Bit Run and Retrievable Wear Bushing
09 August 2011
At a Deepwater DWOP that I facilitated last week in SE Asia, one of the topics discussed was the Bit Run and Retrievable Wear Bushing from GE Vetco.
This allows the wear-bushing to be run with a tool that´s incorporated in the BHA. The bit and part of the BHA are run through the wellhead, past the unprotected seal area (for subsequent pack-offs) until the wear-bushing lands in the wellhead. The tool releases and continues in hole with the assy.
During the trip out the process is reversed. This saves a trip at section TD and also allows regular inspection of the wear-bushing and any remedial action required.
Concerns were raised about the potential for damage to the seal area whilst the bit/assy is run through it.
We are interested to hear member´s experience , especially :
- Has any damage been encountered and, if so, how bad ?
- What precautions you´ve been taking e.g. restrictions on allowable heave, maximum allowable wellhead inclination, bit design, use of BOP (annular) to centralise the string as the bit approaches the seal area.
- Whether your rig has an Active or Passive Heave Compensator.
(MD - Relentless Pursuit of Perfection Ltd)
We have been using the 13 3/8" & 9 5/8" BRWB from FMC on the Gumusut project + Exploration wells (total of 19 wells). No reports of any wellhead/seal face damage and only issues we had was the initial design being awkward for installing the wearbushing at the rotary table sometimes taking up to 1hr to install but modifications hve been done and as a result it is a lot more efficient now. We also experienced the BRWB stab incurring a lot of wear in the drilling BHA. Not sure of the design you intend to use but worthwhile considering the potential wear to the sub during drilling operations.
Dave, we also use the DQ bit runnable/retrievable system here in Ghana with Kosmos. The only issue we have had is with wear on the inner mandrel after long, abrasive hole sections. This could wear down the lugs enough so as not to engage the outer mandrel (in the wellhead) when coming out of the hole. I may add that although we have experienced the wear, it has never been significant enough to cause a problem. Just something to bear in mind if you are planning long, deviated hole sections. Regards, Peter
Tullow have been using these in Ghana for 18 months or so albeit the DQ version, never any damage to the HPWHH.
I have used this Vetco bit run & retrivable tools to run in the BHA to save the trip time. This tool is just a stabiliser with slots to install wear bushing. This tool will not damage the sealing area on the wellhead.
This tool will face same issues as other standard wear bushing tools in terms of BOP and wellhead angle.
Only issue is running tool itself while drilling; if you are drilling with high rpm and hard formation at some point this stabiliser will wear out the pins to retrieve the wear bushing in that case it will fail to retrieve bushing while pullout but it can solved with separate trip. So, you need to have at least 3-4 tools in inventory to start operations.
We used on two well so far and not seen this kind of issue. This is highlighted as a risk but its a time risk and not operational risk.
Thanks & Regards,
I have never run an integral ware bushing puller and setting tool. However I can see the problem with potential damage while a bit is run through an unprotected well head particularly if you run a PDC.
Yessir I am, though it's not an NSP (Nominal Seat Protector) in our case but a full-on wear-bushing.
Thanks for the feedback.
Good morning Dave,
Are you referring to the " BRNSP" from GE Vetco? We have always run this in the Makassar Straits with the Full Bore II System with no issues.
I have never had damage or "hang up" from running a bit through unprotected wellhead with an in-string WB running tool. But I only have about 3 yrs experience with in string WHWB tools. I have seen bit damage by a driller slamming into wellhead at high speed with PDC bit. If you are using compensator and know where you are, I think it is a great tool and very low risk............
Back in 1977 Shell UK Expro did study this subject and the conclusion was that the seat protector/wear bushing should be run shear pinned to the bit shank (not all bits had meat for it) - or even better - to the near bit stabiliser. (Single shear pin snuggly fit into both items.)
The geometry of the seat protector/wear bushing - length, OD and ID - would prevent the Bottom Hole assembly touching or damaging the subsea head seal areas as the inner seal bores are always larger than the bit outside diameter.
The retrievability could be ensured by a Inside spear added at the right spot during the last short trip (Idea based on the popular Regan Offshore subsea heads used by Shell Oil, offshore USA.
We used the vetco system and the Drill quip down in India with Reliance in deep water using Active heave draw works on the Deep water India with Vetco and on the DDKG2 with the vetco and the drill quip with the Active Heave on all occasions the Bulls eyes on the BOP were after latching up were 0.5 deg . Never had any problems running and retrieving just extreme care running through BOP as normal .
On one of the wells it was in the world record water depth of over 3000 m The only thing we did with this one was close the upper Annular and reduce the working pressure to centralise the drill string .
Well Engineering Mgr
In our Atlantic margin drilling campaign we used bit retrievable WBRT from DrilQuip. Seal damage is a non-issue given that wearbushing itself is a good centralizer. Hopefully the well is perfectly upright (<0.75 deg) at that exact point. We've seen no problems setting and retrieving wear bushings.
It is not recommended to trip bit in out at LFJ more than 2.5 deg.
I have never heard of the bit causing any damge that has prevented a seal from being established as the sealing profiles are typically recessed. What I have heard is that you cannot run in hole to quick as there is a chance of shearing the shear pins prematurely if you push the mud quicker than it can displace.
1. Damage to sealing areas does happen, but have in most cases been solved by running a contingency seal type. The cause of such damages are often hard to establish.
2. The wearbushing itself may centralise the bit and BHA, but that will depend on how close to the bit you are able to place the tool. MWD requirements may restrict that option. Centralising by annular have to weighed against the risk of doing some damage to the annular element in deep water and often low temperatures.
It should be noted that we do accept running long strings of often heavily centralised casings through the same exposed sealing area
My experience is with Jack Ups, but it used to be relatively common to run bit retrievable wear bushings that simply sat on top of the top stabiliser in the BHA.
I don't recall any instances of problems with damaging the sealing area in the wellhead by doing this - even in cases where the wear bushing itself showed signifcant wear.
I think the main reason that we went away from using them was the wear bushings had a habit of getting hung up in the BOP Stack on the trip out, or just simply not seating properly.
Presumably Vetco's tool avoids these problems?
If so, I wouldn't be concerned about running a BHA through an unprotected wellhead.