Flowback analysis recently has been considered as a potential tool for assessing induced fractures through corresponding pressure analyses and rate transient analysis. In this paper, we study fracture closure mechanisms during the flowback of fracturing fluid after hydraulic fracturing treatments. Although it is known that flowback can be significantly affected by the geometry of the fractures and closure stress, there has not been any effort to understand the problem from the geomechanical point of view; rather, available studies assume that a fracture closes uniformly with constant fracture compressibility. The coupled geomechanics and fluid flow model presented in this paper help to elucidate how geostresses may affect fracturing fluid recovery under different conditions. We perform a scaling analysis to formulate the occurrence of different fracture closure modes and then use numerical analyses to verify our scaling parameters. The factors governing the flowback process include the mechanical and petrophysical properties of the rock as well as preexisting discontinuities such as natural fractures. Three different closure modes for fracture networks are described and numerically verified. The occurrence of each mode can dramatically affect fracturing fluid recovery. The role of fluid leakoff into the formation, fractures conductivity, and drawdown strategy are examined for each fracture closure scenario.

中文翻译：

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水力压裂返排过程中的裂缝闭合模式

返排分析最近被认为是通过相应的压力分析和速率瞬变分析评估诱发裂缝的潜在工具。本文研究了水力压裂处理后压裂液回流过程中的裂缝闭合机理。尽管众所周知，裂缝的几何形状和闭合应力会极大地影响回流，但是从地质力学的角度来看，并没有做出任何努力来理解该问题。相反，现有研究假设裂缝以恒定的裂缝可压缩性均匀闭合。本文提出的耦合地质力学和流体流动模型有助于阐明地应力在不同条件下如何影响压裂液采收率。我们执行比例缩放分析以制定不同裂缝闭合模式的发生，然后使用数值分析来验证我们的比例缩放参数。控制返排过程的因素包括岩石的机械和岩石物理特性，以及先前存在的不连续性，例如自然裂缝。描述并数值验证了三种不同的裂缝网络闭合模式。每种模式的发生都会极大地影响压裂液的采收率。对于每种裂缝闭合情况，都检查了流体渗漏到地层中的作用，裂缝导流率和回落策略。控制返排过程的因素包括岩石的机械和岩石物理特性，以及先前存在的不连续性，例如自然裂缝。描述并数值验证了三种不同的裂缝网络闭合模式。每种模式的发生都会极大地影响压裂液的采收率。对于每种裂缝闭合情况，都检查了流体渗漏到地层中的作用，裂缝导流率和回落策略。控制返排过程的因素包括岩石的机械和岩石物理特性，以及先前存在的不连续性，例如自然裂缝。描述并数值验证了三种不同的裂缝网络闭合模式。每种模式的发生都会极大地影响压裂液的采收率。对于每种裂缝闭合情况，都检查了流体渗漏到地层，裂缝导流率和压降策略中的作用。