudation in the end of Taodonggou Group sedimentation;(3)tectonic inversion,denudation,fault-block dip and disintegration in Late Indosinian-Early Yenshan Period.The above mentioned transformations determined the characteristics of the source rocks in Tainan Sag such as restricted distribution,lower thermal evolution degree,small source potential and predominant with lower maturity of thick crude oil.Therefore,the oil of huge thick oil pools of Lukqin structure belt should be mainly drived from Taibei Sag.Lukqin trap was formed in late Indosinian epoch and the oil pools were formed in the end of Indosinian-Early Yenshan Period.Then the oil was further thickenen,remigrated and destoried,thus causing Lukqin structural belt to be separated into many fault-blook thick oil pools and asphalt-plugged reservoirs.