Deepwater operations - running and cementing casing with small clearances

Abstract

The petroleum demand is increasing and the line between success and failure is marginal. Thus, the drilling industry moves further into deeper waters, stretching the limits of engineering, economics and new technology to the maximum. A natural consequence of increasing water depths is the decreasing operational window. This is due to the fact that rock is being replaced by seawater, and the resulting overburden gradient is reduced. If the pore pressure is held equal to the hydrostatic gradient of water, the decreasing operational window is evident. The consequences of this in deepwater operations are generally a more complex casing design and increased risk for well control incidents. This thesis takes an in-depth analysis of the as is situation in deepwater drilling today, with an especial focus on the low clearances between the casings and liners. Five wells from Gulf of Mexico (GoM) and Egypt deepwater environments are reviewed. The 13 5/8” section of each section is especially evaluated in terms of running and cementing casing. A pre and post study technique is used to evaluate plan against what actually happened. Simultaneously throughout the thesis, a fictive well, Well 1, is built and used. Well 1 is based on a GoM well and is used to perform simulations in comparison to the five deepwater wells. Well 1 is further analysed in terms of potential solutions and mitigating technologies. Several potential solutions or mitigating technologies are found. These are: • Dual gradient drilling • Managed pressure drilling, MPD • Casing drilling • Liner drilling • Low ECD fluids Furthermore, combined potential solutions were found: • Combined MPD and dual gradient drilling • Liner drilling combined with expandable liners These are currently under development.