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    基于FC-UNet的二维水力裂缝形态代理预测模型研究

    Surrogate Modeling for 2D Hydraulic Fracture Morphology Prediction Based on FC-UNet

    • 摘要: 针对水力压裂缝网形态预测难度大、数值模拟耗时长等工程问题,本文构建了面向水平井二维裂缝形态预测代理模型(FC-UNet模型)。该模型以U-Net为主干,耦合快速傅里叶变换(FFT)、并行卷积(PC)和通道注意力机制(CAM),实现了泵注时序信号与空间地质特征的自适应融合,还将裂缝扩展预测转化为像素级分割任务。利用经现场微地震标定的非常规裂缝模型(UFM)生成了310组正演样本,引入加权交叉熵与Dice联合损失函数缓解裂缝像素类别不平衡的问题。独立测试结果表明FC-UNet模型能精准刻画主裂缝穿透与裂缝偏转特征,交并比(IoU)约为0.84,精确率与召回率的调和平均数(F1分数)均超过0.91。模型单次预测耗时约5 s,可作为相近地质条件下水力裂缝形态的快速预测代理工具。

       

      Abstract: To address the engineering challenges of difficult hydraulic-fracture network morphology prediction and time-consuming numerical simulation, this study develops an FC-UNet surrogate model for two-dimensional fracture morphology prediction in horizontal wells. The model uses U-Net as the backbone and integrates fast Fourier transform (FFT), parallel convolution (PC), and a channel attention mechanism (CAM) to adaptively fuse pumping time-series signals with spatial geological features, thereby transforming fracture propagation prediction into a pixel-level segmentation task. Based on an unconventional fracture model (UFM) calibrated with field micro-seismic data, 310 forward-modeling samples were generated. A joint loss function combining weighted cross-entropy and Dice loss was introduced to alleviate class imbalance caused by sparse fracture pixels. Independent test results show that FC-UNet can accurately characterize main-fracture penetration and fracture deflection features, achieving an intersection over union (IoU) of approximately 0.84 and an F1-score consistently above 0.91. The prediction time for a single case is about 5 s, indicating that the model can serve as a fast surrogate for UFM-based fracture morphology forward modeling under similar geological conditions.

       

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