Study On Production Decline Law Of Horizontal Wells In Low-Permeability Reservoirs

As an important technology for the development of low-permeability reservoirs,horizontal wells have been more and more popular.Study on the law of horizontal wells production decline in low-permeability reservoirs is the focus of the research of horizontal wells.However,due to the complexity of horizontal wells production law,there are many factors affecting the production decline,which makes it difficult to use the conventional production decline models to fit the production decline of horizontal wells in low-permeability reservoirs.Based on the reservoir numerical simulation method,the production decline law of horizontal wells in low-permeability reservoir is studied this thesis;and the main controlling factors are analyzed.The production decline models of oil and gas reservoir are studied,and the curve characteristics and adaptability of each model are analyzed.A new production decline model of horizontal wells in low-permeability reservoir is established on the basis of the available models.Case study shows that the new model is more applicable.Firstly,a mechanism model is established using numerical simulation software Eclipse combining the geologic parameters and fluid parameters of the block.Numerical simulation is processed and the main controlling factors affecting horizontal wells production decline are analyzed.The results show that the production and cumulative production of fracturing horizontal wells increase with the growing of equivalent fracture conductivity,fracture half-length and fracture number.In a certain range,the three parameters show a good contribution to cumulative production while evenly increased,but when the three parameters exceed this range,the contribution become weak.Secondly,based on the definition of production decline,the classification and seepage theoretical basis of conventional Arps decline models are analyzed and derived,and the solving methods are summarized.The Arps models have a good effect in predicting the production decline of conventional reservoirs,but it is not applicable to predict the production decline in low-permeability reservoirs.Finally,this thesis analyzes production decline models of low-permeability oil and gas reservoirs at home and abroad in recent years.The curves of Super-hyperbolic decline model,Stretched exponential decline model and Duong model are plotted,meanwhile,the influence of each parameter of the models on curves is clarified.Based on the available models and development characteristics of horizontal wells in low-permeability reservoirs,a new production decline model for single well of object block is established.Three fitting parameters are employed in the new model representing the production performance in early,middle and late-life period respectively.The model can accurately and efficiently predict horizontal well performance in low-permeability reservoirs.Case study shows that the new model has better fitting effect on the single well production than other models,what more;this new model has a wider application range.