气湿性纳米SiO_2颗粒对岩心润湿反转及解水锁机理

Wetting Transition and Water Block Removal of Gas Wetting Nano SiO_2 Particles on Rock Cores

使用气湿反转剂能解除凝析气藏等温降压开采过程中产生的液锁损害,但目前的气湿反转剂存在价格高、用量大、气湿反转效果差等缺点。为此,通过采用改进的Stober法制备均一粒径的纳米SiO_2颗粒,再对其表面进行功能化修饰,合成出了具备气湿反转功能的纳米颗粒,其最佳合成条件为,正硅酸乙酯和氨水的用量均为1~2 m L,非离子型氟碳表面活性剂FG24的浓度为0.3%。通过接触角法、Owens二液法和自吸吸入法研究了纳米SiO_2颗粒对岩心润湿性的影响。研究表明,用0.3%气湿性纳米颗粒流体处理岩心,水相和油相在岩心表面的接触角可由未处理时的23°和0°增至157°和135°;岩心的表面能由67.9 m N/m降至0.23 m N/m;岩心的液相饱和度由87%和73%降至3.5%和32%,水相和油相的自吸速率由0.26和0.27 m L/min在2 h内降至0。实验还测定了气、油相在气（油）-纳米流体-岩心体系中的接触角,探索分析了气湿性纳米SiO_2颗粒的作用机理。结果表明,该纳米颗粒具备良好的气湿反转功能。

Nano SiO_2 particles of uniform size were prepared using the improved Stober method and their surfaces functionally modified to render the SiO_2 gas wetting.The effect of the wetting nano fluid on the wettability of rock cores was studied using different methods such as angle of contact measurement,Owens method and imbibition method.The studies show thatcores with ultra-strong gas wetting can be made by adding 1-2 mL of ethyl orthosilicate and ammonia,and 0.3%of FG24.Prior to and after treatment of cores with the nano gas wetting fluid,the angles of contact of water and oil on the cores are increased from 23° to 157°,and from 0°to 135,respectively.Imbibition experiments showthat,prior to and after treatment of cores with the nano gas wetting fluid,the water and oil saturations of the cores are reduced from 87%to 3.5%,and from 73%to 32%,respectively,and the imbibition rates of water and oil are reduced from 0.26 mL/min and 0.27 mL/min to 0 mL/min within 2 h.These data indicate that the nano gas wetting fluid has good wetting transition capacity.