基于FrackOptima的币型水力裂缝模型数值计算研究

Numerical calculation of penny-shaped hydraulic fracturing model based on FrackOptima

当压裂液黏度较小使得无量纲韧性取值大于3时,币型水力裂缝数值计算的准确性和稳定性很难得到保证。因此,使用FrackOptima真三维水力压裂模拟软件开展币型裂缝数值计算研究,重点研究无量纲韧性取值大于3时的计算结果。首先分析了币型裂缝的建模理论和半解析解存在的4组参数条件。随后在该参数条件下建立算例,采用该软件计算币型裂缝的扩展过程,并比较数值模拟结果和相关半解析解运算结果。研究结果表明:数值模拟结果和半解析解运算结果之间的误差绝对值不超过10%。尤其是当压裂液黏度取值很小,使得无量纲韧性取值在3~19之间时,数值计算仍能得到较精确、较稳定的结果。为进一步使用该软件优化实际压裂方案,尤其是优化低黏度滑溜水压裂方案,奠定了理论基础。

It is difficult to maintain accuracy and stability of numerical simulation of penny-shaped hydraulic fracture when the low viscosity of fracturing fluid makes the values of dimensionless toughness more than 3.Thus,we studied the penny-shaped hydraulic fracturing model with a fully-three-dimensional simulator FrackOptima,mainly focusing on the values of dimensionless toughness above 3.We first analyzed the penny-shaped model with its modeling theory and the four parametric conditions for semi-analytical solutions.Then,we conducted numerical examples to simulate fracture propagation with FrackOptima under the four conditions.We compared the numerical results of FrackOptima with those of the semi-analytical solutions.The results indicate the absolute values of errors are less than 10%.The simulation still gives accurate and stable results with the values of dimensionless toughness at 3-19 due to extremely low viscosity,thus providing theoretical basis for further optimizing the practical fracturing treatment,particularly the low viscosity slick water fracturing with the numerical simulation.