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Oilfield Technology
January
2016
definition of high-pressure wells called for bottomhole
pressure conditions of 10 000 psi, but the current industry
standards now begin at 15 000 psi, up to extreme
high-pressure conditions of 30 000 psi (Figure 1).
T Service companies perform drillstem tests in these
high-pressure environments; this requires solutions for the
technical challenges when developing equipment specifically
designed for safe operation in this environment. Equipment
must accommodate the sizes and specific pressure,
temperature, collapse, and bursting ratings and associated
procedures developed to successfully execute the job.
In order to meet the requirements of more challenging
downhole high-pressure environments, a series of
downhole tools were developed with the objectives of
simplifying the testing string, reducing potential leak
risks, and using the best combination of testing packers,
sampling capabilities, real time data acquisition, and DST
tools.
The tools that were designed and tested to operate in
this extreme environment were developed at the request
of an operator in the Gulf of Mexico They were required
to work at 5900 ft of water with a total drill depth of
32 500 ft and expected pressures of more
than 25 000 psi at 250˚F. Tools were needed
that could be operated and qualified at
30 000 psi with a 15 000 psi differential
pressure at 450˚F. Qualification tests were
to be witnessed by a third party performing
30 day qualification tests at 25 000 psi
hydrostatic pressure using a ZnBr test fluid
solution. A functionality test was required to
be performed on a daily basis on the tester
and circulating valve. In addition, 16 500 psi
burst and collapse tests were also required.
The tools developed were required to be
multicycle, providing the same functionality
and versatility as conventional downhole
test tools. Based on these requirements,
the following tools were developed and are
currently available for testing operations in
this extreme environment after more than
2600 hours of testing:
Non-rotational set packer to operate up
to 25 000 psi with 15 000 psi differential
pressure, 400˚F rated.
Bi-directional acoustic telemetry system
for real time BHP/BHT measurement
and control of downhole tools; system
designed to 20 000 psi, 350˚F rated.
Tubing conveyed PVT sampling system
for reservoir fluids with acoustic sampler
activation system designed to work up to
20 000 psi, 400˚F rated.
Extra high-pressure tester valve and extra
high-pressure circulating valve tested at
25 000 psi hydrostatic pressure.
Extra high-pressure rupture disk (RD)
pump through safety circulating valve
under 30 day qualification test.
This test was not only performed on
individual tools, a complete integration (SIT)
test was executed to help guarantee that the
system was fully operational under designed
Figure 1.
Well testing environments.
Figure 2.
Integration test.
