渤海海域渤中19-6构造带油气纵向连续分布形成机理研究

渤海湾盆地是中国东部重要的含油气盆地之一,2018年中国东部最大的整装凝析气田——渤中19-6凝析气田的发现,一举打开了该地区深层天然气勘探的新领域,展现了油型盆地天然气勘探的巨大潜力。本文利用气体同位素、金刚烷双质谱、饱和烃色谱-质谱、芳烃色谱-质谱等实验分析技术,深入分析了渤海海域渤中19-6构造带油气藏分布特征,并研究了该构造带“上油下气”纵向连续分布的形成机理。认为:渤中19-6凝析气田凝析油气成熟度均分布在Ro=1.50%左右,其中凝析油裂解程度较低,属于烃源岩在高成熟阶段生成的产物;烃源岩在成熟阶段生成的原生油气早期赋存于深层潜山圈闭中,后期由于受到新构造运动的影响,油藏被破坏,原油发生降解作用且向上逸散运移进入浅层圈闭中,形成渤中19-4油田;而烃源岩在高成熟阶段生成的凝析油气进入渤中19-6圈闭中,形成现今的渤中19-6凝析气田。

Study on formation mechanism of oil and gas longitudinal continuous distributionin of BZ19-6 structural belt,Bohai sea

Bohai Bay basin is one of the important petroliferous basins in eastern China.The discovery of BZ 19-6 gas field,the largest integrated condensate gas field in eastern China in 2018,has played a prologue of deep gas exploration in Bohai Bay basin,showing great potential of gas exploration in oil-type basins.In this paper,by using a series of experimental analysis technologies such as gas isotopes,adamantane double mass spectrometry,saturated hydrocarbon chromatography-mass spectrometry,aromatic hydrocarbon chromatography-mass spectrometry,the distribution characteristics of oil and gas reservoirs in the BZ 19-6 structural belt,Bohai sea were analyzed in-depth,and the formation mechanism of the vertical continuous distribution characteristics of“oil accumulation in shallower part and gas accumulation in deeper part”in BZ 19-6 structure belt was studied thoroughly.The results show that both the maturities of condensate oil and gas in BZ 19-6 condensate gas field fall within the Ro=1.50%or so,and the cracking degree of condensate is low,which belongs to the product of high maturity source rock.In the mature stage,the primary hydrocarbons generated by the mature source rocks occurred in the deep buried hill trap in the early stage.Due to the influence of the late neo-tectonic movement,the oil reservoir was destoryed and the crude oil was degraded and migrated upward into the shallow trap,forming the BZ 19-4 oil field.However,the condensate oil and gas generated by high maturity source rocks entered the BZ 19-6 trap to form the current BZ 19-6 condensate gas field.