准噶尔盆地西北缘二叠纪古构造对层序地层建造及沉积体系的控制

准噶尔盆地西北缘二叠系是一套前陆盆地构造沉积组合.利用该区二叠系丰富的钻井、岩心和三维地震资料,按照构造层序分析的方法对该区二叠系层序地层和古构造对层序建造和沉积体系的控制作用进行了研究.研究表明,二叠系前陆盆地对应1个一级层序、4个与构造幕对应的超层序（二级层序）,超层序Ⅱ,Ⅲ,Ⅳ可识别出10个三级层序.二叠系前陆盆地的古构造格局不但控制了层序地层建造,而且控制了沉积体系和储层在平面上的展布.超层序Ⅱ盆地幕式逆冲挠曲沉降构造作用强烈,发育同沉积逆冲断裂挠曲坡折背景层序.湖扩展体系域发育的扇三角洲前缘砂体和碳酸盐岩（白云岩）储层物性良好,其分布受同沉积逆冲挠曲坡折及水下低隆起控制.超层序Ⅲ,Ⅳ盆地逆冲挠曲沉降构造作用减弱或停止,发育逆断裂坡折、隐伏断裂挠曲坡折背景及缓坡背景层序.逆断裂坡折、隐伏断裂坡折背景层序坡折向湖一侧低位域和湖扩展体系域辫状河道和三角洲前缘砂体是良好储层,其分布受逆断裂坡折和隐伏断裂坡折的控制.由于这些储层就分布在烃源岩内或有断裂与源岩沟通,成藏条件良好,是油气勘探的有利区带.

Controls of Permian Paleostructures on Stratal Architecture of Sequences and Sedimentary Systems Deposited in Northwestern Margin of Junggar Basin

Permian system of Northwestern Junggar basin is a structural and depositional assemblage of foreland basin. Based on well logs,cores,and 3D seismic data,and in the light of principle of analysis of tectonic sequence, this paper investigated depositional sequences and controls of paleostructure on stratal architecture of sequences and sedimentary systems deposited in Permian. Research results indicate that Permian system of foreland basin corresponds to a first-order sequence, and four tectonic episodes corresponds to four second-order sequences. 10 third-order sequences could be identified in Supersequence II , III , and IV of Permian system. Paleostructures of Permian system controlled not only stratal architecture of sequences,but also distribution of depositional systems and reservoirs de- posited in Permian. During suppersequence II ,episodic thrusting, flexing and subsiding were very intense,and sequences in syndepositional flexural slope-break of thrust fault were developed. Sand bodies of fan delta front and carbonate （dolomite） of lake expanding systems tract are good reservoirs,whose distribution was controlled by synde- positional flexural slope-breaks of thrust fault and lower uplift of underwater formed by volcano eruptions. During suppersequence m and IV ,Episodic thrusting, flexing and subsiding were weakened ,and sequences in slope breaks of inverse fault, flexural slop-break of buried fault,and gently slope were developed. Sandibodies of braided fluvial and delta front of lowstand of slope breaks lakeward and lake expanding systems tracts are also good reservoirs,whose distribu tion is controlled by buried faults. Distributing in source rock of Permian system or communicated by faults, these reservoirs have good conditions for hydrocarbon accumulation and are good areas for hydrocarbon exploration.