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Theoretical and Experimental Investigation of WAX Precipitation in Crude Oil Transportation Pipelines

Mashhadi Meighani, Hossein | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51159 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ghotbi, Cyrus; Jafari Behbahani, Taraneh; Sharifi, Khashayar
  7. Abstract:
  8. Wax precipitation may occur in production or transportation of crude oil form field which is a serious problem in petroleum industry. Flow assurance issues concerning wax precipitation make it necessary to develop a precise thermodynamic model to predict the wax appearance temperature and amount of precipitation at different conditions. In this work a new procedure has been proposed to characterize crude oil based on the SARA test considering the wax and asphaltene as single pseudo components. Two scenarios have been investigated for the survey of the crude oil characterization, with and without asphaltene pseudo component. Also, in this work, the Perturbed Chain form of the Statistical Associating Fluid Theory, PC-SAFT, has been developed to evaluate its ability for modeling of wax precipitation prediction. It is demonstrated that the developed PC-SAFT model can correlate the wax precipitation amount better than basic models (multiple solid, solid solution) typically used in the industry. The results obtained with the proposed model show a remarkable matching with the experimental data for wax precipitation values. The obtained results are very promising in providing better approach to model wax precipitation. The obtained results from FTIR spectroscopy and PC-SAFT model were in quite agreement. FTIR spectroscopy determined higher WAT values in comparison to CPM and viscometry which may be due to its higher sensitivity to smaller wax crystals. FTIR method showed much more accuracy in measurement of WAT but it is still required to perform other techniques such as CPM along with FTIR to provide some information about crystals morphology. In this study, the effect of a polymeric crystal modifier (EVA) and an aromatic solvent (toluene) on wax precipitation wax investigated. EVA decreased the pour point of lower waxy crude oils dramatically but slight reduction of pour point was achieved for higher waxy crude oil. Toluene dissolved polar compounds such as asphaltene and consequently decreased WAT and pour point. This observation confirmed that asphaltene supports the wax crystallization and its growth and the hypothesis of inhibiting performance of asphaltene in wax precipitation was rejected
  9. Keywords:
  10. Wax Percipitation ; Rheology ; Asphaltene ; Perturbed Chain From of the Statistical Associating Fluid Theory (PC-SAFT)State Equation ; Fourier Transform Infra Red (FT-IR)Spectroscopy ; Support Vector Regression ; Sensitivity Analysis

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