A novel evaluation of total skin factor and pressure gradients for vertical perforated wells in near-wellbore region

Abobaker, Ekhwaiter (2022) A novel evaluation of total skin factor and pressure gradients for vertical perforated wells in near-wellbore region. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The reservoir productivity index relies on fluid flow performance through the nearwellbore and wellbore regions, which itself is highly dependent on wellbore geometry, completion technique, and specific reservoir parameters. The present study aims to present better understanding of fluid flow in the near-wellbore region by evaluating the effect of formation damage, well completion, well geometry as a function of single and two-phase flow rate conditions, thereby expanding industry knowledge about well performance. An experimental procedure was developed to investigate fluid flow behavior through a cylindrical perforation tunnel and different well completion configurations. The experimental test was carried out using a geotechnical radial flow set-up to measure the differential pressure by injecting the single-phase and the two-phase radially into the core sample. A triaxial experimental set-up was employed in the present work to enable larger scales and high values for parameters (e.g., larger core sample, higher pressure, etc.). The height of the samples used in this study is one foot, the diameter is half a foot, as well as the maximum flow rate reached 4 liter/minute. This set-up also enables different kinds of fluid flow problems to be investigated. Also, the set-up has been appropriately updated to target the monitoring of interaction flows for both well, and near-well areas, including axial well and radial near-well flows. Extensive laboratory testing was conducted to create artificial samples for the perforation tunnel and a cylindrical near-wellbore region that were used in this study. Statistical analysis was coupled with numerical simulation to expand fluid flow investigation in the near-wellbore area that cannot be obtained experimentally. Design of Experiments (DoE) software was used to determine the numerical simulation runs using the ANOVA analysis with a Box-Behnken Design (BBD) model. Also, ANSYS-FLUENT was used to analyze the numerical simulation for near-wellbore region by applying the single and two-phase flow. The three main investigative procedures of experimental, numerical, and statistical analysis showed a clear view of integrating effects of the skin zone (damaged region), perforation parameters, partial completion, inclination of well, the crushed zone around the perforation, and two-phase flow behavior on the total skin factor and the pressure gradient in the near-wellbore region. This study presented a novel experimental and numerical approach for studying the combined effects of well completion configurations and fluid flow behavior on the hydrocarbon production by creating a prototype representing the near-wellbore region. This study provided a comprehensive analysis of fluid flow in the near-wellbore region and developed new correlations that calculate completion configurations' effect on the skin factor. The novel correlations that have been produced from this study simplify the skin factor estimation in different well completion types. The comparison demonstrated good agreement between the proposed correlations and available models results within the range of the study's dimensionless parameters. Moreover, this study will help clarify and understand the effect of well completion on well productivity in the near-wellbore region.

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