塔里木盆地中央隆起区恰尔巴克组与一间房组分布及意义

塔里木盆地中央隆起区共有10口探井钻遇了上奥陶统恰尔巴克组及中奥陶统一间房组,分属上奥陶统良里塔格组/恰尔巴克组/一间房组/鹰山组与却尔却克组/恰尔巴克组/一间房组/鹰山组2种不同的地层层序。恰尔巴克组为紫红、褐、灰色泥晶灰岩、泥灰岩及灰质泥岩,厚度17~25 m,属于斜坡相沉积,底部产Pygodus anserinus化石带。一间房组为灰色泥晶砂屑灰岩、颗粒灰岩及生屑灰岩,厚度80~120 m,属开阔台地—台地边缘相沉积,顶部产Pygodus serrus化石带。恰尔巴克组与一间房组分布在隆起边缘的低洼部位及隆起往坳陷的过渡区,在隆起的主体上分别为沉积缺失与剥蚀缺失。中央隆起区奥陶系分为隆起区、过渡区(A、B)与坳陷区,过渡区的西边界至少西推了100 km,中晚奥陶世区内为开阔台地—台缘—斜坡相沉积,不发育"萨尔干组"型的烃源岩,过渡区具备2套良好的储盖组合,为有利的油气勘探区。

Distribution and significance of the Ordovician Qrebake and Yijianfang formations in the Central Uplift of the Tarim Basin

The Qrebake Formation of the Upper Ordovician and the Yijianfang Formation of the Middle Ordovician have been intersected in ten wells in the Central Uplift of the Tarim Basin.They belong to two stratigraphic sequences: the Lianglitage/Qrebake/Yijianfang/Yingshan formations, and the Queerqueke/Qrebake/Yijianfang/Yingshan formations.The Qrebake Formation is composed of purplish red, brown and grey micritic limestones, marls and calcareous mudstones representative of slope facies.This formation is about 17-25 m thick, and has a Pygodus anserinus zone at the bottom.The Yijianfang Formation is composed of grey micritic sand-clastic limestones, grained limestones and bioclastic limestones representive of open platform and platform margin facies.This formation is about 80-120 m thick, and has a Pygodus serrus fossil zone at the top.The Qrebake and Yijianfang formations are mainly distributed in the lower parts of the uplift edge and the transition area from the uplift to the depression, while a sedimentary gap for the two formations is observed in the Central Uplift.The Ordovician of the Central Uplift is divided into the uplift zone, the transition zone (A, B), and the depression zone.The western boundary of the transition zone should be at least 100 km to the west compared to previous studies.During the Middle and Late Ordovician, the study area was an open platform to platform margin and slope facies, and developed no hydrocarbon source rocks of the "Salgan" type.Two sets of favorable reservoir and cap assemblages have been discovered in the transition zone, showing a good potential for hydrocarbon exploration.