Multiphase displacements in porous media are expected to be stable if the injectant has a smaller mobility than the resident phase and injection velocity is small. We investigate two-phase displacements (aqueous phase displacing oleic phase) at favorable mobility ratios, which are expected to be stable, and find that the presence of low-viscosity irreducible water promotes the formation of viscous instabilities. Microfluidic experiments and Lattice Boltzmann (LB) simulations were utilized to identify the effects of pore-scale mobilization of irreducible water on centimeter-scale flow patterns during favorable displacements. Displacements in glass micromodels showed the presence of low viscosity irreducible water resulted in fingering and early breakthrough compared to experiments with high viscosity irreducible water (glycerol solution). The LB simulations were used to explain that fingers formed because irreducible water was mobilized ahead of the injected water. The low viscosity aqueous front fingered through the oil as the viscosity of the oil was larger than that of the low viscosity aqueous phase bank. Additionally, we conducted a coreflood that showed breakthrough of the aqueous phase occurred slightly earlier when irreducible aqueous phase viscosity was low (1 cp) than when irreducible aqueous phase viscosity was large (69 cp). The novelty of this work lies in showing that presence of low viscosity irreducible water may result in an unstable displacement of medium viscosity oil by high viscosity aqueous solution at small flooding velocities.

如果注入剂的流动性小于驻留相且注入速度小，则多孔介质中的多相位移预计是稳定的。我们研究了两相置换（水相置换油相）在有利的流动比下，预计是稳定的，并发现低粘度束缚水的存在促进了粘性不稳定性的形成。微流控实验和格子玻尔兹曼（LB）模拟被用来确定在有利的位移过程中不可还原水的孔尺度动员对厘米尺度流型的影响。玻璃微模型中的位移表明，与使用高粘度束缚水（甘油溶液）的实验相比，低粘度束缚水的存在导致指法和早期突破。LB 模拟被用来解释手指的形成是因为束缚水在注入水之前流动。由于油的粘度大于低粘度水相库的粘度，因此低粘度水前沿穿过油。此外，我们进行了一次岩心驱油，结果表明，当束缚水相粘度低 (1 cp) 时，水相突破发生的时间比束缚水相粘度大 (69 cp) 时稍早。这项工作的新颖之处在于表明，低粘度不可还原水的存在可能导致高粘度水溶液在较小的驱油速度下不稳定地置换中等粘度的油。由于油的粘度大于低粘度水相库的粘度，因此低粘度水前沿穿过油。此外，我们进行了一次岩心驱油，结果表明，当束缚水相粘度低 (1 cp) 时，水相突破发生的时间比束缚水相粘度大 (69 cp) 时稍早。这项工作的新颖之处在于表明低粘度束缚水的存在可能导致高粘度水溶液在低驱油速度下不稳定地驱替中粘度油。由于油的粘度大于低粘度水相库的粘度，因此低粘度水前沿穿过油。此外，我们进行了一次岩心驱油，结果表明，当束缚水相粘度低 (1 cp) 时，水相突破发生的时间比束缚水相粘度大 (69 cp) 时稍早。这项工作的新颖之处在于表明低粘度束缚水的存在可能导致高粘度水溶液在低驱油速度下不稳定地驱替中粘度油。我们进行了一次岩心驱油，结果表明，当束缚水相粘度低 (1 cp) 时，水相突破发生的时间比束缚水相粘度大 (69 cp) 时稍早。这项工作的新颖之处在于表明低粘度束缚水的存在可能导致高粘度水溶液在低驱油速度下不稳定地驱替中粘度油。我们进行了一次岩心驱油，结果表明，当束缚水相粘度低 (1 cp) 时，水相突破发生的时间比束缚水相粘度大 (69 cp) 时稍早。这项工作的新颖之处在于表明低粘度束缚水的存在可能导致高粘度水溶液在低驱油速度下不稳定地驱替中粘度油。