西西伯利亚盆地北极油气区侏罗系-白垩系储集层气-水系统平衡模拟

Equilibrium modeling of water-gas systems in Jurassic-Cretaceous reservoirs of the Arctic petroleum province,northern West Siberia

为揭示盐水含量较高的含油气盆地中油气和地下水之间的相平衡,采用新的气-水平衡模拟软件对西西伯利亚盆地北极含油气区进行模拟。研究发现,该区域地层水的含气饱和度(Sg)变化较大,饱和系数(Cs)为0.2~1.0,其数值随深度及地层水总含气饱和度的增加而增大。地层水Sg大于1.8 L/L的情况下,气体饱和系数(Cs)均达到临界值1.0,为油气成藏创造了有利条件;而欠饱和水可溶解现有油气藏中的天然气。地层水气体饱和系数与储集层流体类型有关,凝析油气田的气体饱和系数主要为0.8~1.0,而在常规油藏中却相对较低。复杂的气水交换模式表明研究区侏罗系—白垩系储集层中天然气来源具有多样性。

To reveal the equilibrium state of oil and gas and water in a petroliferous basin with a high content of saline water,calculations of water-gas equilibrium were carried out,using a new simulation method,for the Arctic territories of the West Siberian oil and gas bearing province.The water-bearing layers in this area vary widely in gas saturation and have gas saturation coefficients(Cs)from 0.2 to 1.0.The gas saturation coefficient increases with depth and total gas saturation of the formation water.All the water layers with gas saturation bigger than 1.8 L/L have the critical gas saturation coefficient value of 1.0,which creates favorable conditions for the accumulation of hydrocarbons;and unsaturated formation water can dissolve gas in the existent pool.The gas saturation coefficient of formation water is related to the type of fluid in the reservoir.Condensate gas fields have gas saturation coefficients from 0.8 to 1.0,while oil reservoirs have lower gas saturation coefficient.Complex gas-water exchange patterns indicate that gas in the Jurassic–Cretaceous reservoirs of the study area is complex in origin.