Numerical Simulation Of Temperature Field Affected By Complex Fissures In Oil Shale In-situ Mining

In 2019,Chinas net imports of crude oil exceeded the 500-million-ton mark for the first time,and the external dependence of crude oil and oil both broke 70%.There is an urgent need for more oil and gas resources to meet the growing domestic energy demand.At the same time,oil shale,as an unconventional oil and gas resource,is rich in reserves in China.The national oil shale reserves are 719.937 billion tons,equivalent to 47.6 billion tons of shale oil resources,which is 1.5 times the proven conventional oil and gas resources in China.Effective development of oil and gas resources in oil shale can greatly alleviate the shortage of oil and gas resources in China and help Chinas development.Traditional oil shale mining methods include open pit mining and underground roadway mining.After the oil shale is mined,it will be retorted at the surface to produce oil shale oil and gas.But these methods not only cost more,but also cause great environmental pollution.In recent years,oil shale in-situ development technology has received much attention from many parties,reducing the cost and pollution in the mining process,and has great potential for development.There are many types of insitu oil shale mining technology at home and abroad,which can be divided into three methods: direct conduction heating,convection heating and radiant heating according to different heat transfer methods.Convection heating technology uses fluid as a carrier and cracks as channels,which is more economical for Chinas t hin oil shale.In the process of in-situ oil shale mining using convection heating technology,hydraulic fracturing of the oil shale layer is required,combined with the fractures formed in the geological evolution history of oil shale formation,a fracture system has been formed in the oil shale,which affects The temperature field distribution and heating effect in oil shale are discussed.If we can grasp the law of the influence of cracks on the convection heating temperature field and heating effect of oil shale,it is of great significance to the actual in-situ exploitation of oil shale.In order to understand the influence of different fracture systems on the convective heating temperature field and heating effect of oil shale in-situ production,this study conducted numerical simulation and discussion on the following problems by using computer modeling and numerical simulation software MTALAB and Fluent:1.A meshing method for complex fracture model is studied.Aiming at two problems of numerical simulation of fluids in fractures at this stage: the fractures that can be meshed and simulated are relatively simple,the meshing of complex fractures is difficult and the simulation is difficult.A blank grid assignment method is used to perform gridding and numerical simulation calculations.First determine the number of corresponding grids,then mark the grid attributes according to the shape of the crack,and finally output a grid file that can be used for numerical simulation of the fluid temperature field.2.Explore the influence of different fracture types and sizes on the heating range and effect of oil shale.Modeling and simulating cracks of different angles,catastrophic cracks of different sizes and wedge-shaped cracks under the conditions of open cracks and closed cracks,and comparing different conditions by comparing the effective heating range(the range of effective oil generation and gas generation)in the simulation results The influence of lower fissures on the temperature field of oil shale in-situ mining.It is found that it is difficult for the hot fluid to enter the closed fissure,and the open fissure is the main factor affecting the heating range and heating effect,and its effect is far better than the heat conduction between oil shale.The heating effect is related to the length of the open crack.The longer the crack,the better the heating effect.The effect of fracture size and shape on the heating effect of oil shale is very limited.The higher the gas injection rate and the higher the gas injection temperature,the greater the effective oil and gas generation area at the same time,but the heating efficiency does not increase with the increase of both.