1. August 2015 | EPmag.com
Cement jobs in the oil and gas industry are getting
a bad rap. Cementing work has been identified as
the possible culprit in many onshore fracking disputes.
The U.S. Bureau of Land Management reports pro-
vide evidence of the role bad cement work has played
in accidents.
Production optimization begins with a good comple-
tion, and a good completion depends on the integrity of
the primary cement job. Every year poor cement jobs
cause tremendous costs to the oil and gas industry. Poor
cement jobs demand additional cementing operations
such as squeeze jobs. These operations are time-consum-
ing and rig-demanding, which in turn leads to economic
loss. If a poor cement job is left unattended, the result
can be catastrophic.
Clearly, there is room for improvement in cementing
technologies to withstand the rigors of well operations
and any disruptions that might occur. The integrity of
the cement job can use all the help it can get. The man-
ner in which the cement is placed inside the annulus
assists with the integrity aspect of the cementing opera-
tion, and the wellhead can actually help improve effi-
ciency of the cement placement.
A good primary cement job can prevent remedial
work. Successful isolation of the hole and formation is
extremely important in preventing the migration of gas
and fluid and limiting the environmental impact.
Gaining efficiency in horizontal drilling
The achievement of desired technical objectives via hori-
zontal drilling comes at a price: A horizontal well may be
anywhere from 25% to 300% more costly to drill and
complete for production than a vertical well directed to
the same target horizon. But there are advantages:
Operators often are able to develop a reservoir with a
sufficiently smaller number of horizontal wells since
each well can drain a larger rock volume around its bore
than a vertical well could.
An added advantage relative to the environmental
costs or land use problems that may pertain in some sit-
uations is that the aggregate surface footprint of an oil
or gas recovery operation can be reduced by use of hori-
zontal wells. The second key benefit is that a horizontal
well may produce at rates several times greater than a
vertical well due to the increased wellbore surface area
within the producing interval.
Companies can’t overemphasize
well integrity
Cement job integrity can be improved with a rotating mandrel hanger that allows the casing
to be rotated through the heel of the lateral while installing and cementing.
Diane Langley and Moises Nava, Cameron
The nested design of the MN-DS wellhead allows the whole sys-
tem to easily fit under most skidded drilling rigs. The system can
be installed along with all subsequent strings through the
diverter riser/BOP. (Source: Cameron)
AS SEEN IN
AUGUST 2015

2. This approach offers multiple advantages, including
better drainage, lower drawdown and a reduced foot-
print. Its sole purpose is to help operators develop
more of the wellbore. The initial linear portion of a
horizontal well, unless very short, is typically drilled
using the same rotary drilling technique that is used to
drill most vertical wells, wherein the entire drillstring is
rotated at the surface.
Setting the packer and optimal placement of fluids
and cement represent areas of challenge in horizontal
wellbores. Suspension of the hanger represents a
major challenge. The parent hanger body has a ten-
dency to spin before latching once the child is landed,
causing a less-than-safe condition and potential rod
wear. Also, by nature, horizontal wellbores are devi-
ated, causing fluids and cement to migrate to the low
side of the hole, resulting in a less-than-optimal distri-
bution downhole.
Choice of wellhead matters
Because cement integrity is one of the most critical steps
in well completion, Cameron has studied the need for
enhancing cement jobs. Movement of the pipe during
cementing is one of the best methods of improving mud
displacement and reducing the number of mud chan-
nels remaining after cementing. Rotation of casing
helps force the mud from the pipe and formation con-
tact areas and ensures a more even distribution of
cement. Special rotating heads are required to allow
pumping while turning.
The wellhead is a vital pressure-containing component
at surface that can make operational processes more
efficient and flexible and enhance the integrity of the
well. Internal components such as a rotating mandrel
hanger will allow the casing to be rotated through the
heel of the lateral while installing and cementing.
Such a rotating feature can help operators ensure the
production casing runs the full length of the lateral to
achieve a proper cement job. Once the casing mandrel
is landed in the wellhead, slotted mandrel shoulders
permit cement circulation, removing the necessity to
wait on cement with casing slips.
Multibowl nested diverter
snap-ring wellhead system
One such wellhead is Cameron’s multibowl nested
diverter snap-ring (MN-DS) wellhead system. It incorpo-
rates a unique rotating mandrel casing hanger designed
to improve cement job integrity and wellbore stability
for vertical and horizontal gas wells. The hanger enables
the operator to rotate the production casing during
installation, promoting better displacement efficiencies,
effective zonal isolation and less eccentricity in the pipe
during cementing jobs.
The ability to rotate the hanger addresses the devia-
tions inherent in horizontal wells. By rotating the
hanger, slurries can be more evenly distributed inside
the wellbore. On a recent trial with a major South Texas
operator, it was deemed that the rotating hanger saved
an estimated eight to 10 hours rig time as compared to
using a regular slip-style hanger. This time is tradition-
ally spent waiting on cement to reach an acceptable
compressive strength before breaking the BOP stack.
A nested design is new methodology for industry well-
head systems. This design, employed in the MN-DS sys-
tem, reduces the overall height of the wellhead system,
making it ideal for use with today’s high-performance
horizontal skidded drilling rigs.
Rather than the typical design of the hanger on top of
the pack-off, the nested design consists of a hanger that
fits within the pack-off, reducing system height. This
hanger can be either a production casing hanger or a
tubing hanger, providing the option to complete as a
one-stage system if intermediate casing is not required.
Because the system uses a spin-on flange design, no
special tubing head or tree adapter is required. The sys-
tem enables the wellhead and all subsequent casing
strings to be installed through the diverter riser/BOP
without having to nipple down, providing considerable
cost and time savings. The wellhead has the ability,
depending on the string configuration, to be installed
prior to the rig moving to the pad; the only action
required is to nipple up the BOP to the wellhead.
The MN-DS system also offers a higher degree of
safety resulting from an internally locked system, which
eliminates penetrations from lock screws in the housing.
The system is particularly applicable in highly deviated
horizontal wells because it offers a secure method of
protecting the wellbore during drilling operations. Also,
the potential for rod wear is diminished because tension
is maintained throughout the packer-setting process.
Other examples of equipment helping to ensure well
integrity are back-pressure valves and pack-off systems.
These can be installed into the rotating mandrel to pro-
vide a barrier for both the bore and the annulus to
secure the well at surface.
In artificial lift applications, the system’s tubing
hanger keeps the tubing string in tension to better
endure the sucker rods’ constant up-and-down motion,
thereby maximizing the life of the tubing. About 200
MN-DS wellheads have been installed and are operating
successfully in the field.
SHALE DRILLING
OPTIMIZATION
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