塔里木盆地塔中地区奥陶系储层成因类型及分布预测

将塔中地区奥陶系碳酸盐岩有效储层分为古潜山岩溶储层、埋藏溶蚀储层及内幕白云岩储层3大类,其中古潜山岩溶储层又可分为志留纪后古潜山储层及中晚奥陶世古潜山储层2类。志留纪后古潜山储层主控因素为志留纪—泥盆纪,特别是泥盆纪期间的岩溶古地貌及二叠纪岩浆热液(硅化)改造作用;有利勘探领域主要分布于中央断垒带的塔中1—塔中4—塔中403井区、塔中19—塔中9井区及塔中16—塔中15井区。对新发现的中晚奥陶世古潜山储层起主要控制作用的应该是中奥陶世晚期—晚奥陶世早期(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,该储层主要分布于下奥陶统鹰山组中上部,并在塔中凸起—巴楚凸起区均有分布。以上奥陶统良里塔格组为主的埋藏溶蚀储层主要受沉积相(滩相)及准同生暴露淡水溶蚀、埋藏(有机—无机)溶蚀作用、断裂沟通淡水溶蚀作用控制,有效储层主要分布于沿塔中I号断裂带南侧发育的良里塔格组陆棚边缘高能礁滩相带中,并具备形成特大型碳酸盐岩非均质岩溶储层成岩圈闭原生岩性油气藏的条件。下奥陶统内幕白云岩储层主控因素应为沉积相(半局限—局限台地相)、埋藏重结晶作用、埋藏岩溶-断裂沟通淡水溶蚀作用,储层总体呈层状大面积分布,在整个塔中—巴楚凸起区甚至更广的范围内均有分布,以小型孔洞型储层为主。 

GENETIC TYPES AND DISTRIBUTION FORECAST OF AVAILABLE CARBONATE RESERVOIRS IN ORDOVICIAN IN THE CENTRAL AREA OF TARIM BASIN

The available reservoirs of Ordovician carbonate in central Tarim can be classified into 3 types as epidiagenetic paleo-karst reservoir,burial karst reservoir and interlayer dolomite reservoir,and the epidiagenetic paleo-karst reservoir can be subdivided into 2 types as epidiagenetic karst reservoir formed later than Ordovician(EKR-1) and epidiagenetic karst reservoir formed from late Middle Ordovician to early Late Ordovician(Llandeilo to early Caradoc)(EKR-2).The key controlling factors to EKR-1 are paleo-karst morphology from Silurian to Devonian especially in Devonian and silicification by magma heat liquids in Permian.The favorable exploration regions are mainly distributed in areas from Tazhong-19 to Tazhong-9,Tazhong-1 to Tazhong-4 to Tazhong-403 and Tazhong-16 to Tazhong-15.The chief controlling factors to EKR-2 recently-discovered should be paleo-karst morphology from Llandeilo to early Caradoc and fault karstification of several stages.The reservoir is chiefly distributed in the middle-upper part of the Yinshan Fm.of the Lower Ordovician and in the area from the Tazhong Uplift to the Bachu Uplift.The burial karst reservoir mainly distributed in the Lianglitage Fm.of the Upper Ordovician is chiefly controlled by sedimentary facies(carbonate shoal) and the meteoric water dissolution produced from penecontemporaneous exposure,burial(organic or inorganic) karstification and fault-channeled fresh-water karstification.The available reservoir is chiefly distributed in shelf marginal high-energy shoal and reef of the Lianglitage Fm.developed in the southern belt near Tazhong-I Fault,forming a giant primary stratigraphy oil-gas pool traped by diagenetic carbonate heterogenetic karst reservoir.The key controlling factors to interlayer dolomite reservoir in the Lower Ordovician should be sedimentary facies(semi-restricted to restricted platform),burial recrystallization,burial karstification and fault-channeled fresh-water karstification.The reservoir is generally distributed by layers of larger area,and in the whole Tazhong-Bachu Uplift even in other more extensive regions,with small types of pore and cavity.