TOC / APB Issues

04 March 2012 Hi,

On my current project (deepwater exploration well), i was surprised to see that the drilling programme showed a 9 5/8 cement job with TOC below the 13 3/8" shoe, on a well which is not to be tested. Main issue for me being that this will then lead to the requirement to cut/perf the 9 5/8" casing and squeeze cement into the unsealed annulus (as per company policy) for the P&A.

After discussing with the SDE's, the reason is that they had been told to perform APB calculations based on a Worst Case Discharge (in our case 64,000 bbls/day) uncontrolled blowout scenario, with a duration of 90 days. This had apparently been based on new requirements which have came out in the GOM post Macondo (note: the well is not being drilled in the GOM). As expected with such a high flow rate and long duration, the APB (Annulus Pressure Build-up) calcs showed failure of both the 13 3/8" and 9 5/8" casing - hence the reasoning behind TOC choice.

From what i can see on the APB calcs, adopting this strategy means we are basically committing to a more complicated P&A programme on all of our potential wells as it is not possible to cope with APB loads using standard casings, when looking at a WCD flow rate (e.g. our 2nd possible well has a rate of 122,000 bbls/day).

For me, cutting / squeezing cement has its own risks with regards to well abandonment integrity. I suppose it comes down to regulations and weighing up the risks of the more complicated P&A vs the very small chance of such an extreme event - but then obviously how we view things has changed post Macondo.

Is this practice becoming common in the industry or are the majority of engineers / operators still working to the philosophy that APB is not really considered on wells with no test planned?

Any feedback would be appreciated.

Cheers

Gary

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