苏里格低渗砂岩大气田天然气充注运移及成藏特征

Charging,Migration and Accumulation Characteristics of Natural Gas in the Sulige Low Permeability Sandstone Large Gas Field

苏里格气田位于鄂尔多斯盆地伊陕斜坡西北部,属于典型的低渗砂岩大气田。苏里格气田上古生界天然气组分和碳同位素组成特征变化较小,反映其来源和成藏过程的一致性。基于对成藏地质背景、储层物性、天然气地球化学特征、烃源岩成熟度、甲烷碳同位素动力学的综合分析,认为苏里格气田天然气主要为近源充注、近距离运移和聚集,为石炭系-二叠系煤系烃源岩生成的累积聚气。天然气运移输导体系主要包括砂体-孔隙、微裂缝及小断层等,由孔隙和裂缝构成的网状输导体系在成藏过程中起了重要作用,表现为动力圈闭成藏。苏里格气田形成过程经历了早侏罗世末期、晚侏罗世至早白垩世末期、早白垩世末期至今3个演化阶段,存在下生上储和自生自储两种成藏方式。

The Sulige gas field is located in the northwest of Yishan slop in Ordos Basin and belongs to the typical low permeability sandstone gas reservoir.The components and carbon isotopes of natural gases from different wells are little varied in the Sulige gas field,reflecting the similarity of the genesis and reservoir-forming process.Based on the comprehensive analyses of the geological background,reservoir physical property,geochemical character of natural gas,maturity of hydrocarbon source rock,and carbon isotope kinetics of methane generation,it is suggested that natural gas of the Sulige gas field is mainly the near-source gas charging,small distance migration and near-source accumulation.The gases in the Sulige gas field are mainly generated from Carboniferous-Permian coal measure source rocks,belonging to the cumulative gases.The migration systems of natural gas include sandstone-pore,micro-fissure and small fault and so on.The pore-fracture network system plays an important role in migration process and forms the dynamic trap accumulation.Natural gas in the Sulige gas field experiences three evolution stages,i.e.the end of Early Jurassic,the end of Late Jurassic and Early Cretaceous,the end of Late Cretaceous.Two accumulation models,i.e.the source rock-down and reservoir-up accumulation,and the self-source rock and self-reservoir accumulation are existed in this region.