New algorithm to simulate fracture network propagation using stationary and moving coordinates in naturally fractured reservoirs,Energy Science & Engineering

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New algorithm to simulate fracture network propagation using stationary and moving coordinates in naturally fractured reservoirs
Energy Science & Engineering ( IF 3.5 ) Pub Date : 2020-08-22 , DOI: 10.1002/ese3.793
Zhiqiang Li _{1,

2} , Zhilin Qi ₁ , Wende Yan ₁ , Xiaoliang Huang ₁ , Qianhua Xiao ₁ , Fei Mo ₁ , Feifei Fang ₁

Affiliation

Influenced by natural fractures, fracture networks may be created when hydraulic fractures propagate in naturally fractured reservoirs. Simulating fracture network propagation is crucial to fracture design. In this paper, a two‐dimensional mathematical model for the direct simulation of fracture network propagation that considers fluid filtration and reservoir fluid flow is developed, and a simulation method is proposed based on the coupled flow idea of natural fractures and matrices in dual‐porosity media. The model uses dynamic coordinates to represent the extended hydraulic fracture network and static coordinates to describe natural fractures that have not been activated. The activation of natural fractures by a hydraulic fracture is determined according to the hydraulic fracture propagation scenario after an intersection with natural fractures. The geometric shape and size of the network fracture are obtained by changing the size of the simulated area and solving the mass balance, fracture width, and reservoir fluid flow equations numerically in a coupled manner. After validating the new model, a parameter sensitivity analysis is conducted to study the effects of injected fluid volume, fracture height, fracture spacing, elastic modulus, horizontal principal stress difference, pumping rate, and fracturing fluid viscosity on the fracture network shape, fracture network size, average fracture width, and fracture‐reservoir contact area. The numerical results indicate that the model can be directly used to simulate the propagation of fracture networks. The volume of injected fluid is the most critical factor affecting the fracture network size. Increasing the fluid viscosity and injection rate can increase the width of the fracture network and the average width of a secondary fracture. However, the total contact area of the reservoir and fracture will decrease, and the reservoir‐fracture contact area and fracture network size will increase with a decrease in the horizontal stress difference and increase in elastic modulus. Decreasing a fracture's height can significantly increase the size of the fracture network and reservoir‐fracture contact area.

中文翻译：

利用天然裂缝储层中的静止坐标和运动坐标模拟裂缝网络传播的新算法

受天然裂缝影响，当水力裂缝在天然裂缝储层中传播时，可能会形成裂缝网络。模拟裂缝网络的传播对于裂缝设计至关重要。本文建立了一个直接模拟裂缝网络传播的二维数学模型，该模型考虑了流体过滤和储层流体流动，并基于天然裂缝和基质在双重孔隙中的耦合流动思想，提出了一种模拟方法。媒体。该模型使用动态坐标来表示扩展的水力压裂网络，并使用静态坐标来描述尚未激活的天然裂缝。根据与自然裂缝相交后的水力裂缝传播情况，确定水力裂缝对自然裂缝的激活作用。通过改变模拟区域的大小并以耦合方式数值求解质量平衡，裂缝宽度和储层流体流动方程，可以获得网络裂缝的几何形状和大小。验证新模型后，进行参数敏感性分析，以研究注入流体体积，裂缝高度，裂缝间距，弹性模量，水平主应力差，抽水速率和压裂液粘度对裂缝网络形状，裂缝网络的影响。尺寸，平均裂缝宽度和裂缝与储层的接触面积。数值结果表明，该模型可直接用于模拟裂缝网络的传播。注入的流体量是影响裂缝网络尺寸的最关键因素。增加流体粘度和注入速率可以增加裂缝网络的宽度和二次裂缝的平均宽度。但是，随着水平应力差的减小和弹性模量的增加，储层与裂缝的总接触面积将减小，储层与裂缝的接触面积和裂缝网络的尺寸将增大。减小裂缝的高度可以显着增加裂缝网络的大小和储层与裂缝的接触面积。

更新日期：2020-08-22

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