塔北-塔中地区三叠纪岩相古地理特征及油气地质意义

Lithofacies paleogeographic characteristics of Triassic and its petroleum significance in Tabei-Tazhong Area

祝 贺 刘家铎 田景春 孟万斌 杨永剑

成都理工大学油气藏地质及开发工程国家重点实验室，四川 成都 610059

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China

通过对塔里木盆地塔北-塔中地区钻井、测井资料综合分析及岩心观察，结合测井相和地震相特征，识别出三叠系发育扇三角洲、辫状河三角洲及湖泊3种沉积类型。沉积相带的展布格局总体表现为从湖盆边缘向中心依次为：扇三角洲、辫状河三角洲—滨浅湖、沼泽—半深湖及深湖相。在研究和地层对比的基础上，对塔北-塔中地区三叠系岩相古地理时空演化进行了详细分析。研究表明：三叠纪沉积环境经过多次湖侵、湖退的旋回变迁，古地理格局的演化与分布在不同时期既有继承性又有差异性。阿瓦提-满加尔凹陷在中晚三叠世具有较好的油气生成条件，但缺乏油气汇聚形成大中型油气田的条件。储层分布受沉积相控制，生储盖组合属典型的自生自储型。三叠系有利岩相过渡带是今后油气勘探的主要方向。

On the basis of the comprehensive analysis for core, drilling and well logging data in Tabei-Tazhong Area of Tarim Basin, three depositional types, i.e. fan delta, braided river delta and lake, are identified in Triassic through combining the characteristics of electrofacies with seismic facies. Generally, the distribution of sedimentary facies belt successively shows fan delta, braided river delta-shore shallow lake, swamp-semideep lake and deep lake facies from lake rim towards center. Based on the research and strata comparison above, the time-space evolution of lithofacies paleogeography of Triassic in the area is analyzed. The research result indicates that the evolution and distribution of aleogeographic framework reveal the succession and otherness in different periods through the multi-cycle transgression and regression for the depositional environment of Triassic. There are the good hydrocarbon generation conditions in Awati-Manjiaer Sag in Middle-Late Triassic. But the condition of hydrocarbon accumulation is absent for the formation of large-medium oil and gas fields. Because the reservoir distribution is dominated by sedimentary facies, source-reservoir-seal assemblages belong to the typical self-generation and self-storage type. The beneficial lithofacies transition belt of Triassic is the main direction of oil-gas exploration in future.