Adsorption And Flow Behaviour Of Shale Oil On The Nanometer Scale

Nowadays,as global resources are increasingly exhausted,it is difficult for conventional energy to meet social demands.Therefore,unconventional energy represented by shale oil is gradually paid attention to by many countries all over the world.However,the shale reservoir has very low porosity and permeability,bringing difficulty to conventional laboratory experiments,and the complexity of shale oil fluid in nano-pore also brings difficulties to conventional micro-flow simulation.In this paper,the adsorption and flow behaviours of multicomponent shale oil in kerogen nano pores are studied by molecular dynamics simulation.First,a real organic nanopore is constructed based on a real kerogen molecular model,and a multi-component shale oil model is constructed with the simplified the shale oil components.A model of shale oil adsorption and flow system is established by using the kerogen slits model and the multi-component shale oil model.Then molecular dynamic simulation method is used to simulate the adsorption behaviour of multi-component shale oil in kerogen pores,and the interaction analysis of different components is carried out to determine the relationship between the heterogeneous distribution of shale oil.Then,the flow behaviour of shale oil in kerogen nanometer pores is calculated by non-equilibrium molecular dynamics simulation.Besides,the flow equation is established by subsection fitting method,and the driving mode is optimized to get more accurate results.This study shows that the molecular dynamics method can be used to calculate the adsorption and flow behaviours of shale oil in the kerogen slit.The adsorption behaviour of multi-component shale oil in kerogen nanopores is heterogeneous because of the affinity between asphaltenes and kerogen.The heterogeneous distribution of multi-component shale oil can be explained by the free energy distribution of light and heavy components.The intermediate component is the most potential component of shale oil in the process of thermal production.The nanoscale channels close to the size of heavy components will reach the maximum unit adsorption density,which hinder the production of shale oil.The heterogeneous distribution of multi-component shale oil also occurs during the kerogen slit flow,and the distribution is opposite to the adsorption.The higher driving force facilitates the shale oil flow,and its speed platform can be more obviously.At a higher flow rate,asphaltene molecules form asphaltene clusters in the slits,and methane molecules enrich to the boundary layer,reducing the viscosity of the boundary layer.The volume expansion of asphaltene cluster at higher temperature increases the friction resistance between the cluster and kerogen wall,reducing the flow velocity of shale oil.The shale oil flow behaviour under the optimized driving mode is more reasonable and meets the characteristics of subsection fitting.