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Simulation of Asphaltene Slurry Flow for Oil Dominant Systems in Vertical Wells

Tavakkoli, Mohammad | 2013

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 45239 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Taghikhani, Vahid; Pishvaie, Mahmoud Reza; Masihi, Mohsen; Chapman, Walter; Panuganti, Sai
  7. Abstract:
  8. In the upstream asphaltene flow assurance community, both academics and industries are actively involved to predict the asphaltene deposit profile in wellbores and pipelines. The main objective of this study is to contribute to the thermodynamic and transport modeling of asphaltene in order to predict its precipitation, aggregation and deposition. For a better knowledge of the flow properties of asphaltene containing crude oils, it is necessary to understand how asphaltene affect the rheological properties. In this work, the information on such rheological properties of oil-asphaltene slurry systems is provided. The results of rheological experiments for two Iranian crude oils show that the non-Newtonian flow curves can be approximated by the Bingham-Plastic model. Essential information for study of asphatene deposition in wellbores is the amount of asphaltene that can precipitate, and hence deposit. In this work, the Perturbed Chain form of the Statistical Associating Fluid Theory (PC-SAFT) is applied to predict the asphaltene precipitation onset condition as well as the amount of precipitate under pressure depletion and high pressure-high temperature gas injection conditions. The accuracy of the experimental techniques for measuring the precipitated asphaltene amount at high pressure and high temperature conditions is discussed. Previous PC-SAFT asphaltene studies required the compositional data for both flashed gas and flashed liquid. This work shows a PC-SAFT crude oil characterization procedure when only the composition of monophasic reservoir fluid is available. Then, the previously developed asphaltene deposition tool (ADEPT) which is based on axial dispersion model is used to predict asphaltene deposition profile in wellbore. The effect of gas injection as well as asphaltene polydispersity on deposition profile is studied. At high gas concentration, increase of injected gas amount results in lower asphaltene deposition flux in wellbore. An explanation for this behaviour is provided. An interesting trend for deposition profile under CO2 injection conditions is observed which can be justified by investigating the solubility parameter of crude oil and CO2 mixture. Quartz Crystal Microbalance with Dissipation measurements (QCM-D) are done to understand the depositional tendency of asphaltene. Two different systems are studied: model oil and real oil systems. The depositing environment is varied by changing system temperature, asphaltene polydispersity, solvent (asphaltene stability), depositing surface and flow rate. This study discusses the roles of convective, diffusive and adsorption kinetics on asphaltene deposition by modeling the adsorbed mass before asphaltene precipitation onset. After asphaltene precipitation, the transport of asphaltene over the crystal in the flow module follows a multistep process, including precipitation, aggregation, advection, diffusion and deposition. A novel method for the detection of asphaltene precipitation onset is proposed in this study
  9. Keywords:
  10. Flow Assurance ; Oil and Asphaltene Slurry Rheology ; Perturbed Chain From of the Statistical Associating Fluid Theory (PC-SAFT)State Equation ; Asphaltene Deposition ; Quartz Crystal Microbalance (QCM)Experiments

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