四川盆地嘉陵江组天然气成藏主控因素与勘探方向

Main controlling factors and exploration direction of gas reservoir in Jialingjiang Formation,Sichuan Basin

嘉陵江组是四川盆地天然气勘探的传统层系,近年来在川北、川西南等地区连续获得发现,但盆地内仍有大面积的勘探空白区,亟需深化对该层系天然气成藏规律的认识,明确成藏主控因素,进而指出未来的勘探方向。利用天然气地球化学等分析测试,结合构造恢复、盆地模拟等技术,以气源分析为基础,以典型气藏解剖为核心,结合对嘉陵江组成藏条件认识,通过对成藏过程的分析探讨了成藏主控因素,并建立了成藏模式。四川盆地嘉陵江组天然气主要来自下部的原油裂解气,嘉陵江组具有多套优质烃源岩供烃、发育多类型碳酸盐岩储层、通源断裂有效沟通气源的良好成藏条件,主生油期古构造、调整期构造及通源断裂、有利储层类型是嘉陵江组天然气成藏的主控因素;嘉陵江组具有“多源形成古油藏—古油藏裂解供气—通源断裂输导—晚期调整成藏”的成藏模式。基于此指出,分布于川西、川北等地区山前带,主生油期、气藏调整成藏期均处于相对高部位,发育通源断裂、保存条件较好的构造—岩性复合气藏是勘探的首选方向;分布于川东高陡构造带构造稳定区及向斜区的孔隙型岩性气藏是未来的主要勘探方向。

The Jialingjiang Formation is a traditional stratum for natural gas exploration in the Sichuan Basin,and in recent years it has been continuously discovered in northern and southwestern Sichuan,but there are still large areas of exploration blanks in the basin,which urgently needs to deepen the understanding of the natural gas accumulation law of this formation,clarify the main controlling factors of the accumulation,and then point out the exploration direction in the future.By using natural gas geochemistry and other analytical tests,combined with structural restoration,basin simulation and other technologies,based on gas source analysis,with typical gas reservoir anatomy as the core,combined with the understanding of the reservoir conditions of the Jialingjiang Formation,the main controlling factors of reservoir formation were discussed through the analysis of reservoir formation process,and the reservoir formation model was established.The results show that the natural gas of the Jialingjiang Formation is mainly cracked gas from crude oil in the lower part.The Jialingjiang Formation has good reservoir formation conditions such as multiple sets of high⁃quality source rocks supplying hydrocarbons,developing multiple types of carbonate reservoirs,and source⁃connected faults that effectively communicate gas sources.The paleostructures of the main oil generation period,the structures of the adjustment period,the source⁃connected faults,and the favorable reservoir types are the main controlling factors of the natural gas accumulation in the Jialingjiang Formation in the Sichuan Basin.The Jialingjiang Formation has an accumulation model of“multi⁃source charging to form ancient oil reservoirs,ancient oil reservoir cracking and supply gas,source⁃connected faults transport,and late adjustment accumulation”.Based on this,it is proposed that the structural and litholo⁃gical composite gas reservoirs distributed in the piedmont belts of western and northern Sichuan,which are at relatively high positions during the main oil generation period and gas reservoir adjustment and accumulation period,have developed source⁃connecting faults,and have good preservation conditions,are the preferred exploration directions.The porous lithological gas reservoirs distributed in the structurally stable areas and syncline areas of the high and steep structural belts in eastern Sichuan are the main exploration directions in the future.