Feasibility Study Of Natural Gas Flooding On Shale Oil

The natural energy of the Chang 7 shale oil reservoir in the Ordos Basin is insufficient,and energy supplementation is urgently needed.Due to its good injectability,gas can better improve the problem of difficult injection,and is expected to become an effective way of on-site energy supplementation.In this paper,taking block X in the Ordos Basin as an example,through physical simulation and numerical simulation methods,the feasibility of natural gas flooding to develop shale oil is studied.Through physical simulation,the development effect of different gases,reasonable pressure maintenance level and minimum miscible pressure are explored.The development effect and injection method of natural gas are studied through numerical simulation,and the sensitivity of reservoir physical properties,fracturing operation parameters,injection and production parameters are analyzed.The influence degree of different parameters is quantitatively analyzed to get the main controlling factors of the development effect of shale oil with natural gas flooding,and the adaptability boundary chart is drawn.The experimental results show that natural gas flooding has a certain potential for enhanced oil recovery.The reasonable pressure maintenance level should be 85%～95%.Under the conditions of formation temperature and pressure,it is difficult for injected gas to reach a miscible state with crude oil.Reservoir-scale numerical simulation results show that the reasonable well spacing range of the target block is 400～450m and natural gas flooding can achieve better development when the physical properties of the reservoir meet the matrix permeability is between 0.05～0.5×10^-3μm²,the oil saturation is greater than 50%,and the effective reservoir thickness is between 8～20 m.Sensitivity analysis results of fracturing operation and injection-production parameters indicate that the optimal fracture half-length,fracture conductivity,bottom hole pressure and daily injection rate are 160m,80×10^-3μm²·m,9 MPa,3000～4000 m³/d,respectively.The main controlling factor analysis results show that the three parameters of permeability,oil saturation and fracture half-length have the greatest impact on the development effect.When the development period is long,long fracturing fractures should be avoided to delay the gas channeling to ensure the development effect.Natural gas flooding is a potential development method for shale oil,which can better supplement formation energy.This paper provides theoretical guidance for reasonable energy supplementation methods for shale reservoirs,and provides technical support for reasonable parameter selection and design of natural gas flooding in shale reservoirs.