塔里木盆地塔河地区海西晚期火山岩构造特征与油气成藏

通过地震剖面解释,根据断裂的切割层位将研究区火山岩断裂分为3类,即深层断裂、浅层断裂、火山岩内部微断裂。通过编制这3类断裂的平面展布图,对塔河地区火山岩断裂的性质、形成期次、分布特征及形成机理进行了分析。认为深层断裂形成于加里东期-海西期,以逆冲断层为主,走向呈NNE、NE、NNW3组,断裂主要分布于塔河火山岩发育区北部、西北部。浅层断裂形成于燕山期-喜马拉雅期,以正断层为主,断裂走向呈NE、NNE向,主要分布于盐边地带和东南部盐上火山岩分布区。火山岩内部的微断裂在顶部较底部发育,主要分布于塔河地区西部的火山岩中。根据火山岩储层和构造成因类型,将塔河地区火山岩划分为3种圈闭类型,即:构造裂缝和淋滤风化共同控制的圈闭、古凸起不整合遮挡和抬升淋滤风化共同控制的圈闭、埋藏溶蚀和构造裂缝共同控制的圈闭。分析了火山岩圈闭顶部的盖层条件和火山岩的油气成藏条件,认为三叠系底部柯吐尔组泥岩可形成有效的区域性封盖,塔河地区火山岩具有良好的油气成藏条件。

The Tectonic Characteristics and Hydrocarbon Accumulation of Late Hercynian Volcanic Rocks in the Tahe Area, Tarim Basin

The faults in volcanic rocks of the Tahe area can be classified into three types based on the interpretation of the seismic profiles:deep-layer faults,shallow-layer faults and micro-faults within the volcanic rocks.Through compiling faulting distribution map,the fault characters,formation periods,distribution characteristic and origin of the volcanic rock in the Tahe area have been analyzed.It is believed that the deep-layer faults,mainly thrust faults,were formed during the period of Caledonian and Hercynian stages.These faults trending NNE,NE and NNW are distributed in the north and northwest parts of the Tahe volcanic area.The shallow-layer faults,mainly normal faults,were formed during the period of Yanshan and Himalayan Stages.The faults trending NE and NNE are distributed in the volcanic rocks near the salt margin and up-salt volcanic area of the southeast part.The micro-faults within the volcanic rocks,developed in the top of volcanic rocks much more than that in the bottom of volcanic rocks,mainly distribute in the western part of the Tahe area.Three oil-gas trap types of volcanic rock have been classified according to the origin of the volcanic reservoir and structure.They are the traps controlled by structural fissures,leaching and weathering,the traps controlled by paleo-uplift,unconformities,leaching and weathering,the traps controlled by buried-dissolving,erosion and structural fissions.The conditions of the cap-rocks and hydrocarbon accumulation of volcanic beds have been analyzed.It is indicated that mudstone of Ketuer formation of the bottom Triassic may be an effective regional seal bed.The favorable hydrocarbon accumulation conditions may exist in the volcanic beds in the Tahe area,Tarim Basin.