Injection And Production Parameters Optimization Of N₂ Injection In Chang 7 Tight Sandstone Reservoir In North Shaanxi

The prospect of tight sandstone reservoir including Chang 7 reservoir of northern Shaanxi is good.The recovery factor of depletion development is low,while N₂ has low price,wide source,small reservoir damage and can be applied to a variety of reservoir conditions.Therefore,this paper optimized the injection and production parameters of N₂injection for Chang 7 reservoir in northern Shaanxi through experimental and numerical simulation studies.In this paper,the reservoir physical characteristics,petrological characteristics and microscopic pore throat structure characteristics of chang7 tight sandstone reservoir in a block in northern Shaanxi are studied firstly.It belongs to a typical tight sandstone reservoir because of its poor physical properties.At the same time,the microscopic oil displacement mechanism of N₂ oil displacement is analyzed through the experiments.It is found that N₂ had no obvious effect on crude oil expansion and viscosity reduction,but it has certain extraction effect,and miscibility could not be achieved under reservoir conditions.Secondly,the core displacement experiments are carried out to study the N₂displacement under different injection pressures and the N₂-water alternating experiments under different gas-water ratios.It is found that the higher the pressure is,the higher the oil displacement efficiency is.When the gas-water ratio is 1:2,the oil recovery factor is the highest.Then,numerical simulation software is used to fit the core experiment,and the injection and production parameters are optimized for different nitrogen injection methods.The parameters including injection pressure,injection velocity,injection timing and production velocity of N₂ flooding are optimized.The parameters including alternation cycle,injection velocity and gas-water ratio of N₂-water alternating flooding are optimized,N₂ huff-n-puff are optimized for injection timing,well soaking time,production time,gas injection intensity and huff and puff cycles.Next,the optimal schemes of these different gas injection methods are compared.Then sensitivity analysis of injection-production parameters under different gas injection methods are carried out and the principle of optimizing injection-production parameters is given.In this paper,the injection and production parameters optimization of N₂ flooding in chang7 reservoir of a block in northern Shaanxi were studied,which provided a basis and reference for the parameter selection of tight reservoir development using N₂ injection.