准噶尔西北缘中拐地区红车断裂带胶结封闭作用

Cementing and sealing actions of Hongche Fault Belt in Zhongguai area of Northwest Margin of Junggar Basin

中拐地区是准噶尔盆地一个重要的油气富集区,区内断裂带发育,断层封闭性对油气成藏有重要影响。采用普通薄片、扫描电镜、流体包裹体等分析测试技术对断裂内部成岩胶结物类型及胶结特征进行了研究。碳氧同位素分析表明,该区断裂带主要经历了三叠纪中晚期、早中白垩世、古近纪中晚期至新近纪早期3期流体活动,三叠纪中晚期和早中白垩世的热液流体与油气藏为"边充注、边胶结",古近纪中晚期至新近纪早期的流体则主要起到胶结封闭作用。断裂带胶结作用影响范围最大达百米,断层越大胶结物越发育,胶结封闭作用越强。综合断裂带结构划分、胶结物类型及影响因素分析、流体活动期次及流体来源等多方面研究成果,提出了断裂成岩胶结封闭作用机理,为下步勘探目标区优选提供了理论依据。

Zhongguai area in Junggar Basin is an important oil and gas enrichment zone, the faults in the region are well developed, the fault sealing property possesses important influence on the hydrocarbon accumulation. With the help of the analyzing and testing techniques such as using conventional thin section, scanning electron microscopy and fluid inclusion and so on, the diagenetic cement types and cementation characteristics within the fractures were studied. The carbon and oxygen isotope analyzed results show that the fluid activities in the fault zones of the area mainly experienced three periods:Middle-Late Triassic period, Early-Middle Cretaceous period,from Middle-Late Palaeogene to Early Neogene period, in the former two periods, the hydrothermal fluid filled and cemented the petroleum reservoir at the same time, whereas the sealing and cementing actions were mainly played for the liquid in the latter two periods. The impacted cementation range of the fault zone can reach up to a hundred meters, and the larger the fault is, the stronger the cementing-sealing effects will be. By means of the combined study results in many aspects i.e. the structural division of the fault zone, the type of the cement, the influencing factors, the fluid activities period and the fluid source, the cementing-sealing mechanisms of the fracture diagenesis are proposed, thus the theoretical evidences for the optimization of the next exploration target area ares provided.