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Oilfield Technology
June
2016
joints, eliminating the additional cost of an integral sub body
threaded onto the end of a casing joint, which adds length to
the pipe and risks additional potential leak paths within the
casing string.
Traditional centraliser subs are costly due to the premium
threading requirements (to match the casing connection) and
body material that is required to meet or exceed the burst,
collapse and tensile strength requirements of the casing design.
Alternatively, ‘On-The-Pipe-Solutions’ eliminate these costs
by more than 60% in many cases with their direct on-the-pipe
installation method. The (CT) centralisers cost per unit is
substantially lower than a standard centraliser sub due to the
reduced material needed to manufacture the centraliser, lead
time and maintenance required. The design reduces lead-time
by weeks, if not months, in certain applications. With shorter
lead-times, cash flow is greatly improved because the operator
has the ability to manage expenditure commitments closer to
when the product is required. The CT Series also diminishes
the maintenance expense to installed and racked centralisers
by offering protective coatings. Antelope’s onto-the-casing
direct installation method manages casing string changes
and negates requirements to manage and warehouse
supplementary inventory. Unlike the CT Series, subs require the
operator to hold an inventory longer than necessary, raising
the risk of the product becoming obsolete and resulting in
additional costs.
Manufactured from a single-piece of 100% heat-treated
steel, CT centralisers have a restoring force, ideal for all
well conditions. The CT Series includes the RT1, PI1 and PT1
models that offer different anchoring geometrics and allow
the operator to choose the design that provides optimum
centralisation in any given well. The different designs allow
for the casing string to be pushed in, rotated in or pulled in
through the wellbore.
GreenCanyonField
Thechallenge:
While drilling on a deepwater project in the Green Canyon
Field, Whistler Energy, LLC required a centralisation package
for their 3834 ft length of 5.5 in. production liner. The company
wanted to run the production liner to a depth of 11 034 ft.
The liner was required to pass through a 6.5 in. restriction by
previous casing, into a 7.5 in. under-reamed open hole section.
The application required a centralisation product with
attributes for providing low starting and running forces for
smooth passage through the restriction, and high restoring
forces to centralise the liner inside the under-reamed hole.
It was also desired that the centraliser would allow for both
reciprocation and rotation. Lastly, a solution with a short lead
time was required.
Thesolution:
To meet the challenge, the CentraMax PI1 Centraliser and
WearSox external stop collars were recommended. The
CentraMax PI1 is a one piece centraliser that is designed to
be pushed when installed between two external anchoring
devices, and is used when radial annular clearance between
casing OD and restriction ID are sufficient. For this specific
project, the technology was the best on-the-pipe-solution.
Theresult:
Using this centraliser and stop collar, the customer was able to
get the casing straight to bottom with no problems resulting in
a successful cement job.
GulfofMexico
Thechallenge:
An operator drilling in the Gulf of Mexico was faced with a
difficult casing string application that required it to run a very
deep/heavy weight 16 in. liner to a record depth, in a deviated
and under-reamed well bore. Rather than utilise centraliser
subs (a more standard offering), the company opted to run
Antelope’s on-the-pipe-solution as an alternative.
Well parameters:
In the Walker Ridge Field, drilling in 7000 ft of water, the
operator was required to run the 16 in. casing through an
18.25 in. ID restriction at the 18 in. supplemental hanger and
through an 18.125 in. ID restriction at the 22 in. casing shoe
track. The 16 in. liner was to be run to 24 000 ft and centralised
in a 21 in. under-reamed hole with 22˚ of inclination. The liner
was a mixed string of 16 ft 97# and 16.15 in. 127# casing and
weighed more than 2 million lb. The weight was such that the
operator would not have been able to POOH after the shoe
reached 19 000 ft, making the centralisation even more critical.
Thesolution:
Antelope’s team recommended using the RT1 single piece
centraliser with WearSox internal thermal spray metal stops.
The RT1 provides clients an improved alternative to in-line
centraliser subs. It is pulled in both directions when used with
WearSox internal stops. Because of its one-piece design, the
RT1 represents improved mechanical integrity, high yield and
tensile strengths and eliminates the potential of failure of
welds, a critical differentiator when considering the weight of
the casing string.
Theresult:
Using the RT1 with a WearSox internal stop, the customer was
able to run the casing to the bottom and accomplish their
objective of a successful primary cement job. In addition, the
client also realised a savings of greater than 60% by installing
centralisers directly to the casing, as opposed to using in-line
centraliser subs.
Conclusion
In nearly all instances, CentraMax ‘On-The-Pipe-Solutions’
proved themselves as a suitable alternative solution to
centraliser subs when annular clearances allow for installing
products to the casing itself. However, when the annular
clearance is smaller than ¾ in. a centraliser sub is required
because the restriction area is simply too tight. In these cases,
deepwater centraliser subs are manufactured by utilising the
CentraMax CT one-piece centralisers and installing them directly
onto the threaded sub body. The CentraMax Centraliser Subs are
available with pull-through, rotating and push-in technology.
Antelope aims to offer cost-effective and dependable solutions
regardless of the challenges associated with reaching total depth
and achieving a successful primary cement job.
