Influence of crude oil composition and wax crystal structure on the damage and recovery of JH shale oil structure
The current energy development strategy of developing simultaneously oil and gas,as well as conventional and unconventional energy sources,effectively promotes the development process of shale oil,and the attention to its efficient and safe gathering and transportation process technology has been significantly increased.In this paper,the basic physical properties of JH shale oil were determined by indoor experiments,and its characteristics of low freezing point,low density,high wax content,high number of light components,no asphaltene,few colloids and weak wax crystal structure were identified.The wax crystal structure is easy to be destroyed during the gathering and transportation process,which will lead to the rapid decrease of dynamic viscosity near the freezing point.When the temperature of oil gathering is lower than the freezing point,the dynamic yield stress is significantly lower than the static value after stopping the transportation.After stopping the transportation,more wax crystals are precipitated during the static cooling process,which leads to the rapid recovery of condensate structural strength;under the condition of no temperature drop,the structural strength recovery is very slow,and the dynamic yield stress obtained after stopping the transportation for 12h at 9 ℃ below the freezing point is only 8.5％of the static value.In order to ensure the transportation safety,it is necessary to avoid the restart operation under the condition of low ground temperature or large temperature drop after stopping the transportation,and if necessary,intermittent startup can be used to reduce the yield stress of condensate,so as to ensure the restart safety.
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