In this work, we use the steady-state measurement technique to characterize two-phase brine-mineral oil relative permeabilities and residual trapping in water-wet rough-walled fractures induced in Eagle Ford shale rock samples. Furthermore, we systematically probe the effects of flow rate and saturation history on these properties. The influences of capillary, gravity, and viscous forces on fracture flow stability and two-phase relative permeabilities are also investigated under different flow conditions represented by varying capillary and Bond numbers. The results demonstrated significant phase interference for the oil–brine flow in rough-walled fractures, which renders the commonly used x-curve and Corey models inadequate to represent the steady-state oil–brine relative permeabilities measured in this study. The saturation history influenced the relative permeabilities of both the wetting (brine) and non-wetting (mineral oil) fluid phases and the residual saturations during waterflooding. Generally, the residual oil saturation and oil relative permeability decreased with the decline in the initial oil saturation. Furthermore, at similar brine saturations, the oil relative permeability during waterflooding improved as the total flow rate increased. This increase was attributed to the high mobility of the connected oil phase within the fracture and the water-wet characteristics of the fracture walls. The brine relative permeability trend followed that of its counterpart measured under the capillary-dominated regime and only exceeded that at very high brine saturations. At higher flow rates, the residual oil trapping was significantly reduced due to the higher efficiency of the viscous-dominated displacement process. The results suggest that a high total flow rate in water-wet fractures maintains a high non-wetting phase relative permeability over a wide range of water-cut values and reduces the residual non-wetting phase saturation in the fracture at the end of waterflooding. Finally, improved correlation models were devised based on a subset of experimental results generated for fractures with various conductivities. They provide a more accurate description of fractures’ relative permeabilities compared to commonly used models. These correlations were successfully tested against relative permeability data measured for a fracture excluded during the fitting process.

中文翻译：

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粗壁裂缝中的相对渗透率滞后和残余俘获：使用稳态方法对流量和饱和度历史影响的实验研究


在这项工作中，我们使用稳态测量技术来表征两相卤水-矿物油相对渗透率和在 Eagle Ford 页岩样品中诱发的水湿粗壁裂缝中的残留圈闭。此外，我们系统地探讨了流速和饱和度历史对这些特性的影响。还研究了在以不同毛细管数和邦德数为代表的不同流动条件下，毛细管力、重力和粘性力对裂缝流动稳定性和两相相对渗透率的影响。结果表明，粗壁裂缝中油-盐水流动存在显着的相位干扰，这使得常用的x曲线和Corey模型不足以代表本研究中测量的稳态油-盐水相对渗透率。饱和度历史影响润湿（盐水）和非润湿（矿物油）流体相的相对渗透率以及水驱过程中的残余饱和度。一般而言，残余油饱和度和石油相对渗透率随着初始含油饱和度的降低而降低。此外，在相似的盐水饱和度下，注水期间石油相对渗透率随着总流量的增加而提高。这种增加归因于裂缝内相连油相的高流动性和裂缝壁的水润湿特性。盐水相对渗透率趋势遵循毛细管主导状态下测量的对应渗透率趋势，并且仅在非常高的盐水饱和度下超过。在较高流量下，由于粘性主导驱替过程的效率较高，残余油捕获显着减少。 结果表明，亲水裂缝中的高总流量可以在较宽的含水率范围内保持较高的非润湿相相对渗透率，并降低水驱结束时裂缝中残留的非润湿相饱和度。最后，根据针对具有不同电导率的裂缝生成的实验结果的子集，设计了改进的相关模型。与常用模型相比，它们可以更准确地描述裂缝的相对渗透率。这些相关性已成功地根据在拟合过程中排除的裂缝测量的相对渗透率数据进行了测试。