低渗透气藏克氏渗透率影响因素室内实验研究

含有二氧化碳的低渗透气藏的岩石物性及流体物性具有特殊性,无法准确分析气体滑动效应对克氏渗透率和渗流能力的影响。为此,采用室内单相气体渗流实验进行测定与分析。结果表明,气体在岩心渗流过程中存在克氏效应,岩心类型、围压、气体类别和温度是影响其克氏渗透率的主要因素。孔隙型岩心的克氏渗透率远大于微裂缝—孔隙型岩心的克氏渗透率。随着实验围压的增大,气测渗透率与气体平均压力倒数关系曲线的斜率不变,但是克氏渗透率及其变化幅度逐渐减小。由于气体的相对分子质量不同,二氧化碳的克氏渗透率大于天然气和氮气的克氏渗透率。在相同的实验围压和实验岩心条件下,实验温度越高,其对气体渗流的影响越小,即20℃时岩心的克氏渗透率大于50,80和140℃下岩心的克氏渗透率。

Experimental study on factors of KlinKenberg permeability in low permeable gas reservoir

CNPC found a low-permeability gas reservoir with CO2 in Jilin oil fields.Because the rock properties and fluid properties are unique,it is not accurate to analysis the effects of gas slippage effect on KlinKenberg permeability and penetration capacity.In view of this specificity,they are determined and analyzed by single-phase gas flow laboratory experiments.Experimental studies show that the KlinKenberg effect is found in the gas flow process in core and the influence factors are important including the core type,confining pressure,gas type and temperature.The KlinKenberg permeability of porosity core is higher than that of micro-fracture core.With the increasing of confining pressure,the slop of permeability-mean pressure curve is not changed,but the KlinKenberg permeability and its amplitude are decreased.Because of the different molecular weights,the KlinKenberg permeability of carbon dioxide (big molecular weight) is higher than that of natural gas and nitrogen gas (small molecular weight).The influence of temperature on gas flow at low temperature is greater than that at high temperature,that is,the KlinKenberg permeability of 20℃ is higher than that of 50,80 and 140℃.