Depressive Effects Evaluation Of Nano-Hybrid Pour Point Depressant On Waxy Crude Oil

Our country is rich in high waxy crude oil,this kind of oil has high pour point and poor liquidity in low temperature,the traditional solution heat transfer process is effective but there are drawbacks that it needs high energy consumption,allowed throughout range is small,and allowed shutdown time is limited.Waxy crude oil transmission added polymeric PPD is a kind of effective technique improving the economical efficiency and safety of oil pipeline.But some deficiencies still exists in traditional polymeric PPD,such as not ideal effect for some high waxy crude oil,timeliness and ability to resist high-speed shear and repeat heat treatment is not so well.In this article,modified nano clay was hybridizated in polymeric PPD,nano composite PPD was prepared,and effects on waxy oil was evaluated and the impact on mechanism of PPD caused by organic montmorillonite was discussed.Montmorillonite(MMT)was modified with long alky side chain containing quaternary ammonium salt by ion exchange making use of its electric properties,to gain organic modified montmorillonite(O-MMT).Effect on the degree of organic modified montmorillonite of modification conditions(modifier types dosage of modifier,pH)was explored,the structure of modified montmorillonite and dispersity in oil phase was characterized by methods such as XRD,FT-IR,TEM,polarized light microscopy characterization.The results show that interlayer space of montmorillonite increases most and modified montmorillonite has good dispersity in toluene/n-heptane system when pH=3,CTAB modification and the modifier dosage was 1.3CEC.Nano composite PPD(pour point depressant)was prepared by basal PPD and organic montmorillonite using melt blend method,and its structure and dispersity in oil phase were evaluated.The results showed that PA had good compatibility with modified nano montmorillonite,PA molecules inserted into the montmorillonite layers and further expanded the layer spacing and organic compatibility of nano composite PPD.Typical waxy crude oil A produced from domestic oilfield were selected as research object,interaction law between nano composite PPD and waxy crude oil was studied.Among them,waxy crude oil rheology improved by the nano composite PPD research mainly includes: under the condition of different additive,pour point and viscosity at low temperature of waxy crude oil changes caused by nano composite PPD;the performance of nano composite PPD effected by different heat treatment temperature,repeated heating,high speed shearing,standing time.Results show that under the condition of same PA amount,nano composite PPD has more excellent pour point and viscosity depression performance than PA,as well as more excellent resistance to repeated heating and aging stability,but at a temperature range where a lot of wax is precipitating,high-rate shear will greatly reduce the modification effect of PA and nano composite PPD.The study of gel structure of waxy crude oil improved by nano composite PPD shows that at the same temperature,waxy crude oil doped with nano composite PPD had weaker gel structure and lower yield stress.In the end,rheological properties improvement mechanism of nano composite PPD was discussed by means of DSC and polarizing micrograph.Results showed that initial crystallization temperature of nano composite PPD is higher than that of pure polymer PPD and its crystallization temperature range is wider,the WAT of pure oil is higher than that doped with nano composite PPD which is higher than oil doped with PA.Polarizing micrograph shows that wax crystal in oil doped with PA has a tendency to gather together;the size of wax crystal aggregation in oil doped with nano composite PPD get bigger and its structure gets more compact,solid-liquid interface area is reduced.Nano-particles play a role of heterogeneous nucleation in the process of cooling and provide the wax crystal nucleation center.As the template of crystallization of wax crystal,nano-particles helps to improve the micro wax crystal structure and macroscopicly cause the improvement of rheological property of waxy crude oil.