Research On Inflow Performance Relationship And Production Strategy Of Full-cycle Flowback-production By Fractured Wells In Low-permeability Oil Reservoir

With the rapid development and innovation of low-permeability reservoir fracturing and flowback technology and corresponding supporting facilities,the operation mode that integrates flowback and production has been widely promoted for applications in oilfields.During the continuous drainage process,the flowback and production of fractured wells are connected in time dimension,yet current research on flowback and production strategies remain deficient in the integrated consideration,mostly focusing on the efficient flowback process while ignoring subsequent production needs for the formation fluid supply capacity.Therefore,this paper focuses on the coordination between supply and drainage of fractured horizontal wells in oil reservoirs with low permeability,reviews existing studies and the latest trends worldwide,integrates multidisciplinary knowledge and principles,begins with formation fluid supply characteristics,researches full-cycle flowback-production inflow performance relationships and production strategies based on derived theoretical models and simulative examples and proposes a full-cycle research method of flowback and production with the aim to provide a theoretical basis for efficient development of low permeable reservoirs and technical guidance for the integrated operation strategy and management optimization of the flowback and production on-site.As for the flowback process of fractured wells in low permeable reservoirs,herein an oil-water two phases transient seepage mathematic model is established based on material balance with formation stress sensitivity and changes in oil and water physical properties taken into account.The model is then solved iteratively using the NewtonRaphson method and has realized the simulation and prediction of average pressure as well as changes in oil and water saturation in the flowback stage.Meanwhile,based on multiple regression analysis,this paper conducts a quantitative analysis of the influence degree of different reservoir factors on flowback performance and determines the priority of each influencing factor.The paper further proposes the concept of dynamic sweep flowback rate and quantitatively evaluates the flowback performance under different flowback systems and filtration levels.For the production process of fractured wells in low permeable reservoirs,a transient trilinear flow model for both multiphase and single-phase is proposed considering formation heterogeneity and formation stress sensitivity.This paper plots the characteristic curves of dimensionless bottomhole pressure and its derivatives with different flow stages distinguished and investigates the effects of different parameters on transient pressure response through sensitivity analysis.Meanwhile,the paper also plots the transient inflow performance relationship curves under single and multiple phases of fractured wells in low permeable reservoirs,followed by the analysis of the influence caused by key parameters on productivity.For the production strategy of full-cycle flowback-production of fractured wells in low permeable reservoirs,this paper studies the impact of different flowback systems on the fluid supply capacity of production stage,deepens the understanding of the effect exerted by flowback on the post-production process.At the same time,as the continue of formation fluid supply conditions after flowback,this paper realizes the productivity predictions of fractured wells in low permeable reservoirs under different production systems.By understanding fluid supply characteristics of full-cycle flowback-production,the research outcomes are expected to provide theoretical guidance for improving flowback performance and making proper drainage strategies to ensure stable and efficient subsequent production.