低温水侵环境致密砂岩气藏储层润湿性变化

Wettability changes of tight sandstone gas reservoir under circumstances of water invasion with low temperature

气藏储层润湿性严重影响着原油原始赋存方式、单井产能和最终采收率。采用致密砂岩气藏岩心与钢心对比的方式，用油水体积比的变化模拟水侵程度，研究低温水侵环境致密砂岩气藏储层润湿性变化。研究结果表明：气藏储层发生水侵后，油水体积比不断减小，降低了气藏储层砂岩表面与油性组分的接触几率，导致致密砂岩气藏岩心和钢心的润湿性均呈现由亲油向亲水转变的趋势；当水侵程度相同时，钢心的亲油性弱于致密砂岩气藏岩心的亲油性，这是因为，致密砂岩本身含有粘土矿物，可以吸附一些油性组分，使其表面更加亲油；气藏储层砂岩表面接触角的增速随着水侵入量的增加而增大。

The wettability of gas reservoir has great influence on original occurrence of oil,single well production and ultimate recovery.By comparing tight sandstone reservoir core and steel core,the water invasion degree was simulated through evaluating the variation of oil/water volume ratio,and the change of wettability of the tight sandstone gas reservoir under circumstances of water invasion with low temperature was researched.The results show that the oil/water volume ratio decreased continuously and the probability of contact between sandstone surface and oil components in the gas reservoir was reduced after water invasion in the gas reservoir,which results in hydrophilicity instead of hydrophobicity in both steel core and rock core of the tight sandstone gas reservoir.The hydrophobicity of the steal core is weaker than that of the sandstone core under the same water invasion degree.The reason is that the tight sandstone has clay minerals,and the clay minerals can absorb some of the oil components and make more surface area hydrophilic.The rising rate of the surface contact angle of the gas reservoir sandstone will increase with the volume of water invasion.