Layer temperature attenuation laws in abandoned multi-lateral oil wells and the influences of injection parameters on injection and production performance
Applying abandoned oil well to geothermal development is an effective measure to reduce geothermal development cost and promote commercial promotion,and its layer temperature attenuation law has an important impact on the heat extraction effect of the geothermal system.Taking the reservoirs in an abandoned oil well as the research object,this paper classifies the reservoir fractures according to the Voronoi theory,and establishes a 3D oil-water two-phase hydro-thermal coupling numerical model.Then,the layer temperature attenuation laws under different reservoir conditions and well layout structures are analyzed.Finally,the influence of injection parameters and other factors on the geothermal injection-production performance is explored.And the following research results are obtained.First,the maximum difference of production temperature in low-permeability reservoir can reach 22.08 K after 30 years of production,and the layer temperature of high-permeability reservoir(1.0×10-13 m2)is excessively attenuated,resulting in a low long-term heat extraction efficiency.Second,the reservoir oil content is positively correlated with production temperature and generation power,and the maximum difference after 30 years of production is 11.57 K and 0.12 MW,respectively.Third,the lateral well can form a low temperature trough along the vertical direction,where the layer temperature attenuation is higher than the rest of the reservoir,and the increase in quantity has little impact on injection and production.Fourth,the injection rate is positively correlated with generation power and negatively correlated with production temperature,respectively,but the injection rate exceeding 89 kg/s is not favorable for long-term production.In conclusion,the heat extraction performance of the reservoir is the most sensitive to initial permeability,followed by the injection rate and the reservoir oil content,and giving the priority to the development of low-permeability reservoir is conducive to long-term geothermal production.What's more,it is necessary to use oilfield geothermal to reduce the viscosity of heavy oil and form the geothermal aided oil production mode,so as to maximize the economic benefits.Furthermore,the six-lateral well with an injection rate of 89 kg/s can realize considerable heat extraction effects and better economic benefits.
Geothermal systemAbandoned oil wellVoronoiDiscrete fracture networkInitial oil contentLayer temperature attenuationHeat extraction performanceMulti-lateral well
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