塔里木盆地晚震旦世-中寒武世构造沉积充填过程及油气勘探地位

Tectonic-sedimentary Filling History through the Later Sinian to the Mid-Cambrian in Tarim Basin and Its Explorational Potential

南华纪初,受罗迪尼亚(Rodinia)超级大陆裂解的影响,塔里木陆块进入强伸展构造演化阶段,陆内发育了北东-南西向裂谷体系,裂谷区与两侧高隆带构成"两隆夹一坳"古构造格局。这一古构造格局持续控制了晚震旦世至中寒武世碳酸盐岩沉积序列的充填、演化及油气成藏组合,应将受前寒武纪裂谷构造-沉积演化控制的系列碳酸盐岩台地作为一个成因整体进行系统研究。结果表明:晚震旦世-中寒武世碳酸盐岩台地先后经历了5个重要演化阶段,即晚震旦世同裂谷充填期、震旦纪末抬升剥蚀阶段、早寒武世初海侵深水缓坡型富泥质碳酸盐岩台地阶段、浅水缓坡型碳酸盐岩台地阶段,以及中寒武世蒸发潟湖占主导镶边型碳酸盐岩台地阶段。控制了两套烃源岩、两套储层及一套区域盖层的发育,即形成于震旦纪裂陷槽内潜在烃源岩和早寒武世深水缓坡阶段玉尔吐斯组烃源岩、震旦纪末期受剥蚀淋滤形成的上震旦统微生物丘滩相白云岩储层和早寒武世受岩相和早期云化联合控制的肖尔布拉克组丘滩相白云岩储层,以及中寒武统蒸发潟湖相蒸发岩盖层,构成了上、下两套有效油气成藏组合。与已获得重大突破的四川盆地同期德阳-安岳克拉通内裂陷沉积演化序列及油气成藏组合类比表明,与之具有良好的相似性,且主力烃源岩品质、直接盖层的封盖性能更优于安岳特大型气藏,认为塔里木盆地这一构造-沉积单元具有重要的勘探前景与地位,上部成藏组合更具现实勘探价值。

Tarim block evolved into a strong stretching stage affected by the Rodinia supercontinent cracking in the early Nanhua Period. The inter-platform rift system,oriented Northeast-Southwest,developed a"Two Uplifts and One Depression"tectonic framework with north and south high belts. The sedimentary filling sequence,evolution,and hydrocarbon accumulation in the Late Sinian to the Middle Cambrian carbonate platform is obviously affected by this tectonic framework. In this study,the carbonate sedimentary sequence underlying Mid-Cambrian Evaporite and controlled by the Pre-Cambrian rift tectonic-sedimentary evolution was considered to be an integral unit. This unit has experienced five evolution stages,including the Late Sinian carbonate ramp platform,denudation across the SinianCambrian boundary,Early Cambrian deep-water muddy ramp and shallow-water carbonate ramp,and Mid-Cambrian evaporate lagoon dominated rimmed platform. High quality hydrocarbon source rocks in the Yuertusi Formation,an Upper Sinian and Lower Cambrian carbonate ramp mound-shoal facies dolomite reservoir,and Middle Cambrian evaporite caprock developed during the tectonic-sedimentary filling process and contains two sets of an effective accumulation combination. We propose that this dolomite sequence underlying the Mid-Cambrian resembles the DeyangAnyue area in the Sichuan Basin,SW China,which has similar tectonic-sedimentary filling sequence and hydrocarbon accumulation assemblages. The quality of hydrocarbon source rock and direct cap rock is better than that of the Deayang-Anyue giant gas field,and the upper accumulation combination is of great realistic explorational potential.