四川盆地震旦系灯影组天然气晚期成藏特征及意义

震旦系灯影组为四川盆地已发现天然气藏最古老的层系。四川盆地地质历史中经历了多旋回构造运动，但至今仍有大规模天然气藏存在，其重要原因之一是晚期成藏。通过对天然气组分、同位素及流体包裹体特征的分析，结合区域地质资料，得出四川盆地灯影组天然气晚期成藏具有3个显著特征：①广泛烃源(古油藏裂解气、水溶解析气)供给为晚期成藏提供物质基础；②气烃包裹体普遍发育反映喜马拉雅期天然气大范围充注；③喜马拉雅期油气重新调整、聚集，形成新气藏。依据喜马拉雅期构造变形特征，可将震旦系灯影组气藏分为3种类型：原生型、残存型和调整型，最有利的为原生型气藏，其次为调整型。对四川盆地震旦系等古老层系天然气勘探中应高度重视喜马拉雅运动对成藏的影响，其中构造相对稳定的古隆起区及斜坡带具有良好的保存条件，是勘探的有利区。 

The Characteristics and Implications of Late Gas Accumulation in the Sinian Dengying Formation of Sichuan Basin

Dengying Formation is the oldest gas-bearing strata which have ever been found in Sichuan Basin.Since Sichuan Basin experienced polycyclic tectonic movements,the reason why there still are major gas reservoirs is attributed to late hydrocarbon accumulation.According to the analyses of gas components,isotopes and fluid inclusions,combined with regional geological data,three salient features of late gas accumulation in Dengying Formation of Sichuan Basin are concluded: (1) Extensive hydrocarbon sources (oil-cracked gas and exsolved gas from water phase) provide material basis for late gas accumulation|(2) General development of gas inclusions reflects a wide range of natural gas filling in Himalaya period|(3) Readjustment of oil and gas in Himalaya period resulted in the formation of new gas reservoirs.Based on tectonic deformation features in Himalayan period,gas reservoirs of Dengying Formation can be divided into three types.The most favorable type is the native gas reservoir,followed by the adjustable one.The influence of Himalayan movement should be paid great attention to during the exploration of natural gas in Sinian or other ancient strata of Sichuan Basin.The relatively stable paleo-uplift and ancient slope belt which have good preservation conditions are favorable exploration areas.