Research On Factors Affecting The Co-Production Capacity Of Oil-Heat-Electricity From Abandoned Oil Wells

Geothermal energy is one of the most promising energy sources in the field of energy.At its heart,the Earth is one big hot rock and globally we are beginning to realize just how much we can tap into that heat as a source of energy production.Usually,when on-shore wells are no longer economically viable in terms of production,they are simply abandoned.However,it is increasingly found that abandoned oil wells have the potential to develop geothermal energy.After using conventional methods to produce crude oil(primary and secondary methods),a large part of crude oil in the reservoir cannot flow.Enhanced oil recovery(EOR)technology is the key to the further exploitation of irrecoverable remaining oil.The remaining oil saturation of many abandoned reservoirs is above 30%.This research studies the feasibility of using air injection in-situ combustion method to extract oil and geothermal energy from abandoned oil layers at the same time.The crude oil is oxidized and heated by injecting air.The temperature of the fluid in the reservoir increases and it is produced to the surface through the oil well.There are many researches on residual oil in-situ combustion technology,but there are few researches on how to use the high-temperature heat generated by it for effective power generation.By injecting air to oxidize the crude oil and heat the reservoir,the reservoir temperature can reach about300?after gas injection combustion.A new type of concentric casing is used to install a thermo-voltaic generator(TEG)on the outer wall of the downhole tubing and inject cold water(20°C)into the annulus.The temperature difference between cold water and high temperature and pressure fluid produced by in-situ combustion is established on both sides of TEG module to convert heat energy into electric energy.In this study,the in-situ combustion in homogeneous porous media is simulated.The influence of gas injection rate(500,1500,2500,3500 m~3/s)on the reservoir temperature and fluid production is studied.The higher the gas injection rate is,the higher the reservoir temperature is,and the higher the liquid production is.The simulation results are verified by comparing with the previous results.Temperature and flow rate are the key parameters that affect the power of thermal power generation.The simulation results of in-situ combustion are coupled to the simulation of the thermal volt power generation system as the initial conditions.A thermal volt power generation system can contain multiple thermovoltaic generating modules;one hot volt generating module includes 6 thermo-voltaic generators,which are distributed vertically in hexagon form outside the oil tubing with a height of 4cm.The simulation results show that the output power of thermo-voltaic power generation module increases with the increase of bottom-hole temperature,and the bottom-hole temperature is 200°C.One thermo-voltaic power generation module can generate 18.2 W power output,25 thermal-voltaic generating modules can be installed within 1m range,with the total power up to 455 W.The maximum output power of the thermal voltage generation system in the 10m range is 4.55 k W.And the maximum output power of the 100 m range of thermal-voltaic power generation system is45.5 k W.When the combustion front reaches the downhole TEG system,the fluid temperature and the corresponding power generation are significantly increased.In conclusion,it is of great significance and great economic benefit to use in situ combustion technology to utilize geothermal resources in oil fields.