基于盆地模拟的断盖配置研究——以塔里木盆地玉北地区奥陶系油气藏为例

Study on fault-cap coupling based on basin simulation:Case study of Ordovician reservoirs in Yubei area,Tarim Basin

断裂和盖层的相互配置是控制塔里木盆地西部玉北构造带深层油气富集的关键。首次采用盆地模拟的手段探讨了玉北深层油气断盖要素的不同配置关系及其对奥陶系油气富集的影响。对烃源岩热演化历史模拟显示该区下寒武统烃源岩从加里东晚期到燕山期一直处于成熟阶段,喜马拉雅期进入高成熟阶段,现今仍然具备较好的生烃潜力。断膏配置类型的动态模拟表明断裂和膏岩的相互作用是控制玉北深层盐上和盐下油气系统分布的关键因素,深层断裂的结构特征比侧向封堵性对油气运移影响更大。不同断盖组合控制了奥陶系油气的富集程度,其中未断穿型和弱断穿型断盖组合最有利,喜马拉雅期圈闭的保存条件对晚期次生油气藏的形成意义较大。综合认为玉北地区奥陶系发育“长期生油、断膏控注、断盖控聚”的成藏特征,基底卷入断裂和逆冲走滑的拼接程度是评价盐下油气富集的重要因素。论文采用的动态正演模拟方法为玉北地区及台盆区深层断控油气富集规律研究提供了新的思路和借鉴。

Fault-cap coupling is the key to controlling hydrocarbon accumulation in deep layers of the Yubei area in the western Tarim Basin.In this paper,the influence of the configuration of hydrocarbon source and fault-gypsum-cap elements on hydrocarbon accumulation in the deep layer was discussed by basin simulation for the first time.The 2D thermal evolution of source rocks shows that the Lower Cambrian source rocks were in the mature stage from the Late Caledonian to the Early Yanshan Period and entered the high mature stage in the Himalayan period,and still have good hydrocarbon generation potential.The dynamic simulation of the fault-gypsum combination shows that the interaction between fault and gypsum is the key factor controlling the hydrocarbon distribution post-salt and pre-salt hydrocarbon system in Yubei area.The structural characteristics of deep faults have more influence on the hydrocarbon migration than the lateral sealing property of fault plane.Different faultcap assemblages controlled the accumulation of the Ordovician hydrocarbon,and the fault-cap assemblages of non-fault-cap and weak fault-cap assemblages are most conducive to the accumulation of marine oil and gas in this area.The preservation conditions of traps in Himalayan period were of great significance to the formation of late secondary reservoirs.The results of the petroleum system simulation show that the hydrocarbon accumulation of Ordovician carbonate rocks in the Yubei area has the characteristics of long-term oil generation,faultgypsum controlled charging,fracture-sealing controlled accumulation.The degree of splicing of basement involved fault and reverse strike slip is an important factor to evaluate subsalt oil and gas enrichment.This paper provides a new idea and reference for the study of deep fault-controlled hydrocarbon accumulation law in the Yubei area and Tarim Basin.