Prediction model for rock elastic modulus based on TPE optimized ensemble learning
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摘要: 油气工程中常利用地球物理资料获取地层弹性模量并结合小样本的岩心实验数据进行校正,但这种方法在复杂地质条件下往往表现不佳。【目的】为提高岩石弹性模量的预测精度和泛化能力,提出了一种利用基本岩石物性参数的弹性模量智能预测模型。【方法】分别采用三种集成学习算法(RandomForest,XGBoost,LightGBM)构建了岩石弹性模量智能预测模型,并采用TPE方法对模型进行超参数优化,最后利用SHAP归因分析探讨了各输入变量对模型的贡献,【结果】结果表明:(1)提出的智能预测模型明显优于传统模型,能够实现弹性模量的精确预测并具有较强的泛化能力,其中XGBoost模型表现最佳(R2=0.87,RMSE=6.94,MAE=4.96);(2)横波速度对模型贡献最大,纵波速度次之,密度最小,精确横波速度对弹性模量预测有重要意义。【结论】该方法无需对工区及地层进行预先识别即可实现弹性模量的精准预测,对油气工程设计及实施有重要参考意义。Abstract: [Objective] Geophysical data is often used to determine the elastic modulus of formations in oil and gas engineering, with experimental data from small sample cores used for calibration. However, acquiring core samples from every stratum is impractical, which often leads to this method's inadequate performance in complex geological settings. To improve the predictive accuracy and generalizability of rock elastic modulus, an intelligent prediction model based on fundamental rock physical properties has been introduced. [Methods] Using 397 sets of core experimental data from diverse sources, with compressional wave velocity and shear wave velocity and density as input variables, intelligent prediction models for rock elastic modulus were developed based on three ensemble learning algorithms (RandomForest, XGBoost, LightGBM), the TPE method was employed to optimize the models. The dynamic elastic modulus and static elastic modulus regression model was constructed according to the methods currently used in petroleum engineering was used to provide a comprehensive assessment of the performance of the intelligent predictive model using statistical indicators. Additionally, the SHAP method was utilized to assess the contribution of each input variable to the model. [Results]The research findings indicate that: (1) The ensemble learning model optimized using TPE is significantly better than traditional statistical regression models, and can achieve accurate prediction of elastic modulus without distinguishing geological layers, with strong generalization ability. Among them, the XGBoost model performs the best (R2=0.87, RMSE=6.94,MAE=4.96). (2) Shear wave velocity makes the greatest contribution to the model, followed by compressional wave velocity, with density having the least impact. Accurate shear wave velocity is crucial for predicting elastic modulus. [Conclusion] This method allows for the precise prediction of elastic modulus without the need for prior identification of the work area and strata, providing valuable insights for the design and implementation of oil and gas engineering projects.
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