塔中地区中晚奥陶世古潜山岩溶储集层特征

通过岩心观察、测井储集层分析等手段,识别出塔中凸起区广泛分布形成于中奥陶世晚期-晚奥陶世早期(兰代洛世-卡拉道克世早期)、发育于下奥陶统鹰山组中上部碳酸盐岩中且被上奥陶统良里塔格组覆盖的古潜山岩溶储集层,其原岩主要为开阔-半局限台地相颗粒灰岩、泥晶灰岩、藻灰岩夹白云岩。有效储集层主控因素是兰代洛世-卡拉道克世早期的岩溶古地貌及多期断裂岩溶作用,其储集空间演化主要经历了兰代洛世—卡拉道克世早期长达10×106 a以上的暴露淡水岩溶及3期(晚奥陶世-泥盆纪、二叠纪-三叠纪、古近-新近纪以来)埋藏岩溶等建设性成岩作用的改造。有利储集层主要分布于岩溶斜坡、次级岩溶高地及断裂-裂缝发育带附近。区域对比分析表明,推测巴楚凸起区特别是玛扎塔格断裂带与吐木休克断裂带之间的地区也广泛分布了该鹰山组中上部古潜山岩溶储集层,在塔北隆起区与之相当的是发育于中下奥陶统一间房组上部的古潜山岩溶储集层。这些古潜山岩溶储集层的发育是中奥陶世晚期-晚奥陶世早期波及全盆地的构造挤压运动在隆起区的表现,该期构造运动推测主要与昆仑-阿尔金岛弧与塔里木陆块的碰撞有关。

Characteristics of Paleo-Karst Reservoirs of Middle-Late Ordovician in Tazhong Area, Tarim Basin

By means of core observation and log analysis of reservoir,it is recognized that widely distributed Tazhong uplift is formed from the late of Middle Ordovician to the early of Late Ordovician(from Llandeilo to Early Caradoc).The buried hill paleo-karst reservoir developed in the carbonate rocks of the mid-upper section of Yingshan formation of Lower Ordovician and covered by Lianglitag formation of Upper Ordovician is dominated by lithology of granular limestone,micritic limestone and algal clastic limestone interlayered with dolomite of open to semi-restricted platform facies.The chief controlling factors to available reservoir are paleo-karst morphology in Llandeilo to Early Caradoc and multi-stage faulting and karstification.Its evolution of reservoir space chiefly suffered the reconstruction of diagenesis such as epidiagenetic karstification uncovered for over 10 Ma in Llandeilo to Early Caradoc and 3-stage burial karstification since Late Ordovician to Devonian,Permian to Triassic and Tertiary.The favorable reservoir is mainly distributed in karst slope,karst hypo-upland and areas near fault-fissure belt.The analysis from regional correlation indicates that the buried hill paleo-karst reservoir of also occurs in Bachu swell area,especially in area between Mazhatag fault and Tumuxiuke fault of the mid-upper section of Yingshan formation,compared with the paleo-karst reservoir developed in the upper section of Yijianfang formation of Middle-Lower Ordovician in Tabei uplift.The occurrence of these paleo-karst reservoirs is the exhibition in the uplift area by tectonic compressive movement throughout the whole Tarim basin in late of Middle Ordovician to early of Late Ordovician.It is presumed that this stage movement could be related with collision between Kunlun-Altun island arc and Tarim landmass.