准噶尔盆地玛湖凹陷二叠系风城组烃源岩生烃动力学特征

Hydrocarbon generation kinetics of source rocks of Permian Fengcheng Formation in Mahu Sag,Junggar Basin

准噶尔盆地玛湖凹陷及其周缘累计探明石油地质储量近30×10;t,油源主要来自凹陷内的二叠系风城组碱湖相烃源岩。通过黄金管热模拟试验,并采用Kinetic软件进行计算,获得了玛湖凹陷二叠系风城组烃源岩的各类烃产率和动力学参数,建立了生烃模式,进而对该套烃源岩的生烃能力进行了综合评价。研究结果表明:(1)玛湖凹陷二叠系风城组碱湖相烃源岩总烃产率高达412.24 mg/(g·TOC),其中液态烃类产率随温度升高先增加而后降低,高峰温度为420~460℃,气态烃产率持续增加,总产油率高于产气率,气态烃碳同位素具油型气特征。(2)风城组碱湖相烃源岩C_(1),C_(2)—C_(5),C_(6)—C_(14),C_(14+)的生成活化能主峰值分别为268 k J/mol,255 k J/mol,251 k J/mol,247 k J/mol。(3)玛湖凹陷风城组碱湖相烃源岩的生烃模式与国内外14个不同盆地具有相似性,均为早期出现生油高峰、晚期持续生气的特征,且单位TOC的生烃能力中等偏上。

The total proven reserves in Mahu Sag and its surrounding areas in Junggar Basin are nearly 30×10~8t,and the oil mainly comes from the alkali lacustrine source rocks of Permian Fengcheng Formation in the sag.Based on thermal simulation data of gold tube experiment,combined with the calculation with Kinetic software,various hydrocarbon yields and kinetic parameters of the source rocks of Permian Fengcheng Formation in Mahu Sag were obtained,the hydrocarbon generation model was established,and then the hydrocarbon generation capacity of this set of source rocks was evaluated.The results show that:(1)The total hydrocarbon yield of alkali lacustrine source rocks of Fengcheng Formation in Mahu Sag is as high as 412.24 mg/(g·TOC),in which the liquid hydrocarbon yield first increases and then decreases with the increase of temperature,the peak temperature is between 420℃and 460℃,the gaseous hydrocarbon yield continues to increase,the total oil production rate is higher than the gas production rate,and the carbon isotope of gaseous hydrocarbon has the characteristics of oil-formed gas.(2)The peaks of activation energy of C_(1),C_(2)—C_(5),C_(6)—C_(14)and C_(14+)of the source rocks of Fengcheng Formation are 268 k J/mol,255 k J/mol,251 k J/mol and 247 k J/mol respectively.(3)The hydrocarbon generation model of alkali lacustrine source rocks of Fengcheng Formation in Mahu Sag is similar to that of source rocks in 14 different basins at home and abroad.It has the characteristics of early oil generation peak and late continuous gas generation,and per unit TOC has upper-middle hydrocarbon generation capacity.