After some issues getting our 13 3/8” casing strings to bottom (due to
suspected ledges), we experimented with a couple of different casing shoe designs.
Initially we went with conventional shoes but then moved on to eccentric pilot guide
shoes and have discussed running reamer shoes, but we do not have the ability
to rotate our casing string due to the design of the subsea casing hanger and
wellhead system. To provide context we are drilling in about +/- 4,500’ of
water building in our 17 ½” section from around 30° at +/- 6,500’ MD up to 90°
by around 9,000’ MD.
1) As we cannot rotate the casing I feel we are not getting much benefit
of either an eccentric nosed or reamer shoe and furthermore if the nose of the
tool is orientated to the low side of the hole it may actually be a hindrance
in terms of passing any obstructions. It has been suggested that orientate the
nose of the shoe to the high side of the hole when we run it through the rotary
as in theory it should not rotate and stay pointed to high side.
2) One of the other options we have considered is the use of an indexing
or ratcheting shoe which self-orientates down the hole by setting down on
bottom then picking back up. I have had some feedback from our N American
drilling teams that they have had issues drilling these out, but I would like
to have a broader offset.
Does anyone have any feedback on the above points that they would like
For what it's worth, I agree with Peter that running solid centralisers in that hole configuration would not be wise.
He's also correct in that if you put your effort into solving why those ledges are occurring in the first place, this will put you ahead of the game.
For an off-the-wall-he's forgotten-to-take-his-meds-again idea, how about running a Mud Motor locked into a sub in the casing shoe?
TESCO were doing this a couple of decades ago and casing-while-drilling was very much in vogue for a while.
With smaller casing sizes, they were even doing directional wells with bent housing PDM's.
Their modus operandii was to use a bit c/w an under-reamer or expandable hole opener to get the correct hole size.
At TD the BHA was recovered with the sandline (do many Rigs still have these?) and insert float equipment run in it's place.
In your case just running casing, then I doubt an UR or expandable H/O would be practical, so you'd either have to hope a 12 1/4" bit helped you get over/through the ledge.
Or perhaps use the expandable bit that was doing the rounds a few years ago - I think that was from Weatherford?
I know - I'll go and take my Meds....
All the best
Responses from Les and Paul are very valuable and I have very little to add, except we ran a 'shark nose' float shoe on a 9-5/8" casing string many years ago, which we had to pull out of hole as it stood up on a ledge. Once at surface the 'nose' had broken off ....
Stiffening up the shoe track and running solid centralizer into a directionally drilled 2500ft section that builds from 30 to 90deg (With suspected ledges and doglegs)? Is ill advised from my knowledge experience and initial risk assessment conducted.
Solid centralizers in deepwater sedimentary sequences should be kept to casing inside casing only.
That apart lets explore Deepwater shallow sedimentary interbedded EVIDENT environments a little bit further?
e.g. Even in vertical wells we have experienced the significant problems that stringers, interbeds bring to deteriorate wellbore quality via ledges and doglegs.
On one particular exploration project (in vertical wells), doglegs and ledges was by far the biggest EVIDENT problem/issue via first few wells drilled.
Due to the facts that within vertical wells it is however far easier to note exactly what happens at the bit, when one forces a less than optimal PDC bit/BHA through a deepwater interbedded sequence that may be thin stringer prone (i.e. the vibrational traffic lights on the MWD surface readout instrumentation from on bottom bit/BHA/wellbore conditions quickly go orange and red).
The simple solution to avoid later and often very times consuming operational delays was to instruct drillers to do what ever was needed to maintain on bottom parameters in the green as best as they could while drilling these intermittent stringers. e.g. They were instructed to pick up off bottom play with parameters to mitigate the risk and consequences of what resulted if on bottom conditions remained in orange/red. i.e Big doglegs and ledges resulted to create a domino effect of operational problems later on.
Therefore instantaneous doglegs and ledges (that are very common in offshore environments) and can quite readily result due to the stratigraphic features so often presented, were better maintained managed and controlled through better practices used.
Once more time was take to drill stringers (in the green) we immediately started to experience virtually no connection, tripping, wireline hang up, casing running problems on the next several wells till the end of the campaign. Tripping out on elevators became the norm vs backreaming as had previously resulted.
In directional wells as you have outlined, the same on bottom vibrational warning signs will likely become more suppressed, where tell tails and warning signs of high instantaneous doglegs and ledges are far more difficult for drillers to recognize analyse and SEE (Safe (loss/waste free) Effective (how to assure we do the right things) and Efficient (how to assure we get things right first time)) for optimal wellbore operations to result.
However again based on experience exercising more control in planning design and engineering, w.r.t. stringer drilling within deepwater interbedded sequences, (simply taking more time to drill these thin short intervals), improving bit/BHA systems design, operational practices used to assure a more perfect cylinder is drilled.
May be a better way to prevent reduce and mitigate your operational issues in my view.
If they still exist? and cannot be eliminated as suggested, then as Paul outlined a best practice approach to guide the casing through such intervals is perhaps also yet required.
Wishing you success on your future wells.
As you may know I have been involved with the kinds of casing accessories you mention for many years. In fact Caledus developed and ran the first casing/liner orientation subs for moving guide shoes and reamer shoes around mechanically down-hole in the early 2000's when the whole string could not be rotated. We also developed reamer shoes with eccentric noses and flush OD guide shoes again with eccentric noses. My response is therefore knowledge and direct experience based. I doubt surface orientation of any item on the end of the casing would remain in the same place once it went down-hole. One of the issues with running any accessories of a particular design and reaching TD with issues or without them is the assumption that the design aided or caused the success when actually that is often not easy to prove. For example when running reamer shoes and having to ream to get to TD, it is because you have a reamer shoe on the pipe with a large bladed OD that you are forced to ream and had you run a flush OD guide shoe would you have needed to ream at all? The vendors, and I include myself in this from the past, call it a success if you have to ream and get to TD but none of us really know if the reamer shoe was the cause or the cure. I apply the same logic to eccentric nosed shoes, and in 35+ years of being involved in these kinds of casing accessories I have never really been able to determine if the eccentric nosed element aided getting over ledges or through wash-out's and if a plain cone shaped nosed shoe had been run would the same success have occurred. There is a difference between a ratcheting sub that mechanically forces the item below it around a few degree's at a time each time it is picked up and down due to an auto-jay mechanism and these can be used to orientate reamer shoes around or eccentric nosed flush OD guide shoes. These orientation subs and noses on the shoes should not be any more difficult to drill out as they are rotationally locked, none of the parts should be able to spin during drill-out. However, self orientating eccentric nosed items are effectively swivel noses and are not rotationally locked, they are free to spin, or must have some kind of cleverly designed feature that makes them lock some-how during drill-out. If you elected to try one of these systems I would suggest a orientation sub with a eccentric nosed flush OD guide shoe rather than a reamer shoe on it and rather than a free spinning eccentric nosed item. My feeling is that the reamer shoe would be a OD hinderance rather than a help and being able to rotate the eccentric nose only would be of more benefit if it is indeed ledges that are your root cause. If you are unsure about the use of the orientation sub and eccentric nose then actually I would recommend a bullet shaped nose, one that is fairly long and smoothly tapered. My justification for this is a bullet shaped nose should be able to ride over significant ledges as the OD of the body of the shoe should be around 14.375" and as the nose tapers smoothly to a final rounded cone on the end nearly half of its diameter is a smooth OD transition and I would say it should be able to ride ledges that are more than 6" high from the low side. You could improve this further if you centralised the shoe with an appropriate centraliser directly behind the shoe. Those are my observations and experienced based recommendations. As with all my posts I would ask that you come back and let us know what you did and how it went. We all come on and ask for advice but rarely to people come back and say what they did and how it went. Regardless of what you decide to do good luck on the next run.