Degree
Doctor of Philosophy (PhD)
Department
The Craft and Hawkins Department of Petroleum Engineering
Document Type
Dissertation
Abstract
Conventional methods of managing Gas-in-Riser events are not optimal when the riser is isolated from the formation by a closed subsea blowout preventer (BOP) on rigs equipped with Mud-GasSeparator (MGS), Managed Pressure Drilling (MPD), or Riser Gas Handling (RGH) equipment. As the use of adaptive drilling processes like MPD facilitates drilling of otherwise non-drillable wells with faster corrective action, the drilling industry should include the effect of gas solubility, dispersion, bubble suspension, fluid compressibility as well as riser ballooning to avoid overestimation of riser pressure and produce more efficient well control methods. The IADC Deepwater Well Control Guideline recommends always addressing riser gas first, before proceeding to control the well in a well control situation. The intent was to remove the risk of gas reaching the surface and the rig floor, putting personnel and assets at risk. However, the availability of equipment on the rig dedicated to handling gas, and the fact that the riser is isolated from the wellbore and the atmosphere reduces the level of risk of gas-in-riser, whereas the well below the subsea BOP poses a greater risk. This research discusses results from fullscale experiments conducted in LSU Well-2 in water, and Synthetic-based mud and demonstrates that the riser pressures resulting from the upward transport of riser gas are much lower than values estimated in the industry. This research explains the danger of using an open-top riser top during the monitoring of a gas-in-riser. This research also demonstrates the minimal fluid bleed-off volumes required to reduce pressure build-up consequences in a fully closed annulus. A differential pressure methodology was used in this research for detecting the presence, position, void fraction, and lead and tail velocity of the gas column to make real-time decisions during the tests. Results from a successful application of the industry's first test of the Fixed Choke Constant Outflow (FCCO) circulation method for riser gas removal are presented.
Date
5-18-2023
Recommended Citation
Kunju, Mahendra Kumar, "Behavior of Gas Influx in Riser and Considerations for Riser Gas Handling" (2023). LSU Doctoral Dissertations. 6150.
https://repository.lsu.edu/gradschool_dissertations/6150
Committee Chair
Almeida, Mauricio
DOI
10.31390/gradschool_dissertations.6150