Classifier-assisted level-based learning evolutionary search for heat extraction optimization of enhanced geothermal systems

Enhanced geothermal systems are essential to provide sustainable and long-term geothermal energy supplies and reduce carbon emissions. Optimal well-control scheme for effective heat extraction and improved heat sweep efficiency plays a significant role in geothermal development. However, the optimization performance of most existing optimization algorithms deteriorates as dimension increases. To solve this issue, a novel surrogate-assisted level-based learning evolutionary search algorithm (SLLES) is proposed for heat extraction optimization of enhanced geothermal systems. SLLES consists of classifier-assisted level-based learning pre-screen part and local evolutionary search part. Specifically, the classifier-assisted level-based learning strategy employs probabilistic neural network as the classifier to classify the offspring into pre-set number of levels. The offspring in different levels uses level-based learning strategy to generate more promising and informative candidates pre-screened by classifier to conduct real simulation evaluations. In the local evolutionary search part, a surrogate model is constructed at the local promising area. The optimum of the surrogate model obtained by the optimizer is selected to conduct real simulation evaluations. The cooperation of the two parts is able to achieve balance between the exploration and exploitation during the optimization process. After iteratively sampling from the design space, the robustness and effectiveness of the algorithm are proven to be improved significantly. To the best of our knowledge, the proposed algorithm holds state-of-the-art simulation-involved optimization framework. Comparative experiments have been conducted on benchmark functions, a two-dimensional fractured reservoir and a three-dimensional enhanced geothermal system. The proposed algorithm outperforms other five state-of-the-art surrogate-assisted algorithms on all selected benchmark functions. The results on the two heat extraction cases also demonstrate that SLLES can achieve superior optimization performance compared with traditional evolutionary algorithm and other surrogate-assisted algorithms. This work lays a solid basis for efficient geothermal extraction of enhanced geothermal system and sheds light on the model management strategies of data-driven optimization in the areas of energy exploitation.