基于能量守恒的半解析半数值多裂缝扩展模拟方法

为研究水平井在进行水力压裂时的裂缝扩展机理,将无量纲近似解与能量守恒相结合,建立一种半解析半数值的多裂缝扩展模拟新方法,并开发高精度和高效率的裂缝扩展程序C5Frac。使用该方法分别针对单裂缝和多裂缝扩展进行模拟,并使用隐式水平集算法(implicit level set algorithm,ILSA II)进行对比验证。结果表明:单裂缝扩展时,C5Frac计算得到的裂缝半径、缝口宽度和进液效率与参考解的误差均在1%以内;多裂缝扩展时,C5Frac计算得到的裂缝半径、缝口宽度和缝内流量与ILSA II非常接近,裂缝总面积与ILSA II的误差保持在5%以内,且运算效率得到明显提高。该模拟方法可以在保证结果准确性的同时大大减少计算时间,可为多裂缝扩展数值模拟研究提供新思路。

Semi analytical and semi numerical simulation of multiple fractures propagation based on energy conservation

To investigate the fracture propagation mechanism of horizontal wells during hydraulic fracturing, a new semi-analytical and semi-numerical simulation method for multiple fractures propagation is established to simulate the competitive propagation of multiple fractures by combining the dimensionless approximate solution with the energy conservation. A high-precision and high-efficiency fracture propagation program named C5Frac is developed. The method was used to simulate the propagation of single and multiple fractures, and ILSA II was used for comparative verification. The results showed that: For single fracture propagation, the error between C5Frac and the reference solution in terms of fracture radius, width at fracture mouth and fluid efficiency was within 1%; for multiple fractures propagation, the simulation results of dimensionless fracture radius, flow rate inside fracture and width at fracture mouth are very close between C5Frac and ILSA II, and the error of total fracture area is within 5%. In addition, the computational efficiency is significantly improved. The method can greatly reduce computational time while ensuring the accuracy of the results, which provides a new approach for the numerical simulation of multiple fractures propagation.