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Experimental and Numerical Study into the Performance Assessment of Stand-alone Screens in Steam Assisted Gravity Drainage Operations
- Author / Creator
- Wang, Chenxi
Sand production is a significant issue for weakly consolidated and unconsolidated formations. Sanding can erode the wellbore and surface facilities and plug the wellbore. In SAGD operations, wellbores are typically completed by stand-alone screens such as slotted liners (SL), wire-wrapped screens (WWS), and punched screens (PS). These screens have different characteristics, including open-flow-area (OFA), aperture geometry, etc. Thus, they perform differently under the same operational condition and need to be appropriately designed to optimize their performance.
Past experimental studies have guided sand control testing and design but suffer deficiencies in testing analysis. For instance, the existing testing design ignores some influential factors, including particle size distribution (PSD), slot density, fluid properties, and fluid phase change. Therefore, existing performance analyses are not solid and comprehensive. This research aims to analyze and compare the stand-alone screens’ performance comprehensively through experimental and numerical study. The design criteria for each screen will also be generated and presented in this thesis. The comprehensive performance comparison results will create the optimal screen selection protocol for SAGD operators.
The stand-alone screen performance is analyzed using a large-scale sand control testing facility. The testing procedure incorporates several key factors, including PSD, slot density, aperture size, fluid properties, and fluid-phase change. Sand production and retained permeability are the two main indicators to characterize the stand-alone screens' sanding and flow performance. Three representative oil sands with different PSDs from the McMurray Formation are used in this experimental study. The testing results are used to generate the design criteria for these three PSDs. The design criteria are presented graphically by the “Traffic Light System (TLS).” Proposed design criteria are given by two conditions: normal SAGD condition and aggressive SAGD condition. Also, empirical correlations are built using dimensionless factors to predict the safe design window mathematically by curve fitting. Moreover, numerical models using Computational Fluid Dynamics (CFD) are built to characterize the formation damage caused by fines migration and flow convergence during the testing. The numerical models simulate the flow condition without fines migration. The pressure data obtained in the near-screen zone are used to calculate the formation damage due to the flow convergence. The formation damage due to the fines migration can be calculated by deducting the formation damage due to the flow convergence from the total amount of formation damage.
The sand production results show that fluid-phase change due to water and gas breakthrough causes more sand production. Particularly, massive sand production is observed under the gas associated flow condition. The retained permeability results indicate that higher OFA of the screen and lower fines concentration of the PSD lead to a better flow performance. The design criteria obtained based on the sand production and retained permeability results are presented graphically by the “TLS.” The TLS simply uses the three colour codes to illustrate the design criteria, in which red means unacceptable design, yellow means marginal design, and green means acceptable design. Also, empirical correlations using dimensionless factors are formulated to obtain a safe aperture design window mathematically. The simulation results show that the WWS has linear flow streamlines, creating negligible pressure drop by the flow convergence. However, due to the low slot density nature, the SL and PS show highly converged flow streamlines. The formation damage calculation results indicate that most of the formation damage created by the WWS is due to the fines migration. For the SL and PS, both fines migration and flow convergence play roles in the total formation damage. However, in the dirty formation, fines migration is the dominant parameter in the formation damage. Regarding the screen selection protocol, the WWS is recommended to be used in DC-I formation for its superior flow performance. SL and PS shall be implemented in DC-II and DC-III due to their low cost and comparable performance with the WWS.
This thesis compares the performance of three stand-alone screens comprehensively by using experimental and numerical methods. The graphical and mathematical design criteria are created for each screen under SAGD conditions. The comprehensive performance comparison leads to the optimal screen selection protocol that can be used by SAGD operators in the screen selection and design.
- Subjects / Keywords
- Graduation date
- Fall 2021
- Type of Item
- Doctor of Philosophy
- 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.