Owing to intricate geological and engineering factors, the hydraulic fractures in shale oil reservoirs sometimes are in heterogeneous and random lengths, which brings a difficulty in fracture estimation. To improve this situation, a simple and quick well-testing method is presented for fracturing evaluation and parameter estimation of multiple fractured horizontal wells with non-uniform fractures. The semianalytical method and Laplace transformation are used for model solution. With the proposed model, we estimate the properties of non-uniform fractures in shale oil wells from the Ordos Basin based on the buildup testing data. Results from the case studies show that there is a good relationship between fracturing treatment parameters and generated fracture properties, including fracture length and storativity ratio (or fracture volume ratio). The fracture parameter values increase with the increase in fracturing liquid volume, especially the inner region permeability and storativity ratio. When the fracturing liquid volume per stage increases by 200-300 m³, the fracture impacts are weaker on generated parameters, which indicates that there would be an optimized fracturing liquid volume in the field case.

The CO₂ enhanced oil recovery (EOR) method is widely used in actual oilfields. It is extremely important to accurately predict the CO₂ minimum miscibility pressure (MMP) for CO₂-EOR. At present, many studies about MMP prediction are based on empirical, experimental, or numerical simulation methods, but these methods have limitations in accuracy or computation efficiency. Therefore, more work needs to be done. In this work, with the results of the slim-tube experiment and the data expansion of the multiple mixing cell methods, an improved artificial neural network (ANN) model that predicts CO₂ MMP by the full composition of the crude oil and temperature is trained. To stabilize the neural network training process, L2 regularization and Dropout are used to address the issue of over-fitting in neural networks. Predicting results show that the ANN model with Dropout possesses higher prediction accuracy and stronger generalization ability. Then, based on the validation sample evaluation, the mean absolute percentage error and R-square of the ANN model are 6.99 and 0.948, respectively. Finally, the improved ANN model is tested by six samples obtained from slim-tube experiment results. The results indicate that the improved ANN model has extremely low time cost and high accuracy to predict CO₂ MMP, which is of great significance for CO₂-EOR.