塔里木盆地北部塔河油田奥陶系加里东期岩溶作用及其油气地质意义

详细的钻井地质学、地球物理和地球化学研究表明,塔河油田南部奥陶系内部和顶部发育多幕次的加里东期岩溶作用,主要表现在奥陶系内部牙形石带缺失、钻井放空和泥浆漏失、地震剖面上奥陶统反射波组底部上超和顶部削截,以及溶洞充填方解石的Sr同位素特征等方面。加里东期岩溶储层主要受不整合面、断裂、岩性和古地貌等因素控制,表现出明显的断控和层控特征。由此预测该储层发育区位于古风化壳剥蚀区、加里东期断裂发育区和滩相储层发育区的叠合部位,主要位于阿克库勒凸起的轴部倾没端和塔河西南部、东南部的北东向、近南北向断裂发育区。

Caledonian karstification of Ordovician carbonates in the Tahe oilfield,northern Tarim basin,Northwest China,and its petroleum geological significance

Intensive geological, geophysical and geochemical studies indicate that polyphase Caledonian karstification occurred inside and at the top of the Ordovician in the southern part of the Tahe oilfield. The karstification is mainly manifested by the absence of the conodont zone, caving of wells and mud leaking in wells, onlap of the base of the upper Ordovician reflection wave group in the seismic section and erosional truncation of its top and Sr isotope features of calcites filling in core caves. The Caledonian karst reservoirs were mainly controlled by such factors as unconformity, faults, lithology and paleogeomorphology, showing distinct fault-controlled and stratabound features. Thus it is predicted that the areas of favorable reservoir rocks would be located in stacked sites of erosional areas of paleoweathering crust, areas of Caledonian faulting and areas of shoal reservoir rocks, e.g. the plunging crown of the axial zone of the Akekule anticline and the NE- and nearly N-S-trending fault zones in the southwest and southeast parts of the Tahe oilfield.