The Ensemble-based Optimization Of Horizontal Well Design Parameters For Shale Gas Reservoir Development With Hough Transformation

Shale gas reservoir has the characteristics of low permeability and great difficulty in development.Currently,the proven method to develop shale gas reservoir economically and effectively is fractured horizontal well.The selection of design parameters of fractured horizontal wells is directly related to the development effect and economic benefits of shale gas reservoir.Based on the analysis of the advantages and disadvantages of the current optimization methods,this paper proposes ensemble-based optimization method to optimize the design parameters of fractured horizontal wells.By introducing the Hough transform method,the limitation of the ensemble-based optimization method in the design parameters optimization of horizontal wells in shale gas reservoir is broken through,and the effectiveness and practical application effect of the ensemble-based optimization method based on Hough-transform are verified.Firstly,shale gas reservoir fracturing horizontal well geological model is established.In order to simulate a large number of natural fractures in shale gas reservoirs,the equivalent permeability tensor is used to treat the natural fractures as matrix permeability.The hydraulic fractures are simulated by embedded discrete fractures method,which can simulate the complex fracture and preserve the details of the fracture.The combination of the two fracture treatment methods not only guarantees the calculation accuracy but also improves the calculation efficiency.Secondly,sensitivity analysis of design parameters is carried out to determine the impact of design parameters of fractured horizontal wells on the economic benefits and productivity of gas reservoir development,and the sensitivity of parameters is ranked.Thirdly,according to the results of parameter sensitivity analysis,the single-factor optimization s of design parameters is carried out.For well location parameters that cannot meet the Gaussian assumption of ensemblebased optimization,the Hough transform method is used to transform well location parameters into Hough space,and the ensemble-based optimization is carried out after the ensemble of parameters to be optimized is established.Finally,the ensemble-based optimization method is applied to the actual shale gas reservoir developed by hydraulic fractured horizontal wells to further optimize the hydraulic fractured fractures.By comparing with the single factor optimization with ensemble-based optimization results can be seen that the ensemble-based optimization method to avoid the problem of splitting when optimizing parameters of horizontal wells,hydraulic fractures,production system and other parts in the conventional optimization method.By fully considering the correlation between the parameters,the design parameter combination can be found to make the shale gas reservoir development more economical,which proves the effectiveness of the ensemble-based optimization method.The application results of the ensemble-based optimization of real shale gas reservoirs show that the ensemble-based optimization method can be adjusted according to the actual situation and has a good effect on the economic benefit optimization of real shale gas reservoirs,which proves the flexibility and practicability of the ensemble-based optimization method.