After the start of the heating furnace in the upstream station of the hot oil pipeline, the unsteady trend of the oil temperature in the downstream inlet station will affect the hot⁃washing operation of the pipeline before the pigging and the emergency treatment for abnormal shutdown. Accurate prediction of unsteady oil temperature trend changes can effectively improve the safe operation of pipelines and energy conservation and consumption reduction. A deep learning framework is adopted to take the unsteady process of upstream and downstream oil temperature as the mapping relationship from sequence to sequence, and the classical seq2seq algorithm of Recurrent Neural Network (RNN) was used to establish a predictive model of unsteady oil temperature. Through the correlation analysis, the parameters such as the unsteady oil temperature, pipeline flow and ground temperature in the upstream outbound station are selected as the model influence factors. In the SCADA system database of the HY hot oil pipeline, the relevant parameter historical data is downloaded as sample data, and after the data is preprocessed, the model is trained and tested. The error between the predicted value and the true value is ±0.2 °C, the correlation coefficient R and the root mean square difference RMSE are 0.96 and 0.99. At the same time, the verification model can effectively predict the unsteady oil temperature of the downstream station, which has high accuracy and good generalization.

The cost of the scheme can be reduced by selecting the appropriate test method and result of wax appearance point (WAT).The WAT of high pour point oil in SY and KF oilfields under different conditions was measured by four test methods.The results showed that the WAT measured by microscopic observation,differential scanning calorimetry,laser and rheological methods decreased in turn. It can be divided into the crystallization temperature,critical wax deposition temperature and deposition influence temperature according to the test conditions.The WAT was independent of wax content,and was greatly influenced by high carbon paraffin.The WAT of live oil near saturation pressure was the smallest,which decreased by 9 ℃ compared with the degrassed crude oil.When the pressure of degrass crude oil increases from 0.1 MPa to 24 MPa,the wax evolution temperature increases by 3.1 ℃.The WAT decreased by 2.9 ℃ when the shear rate of live oil increased from 10 s-1 to 1 191 s-1 under the same pressure.Influenced by the asphaltene deposition, the deposition temperature is higher than the critical wax deposition temperature when the pressure was lower than 15 MPa.The rheological test results meet the engineering needs, and the activation energy method can be utilized to deal with the experimental results.This study can provide theoretical and technical support for the selection of WAT in engineering.

Using differential scanning calorimeter （DSC ）， the crystallization abilities of polyacrylate （PA） pour point depressant and waxy crude oils doped/undoped with PA were studied；then the morphology of wax crystals in the waxy crude
oils doped/undoped with PA was investigated through a polarized light microscope and the depressive effect of PA on Changqing and Qinghai waxy crude oils was evaluated by the pour point tests and rheological experiments．The results show that the crystallization ability of PA improved greatly by increasing the alkyl side chain length of PA but kept unchanged with the increase of average molecular weight of PA．The addition of PA can inhibit the wax precipitation and decrease the wax appearance temperature of waxy crude oils．The size of wax crystals become larger and the structure of them become compact after PA addition，leading to the great improvement of the low temperature rheology of waxy crude oils．The depressive effect of PA on waxy crude oils are related to the crude oil composition and the molecular structure of PA．With the increasing of wax content and the fraction of wax with large carbon number， the depressive effect greatly decreased． The average molecular
weight of PA affected its depressive effect by controlling the solubility of PA in waxy crude oils：the solubility of PA in crude oils decreased with increasing the average molecular weight of PA， thus reducing the interactions between waxes and PA molecules and inhibiting the depressive effect of PA．The better matching the alkyl side chain of PA with the carbon number ofwax in crude oils，the better depressive effect of PA．