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Mathematical Modeling and Experimental Investigation in Rheological Behavior of Drilling Fluids Containing Synthetic Polymers

Kariman Moghaddam, Ali | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55068 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ramazani Saadatabadi, Ahmad
  7. Abstract:
  8. Drilling fluid is one the most important part of drilling operations in the oil and gas wells digging. From an economic point of view, almost 25 to 45% of drilling costs are allocated to drilling fluid. Drilling fluids consist of several components with different physical and structural forms which can be assumed as complex fluids. Optimum performance of the drilling process could be obtained through the dynamic fluid computation which requires a reliable mathematical model capable to predict transient-state and steady-state rheological behavior of drilling fluid. Generalized Newtonian models, such as the Bingham-plastic model, the power model, and the Herschel-Bulkley model, are the most popular models for drilling fluids due to their simplicity, despite their inabilities to predict transient and elastic behavior of such fluids. In addition, theoretical models have been developed to investigate the thixotropic behavior of drilling fluid. Despite vast experimental studies on the rheological behavior of drilling fluid, mathematical modeling of viscoelastic behavior and microstructural properties of drilling fluid has always been neglected. Furthermore, the previous models are not able to predict the effect of each additive on the drilling fluid rheological behavior separately. In this study, we have developed a mathematical model to predict transient and steady-state rheological behavior of the complex fluids on the scale between the microscopic and macroscopic which is named mesoscopic scale. Constitutive and governing equations are obtained using the generalized bracket formalism which is based on the thermodynamics of flowing systems in that Hamiltonian mechanics has been used to describe the transport phenomena of internal microstructures. Rheological models were developed for three drilling fluid systems, including water-bentonite-polymer suspension system, water-bentonite suspension system considering the effect of electrolytes, and water-bentonite-polymer and limestone suspension system. In addition, the accuracy and validity of the developed models were checked by performing experimental experiments including microstructural studies and rheological tests. Comparison of model prediction with experimental data shows that the models can predict the rheological behavior of different drilling fluids satisfactorily. Practically, the advantage of the model is gathering the normal stresses of fluid during its movement, which can be used in fluid dynamics calculations and stresses on walls for well stability performance, while the previous models are not able to predict these properties.
  9. Keywords:
  10. Drilling Fluid ; Rheological Behavior ; Microstructure ; Modeling ; Experimental Investigation ; Generalized Bracket Formalism ; Synthetic Polymers

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