End of Tubing (EOT) Placement Effects on the Multiphase Flow Behavior in Horizontal Wells

Randi Dinata, Research Assistant, MSc Student

Horizontal well drilling and completion have been steadily increasing over the last three decades. Although the optimum End of Tubing (EOT) location in vertical wells is well understood, our understanding may not be applicable for horizontal wells due to their significantly different flow behavior. Since there are no guidelines available for selecting EOT location in horizontal wells, horizontal wells are commonly completed with EOT in the vertical section to avoid installation challenges while others are installed in the buildup section to reach a certain flow pattern and reduce backpressure from liquid accumulation. In some cases, the EOT location is determined based on a trial-and-error procedure or an anecdotal approach.

It is essential to propose guidelines for determining the optimum EOT location for varying wellbore configurations and flow rates. Knowledge of optimum EOT placement is required to design the well’s completion properly and prevent production issues such as excessive backpressure to the reservoir, low reservoir production flow rates, severe slugging and poor unloading performance. In addition EOT location is important for a better performance of artificial lift systems. This study thoroughly investigates the dynamic flow behavior of various EOT locations and well configurations using both experimental and modeling approaches. A VBA-based well simulator, named Tulsa University Horizontal Well Simulator (TUHWS) has been developed to accommodate the findings and methodology to determine optimum EOT location proposed in this study. In addition, it also covers the liquid loading evaluation, EOT analysis with artificial lift systems and reservoir coupling.

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