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Oilfield Technology
September 2016
The stimulation sleeves are opened in sequence by circulating the
correct sized ball at pressure down to the integral ball seat. By applying
a pressure differential, this sheers the sleeve into a locked open position,
allowing the stimulation fluid to stimulate the selected zone. The ball is
held on seat during stimulation, which protects and isolates lower zones.
The successful opening of the zones can bemonitored and recorded
in real time by using the DTS fibre optic temperature systemandQuest
software.
The ball catcher sub is run as part of the frack string, just above the
guide shoe, and the sub acts as ameans to set any hydraulic set packers.
Cost-effectivecombination
Another important component of the Tendeka systemhas been the
development of the DHP liner hanger, which provides completion
cost-efficiencies by combining the liner hanger and the top packer into one
component. The tool has aworking pressure of 10 000 psi alongside a load
capacity of 200 000 lb.
Bakkenperformance
The FracRight DHP liner hanger has been specifically designed for usewith
open-holemulti-zone completions focusing on leading edge operations.
It is the combination of hydraulic fracturing and horizontal drilling
techniques that hasmade the Bakken one of themost important sources
of newoil production in theUSA. With an estimated 400 billion bbls in
place, the prize for increasing recovery is great and operators here have
led theway, extending lateral lengths and increasing fracture stages.
The combination of shale and dolomite in the Bakken and Three Forks
formations, and the presence of vertical to sub-vertical natural fractures
make open-holemulti-zone completions themost effective solution. An
averagewell drilled in the Bakken today is 10 000 ft longwithmore than
60 frack stages delivering 3 - 6%recovery rates.
Reliable performance of the completion is a prerequisite for economic
operations, andwhilemost frack sleeves do deliver, the liner hangers
have not alwaysmet this requirement. Many hangers have been adapted
fromuse in conventional cemented applications or were designedwith
shorter, lighter open-hole systems. Combining local experiencewith
innovative completion design capability, Tendeka developed a robust
and reliable liner hanger systemthat is effective and economical in such
unconventional plays.
The FracRight DHP liner hanger has simple functionality combined
with fail-safe features tomake it a reliable deployment system for
multi-stage frack completions. The threemain areas of operation, as
outlined belowdefine key functionalities:
Deploy
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200 000 lb tensile and compressive load capability for deployment of
up to 100 sleeves in a 10 000 ft lateral.
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Rotational lock to allow for high torque to be applied in tight
wellbores.
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Built-in anti-preset feature combining pressure activated shear pins
and dogs to eliminate the risk of premature setting or release from the
hanger.
Hang
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Hydraulic settingmechanismwith double grip slips to safeguard
hanging systemagainst potential overload.
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Efficient hydraulic release features initiated during the setting
procedure allows the setting tool to be released by straight pull.
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Secondarymechanical rotational release to ensure successful
operation.
Pack
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Utilises hydraulic and compression forces to create an effective
10 000 psi seal.
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Anti-extrusion back-up rings on element, the DHPmeets the
standards of ISO 14310 V3.
In July 2015, the company’s firstmulti-stage FracRight system,
incorporating the DHP liner hanger, was deployed to complete a
three-well, 120 stage pad for amajor NorthDakota Bakken operator using
4½ in. liner.
The three Bakken wells were completed for a leading
unconventional operator with the full FracRight system. A hybrid frack
design was used, consisting of 30 ball-drop stages and 10 composite
frack plugs. The 10 000 ft long 4½ in. liners were deployed and anchored
using the DHP liner hanger system. The liners were successfully pressure
tested to 9500 psi, and no pressure build up was observed over three
months thanks to the 10 ksi rated liner equipment selected for the job.
For access to the reservoir, 30 of the FracRight solo sleeveswere
installed to provide ball-drop activation for each frack stage. The
composite frack balls are designed tomaximise ball seat support using
a sophisticated interference design algorithmto select the optimal
ball diameters. Each ball seat was rotationally locked for easymill-out,
and each of the frack stageswas compartmentalised using SwellRight
water-swellable packers.
InOctober 2015, the threewells on the padwere successfully
stimulatedwith no downtime and nomissed stages. All 30 of the
sleeve activation pressureswere easily observed in both the Bakken
and Three Forks reservoirs. The remaining 10 stages in eachwell were
stimulatedwith composite frack plugs, also isolatedwith the same
water-swellable packers.
The company recently completed the installation on a four-well,
160 stage pad. A third pad is currently beingworked onwith the same
operator, which is also a four-well, 160 stage project.
Conclusion
The development of technologies to generate and exploit
multi-phase hydraulic stimulation, aligned with the need to
maximise recovery in a low oil price environment, is encouraging
the industry to consider increasingly innovative solutions to the
challenges faced.
It is no longer deemed acceptable for operators to have an
approximate idea of howmany zones in awell are open and operating
to their optimumperformance; and neither is it necessary. Through
the deployment of an effective hydraulic fracturing system, aligned
with real time distributed temperaturemonitoring, operators can
nowbetter understand the performance of each zone in awell, and
thewell in total, to enable the greatest exposure to the reservoir. Such
technologies have the potential to assist operators inmaintaining
production in a price downturn.
Figure 4.
Pressure applieddown to the integral ball seat.
