Cementing 30" With No Vent Valve
29 June 2006
BG are curently installing Cameron Pre packed wellheads - ie, 30.00"
Conductor string c/w X over to a 20.00" Cement shoe with the 18 3/4"
Wellhead housing pre installed into the 30.00" Housing. The
conductor string is run utilising the 18 3/4" Housing running tool.
The problem we have encountered is that there is no vent valve on
the Cameron running tool to allow air to be expelled from the
conductor string. This has caused problems when cementing due to the
volume of air trapped in the conductor / possibility of cementing in
drill pipe stinger / placement of cement.
Have other operators experienced this problem with the Cameron
system / other wellhead systems and what methods have been used to
overcome the problem of trapped air in the conductor prior to
cementing when no vent valve is installed on running tool.
Very surprised to see no vent valve on the running tool. If
concerned cementing in cement stinger below the RT, just run minimum
length of cmt stinger - ie poorboy cmt job. We have done this
successfully in the past. High probability you will have to do a top
up job anyway. Does the PGB have guide funnels?
This is not an usual operation and Cameron should supply a solution
(install a vent valve).
Hope this helps.
Norsk Hydro [Harald Strand, now PetroConsultants] introduced those
fibreglass cement stingers.
You must be careful though QUOTE *1992 Wk #42 Dinsdag: Cementing
string fiberglass tail pipe lost in hole unnoticed UNQUOTE
Odfjell Drilling (Norway)
If you use fiber glass inner string you could hold tension and WOC.
Twist string off prior of pull out. The problem with DP string and
WOC you probably are aware of cementing both string and R.T.
Without a drawing it is hard to comment.
1. What are you doing with the 30" housing outlets, for the 20"
cement returns? They are o nly covered by the 30" housing running
tool, but not by the 18 3/4" housing.
[You can fit check valves there allowing seawater in; one of the
outlets could have an air bleeding hose going to surface with a
valve to close the system after bleeding the air and prior to pump
2. Why do you place the float shoe on the 30" extension and not on
the string attached to the 18 3/4" housing?
In my mind, what is paramount is the pressure vessel, its anchoring,
and its stifness. Having it set deeper, we can resist the riser top
tension and vessel excursion]
3. On such strings the float equipment is only required to prevent
cement back flow - there is no need of it as an internal BOP as
there is no External BOP yet installed.
Either you use sel-fill-up float equipment or - my preference - you
add the float valve as part of the rubber displacement plugs [see
DART Oil Services/Odfjell Drilling & Consulting Services; Peter J.
Hogarth, the designer].; Shell UK Expro used it extensively under
Bob Baker and Henk Wijsbeek.
Again without a drawing the comments can be misdirected.