Abstract

In order to improve the measurement speed and prediction accuracy of unconventional reservoir parameters, the deep neural network (DNN) is used to predict movable fluid percentage of unconventional reservoirs. The Adam optimizer is used in the DNN model to ensure the stability and accuracy of the model in the gradient descent process, and the prediction effect is compared with the back propagation neural network (BPNN), K-nearest neighbor (KNN), and support vector regression model (SVR). During network training, L2 regularization is used to avoid over-fitting and improve the generalization ability of the model. Taking nuclear magnetic resonance (NMR) T2 spectrum data of laboratory unconventional core as input features, the influence of model hyperparameters on the prediction accuracy of reservoir movable fluids is also experimentally analyzed. Experimental results show that, compared with BPNN, KNN, and SVR, the deep neural network model has a better prediction effect on movable fluid percentage of unconventional reservoirs; when the model depth is five layers, the prediction accuracy of movable fluid percentage reaches the highest value, the predicted value of the DNN model is in high agreement with the laboratory measured value. Therefore, the movable fluid percentage prediction model of unconventional oil reservoirs based on the deep neural network model can provide certain guidance for the intelligent development of the laboratory’s reservoir parameter measurement.

Highlights

  • The fluids in unconventional oil reservoirs can be divided into two categories according to their existence states: one is bound fluid, and the other is free fluid [1]

  • The movable fluid percentage of the reservoir was predicted based on the shape characteristics of the core nuclear magnetic resonance (NMR) T2 spectrum of unconventional oil reservoirs

  • In order to further verify the prediction effect of the deep neural network model on the percentage of movable fluid in unconventional reservoirs, we performed the prediction of the percentage of movable fluid in 10 unconventional reservoir cores from Changqing

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Summary

Introduction

The fluids in unconventional oil reservoirs can be divided into two categories according to their existence states: one is bound fluid (immovable fluid), and the other is free fluid (movable fluid) [1]. The bound fluid in the smaller pores is difficult to flow due to the large capillary force; the fluid in the middle of the larger pores is subject to the smaller capillary force It can flow under a certain driving pressure, so it is called movable fluid. Mohamed used machine learning methods to study lithology classification, and concluded that the classification accuracy of supervised learning algorithms was better than that of unsupervised algorithms [6]; Liuqing predicted the porosity of sandstone reservoirs based on deep neural network and logging data. In order to improve measuring speed and accuracy of the movable fluid percentage of unconventional reservoirs, this article is based on the deep learning method and the unconventional reservoir core NMR T2 spectrum data of laboratory measurement to predict movable fluid percentage of unconventional oil reservoirs

Correlation Analysis between NMR T2 Spectrum and Percentage of Movable Fluid
Data Source and Preprocessing
Correlation
Principles of Deep
Feedforward Algorithm of Deep Neural Networks
Back Propagation Algorithm of Deep Neural Networks
Adam Optimization Algorithm
BP Neural Network Model
K-Nearest Neighbor Regression Model
Support Vector Regression Model
Model Evaluation Method
Optimization of Deep Neural Network’s Hyperparameters
Optimization of Learning Rate
It can Figure be seen4 neuronslayer in different models is shown in Table
Training and Evaluation Results of Different Models
Application Results of the Deep Neural Network Model
Conclusions
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