吐哈盆地台南凹陷二叠系充填特征及其研究意义

Filling Characteristics and Research Significance of Permian in Tainan Depression of Tuha Basin

以高分辨率层序地层学为指导,结合台南凹陷幕式构造演化特征,利用岩心观察、试油数据、地球物理及化学数据等,对台南凹陷二叠系进行了层序地层分析。研究表明研究区二叠系层序地层充填特征、烃源岩和储层分布受控于幕式构造演化,具有明显阶段性。断陷盆地结构特征控制着岩性叠加样式和沉积展布:LSC1沉积时期,南部觉罗塔格山脉崛起,北部陡坡带发育扇三角洲和水底扇沉积,南部缓坡带发育辫状河三角洲沉积体系;LSC2沉积时期,西部鲁西凸起和东部塔克泉凸起逐渐形成,南部物源减弱,东西物源逐渐占主导地位;LSC3沉积时期,北部博格达山脉崛起,地层南北向掀斜,北部物源逐渐发育,断陷短轴方向以扇三角洲沉积体系为主,长轴方向以扇三角洲沉积-辫状河三角洲沉积-湖泊沉积逐渐过渡。分析台南凹陷层序地层叠加样式对烃源岩和储层的控制作用后认为:LSC2水进体系域晚期和高水位体系域早期发育的大段泥岩为有利烃源岩,其上部LSC3低水位体系域发育的大套砂岩为油气主要储集层段。

Taking high resolution sequence stratigraphy as a guidance,combined with episodic tectonic evolution characteristics of Tainan depression,the author analyzed the Permian stratigraphic sequences of Tainan depression by using core observation,oil test data,geophysical and geochemical data.The studies show that the filling characteristics of stratigraphic sequences,source rocks and reservoir distribution are controlled by tectonic evolution with significant stages.The lithology stacking patterns and sedimentary distribution are controlled by the structural characteristics:during the LSC1 deposition period,the southern Sleep Tarot Mountains rose,the northern steep slope developed fan delta and underwater fan deposits,and the southern gentle slope developed braided river delta sedimentary system;during the LSC2 deposition period,the western Luxi uplift and eastern Takequan uplift gradually form ed,and the provenance decreased in the so u th,but increased in the east and w est;during the LSC3 deposition period,the northern Bogda Mountains ro se,the strata tilted from north to south,the provenance gradually developed in the no rth,the fan delta developed on the short axis of the fault depression,and the fan delta sedimentary system-braided river delta sedimentary system-lacustrine depositional system transited gradually on the long axis of the fault depression.Through the analysis of the sequence stratigraphy of source rocks and reservoirs,the author believes that the mudstones developed in the late stage of LSC2 transgressive system tract and early stage of high system tract are the main hydrocarbon rocks,and the sandstones developed in the upper LSC3 low water level system tract are the main reservoirs of oil and gas.