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Stripping set up on your rig?
31 August 2020
After we completed our advanced one weeks well control course in the mid 80's at the Shell test well training facility in the North of Holland.  We all got the gist of volumetric killing stripping etc and had many things to change our supervisory ways when we returned back to our assigned rig site . 

e.g. There after one would be pretty foolish not to take the safety time out to strip a stand, prior to drilling out an intermediate or production casing string, prior to drilling into a transition of reservoir hydrocarbon bearing zone.  

One particular learning instance to share, was a offshore wildcat well on the East coast of Canada in 1992, in fairly shallow water prior to drilling out the 13 5/8" casing with a WBM. We quickly realised that in an IN-compressible fluid you won't get that much pipe in the hole before you need to bleed off pressure etc (as we expected) This was a real eye opener. 

Also during the drill we experienced choke handling issues that identified a need for repair and rectification. Which we did (offline) and in time before drilling ahead.       
All to assure we were in good shape, with people, equipment and numbers if we experienced real things that can arise.

We crew changed and handed over our back-to-backs and although they did not have to strip, they experienced drilling into an unplanned abnormally high pressure shallow flow (that was thankfully brine not gas) that was not on the G&G hazard/risk register.
The crew detected and reacted early as trained. That in such a dynamic shallow high permeable situation that can result, expect a fairly hefty kick. In this case, if correct it was 25-35bbls.    

Where if the choke problems had not been identified during the drill out drill?, the well would have taken a far bigger kick before this problem was realised, and probably kick that resulted could have broken down at the shoe. Emphasising the importance of these drills.

Where my current sharing questions are in respect to current drill and drill out practices being used/applied.

How are we set up on rigs today for stripping?
How many (fixed) land or offshore rigs have a stripping bottle?
MODU Subsea stripping how are we rigged up? 
Who are and who are not conducting a full well control /stripping drill prior to drilling into a higher risk transition or reservoir zone.

What else have we learned, experienced and have to share in such respects?

i.e. To assure competency training is afforded to crews, all well control equipment is verified to work as planned and that we have a set of base case numbers to work a pre-plan in place,  should a real well control event result.

Appreciate thoughts, views, experiences, company standard on this. 


  

5 answer(s)
Scott_McNeil
Consultant
SPREAD Associates
Total Posts: 161
Join Date: 05/03/08
Hi Peter,

Yet to see a stripping bottle on any land rig.

Normal practice is to hold a dummy flow check and kick drills (including starting and stopping the pumps while going through the choke) prior to drilling out the casing shoe after the BOP Stack has been installed.

The drill is repeated with each new crew on the next trip into / out of the hole after they get on the rig, and again prior to drilling out any casing shoe.

To answer Ramon's question, land rigs frequently don't have the substructure height to accommodate an RCD and would usually require a deeper cellar if it's needed - which in itself may bring other complications.

All the best!

Scott
snas
Wells Mgr - Wellspec
WellSpec
Total Posts: 44
Join Date: 23/03/16
Very few rigs are set up for stripping.

No stripping bottles are installed and most of the modern offshore rigs have a 5 or 10 bbl stripp tank installed that comes directly off the the choke manifold and often with a pump installed to empty the tank back into the flow line. That is pretty much only good for inflow testing.

Not at all the right setup without the trip tank and the stripping tank it makes it impossible to track volumes.

Stripping back to bottom is a relative simple operation but it needs to be practiced and the setup on the rig needs to be correct 

Very rarely have I seen stripping drills. Michael pretty much covers what appears to be the procedure when an influx is taken with the bit off bottom.
Michael_Hall
Well Control Specialist
Cudd Well Control
Total Posts: 2
Join Date: 08/06/19
I agree about flushing and cleaning because it is paramount to maintaining a healthy well control system. As a former rig manager in Saudi it was common to to see 140-150pcf mud weights and 20-25% solids. With that much barite in the system there was always issues with valves and chokes regularly. Flushing was performed on a regular basis, as was the chokes being tested when we tested the entire choke manifold.

In other countries that I have worked in I have seen stripping bottles on land rigs, but it is not the "norm".
zambrarr
MPD Consultant
SPREAD Associates
Total Posts: 4
Join Date: 28/12/15
For what I have seen in MENA, most of operators follow the well control drills before a new section is drilled, with an emphasis on sections where there are uncertainties, high temperature or high pressure. What is frequently miss, is the flush and cleaning of choke lines, MGS lines, choke inspections, choke test and casing pressure gauges calibration, seen many times even when the choke drills are done. 

Never seen a stripping bottle on a land rig. For semi, I have see it used with and RCD to be able to change the bearing assembly with pressure in the riser. 

On the other hand, not sure why the use of RCD's is not contemplated for land rigs from 17 1/4" sections down and also for offshore in DW rigs where this equipment can take most of the punishment just for stripping under the safety margin and save the annulars in good shape and ready for higher pressure levels, I am sure the cost now days is a lot more competitive and for land is a simple rig up, where DW rigs needs planning and more investment. This will be a good option for stripping issues. This may not answer all the questions but is an option to stripping issues. 
Michael_Hall
Well Control Specialist
Cudd Well Control
Total Posts: 2
Join Date: 08/06/19
Where I am located we do not strip at all, except for MPD operations where an RCD is present. Stripping is to be avoided at all costs

None of the rigs have stripping bottles. I don't agree with it, but it is not my decision to make.

Usually, if a kick is taken off bottom, the well will be top killed and verified that well is no longer flowing and that the pressures are zero. After the flow check is negative, the BOP is opened and the string ran in.

If the string makes it to bottom with no issues the BOP will be closed and then a WW or Drillers performed to regain primary well control.

If the string runs into the kick while still off bottom and the well flows, then the string is stopped and the well will shut in again. The influx will be circulated out at that depth. After which the pressures will be verified and a calculated kill fluid will be circulated around. Once the pressures are zero and the well flow checked, the BOP will be opened and the string continued running in to bottom.

Once again, if the string makes it to bottom with no issues the BOP will be closed and then  a WW or Drillers performed to regain primary well control.

The process above takes a lot longer and uses more materials, but nevertheless it is effective.

Definitely not the ideal situation and personally I would rather strip because it is safer. 








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