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Experimental and Theoretical Investigations of Particle Removal from Sand Bed Deposits in Horizontal Wells Using Turbulent Flow of Water and Polymer Fluids
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- Author / Creator
- Bizhani, Majid
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Turbulent flow of water and polymer fluids over the sand bed deposits in horizontal annuli was studied using a large-scale flow loop equipped with particle image velocimetry (PIV) tool. Tests have been conducted to investigate the effects of near wall turbulence, fluid rheological characteristics and the particle size on the critical flow rate of the bed erosion. Measurements of the velocity profiles over the sand bed interface were used to quantify the equivalent sand bed roughness. The equivalent roughness was found to be a function of the boundary roughness Reynolds number and could be several times higher than the particles size in the bed. Additionally, bedload transport of particles in the form of a moving layer of particles caused the bed roughness to increase significantly. The analysis of the flow over stationary sand beds revealed that the addition of polymer significantly delays the transition from smooth to rough flow regime. The delay in transition from the smooth to the rough flow regime further causes the momentum transfer to be slow for polymer fluids comparing to water. Hence, causing the delay in the bed erosion. The average and interfacial friction factors for the flow of water over the sand beds of varying heights in the eccentric annulus were evaluated. The average friction factor for the flow of water over the sand bed was 45% higher than the flow in the annulus without any sand bed. It was also found that the interfacial friction factor could be significantly different from that of the average friction factor. The onset of the particle movement caused the interfacial friction factor to increase sharply. The impact of the flow turbulence on particles dislodgment from bed deposits was investigated using the measurement of instantaneous velocity profiles. The results indicated that the effective fluid velocity felt by the sand particles could be several times higher than the time-averaged velocity. Additionally, the drag force experienced by the particles could be significantly different from the average drag force. Therefore, it is imperative to consider flow turbulence in any solid transport models in horizontal wells. Critical flow rates for the onset of bed erosion were measured and compared to the flow of water (90 lit/min) and a dilute polymer fluid (0.032% w/w, 200 lit/min). The PIV data revealed that the polymer fluid has a higher local fluid velocity near the stationary cuttings bed interface at the onset of particle movement from bed deposits. Comparison of the Reynolds shear and normal stress profiles showed that the polymer fluid had much higher level of turbulence activity near the cuttings bed interface. Additionally, the bed shear stresses were also evaluated and compared. The minimum bed shear stress for the polymer fluid was much higher than that of water. Analysis of the PIV results together with the bed shear stress data confirmed that the polymer fluid exerted a larger drag force on the sand bed than that of water at the onset of the particle movement. A comparison was also made between fluids with two different polymer concentrations (i.e., 0.032% and 0.064% w/w) at the same flow rate (i.e., 200 lit/min). It was observed that the local fluid velocity near the cuttings bed was not affected significantly by the change in polymer concentration. Analyses of the near wall velocity data combined with the bed shear stress calculations also showed that increasing polymer concentration at the same flow rate led to an increase in the fluid’s drag force on the sand bed. However, this increase in the drag force did not lead to a bed erosion either. To explain this rather, controversial phenomenon, we have looked at the impact of the viscoelastic polymer fluid rheological properties on the bed erosion. It was shown that for viscoelastic polymer fluids, an additional normal force appears that hinders the removal of the particles from sand bed deposits. The normal force arises due to the non-zero first and second normal stress differences in polymer fluids. This additional force causes the sand bed to become more consolidated while imposing an additional resistive force against mobilization of the particles. Estimation of the normal fluid force shows that this force can be considerably higher than the submerged weight of the cuttings.
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- Graduation date
- Fall 2017
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.