An offshore operator had seven similarly drilled deepwater wells in the
Gulf of Mexico that were reaching the end of their productive lifetimes and due
to be decommissioned. A consistent and practical solution was sought to abandon
the seven wells while meeting the regulatory requirements laid-out by the local
compliance entity. Successful implementation would offer a potential solution
to similar abandonment requirements globally. Due to the nature of abandonment
work, some assumptions were required during the planning and preliminary cement
design phase. Detailed well information would not be available until the rig
was able to latch onto the wellhead and assess the well's condition.
this uncertainty, and allow for flexible design, the base cement slurry for
each section was designed with additives exhibiting low sensitivity to certain
downhole conditions. These focused on keeping the slurry thickening time stable
at a range of temperatures and slurry rheology consistent with surface to
downhole conditions. The operator was successful in abandoning the seven wells
as per the regulatory requirements, with 45 cement barriers put into place.
Applying similar designs from one well to the next allowed for faster cement
design turnaround and improved materials management.
solutions, the challenges controlling the slurry behavior at varying conditions
were overcome. Cement additive concentrations were refined over the course of
the project, but the iterative approach meant that fewer changes were needed
later in the project due to the increase in operational experience and design
data. Contingency cement systems were prepared ahead of, and continuously
updated during, the project to address probable risks, adding to the database
of slurries that could be referenced for future work and potentially increasing
Developing this standardized process approach to well
decommissioning saved an average of 11 days per well, 32% of the time, when
comparing the first three and the last three wells. Using a similar model, a
more effective decommissioning plan can be created to conceivably allow for an
increase in the scope of future abandonment projects to offset time savings.
This process can be tailored to offshore and land wells around the world,
especially where similarly behaving cement materials are locally available.
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