Well Pattern And Schedule Optimization For Gas Flooding Of Nanpu Low-permeable Reservoir After Water Flooding

The Nanpu low-permeability reservoir is characterized with deep burial depth,low porosity and permeability,poor physical properties,and weak natural energy.this reservoir was developed with fractured oriented wells and water flooding,which however,is associated with the issues of severe water figuring through fractures,high water cut increase rate and low recovery factor.Therefore,this thesis focuses on investigating the proper injecting gas species,well patter and schedule optimizations through the combination of laboratory experiments,numerical simulations and theoratical analysis.First,relevant researches are carried out on the adaptability of gas injection development in target reservoirs,the optimization of injected gas types,and the potential of gas flooding to enhance oil recovery.Secondly,the idea of combining numerical simulation methods and reservoir engineering methods is adopted,a series of conceptual models are established based on actual reservoir parameters,and the well pattern parameters and fracture parameters of the target block after water flooding are converted to gas flooding are optimized,and construction is carried out to adapt to the current situation.Relevant research on gas flooding system of well pattern.Finally,a numerical simulation method is used to carry out relevant research on the optimization of gas injection mode and injection-production parameter optimization in the target block on the basis of the aforementioned research.The research results show that considering factors such as gas source conditions,safety risks,energization effects,oil displacement efficiency,economic cost,etc.,nitrogen is preferred as the type of gas injected after water flooding in the target block;Under the conditions,immiscible flooding is formed.The long core flooding experiment measured that the gas flooding enhanced oil recovery rate was about 23.7%.The nuclear magnetic resonance experiment results showed that nitrogen can effectively use the remaining oil in the pore diameter above 10 nm,which improves the recovery compared with water flooding The rate range can reach more than 20%;the main controlling factors that affect the potential of gas flooding after water flooding to increase oil recovery are screened out,which are water cut,oil saturation,water body energy and crude oil viscosity,so as to establish a suitable area for the target area.Block’s gas drive potential evaluation parameter system;the research shows that the optimal well pattern form of the target block after water drive is converted to gas drive is staggered well pattern,well spacing 350-400 m,row spacing 250-300 m,and artificial fractures.The fracture length is 90 m,the conductivity is 15μm²·cm,and the optimization plan for the construction of the displacement system is gas injection in the high and low parts,and oil recovery in the waist,which can increase the recovery rate by 10.4%;it is clear that the target block is the best to switch to gas flooding after water flooding The gas injection method is gas-water alternate injection,the gas injection intensity is 2000 m³·d^-1·m^-1,the gas-water ratio is（1-1.5）:1,the gas injection slug size is 0.1 HCPV,and the total gas injection volume is 1.3 HCPV,which can be used to guide the development of the mine field.