U.S. patent application number 12/085171 was filed with the patent office on 2009-08-13 for all electric subsea boosting system.
Invention is credited to Geir Aalvik, Bernt Bjerkreim, Asbjorn Eriksen, Harald Arnt Friisk, Karl Olav Haram, Ola Skrovseth.
Application Number | 20090200035 12/085171 |
Document ID | / |
Family ID | 35529620 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090200035 |
Kind Code |
A1 |
Bjerkreim; Bernt ; et
al. |
August 13, 2009 |
All Electric Subsea Boosting System
Abstract
The present invention relates to an all electric subsea boosting
system for well fluid boosting by compressing hydrocarbon gases
and/or pumping hydrocarbon liquids where said system comprises one
or more subsea boosting stations and one or more long step-out
power supplies.
Inventors: |
Bjerkreim; Bernt; (Vestby,
NO) ; Friisk; Harald Arnt; (Oslo, NO) ;
Eriksen; Asbjorn; (Skallestad, NO) ; Haram; Karl
Olav; (Oslo, NO) ; Skrovseth; Ola; (Osteras,
NO) ; Aalvik; Geir; (Haslum, NO) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
1030 15th Street, N.W.,, Suite 400 East
Washington
DC
20005-1503
US
|
Family ID: |
35529620 |
Appl. No.: |
12/085171 |
Filed: |
November 10, 2006 |
PCT Filed: |
November 10, 2006 |
PCT NO: |
PCT/NO2006/000413 |
371 Date: |
November 13, 2008 |
Current U.S.
Class: |
166/335 |
Current CPC
Class: |
E21B 43/01 20130101;
F17D 1/14 20130101 |
Class at
Publication: |
166/335 |
International
Class: |
E21B 43/36 20060101
E21B043/36; E21B 43/01 20060101 E21B043/01; E21B 43/12 20060101
E21B043/12 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 5, 2005 |
NO |
20055727 |
Claims
1-12. (canceled)
13. A subsea boosting system for a subsea installation, for
boosting well fluid pressure when compressing hydrocarbon gasses
and pumping hydrocarbon liquids, said system comprising at least
one long step-out power supply and at least one subsea boosting
station, each boosting station comprising at least one separator
for separating gas and liquid phases, at least one gas compressor
and at least one liquid pump, both arranged after said separator,
the system further comprising inlet and outlet Manifolds and at
least one high voltage electric system, and each long step-out
power supply terminating in a power umbilical termination head
attached to a main transformer in a boosting station, said system
being characterized in that each subsea boosting station further
comprises electrically actuated valves, an all electric utility
power system and an all electric control system.
14. The system of claim 13, characterized in that at least one of
said subsea boosting stations further comprises circuit breaker
modules and a barrier system.
15. The system of claim 14, characterized in that said at least one
subsea boosting station further comprises at least one inlet cooler
and an inlet sand trap.
16. The system of claim 13, characterized in that said at least one
subsea boosting station comprises at least one compressor module,
at least one compressor VSD, at least one anti-surge valve and
actuator, at least one anti-surge cooler, at least one separator
and/or scrubber module, at least one pump module, at least one pump
VSD, remotely and manually operated valves, interconnection piping
and control system including control modules.
17. The system of claim 13, characterized in that each long
step-out power supply comprises a subsea main transformer with
pressure compensation system, high voltage penetrators, an
umbilical termination head and a power and control umbilical
including main electrical supply, utility power, and fibre optic
lines for control signals.
18. The system of claim 16, characterized in that each compressor
module comprises at least one compressor which is directly driven
by a variable speed controlled (=VSD) high-speed electric motor
with magnetic bearings, said motor being cooled by hydrocarbon
gas.
19. The system of claim 16, characterized in that said anti-surge
cooler is designed for heat transfer by convection with the sea
water.
20. The system of claim 16, characterized in that said separator
and/or scrubber module is designed to absorb liquid slugs, ensure
sufficient gas and liquid levels for safe operation of compressor
and pump modules by level control, and prevention of internal solid
buildups by possible re-circulation of liquid.
21. The system of claim 16, characterized in that said liquid
pump(s) is designed to be solid tolerant and can be operated either
with variable speed by means of a variable speed drive or operated
on fixed speed with control of discharge flow and pressure by a
regulating valve, said valve discharging liquid back to the
separator/scrubber module.
22. The system of claim 21, characterized in that said liquid
pump(s) is designed with an electrical motor cooled by hydrocarbon
gas or a liquid.
23. The system of claim 18, characterized in that said control
system including control modules is designed for control and
monitoring of at least one subsea compression train, further for
control of all other functions on the boosting station, and to
include direct communication with a receiving facility and any
local closed loop required to operate the boosting station in a
safe and operational friendly manner.
Description
[0001] The present invention relates to an all electric subsea
boosting system for well fluid boosting by compressing hydrocarbon
gases and/or pumping hydrocarbon liquids comprising one or more
subsea boosting stations and one or more long step-out power
supplies. A boosting station may consist of compressor(s) and/or
single or multiphase pump(s).
[0002] An offshore gas field may be developed with seabed
installations which are tied back to a terminal onshore or an
existing platform. The seabed installation comprises of one or more
production templates where each template produces well fluid
through manifold headers which are connected to one or more
pipelines. Said pipelines transport well fluid to an onshore
terminal or, an existing platform (receiving facility) for further
processing. Processed gas and condensate are exported to the
market. One or more umbilicals for power, control and utility
supplies are installed from the receiving facility to said subsea
installations.
[0003] For the initial production phase, well fluid may flow to the
receiving facility by means of the reservoir pressure. Later in the
production phase, or at start-up of the production, well fluid
boosting is required in order to maintain the production level and
to recover the anticipated gas and condensate volumes. The
conventional solution for such well fluid boosting facility is an
offshore platform. However, a subsea boosting system may be an
alternative to or in combination to said platform solution.
[0004] The present invention seeks to provide an all electric
subsea boosting system to replace or assist the use of an offshore
platform.
[0005] That the system is all electric means that it is controlled
and operated with electrical power, and does not have a hydraulic
system for assisting opening and closing of valves.
[0006] In accordance with the present invention, this object is
accomplished in an all electric subsea boosting system where said
system comprises one or more subsea compression stations and one or
more long step-out power supplies.
[0007] An all electric subsea boosting system in accordance with
the present invention has a number of advantages compared to a
booster platform solution.
[0008] Said system is safe to human injuries and fatalities due to
remote operation, reliable, cost effective, environmental friendly
and comprises few parts which make the system less complicated and
easy to operate.
[0009] The present invention will now be described and with
reference to the accompanying drawings in which:
[0010] FIG. 1 shows a schematic overview of the all electric subsea
boosting system in accordance with the present invention.
[0011] FIG. 2 shows a subsea main power system single line
diagram.
[0012] FIGS. 3 and 4 show a typical all electric subsea boosting
station layout in accordance with the present invention.
[0013] FIG. 5 shows a boosting station process flow diagram.
[0014] FIG. 6 shows a schematic overview of main modules and parts
in a subsea boosting station according to the present
invention.
[0015] FIG. 7 shows a typical power and control architecture for a
subsea boosting system.
[0016] FIG. 1 illustrates the all electric subsea boosting system.
Said system comprises one or more subsea boosting stations and one
or more long step-out power supplies.
[0017] The long step-out power supply is defined from the
connection point at the receiving facility to and including the
main subsea transformer.
[0018] Such long step-out power supply comprises the following
subsea components: [0019] Subsea main transformer with pressure
compensation system [0020] High voltage penetrator(s) [0021]
Umbilical termination head [0022] Combined or separate power and
control umbilical, including: [0023] Main electrical supply [0024]
Utility power (optional) [0025] Fibre optic lines for control
signals [0026] Barrier lines (optional)
[0027] The boosting station is connected directly to at least one
subsea production template and is designed for boosting well fluid
from said production templates. Well fluid from the production
templates is routed via one of the template manifold headers, via
the infield flow lines and to connectors on the suction side of the
boosting station.
[0028] The boosting station is connected to export pipelines with
flow lines to each pipeline. Compressed gas will be transported in
said export pipelines to the receiving facility.
[0029] FIG. 2 shows a main power system single line diagram for a
subsea boosting system.
[0030] High voltage power, control and utilities are supplied from
receiving facilities with one or more power and control
umbilicals.
[0031] The high voltage (HV) power cables will be connected to the
subsea main step-down transformer and the transformer will be
installed on the subsea boosting station with the umbilical
attached.
[0032] The single line diagram shows the power distribution system
for the main subsea electrical consumers.
[0033] FIGS. 3 and 4 show a typical subsea compression station
layout.
[0034] The subsea boosting station, comprises the following modules
and parts: [0035] One or more compressor trains and/or single or
multiphase pump(s) [0036] One or more circuit breaker modules
[0037] Inlet and outlet manifolds [0038] Inlet coolers [0039] Inlet
sand trap [0040] Parking location for main transformer and power
umbilical termination head [0041] Required installation tools
[0042] High voltage electrical system [0043] Process system [0044]
Utility power system [0045] Control system [0046] Barrier
system
[0047] The compressor train is the main equipment required for
compressing the well stream. The compressor train comprises the
following modules and parts: [0048] Compressor module [0049]
Compressor Variable Speed Drive (VSD) [0050] Anti-surge valve and
actuator [0051] Anti-surge cooler [0052] Separator/scrubber module
[0053] Pump module [0054] Pump VSD [0055] Remote and manually
operated valves [0056] Interconnection piping [0057] Control system
including control modules
[0058] Common to the compressor trains is a power and control
umbilical connection system and a valve manifold fitted with flow
line connection systems.
[0059] The station power distribution system consisting of
removable circuit breaker modules and variable speed drive modules
are arranged together at one end of the station structure adjacent
to the subsea main transformer. The actual mating mechanism for the
high voltage wet mate connectors will be dependent upon the chosen
power connection system.
[0060] The piping manifold is formed to provide a balanced
symmetrical routing through each of the compressor trains. Emphasis
is given to avoid high stress levels, ensuring flexibility for
connection operations.
[0061] The modules are provided with local guiding/docking and are
locked into position by dedicated mechanisms.
[0062] Intervention for ROV is designed for minimum top and one
side access.
[0063] Access to modules for vertical removal/installation is
provided from the top and sides of the protective structure.
[0064] Smaller removable modules such as control pods, control
valves and certain instrumentation units are provided as individual
units and/or included within one of the main modules as removable
items, these modules/items are run on dedicated intervention
running tools.
[0065] The compressor is directly driven by a high-speed motor. The
electrical motor is cooled with hydrocarbon gas with a pressure
regulated to be equal to or as close to the suction pressure as
possible. Said gas source can either be conditioned gas supplied to
the subsea compression station from an external source, discharge
gas from the compressor module or suction gas to the compressor
module. Said hydrocarbon gas for electrical motor cooling might be
conditioned prior to entering into the electrical motor and said
hydrocarbon gas might also be replaced by other suitable gases.
Alternatively the motor may be fully canned with main cooling from
the gas flow.
[0066] The compressor is able to meet the design operational
conditions over the production period with declining production
wellhead pressure. Re-bundling of the compressor can be performed
as part of a maintenance program.
[0067] A magnetic bearing system is used for each of the subsea
compressor modules.
[0068] The system includes magnetic radial and axial bearings as
well as run-down bearings.
[0069] Material properties of the compressor unit is suitable for
operation with relevant content of H.sub.2S and CO.sub.2.
[0070] The compressor and material properties are designed for the
liquid fractions and solids content coming with the gas stream from
the upstream separator. The size and distribution of the liquid
droplets and solids particles is dependent on the separator
design.
[0071] The boosting station manifold is equipped with a remote
operated isolation valve facilitating by-pass of the compression
trains.
[0072] The boosting system is designed to handle the continuous
fines/sand production. The rotating equipment is protected against
wear and degradation from solids. This will ensure high efficiency,
long life and reliability.
[0073] The compressor(s) have anti-surge control recycle line
designed for full recycle flow at maximum continuous speed (105%).
The anti-surge control valve is electrical actuated, axial stroke
and is located close to the compressor discharge at high point. An
anti-surge re-cycle cooler is included downstream of the anti-surge
valve in the re-cycling pipe loop.
[0074] The compressors have a discharge pipe equipped with a remote
operated isolation valve. A non-return valve is fitted in the
compressor discharge pipe upstream of the isolation valve.
[0075] The boosting station is able to handle liquid backflow from
the downstream export pipeline. The boosting station is isolated
and pressurised to avoid liquid ingress due to back-flow from
multiphase export pipelines.
[0076] The separator separates liquid/solids from the gas which in
turn is ingested into the pump and compressor, respectively.
[0077] The separator is designed to separate liquids and solids
from the gas flow to avoid excessive erosion of the compressor.
Right separator design is chosen to secure that solids are not
clogged or fixed anywhere in the separator or its internals.
[0078] The condensate pumps are able to handle the liquid
production and boost it up to the required discharge pressure. The
pumps are variable or fixed speed driven.
[0079] The pumps are able to handle the continuous and intermittent
sand production in the liquid stream from the separators.
[0080] The boosting station has tie-in connection for well fluid
discharge. Each of these are equipped with ROV (remotely operated
vehicle) operated valves for routing of the well fluid to the
different pipelines.
[0081] FIG. 5 shows a subsea boosting station process flow
diagram.
[0082] The process in the subsea boosting station is envisaged in
the following paragraphs.
[0083] The well fluid from a tied-in production template is
distributed to a separator equipped with an electric actuated
isolation valve in the inlet pipe. The well stream is further
routed via the compressor by-pass line before compressor start-up
and the by-pass valve is closed when the compressor(s) are brought
into operation.
[0084] The need for inlet/input coolers will depend on required
compressor inlet temperature and the physical location of the
compressor station in relation to the production template(s) and
the heat transfer from the connecting flow lines to the seawater.
The cooling required is dependent on the well stream inlet
temperature, the required inlet temperature to the boosting system
and the hydrate formation temperature. Additional cooling in the
in-field flow lines from the production templates is possible.
[0085] The compressor allows recirculation for anti-surge
protection and start-up/shut-down operations. The recycle cooler
and recycle loop is designed for full recycle flow at compressor
maximum continuous speed (105%).
[0086] Most of the solids are removed in the separators.
Sand/fines/solids entering the boosting station will be separated
out in the separator and transported via the liquid pump to the
discharge pipeline. However, a sand trap for accidental sand
production may be used to remove sand from the inlet well
fluid.
[0087] Gas demisting and gas-liquid separation is performed by use
of scrubbers. Tolerance to sand/solids/fines in the well stream is
made acceptable with regard to entrainment, clogging in demisting
equipment and drainage system and also accumulation in vessel
bottom. Continuous production of fines is handled in the boosting
station, without jeopardizing operation and performance.
[0088] Terrain induced slugging and transient slugging may be
expected. The separation vessel is designed to have safe and
efficient handling of liquid slugs. The slug handling philosophy is
to accumulate the specified slug volumes in the separator units.
The liquid slugs entering the boosting station will accumulate in
the separator before being pumped to the station discharge by the
liquid pumps.
[0089] The design also ensures stable operation for moderate
slugging with minimum use of liquid level control devices and
minimum impact on compressor operation due to inlet pressure
transients. The internals are designed for the thrust and vibration
caused by the expected slugging.
[0090] The liquid boosting system consists of single or multiphase
condensate pumps with fixed or variable speed drives. The pump
discharge pipes are equipped with a non-return valve upstream of
the discharge isolation valve.
[0091] Anti-surge control is made possible by monitoring the
compressor suction flow rate, temperature, pressure together with
compressor discharge pressure and temperature.
[0092] The well stream is inhibited by MEG injection at the
wellheads to prevent hydrate formation.
[0093] The MEG, condensate and water is separated out in the
separator in the boosting station and pumped to the station
discharge header by the condensate pumps. Sufficient MEG content
will ensure hydrate prevention of these parts of the system.
[0094] The gas separated out in the separator will have none or
only small quantities of MEG.
[0095] A schematic overview of main modules and parts in a subsea
boosting station pilot set-up used for tests in the intended
environment is shown in FIG. 6.
[0096] The subsea facilities comprise remotely actuated valves to
control the flow of produced gas and the injection of chemicals.
The remotely operated valves are electrically actuated
[0097] Local instruments (transmitters) is provided to measure
pressure, temperature, gas flow rate and record the anti-surge
valve position.
[0098] The different types of valves, the condition monitoring
system and the transmitters are interfaced via the subsea control
modules.
[0099] Interfaces with subsea variable speed drives and circuit
breakers, distributed control system and emergency shut down
systems are foreseen.
[0100] A typical power and control supply architecture use for the
boosting system architecture is shown in FIG. 7.
[0101] Interface and closing of control loops between the variable
speed drives circuit breakers and compressors control system may be
via the receiving facilities control system main bus. All
information, alarms and interlocks between the two systems should
be handled by the distributed control system.
[0102] The receiving facilities distributed control system controls
all control loops defined "slow". This is typically opening and
closing of manifold valves and condition monitoring systems. The
subsea control system has inter-connection links to handle
potential subsea shutdown requirements.
[0103] Dynamic control loops, which requires quick response, are
the anti-surge controller and the magnetic bearing controller.
These loops shall be closed subsea if required.
[0104] Anti-surge algorithms are identically implemented for all
compressor stages. The control algorithms include features for
suction and discharge pressure override, i.e. limiting the
discharge pressure or increasing the suction pressure.
* * * * *