Innovative technologies help
lower subsea boosting costs
Investments in low-cost boosting systems yield high rates of return. Reductions in upfront capex requirements for mudline boosting systems, combined with the in- creased returns that the systems enable,
indicate that mudline boosting can provide the
highest return on capital employed (ROCE)
amongst competing IOR technologies. Conse-
quently, capital cycle times are reduced, freeing up cash for additional revenue generation.
Analyses of well and reservoir conditions
suggest that there are hundreds of wells
worldwide that have the economic potential
for low-cost subsea boosting systems. The
return on investment (ROI) for the subsea
boosting system in these cases can range
from 250% to greater than 500%.
Developments to reduce complexity, intro-
duce standardization, minimize the size and
weight of boosting stations, implement inte-
grated project strategies and maximize the use of
existing infrastructure in brownfield applications
have enabled operators to unlock a tremendous
amount of value with subsea boosting systems.
Further, opex reductions, achieved through
minimizing startup time with innovative bar-
rier-fluid systems, reducing pump repair and
refurbishment time and improving reliability,
have reduced the cost of ownership. As a result,
multiple subsea boosting projects have been
awarded in a low commodity price environment.
To quantify the benefits attainable with the
new low-cost boosting systems, a case study
was developed which demonstrates the benefit
of the addition of a pump to a brownfield instal-
lation. The results show that a 500% ROI can be
achieved for this case, with oil prices
at $50/bbl. Similar results have been
obtained in analyses of other fields.
The goal here is to describe the
case study that provides guidance on
the ROCE benefits, and describe the
improvements that have been made
to enable such benefits.
The need to reduce the backpres-
sure on producing wellheads, and
increase the recovery factor from
oil and gas reservoirs, is omnipres-
ent in subsea fields. The decision to
install subsea boosting at the mud-
line is made in the context of the
incremental improvement in recov-
ery achievable with a subsea pump
versus the recovery achievable by producing
the field naturally or by other IOR technolo-
gies. Operators have studied key oil-producing
regions and have identified many instances
in which mudline boosting is the most-viable
alternative. Additionally, the installation of a
mudline pump can enable field-layout opti-
mization and/or increased tieback lengths.
One of the more promising market opportunities for brownfield investment is low-cost
subsea boosting systems in deepwater basins.
Brownfield applications do not require the drill-
ing of new wells or significant infrastructure
investments in new subsea equipment or new
topside facilities. Incremental investments in
low-cost boosting systems result in substantial
increases in revenues and, therefore, high rates
of return. Modifications to brownfield systems
can be less capital intensive than greenfield
developments. As such, they present an attractive investment alternative.
The economic benefit of the cost reductions
can be put into context by reviewing a brown-
field subsea multi-phase pump example, the
results of which show that by incorporating the
innovations described above, the total subsea-
boosting-system capex has been reduced by
50%. The potential ROI obtained as a result of the
production improvements and capex and opex
reductions indicate that between 250 and 500%
ROI can be achieved, contingent upon oil prices.
In this example, an existing field is identi-
fied to have a low recovery factor and a re-
sultant low topsides utilization, and is hence
a candidate for mudline boosting. Other IOR
technologies can be analyzed in a similar fash-
ion; the purpose here is to illustrate how the
investment in a mudline pump can produce
considerable returns. The host facility is lo-
cated in a water depth of 4,300 ft; fed from
wells in 4,000 ft of water. Produced fluids
have an API° of 27 and a GOR of 700 scf/stb.
Tieback distance is 7 mi. The pump is modeled
with the recommended five years mean time
between maintenance (MTBM).
High GVFs (gas volume fraction) occur towards the end of the field life when the wellhead pressure is at its lowest. GVF values up
to 80% are estimated in 2027. The PM motor
is able operate the pump at speeds up to 6,000
rpm and achieve the boost pressure necessar y
to increase production even during the late life
high GVF scenarios, and therefore provide benefits across the life of the field. Consequently,
the estimated production improvements show
an increase of 31% cumulative oil recovery.
Subsea boosting systems are a robust and
mature technology; worldwide, more than 65
mudline units and more than 50 submersible
pumps have been installed. Consequently, 19
operators have addressed production chal-
lenges with subsea boosting technology.
Key applications have used subsea pumps
as part of a subsea processing station. For
example, subsea pumps were installed to
boost liquids separated subsea in three-phase
separation systems, for the purposes of de-bottlenecking topside facilities, in the Petrobras Marlim project and the Statoil
Tordis project, the former with
horizontal pipe separator technol-
ogy and the latter with conventional
horizontal three-phase separator
Subsea pumps have also been
installed downstream of gas/liquid
separators in Angola’s block 17 in
the Pazflor field. This application
enabled a higher-pressure boost
than could be achieved by multi-phase pumps available at that time.
The separation of the gas from the
3. 2 MW subsea pump module
within submerged test pit.
(All images courtesy TechnipFMC)