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页岩储层中广泛发育着各种尺度的天然裂缝,这些天然裂缝小到纳米、微米量级,大到毫米甚至是工程量级,显著影响着压裂后的裂缝网络形态.同时,在页岩压裂施工过程中,压裂液会进入到这些不同尺度的天然裂缝中,在天然裂缝内部存在气-液两相流体,产生毛细管力.当天然裂缝尺度不同时,在裂缝中产生的毛细管力大小不同,尤其是当天然裂缝尺度较小时,在其内部会产生较大的毛细管力,进而显著影响天然裂缝内压裂液的流动以及压裂裂缝网络的扩展.本文建立了同时考虑天然裂缝尺度以及压裂液与储层岩石润湿特性的页岩压裂缝网扩展模型,研究了在毛细管力影响下的压裂裂缝网络的扩展特征.通过研究发现,当天然裂缝初始长度较长、缝宽较小、压力液与储层润湿性较强时,天然裂缝更容易扩展,形成较大规模的裂缝网络.当天然裂缝尺度各异时,将形成复杂的裂缝网络,该模拟结果与室内大型页岩水力压裂实验中观察到的裂缝网络扩展形态相同.
Natural fractures of various scales are widely developed in shale reservoirs, and these natural fractures are as small as nanometers, micrometers, millimeters and even engineering magnitudes, which significantly affect the fracturing network morphology after fracturing.At the same time, In the process of rock fracturing, the fracturing fluid will enter into these natural fractures with different scales, and the gas-liquid two-phase fluid exists in the natural fractures to generate the capillary force. When the natural fractures have different scales, the capillaries generated in the fractures Especially when the natural fracture size is small, there will be a large capillary force in the interior, which will significantly affect the flow of fracturing fluid in the natural fracture and the expansion of the fracture network.In this paper, Scale and fracturing fluid and reservoir rock wetting characteristics of shale fracture network expansion model to study the expansion of the fracturing network under the influence of capillary forces characteristics of the study found that when the initial length of the natural fracture longer seam When the width is small and the pressure fluid and reservoir wettability are strong, the natural fractures expand more easily to form large-scale fracture networks. When the natural fractures have different scales, a complex The result of the simulation is the same as that of the fracture network observed in the experiment of hydraulic fracturing in the large-scale indoor shale.