裂缝性致密砂岩油藏渗吸驱油效果影响因素

裂缝性致密砂岩储层物性较差,非均质性强,且发育微裂缝,注水开发效果较差,渗吸驱油作为致密油储层水驱采油的一种主要机理受到越来越多的关注。室内以鄂尔多斯盆地某油田裂缝性致密砂岩储层天然岩心为研究对象,通过自发渗吸实验,评价了原油黏度、注入水矿化度、温度、渗透率、润湿性以及表面活性剂对渗吸驱油效果的影响。结果表明,原油黏度越低,注入水矿化度越低,温度越高,渗透率越大时,渗吸驱油采收率越高;其中润湿性对渗吸采收率的影响最为显著,岩石越亲水,渗吸驱油效果越好;阴离子型表面活性剂ZYL-1能够通过改变岩石表面润湿性和降低油水界面张力来提高渗吸驱油采收率;加入0. 3%ZYL-1后的周期注水最终采收率可以达到45. 6%,远远高于单独水驱时的28. 9%。矿场试验结果表明,注入表面活性剂ZYL-1关井渗吸驱油后,取得了显著的增产效果,说明间歇式周期注水和表面活性剂渗吸驱油相结合的方式能够提高裂缝性致密砂岩油藏的采收率。

Influence Factors of Imbibition Oil Displacement in Fractured Tight Sandstone Reservoirs

Fractured tight sandstone reservoirs are characterized by poor physical properties, strong heterogeneity, micro-fractures and poor water flooding effect. As a main mechanism of water flooding and oil recovery in tight reservoirs, imbibition flooding has attracted more and more attention. Taking the natural core of fractured tight sandstone reservoir in an oil field of Ordos Basin as the research object, the effects of crude oil viscosity, salinity of injected water, temperature, permeability, wettability and surfactant on the oil displacement efficiency were evaluated through spontaneous imbibition experiments. The results show that the lower the viscosity of crude oil, the lower the salinity of injected water, the higher the temperature and the permeability, the higher the oil recovery by imbibition flooding; the wettability has the most significant effect on the oil recovery by imbibition; the more hydrophilic the rock is, the better the oil displacement by imbibition; the anionic surfactant ZYL-1 can change the wettability of rock surface. The final recovery rate of cyclic water injection can reach 45.6% after adding 0.3% ZYL-1, which is much higher than 28.9% when water flooding alone. Field test results show that the injection of surfactant ZYL-1 after shut-in and imbibition flooding has achieved remarkable stimulation effect, indicating that the combination of intermittent cyclic water injection and surfactant imbibition flooding can improve the recovery of fractured tight sandstone reservoirs.