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Two stage cementing tools for 20″ surface casing
20 September 2013
Dear Forum,

I was looking for members' experience with two stage cementing tools for 20" casing, specifically the TAM port collar + external casing packer (20" TAMCAP).

We will be running a faily long 20" casing string (± 1000m), water depth 1400m. We have some concern in being able to get cement to seabed when cementing this string, so an option we're looking at is placing the ECP + port collar about 85m BML (inside the 36" conductor) and if we do not get good cement returns to seabed during the primary job, we would use the TAM combo tool to inflate the packer inside the 36" conductor, then open the port collar and place cement from there to seabed.

We're interested in having this section of the pipe cemented not only to isolate the annulus, but also as structural support (for bending and fatigue of the 20" and 36" below the wellhead) as we're putting a 350 ton (buoyed) BOP on it.

We've identified the following drawbacks:
  • slightly increased ECD while cementing the first stage due to the ECP restricting the annulus (although it is 23" OD before inflation, inside 33" ID conductor pipe)
  • Have to do a dedicated run to set the high pressure wellhead housing wear bushing, as it cannot be run pre-installed in the wellhead because the combo tool (for inflating the packer and oopeining the ports) cannot be run through the wear bushing.

But other than this we see this as good option to guarantee cement on the top 85m of the surface casing.

Has anyone had good or bad experiences with these tools, packer not inflating, port collar not opening, port collar not closing after job, stuck combo tool, junk in hole, etc? Any statistics you might have on running this equipment?

thanks
5 answer(s)
ianpetitt
(retired) Well Fluids Team leader
SPREADAssociates
Total Posts: 40
Join Date: 14/06/06
Patricio, Why not use a foam cement as elsewhere in deep water West Africa - no need even for a cap slurry in this water depth. I would always recommend ensuring achieving cement to surface of the two outer casing strings for a variety of reasons. 

Regards Ian
Companyrep
Drilling Specialist/Well Engineer/Training Consultant
Kingdom Drilling
Total Posts: 362
Join Date: 10/01/05
Steve,

I picked this out of a document I have. Relevant pages attached.  

"The contribution of concentric strings to the strength of the structural casing is small and difficult to quantify due to the unpredictability of the cement linking the internal strings to the structural casing.

Assuming that the annuli will be cemented doesn´t improve the structural strength of the system. Appendix H outlines the results of tensile test of cement. Cements have a very low tensile strength and low Young´s Modulus relative to steel. The contribution of "uncracked" cement is minimal due to the low Young´s Modulus relative to steel. The cement will crack during high bending loads reducing EI (Young´s Modulus and moment of Inertia) of the cement."

Good cement, well centralised pipe, a good slurry pumped at a good rate will help to assure well integrity. Getting it to surface is not essential. Getting above the maximum bending load point of fixivity perhaps is?

The key hazard/risk is surely a problem zone identified or known just below the conductor that cannot support the weight of the cement column. And why even conventionally we would pump a light lead wait until we see returns at surface then pump a heavy tail at the end. If no returns then you are into running a top up string. An extra trip where at about $1 - $2m trip time costs the light weight cement seems a cheap and more assured option for many.

 

 

 











elman
Drilling Engineer
BP
Total Posts: 14
Join Date: 01/09/12

Patricio,

We have been using 20" TAM ECP system in 30" countless time now.

They have been pretty reliable with one or two failures mainly because of the human error. One I can remember was incorrect pumping procedure to inflate the packer.

But these are mainly on platforms and shallow waters ~150m. So manipulating port collars with combo tools may be easier in our case.

With your cementing flow rate inside 36" conductor this ECP will hardly add any additional ECD. We don't notice in 30".

cheers.

Elman.

stevedev
Drilling Consultant
SPREADAssociates
Total Posts: 38
Join Date: 11/02/09
Hello Patricio,

I have to question your reasons for wanting to get cement back to the seabed. It will not add significantly to bending or fatigue resistance; stiffness (resistance to bending) increases as the fourth power of the OD. A 20" pipe will only add about 10% to the stiffness of a 36" pipe if you get cement to fill the annulus.

As for isolation, if you drill with returns to the seabed and the well doesn't flow when you circulate clean, then what is it you're trying to isolate? There are few scenarios where cement to seabed will help. One is, if the 36" slumps and the 20" isn't cemented into the bottom of the 36" then the 20" would buckle, which could give you high wear as you drill ahead. However rigid centralisers would constrain the buckling if run correctly. Adding the weight of cement inside that annulus to the system makes slumping more, not less likely. Often we cement to seabed, sometimes at great cost (Lightweight cements can be 10x the cost of normal cements) without creating anything of value.

Good luck,
Steve.
Companyrep
Drilling Specialist/Well Engineer/Training Consultant
Kingdom Drilling
Total Posts: 362
Join Date: 10/01/05
In my view you are complicating the process and not looking at a fit for purpose solution.

first Label the problem? 
E.g. why do you think you will not get Cement to seabed? 

What are the solutions?

We have been cementing 20in casing in 2500 to 3100m water depth and have no issues getting light weight cement to surface. 
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