Fracture Parameters Optimization Of Multiple Fractured Horizontal Wells In Tight Gas Reservoir

Production research on unconventional gas reservoirs has been a hot spot in petroleum engineering for a long time.Fractured horizontal wells play a vital role in the development of unconventional gas reservoirs.The selection and optimization of fracture parameters of these wells determine their production abilities directly.The conventional single-well fracture parameter optimization has certain limitations due to the single factor analysis of fracture parameters.This paper aims to establish a multi-wells productivity model based on the single-well fracture parameter optimization method and the numerical situation of the study area,and obtain optimal parameters.Pieces of advices are also provided for the stimulation treatments of the production wells and the layout of new wells.Firstly,according to the history and development status of a gas field,using log data interpretation and laboratory measurement methods to re-characterize the reservoir properties in the study area.The results show that after 7 years production,the formation pressure level in the study area is low.The daily production of the production well is low too.The reservoir could be described as ultra-low porosity and ultra-low permeability reservoirs with strong heterogeneity.Then discuss the applicability of COMSOL software for this study.The strong stress-sensitivity effect of the study area is confirmed by the variable confining pressure permeability test and the stress sensitivity coefficient calculation.The high-speed non-Darcy effect,low-speed non-Darcy effect and slip effects are negated in the study area by using the critical Reynolds number and the Knudsen number calculation.Combined with the numerical situation,a single-phase gas,simplifying the matrix-artificial fracture-wellbore model of the heterogeneous formation is established.In this paper,based on the finite element method,the model is solved,and the influence of the angle between secondary fracture and artificial fracture,stress sensitivity effect,fracture half length,fracture spacing and fracture conductivity on the productivity of fractured horizontal wells is analyzed.According to the pressure wave tangency standard,the limitations of single factor analysis in single well fracture parameter optimization.In addition,due to the possibility of complex fracture networks in the horizontal wells of tight gas reservoirs,this paper also analyzes the effects of different network patterns on the productivity of fractured horizontal wells and gives two ways based on petroleum engineering theory and computer graph theory to describe the complexity of these networks.According to the researches above,the orthogonal test method is used to optimize the single-well fracture parameters.Consequently,the improvement of fracture length and the number of fractures are applied to the production wells.The results show that the single-well production is improved after the optimization.Finally,based on the results of single well fracture parameters,a multi-level well parameter optimization model was established in COMSOL,and the appropriate well pattern parameters were obtained by orthogonal test analysis and control area calculation by MATLAB.With five-year production prediction,the total production and recovery are ideal.