Study On Well Selection Method And Injection Production Parameter Optimization Of Nitrogen Huff And Puff In Complex Fault Blocks

Complex fault block reservoirs have many complex faults.If the development of reservoirs only relies on natural energy,the output will decline rapidly,and the recovery percent will be low.The gas injection stimulation can effectively supply the producing energy.Compare to CO₂ and natural gas,N₂ is difficult to compress and easy to obtain.At present,N₂ stimulation pilot tests are carried out in various oil fields,and the throughput effects vary greatly.In particular,N₂ throughput of complex fault block reservoirs requires well selection methods and optimization of injection and production parameters.This paper takes the complex fault block reservoir of S Oil Field as the research object,the case of N₂ throughput in complex fault block reservoirs has been analyzed,the N₂ throughput efficiency mechanism has been summarized,and the complex fault block reservoir has been divided into two types with natural energy and without natural energy.The reservoir numerical simulation method was used to analyze and evaluate the influence of geology,fluid and development,and then screen the main control factors of N₂ stimulation in complex fault block reservoirs,and propose well selection method for complex fault block reservoirs.For typical complex fault block reservoirs,the N₂stimulation injection and production parameters are optimized based on the fitting of development history.The main research findings are as follows:?1?The wells in the two types of complex fault blocks are located at the waist or top of the fault blocks.When the fault block is well closed and has a certain inclination angle,it is more conducive to exerting the gravity differential effect of N₂.?2?There are many main control factors for N₂ throughput in complex fault block reservoirs.According to three cycles,the sensitivities of geological,fluid,and development factors are clarified.With energy,the deposition rhythm,cycle injection rate,vertical permeability,vertical heterogeneity,etc.are extremely sensitive factors;without energy,small layer,crude oil viscosity,horizontal permeability,vertical permeability are extremely sensitive factors.?3?When the complex fault block has energy replenishment,the timing of single well stimulation should be selected when the water saturation is about 50%,the remaining oil saturation is higher than 40%,and the production wells are close to the top of the structure.When the complex fault block has no energy replenishment,the timing of single well stimulation should be selected when the formation pressure is near the bubble point pressure,the remaining oil saturation is higher than 40%,and the production well is close to the waist of the structure.?4?When the complex fault block has energy replenishment,the optimal injection and production parameters for N₂ stimulation in H3 well are:Gas injection rate is30000m³/d,gas injection volume is 250,000m³,soak time is 30d,and fluid production rate when openning well is 15m³/d.When the complex fault block has no energy replenishment,the optimal injection and production parameters for N₂ stimulation in H31well are recommended as follows:gas injection volume is 150,000m³,gas injection rate is 50000m³/d,soak time is 45d,and fluid production rate when openning well is 2.5m³/d.