Date of Award
December 2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Petroleum Engineering
First Advisor
Andreas A. Michael
Abstract
In the aftermath of a blowout, a well undergoes a period of unrestricted fluid discharge (de facto primary recovery) followed by pressure buildup after its shut-in, which can adversely impact wellbore integrity. The quintessential example is Union Oil’s 1969 “A-21” well blowout in California’s Santa Barbara Channel, where seafloor-broaching incidents (oil “boilups”) kept taking place from the sides of the well following several failed well-capping attempts, until reservoir depletion eventually allowed a successful shut-in.Analytical and numerical reservoir depletion models are coupled with near-wellbore geomechanics to quantify yardsticks related to the post-blowout discharge utilized to indicate dangers for underground blowouts, in the form of tensile failures on the borehole walls, occurring after well capping. Following the MC 252-1 “Macondo Well” blowout in 2010, as part of blowout-contingency planning, U.S. laws mandate “worst-case-discharge” (WCD) flowrate and volume calculations, before an offshore well is spudded. Predictive tools can assist blowout-contingency planning through comparisons between these pre-spud WCD predictions and critical discharge amounts (quantifying fluid volumes required to be withdrawn from the reservoir before a specific shut-in can be implemented successfully) for selecting an appropriate well-capping strategy, ensuring that the pressures inside the wellbore after shut-in remain below the formation’s tensile failure limits, suppressing underground blowouts that can potentially lead to seafloor broaches. The likelihood of “passive” self-killing via borehole collapse (while the kick evolves to a blowout) was found to be an unreliable operational strategy upon which contingency plans cannot be relied. For “active” post-blowout response options, the developed workflow assists selections between two surface-controlled intervention categories, where the blown well’s shut-in is facilitated by a subsea-capping stack (SCS) installed on the damaged blowout preventer (BOP): an immediate “Cap-and-Restrain” or a delayed “Cap-and-Divert” approach. Leveraging three-dimensional, two-phase reservoir simulations, this workflow was applied a-posteriori to Macondo Well’s blowout conditions, generating pressure-response-curve (PRC) sets through history-matching against field data. Such simulation outputs can be used to derive data-driven corrections for existing physics-based models. Before the appropriate threshold is reached, Cap-and-Divert is necessary to reduce reservoir pressure, allowing the SCS to be safely shut-in. Once this threshold is surpassed, a Cap-and-Restrain strategy becomes viable.
Recommended Citation
Khouissat, Abdelhakim, "Dynamic Wellbore-Integrity Framework For Post-Blowout Capping Of Offshore Wells" (2025). Theses and Dissertations. 8228.
https://commons.und.edu/theses/8228