Research On Comb-like Copolymers Pour Point Depressant And PSQ Microsphere Synergistically Improving The Rheology Of Changqing Crude Oil

China is rich in waxy crude oil,this oil has a high pour point,high viscosity at room temperature,resulting in poor liquidity of crude oil.The addition of polymer-type pour point depressant to waxy crude oil is a kind of oil transportation technology which can effectively improve the economic and safety of pipeline transportation.However,there has been a long-standing understanding of the traditional pour point depressants and the lack of traditional pour point depressants themselves.It is mainly manifested in the fact that the content of polar groups in the polymer is higher than that of the polymer type pour point depressant The effect mechanism of the effect can not fully understand;followed by the traditional polymer-type pour point depressant still exists for some high waxy crude oil viscosity reduction sticky effect is not ideal,poor timeliness and many other deficiencies.The polyoctadecyl acrylate(POA),polyoctadecyl acrylate-vinyl acetate(POA-VA),polyoctadecyl acrylate-maleic anhydride(POA-MA)and polyoctadecyl acrylate-styrene(POA-St)were synthesized and used as pour point depressants(PPDs).The performance of comb-like polymers on waxy crude oil are investigated by using pour point measurement,rheological test,differential scanning calorimetry method and polarized microscopic observation.The performance of the PPDs first increases with the increase of polar group(MA or VA)content,and then decreases with the further increase of polar group(MA or VA)content.The POA-VA PPDs show the best performance at the OA:VA molar ratio 3:1.In particular,POA-VA-4(OA:VA=3:1,molar ratio)is the best PPD in optimizing rheological properties of the waxy crude oil.After the addition of 400 mg/kg POA-VA-4,compared with original waxy crude oil,the pour point of crude oil decreases by 22℃ and its average viscosity decreases by 51.45%.Based on the crystallization exothermic characteristics and wax crystal morphology of crude oils after the addition of POA and POA-VA,the mechanism of the effects of VA content on the performance of comb-like copolymer PPDs is proposed here.while the POA-MA PPDs shows the best performance at the OA:MA molar ratio 7:1.The performance of POA-St PPDs decreases outstandingly with the increase of the non-polar St molar fraction.The effects of PSQ microspheres with different particle size and pour point depressant-PSQ microspheres on the rheological properties of Changqing oil B were investigated.It was found that the PSQ microspheres with particle size of 5μm could reduce the apparent viscosity of the oil sample by 60.25% when the addition of PSQ micro/nanospheres was 100mg/kg.The best POA-VA-4 was chosen as the polymer type pour point depressant and PSQ microspheres in different proportions(5% and 10%).The influence of compound pour point depressant on the crystallization characteristics and rheology of B oil samples was studied by means of pour point measurement,rheological experiment and polarizing microscopy.The experimental results show that the compound pour point depressant PSQ-VA-7 can effectively reduce the freezing point of 14 ℃ and the average viscosity reduction rate of 74.49% when the dosage is 200 mg/kg.