Shutting in the well on a jack-up : Annular or Pipe Rams
10 February 2011
At a recent HTHP Well Control Manual Review, the topic of shut-in methods came up. We are still debating the pros and cons of shutting in initially using the annular vs. Upper Pipe Rams.
We would be very interested in member's opinions on this and, in particular, what your company policies state.
It's a jack-up, so tooljoint location won't be difficult to ascertain in an emergency.
Relentless Pursuit of Perfection Ltd
I agree with the others regarding using the rams rather than the annular. But there's another reason other than speed which hasn't been mentioned, and it's something I try to instill in the minds of all the crews on my wellsites.
Packing elements in both rams and annular preventers are consumable parts. They are expected to wear over time, and eventually be replaced. The 'time' factor is also related to the number the number of functions made, though, and in this respect a ram packer can be usually expected to outlive that of the annular very significantly. Each time that annular is functioned (even just simply for a test), its lifetime has been shortened. One day it will fail, and almost invariably, that occasion won't be a test, it'll be the real thing.
The annular should be used as parsimoniously as possible.
A few considerations.
Bearing in mind we are talking Hpht where a 0.5bbl kick could potentially unload a marine riser. i.e we experienced this back in the 90"s.
So primary control is first and foremost on these wells.
Positive indications or warning signs of flow that has to be closed in are likely to be;
While drilling, tripping, on a connection or perhaps during running casing or during cementing.
In all cases the method that assures earliest detection and snallest influx will deliver the least risk and more manageable outcome.
Hard shut in is preferred but sometimes annular is required.
Dependent on pressure of well - HPHT usually out side annular rating.
Suggest Hard shut in using RAM to minimise shut in time and influx volume.
Snr Drilling Engr
Jo'burg, South Africa
Just to add one more data point for you. We (Maersk Oil UK) shut the well in using the pipe rams so that the shut-in is as quick as possible and therefore the influx as small as possible. On high temperature wells there's perhaps also a possibility that the annulus doesn't perform that well due to its lower temperature design limitation compared to the pipe rams, but it's mainly the speed of shut-in that leads us to using the pipe rams.
Maersk Oil UK
I would opt for closing the positive rams first, provided the ram configuration would allow it and that we have a choke line outlet underneath the ram.
The positive ram is faster, more reliable and less costly to operate.
The bag preventer is slow and sometimes do not drift properly after closing on a small dimension.
Of course it is the only preventer that allows for pipe movement through - stripping, for instances. The regulator valve should be set to allow for some hole fluid weeping to ensure lubrication of the elastomer.
Maintenance of preventers also favours the ram preventer. The room needed above annular preventer to replace the seal is considerable and often awkward to get it free of pipes.
Augusto Carmona da Mota
Hard vs. soft shut in doc attached.
I was involved in the highest kick ever recorded in the North Sea where we drilled into a formation 6 ppg underbalance. My oppo had the tenacity as he was getting the first tool joint under the kelly to the rig floor, even though the mud pump relief line had blown, and mud was now able to return to the mud pits through various channels, to close the welll in using only the pipe rams.
In this situation you would think closing in on a well trying to evacuate itself with a BHP of 15k would give more problems, but we did not see any damage except for when we circulated out the kick.
For the amount of time it takes to close a Ram preventer, the resulting pressure wave would be limited as the ram acts like a choke slowly shuttting off the pressure. By having a down stream valve open before closing either the annular or rams would negate any pressure wave.
When you are drilling in a formation with a hydrostatic close to fracture pressure, any pressure wave could be detrimental to the well integrity.
The pros and cons are not simple, but at the end of the day I myself will not hang around waiting on the annular knowing I have an extra 15 sec from my rams to secure the well.
Next stop go MPD.
Snr Project Engr
On the topic of using annular or pipe rams to shut in a kick I'd suggest that we need to treat them as redundant systems where you use the highest one first (annular) and if it starts to leak you have the pipe rams as the next line of defence. The advantage with this is that you can then work to repair your annular preventer while you are working to control the well with the pipe rams closed. Of course I'm a land lubber where we are still using lots of BOP's with only 1 pipe ram.
Well Construction perforamnce Champion
Priority should be keeping the size of any influx as small as possible. Most effective way to do this is by closing the well in as fast as possible. The solution in this case is to use the pipe rams over the annular preventer.
Well Delivery Mgr
Johannesburg, South Africa
Hard shut in on the upper pipe rams gives the fastest shut in time.
As you say, space outs are easy on a jack up.
Although you are asking about operators policy, unless you have a sustained campaign, you will most likely be using the Drilling Companies Well Control Manual.