Molecular Dynamics Simulation of Wax Deposition in Shale Oil Wells:Variation of Mechanical Properties and Characteristics
In view of the unclear understanding of the variation law of mechanical properties of wax blocks during the wax deposition process in terrestrial facies shale oil and gas fields,taking nC5H12-nC24H50 as an example,the dif-fusion and aggregation behavior of wax molecules in waxy shale oil were studied by molecular dynamics simulation,the mechanical parameters of wax blocks and their variation with temperature were analyzed.The findings reveal that when the temperature exceeds 50℃,the wax molecules are loosely distributed,and the elastic modulus and Poisson's ratio of waxy shale oil are 0.With the decrease of temperature,the distance between wax molecules decreases,and the viscosity,elastic modulus and Poisson's ratio of waxy shale oil increase,and ultimately evolving into wax crys-tals.At the same temperature,the shear modulus of the wax block is lower than its bulk modulus,making the wax block more susceptible to detachment from the pipe wall due to shear forces.When the temperature falls below 50℃,the shear modulus of wax becomes positive,indicating the onset of wax deposition in the wellbore,and the wax removal operation needs to be carried out.As the shear modulus of wax increases,the sequence of wax removal methods is hot washing,chemical wax removers,and wellbore scraping.This study quantitatively obtained the varia-tion law of mechanical parameters of wax deposition in shale oil and gas wells with temperature,which is helpful to guide the formulation of wax removal and prevention measures.
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