托甫台地区奥陶系碳酸盐岩储层特征及控制因素分析

Characteristics and controlling factors of Ordovician carbonate reservoir in Tuofutai area

依据钻井、测井资料,对岩心观察并详细的分析得知,研究区储层岩石以发育开阔台地相(微)泥晶灰岩为主,颗粒灰岩次之。结合测井解释和对岩心孔洞及裂缝的统计表明,研究区主要储集空间类型为溶蚀孔洞和半充填—未充填低角度溶缝。上奥陶统发育的巨厚非岩溶性地层阻碍了海西期岩溶对奥陶统储层的后期岩溶改造。岩溶储层主要在加里东期平行不整合面下部附近发育,储集性能远不如上奥陶统缺失的塔河油田主体地区储层,呈现离塔河油田主体越远发育越差的特点,具有极强的非均质性。纵向上,储层集中在靠近一间房组顶部发育,随着深度的加大其发育程度逐渐降低。储层发育程度主要受沉积相、加里东中期岩溶和断裂、裂缝系统联合控制,形成以奥陶系一间房组为主力和油气突破的储层储集空间。

Based on well drilling and logging, as well as core observation, the reservoir rocks in the study area are mainly cryptite in open platform facies, followed by granular limestone. Combined with well logging interpretation and statistical data of fractures and cavity of core samples, it is concluded that the main reservoir space types are dissolved cavity and low angle dissolved fracture that is semi-filled and unfilled. The thick Upper Ordovician un-karstic strata made the Ordovician reservoir obstructed from the karst alteration. The paleokarst reservoir developed mainly below Caledonian parallel unconformity, and the reservoir quality is much poorer compared with the reservoirs in the main region of Tahe Oilfield where Upper Ordovician is absent. It is well developed when closer to the host of Tahe oilfield. The paleokarst reservoir developed at the top of the Ordovician Yijianfang Formation and the reservoir development decreased with the increase of burial depth. The reservoir development is controlled by sedimentary facies, Caledonian karstification, fault and fracture. It is concluded that Ordovician Yijianfang Formation may be the main reservoir space.