不同含水饱和度低渗透岩石气体滑脱效应研究

低渗透岩石气体滑脱效应的研究是油气开采与存储领域十分重要的内容,但目前关于低渗透岩石气体滑脱效应的研究大多是在气体单相流下进行的,对于气–液两相流时,液体对气体滑脱效应的影响,所做的研究不足。因此,利用研发的低渗透岩石惰性气体渗透性测试系统,对含水饱和度为0~70%的低渗透砂岩,进行了不同含水饱和度的低渗透岩石气体滑脱效应及有效渗透率变化规律的研究,试验结果表明:(1)二次公式k_g=k_∞(1+b/q-a/p~2)可以较为准确的解释低渗透岩石的气体滑脱效应,准确性明显高于Klinkenberg公式。(2)含水饱和度对低渗透岩石的气体滑脱效应有明显影响,气体滑脱效应随着含水饱和度增大而减少,在含水饱和度超过50%时,气体滑脱效应几乎完全被限制。(3)由于水的作用,含水的低渗透岩石随着围压增大,气体滑脱效应减少,这与克氏理论的结论相反。(4)含水饱和度对低渗透岩石的有效渗透率影响显著,随含水饱和度的增大有效渗透率减少,且围压越大,低渗透岩石的有效渗透率对含水饱和度变化越敏感。(5)低渗透岩石的有效渗透率与含水饱和度符合幂函数关系,即k_∞=k_0(1-S_w)~c。

Gas Klinkenberg effect of low-permeability rocks with different degrees of water saturation

The research on gas Klinkenberg effect of low-permeability rock is an important issue in the field of underground oil and gas storage, but the current one on gas Klinkenberg effect is most conducted under single-phase flow of gas, lacking in the research on the action of fluid on gas Klinkenberg effect under two-phase flow (gas-liquid) condition. Therefore, using the low-permeability rock permeability test system, the change laws of gas Klinkenberg effect and the effective permeability of low-permeability rocks with water saturations ranging from 0% to 70% are studied. The experimental results show that: (1) The quadratic formula k_g=k_∞(1+b/q-a/p²) can accurately interpret the gas Klinkenberg effect of low-permeability rocks, and its accuracy is significantly higher than that of the Klinkenberg equation. (2) The water saturation of low-permeability rocks has significant effects on the Klinkenberg effect. The gas Klinkenberg effect decreases as the water saturation increases, and the gas Klinkenberg effect is completely limited when the water saturation is more than 50%. (3) Owing to the effect of water, the gas Klinkenberg effect of water-filled low-permeability rocks declines with the increase of confining pressure, and it is opposite to the Klinkenberg's theory. (4) The water saturation has significant effects on the effective permeability of low-permeability rocks. The effective permeability decreases along with the increase of water saturation, and the sensitive degree of the effective permeability of low-permeability rocks to water saturation decreases with the increase of confining pressure. (5) The relationship between the effective permeability and the water saturation agrees with the power function relationship, namely, k_∞=k₀(1-S_w)^c.