Akpo
COMPANY ref:
CONTRACTOR ref:
Akpo
NIGERIA – OML 130
AKPO Field Development Project
Project
NG50-7-070-FAS-SP-AB-00-0001
J12126-RT-001
Revision:
--
01
Status:
IFA
--
Project
Class:
1
date:
page:
--
--
45
--
OLGA SUBSEA MODELLING
Design Premise
Reserved to COMPANY
The document is:
Approved
code 1
Approved with minor comments code 2
Rejected
code 3
Reviewed with comment
code 4
date:
ASB final acceptance
code 5
date:
Remarks:
01
REV
Issued for Approval
DATE
DESIGNATION
Genesis Company
Obinna Isu
Obinna Isu
Initiator
Reviewed by
Approved by
NG50-7-070-FAS-SP-AB-00-0001.doc
This document is the property of TOTAL and shall not be disclosed to third parties or reproduced without permission of the COMPANY.
Akpo
Project
CLIENT:
TOTAL UPSTREAM NIGERIA LIMITED
PROJECT/JOB TITLE:
AKPO Field Development Project
DOCUMENT TYPE:
Report
OLGA Subsea Modelling
DOCUMENT TITLE:
DESIGN PREMISE
GENESIS JOB NUMBER: J-12126
GENESIS DOCUMENT NUMBER: J12126-RT-001
1
Issued For Approval
SLE
SJA
SJA
0
Issued For Approval
SJA
SEA
SJA
A
Issued For Review
SJA
SEA
SJA
Issued By
Checked
By
Genesis
Approval
Rev
Date
Genesis France
Description
TOTAL
Approval
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Akpo
Project
J12126-RT-001 Rev 0
Page 2 / 45
Table of Contents
1
INTRODUCTION................................................................................................. 4
1.1
1.2
1.3
2
ENVIRONMENTAL DATA .................................................................................. 7
2.1
2.2
2.3
2.4
3
AIR TEMEPRATURE.................................................................................................... 7
SEAWATER TEMEPRATURE ........................................................................................ 7
SOIL TEMEPRATURE .................................................................................................. 8
CURRENT ................................................................................................................. 9
FIELD DEVELOPMENT ARCHITECTURE ...................................................... 11
3.1
3.2
3.3
3.4
3.5
3.5.1
3.5.2
3.5.3
3.6
3.6.1
3.6.2
3.7
3.7.1
3.7.2
3.7.3
4
GENERAL PRESENTATION OF AKPO .......................................................................... 4
AIM OF THE DOCUMENT ............................................................................................. 5
REFERENCES ............................................................................................................ 6
FIELD LAYOUT ......................................................................................................... 11
WELL DISTRIBUTION ................................................................................................ 12
PRODUCTION LINES BATHYMETRY ........................................................................... 13
SCR DESCRIPTION ................................................................................................. 15
SINGULAR GEOMETRIES .......................................................................................... 16
Wellhead / Jumper Input in OLGA simulation.............................................................................. 16
Manifold / Spool / Sled Input in OLGA simulation ....................................................................... 17
Valves............................................................................................................................................ 17
TOPSIDE PROCESS ................................................................................................. 18
Separator Train ............................................................................................................................ 18
Temperature required at first stage separator.............................................................................. 18
PRODUCTION LINES CHARACTERISTICS ................................................................... 19
Insulation Thermal Properties...................................................................................................... 19
Pipe Wall Thickness...................................................................................................................... 19
Pipe Roughness............................................................................................................................. 20
RESERVOIR AND WELL DATA ...................................................................... 20
4.1
4.2
4.3
4.4
4.5
4.6
4.6.1
4.6.2
4.6.3
4.6.4
4.6.5
WELL ARCHITECTURE ............................................................................................. 20
MATERIAL CHARACTERISTICS .................................................................................. 22
RESERVOIR PRESSURES ......................................................................................... 23
RESERVOIR TEMPERATURES ................................................................................... 23
WELL PRODUCTIVITY INDEXES ................................................................................. 24
RESULTS OF RESERVOIR SIMULATIONS.................................................................... 25
All Production Loops .................................................................................................................... 26
Production Loop P10.................................................................................................................... 26
Production Loop P20.................................................................................................................... 27
Production Loop P30.................................................................................................................... 27
Production Loop P40.................................................................................................................... 27
5
FLUID COMPOSITION ..................................................................................... 28
6
SCOPE OF WORK ........................................................................................... 34
6.1
6.2
SOFTWARE ............................................................................................................. 34
OLGA MODEL ........................................................................................................ 34
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.3.6
6.4
6.5
Project
J12126-RT-001 Rev 0
Page 3 / 45
6.3
Akpo
OLGA 2000 SIMULATIONS ...................................................................................... 35
Steady State Runs.......................................................................................................................... 35
Branch Packing ............................................................................................................................ 36
Cooldown...................................................................................................................................... 36
Depressurisation........................................................................................................................... 36
Start-up sequence.......................................................................................................................... 37
Slugging analysis .......................................................................................................................... 37
DELIVERABLES ........................................................................................................ 37
SCHEDULE .............................................................................................................. 38
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Akpo
Project
J12126-RT-001 Rev 0
Page 4 / 45
1 INTRODUCTION
1.1
General Presentation of AKPO
The AKPO field lies Offshore Nigeria within OML 130, some 200km South of Port
Harcourt, in water depths ranging from 1 250 m to 1 480 m. TOTAL, as Operator
with a 24% share, and its partners SOUTH ATLANTIC PETROLEUM (60%) and
PETROBRAS (16%) are developing the AKPO Field, estimated to contain reserves
of 1 billion barrels of oil and 4 trillion cubic feet of natural gas.
In summary, the overall AKPO Field Development Project consists of the following
main elements:
A Floating, Production, Storage and Offloading unit (referred to as the FPSO),
including hull, mooring, risers structure, accommodation, process (oil, gas, water as
needed), gas and water re-injection, flaring, oil storage and export facilities (pumping
and metering), gas export and associated control systems. Such unit shall be
designed with the following general characteristics:
•
•
•
•
•
•
•
•
•
•
Spread moored (3 x 4 lines) FPSO in 1325 m water depth
Stabilised oil (max): 185,000 Standard bopd maximum oil
production rate
Total liquids: 235,000 bpd
Produced gas: 530 Mscfd
Injected gas: 215 Mscfd (@ ~ 400 barg)
Export gas: 320 Mscfd (@ ~ 200 barg)
Fuel gas: 25 Mscfd
Injected water: 420,000 bwpd (@ ~ 220 barg)
Produced water: 150,000 bwpd
Crude storage: circa 2,000,000 stb
An Offshore Loading Terminal (OLT), consisting of an Offloading buoy (deep water
CALM) moored down wind of FPSO in 1295 m water depth (connected to buoy via 2
x 16” I.D. steel lines).
The Subsea Anchoring Systems, as needed for the FPSO and the OLT.
The Subsea Production System (referred to as the SPS) including around 44 subsea
wells
(Wellheads, Xmas trees and associated control systems) subdivided as follows:
•
•
•
Genesis France
22 Oil producer subsea wells
2 Gas injector subsea wells
20 Water injection subsea wells
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Akpo
Project
J12126-RT-001 Rev 0
Page 5 / 45
The Umbilicals, Flowlines, Risers and Pipelines (referred to as UFR) consisting of:
•
•
•
•
•
•
•
4 x 10” I.D. production flow loops (P10, P20, P30 and P40) & steel
catenary risers,
1 x 8” I.D. gas injection line (GI 40) & steel catenary risers,
3 x 10” I.D. water injection lines (W10, W20 and W30) steel
catenary risers,
4 x Production umbilicals,
4 x Injection umbilicals,
Steel Catenary Risers hung off exterior of FPSO,
1 x Export Gas 16” pipeline to Amenam AMP2 Platform –
approximate total length 150 km.
The AKPO facilities will be designed with the following reservations and preinvestments for the potential future evolution of the development concept:
• Spare riser porches and receptacles will be available on the FPSO
for the potential tie-in of additional risers / umbilicals in the future,
• Spare slots will be available on the subsea manifolds to facilitate
the tie-in of additional production wells and spare in-line tee for the
tie-in of future injection wells.
1.2
Aim of the Document
The purpose of this document is to define the scope of work and the basis for design
concerning the dynamic subsea model to be build up for the AKPO field
development project.
This model will later be used for various studies: Operations studies (start-up,
preservation optimisation), topside studies (Dynamic simulations, OCWR design)
and by OTS.
Consequently, the quality of this model should be ensured by the use of the most upto-date data, by an extensive testing program and with clear interfaces. The update
of some basis of design should be easily possible, which means well documented
input files.
This model is not built for design purposes, but for design validation, procedure
preparation and training.
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 6 / 45
1.3
Akpo
Project
J12126-RT-001 Rev 0
References
[1] Metocean specification
NG50-1-CO-MET-PS-AB-000-001
[2] Surface and subsea Field Layout rev10C
NG50-PJ-PJM-GEN-KE-0003 rev 3
[3] Surface and subsea Field Layout
NG50-3-BE-PLR-DW-AB-000-604
rev10C
[4] Impact on revised reservoir data and revised field layout on production and gas
systems
DED.2316_Rev0 FA impact of 10C layout
[5] Flow assurance strategy
NG50-7-BE-FAS-CN-AB-00-0001
[6] Subsea operating philosophy
NG50-2-300-SPS-PH-AB-30-0281
[7] Manifold assembly drawing
NG50-2-300-MAN-DW-SM-300232-manifold_detailed.pdf
[8] Flow Assurance Reservoir Model 1
NG50-7-BE-FAS-TR-AB-00-0006
(Basis of Design)
[9] Production FLET TYPE F-P11
NG50-3-200-ENG-DW-AB-30-2400 rev 1
(Preliminary Arrangement)
[10] AKPO fluid temperature Dec04
EP/GSR/VDG/AKPO
[11] WHSP & WHFT update
NG50 - 090 # 000 - M.0001
[12] Production FLET TYPE FP1
NG50-3-200-ENG-DW-AB-30-2432
Rev 0
(Arrangement & Isometric)
[13] Well Program – Dec05
[14] Process Systems Description
NG50-5-500-PRO-PH-AB-00-0005
Rev 0
[15] Flow Assurance – Olga Model Build-up – Scope of Work and Basis of Design
NG50-7-070-FAS-GN-AB-00-0002
[16] Heat and material balance
NG50-5-500-PRO-CN-AB-00-002
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 7 / 45
Akpo
Project
J12126-RT-001 Rev 0
2 ENVIRONMENTAL DATA
All the data given in the present chapter are coming from the Site and environmental
Survey [1]. They are required for heat transfer calculation in the flowlines and risers.
2.1
Air Temeprature
The air ambient temperature is between 18.1°C and 32.6°C. Minimum temperature
will be used in the simulations.
2.2
Seawater Temeprature
The following graph gives the plots of the sea temperature versus the water depth,
This was obtained during a one-year survey.
From the graphic here above, the minimum, mean and maximum values of the
temperature profiles have been considered and are given in the next table.
Genesis France
February 2006
Akpo
Total Upstream Nigeria Limited
AKPO Field Development Project
Project
J12126-RT-001 Rev 0
Page 8 / 45
Table 1: Temperature min & max vs water depth
The minimum values will be used in order to obtain the maximum heat exchange
with the surroundings and therefore the minimum fluid temperatures through the flow
line.
2.3
Soil Temeprature
The figure below illustrates the temperature gradient across the reservoir and the
geothermal gradient to the seabed.
The soil temperature profile to be used in OLGA model is issued from the results of
the environmental data. But this temperature profile does not take into account the
reservoir temperature associated to each well.
As a consequence the soil temperature profile will be modelled in 2 steps:
- From the mud line to the end of last casing, the temperature profile
is deduced from the data presented in the figure below.
- Upstream reservoir bottom hole, a linear regression is used:
- The reservoir temperature is used as the reference point
- The upstream temperature is extrapolated using the linear
temperature slope at of the bottom of the temperature curve
presented below.
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 9 / 45
2.4
Akpo
Project
J12126-RT-001 Rev 0
Current
On behalf of Total Upstream Nigeria, Fugro GEOS have undertaken a year long
measurement programme in the Akpo field. Current speed and direction profiles
were measured at 20 minute intervals between 12 May-2001 and 19 May 2002. The
water depth at the measurement location was 1376m.
Extreme current speeds derived by the independent extrapolation of time series at
each depth level are presented in the following Table.
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 10 / 45
Akpo
Project
J12126-RT-001 Rev 0
Most of the time (90%) the current velocity is around 0.02 m/s from 100 m to 1500 m
below sea level. Between 100 m and 10 m below sea level, it increases up to 0.08
m/s.
In order to maximise heat exchanges between production flowlines and the
environment, profile of maximum measured current speed will be used in the subsea
model.
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 11 / 45
Akpo
Project
J12126-RT-001 Rev 0
3 FIELD DEVELOPMENT ARCHITECTURE
3.1
Field Layout
In summary, the overall AKPO field layout selected for the flow assurance studies is
based on the one issued on August 2005 [2 & 3]. Note that in previous models, some
margins have been added on each production and injection line in order to take into
account any further layout modification, but the current should not take any margin, it
should be as per frozen layout.
The following values are given with no margin and including the steel catenary riser:
• Spread moored (4 x 4 lines) FPSO in 1314 m from Mean Sea Level (MSL),
• Offloading buoy moored down wind of FPSO in 1285 m water depth below MSL
(connected to FPSO via 16” ID flexible lines),
• 147 km 16” N.D. gas export pipeline to Amenam (AMP2),
• 4 x 10” ID production flow loops & steel catenary risers – total length 50.72 km,
• 1 x 8” ID gas injection line & steel catenary riser – total length 9.93 km,
• 4 x 10” ID water injection line & steel catenary risers – total length 38.44 km,
• 4 x production umbilicals – total length 26.4 km,
• 3 x water injection umbilicals - total length 33.79 km.
• 1 x gas injection umbilical - total length 5.67 km.
• 22 oil producers on 4 production loops (P10, P20, P30 and P40)
• 20 water injectors on 4 water injection loops (WI10, WI20, WI30 and WI50)
• 2 gas injectors on 1 gas injection loop
• 14 spare production slots
It is important to note that the risers are steel catenary. Only production system will
be included in the OLGA subsea modelling.
Detailed field layout is given in Ref. [2 & 3].
Several comments can be made on this layout:
- All production loops are up sloping toward the FPSO. This slope is due to the steel
catenary configuration because the bathymetry shows that the mud line is down
sloping from the touch down point to the FPSO location.
- All the production loops have two manifolds, except P40 which has three manifolds,
- Each production well can be tied-in to either branch of the loop,
- The longest flow line is P20, with 7.11 km per branch (including the riser)
- The length of the overall production lines is 48.36 km
Genesis France
February 2006
Akpo
Total Upstream Nigeria Limited
AKPO Field Development Project
Project
J12126-RT-001 Rev 0
Page 12 / 45
3.2
Well Distribution
The following tables give for each loop the well sharing per branch for the full field.
Loop
P10
P20
P30
P40
Header
FULL
FIELD
Manifold
START UP
First
End
A123_P1 &
A123_P2
Right Header
A568_P1
Left Header
A4_P1 & A123_P4
Right Header
A568_P2
A9_P2 &
A456_P2
Left Header
D_P2 & A68_P1
A123_P3
Right Header
A689_P1
B_P2
Left Header
A9_P1
G_P2
Right Header
D_P1
Full of dead oil
Left Header
D_P3
G_P1
A456_P1
Manifold
Loop
Header
P10
Right Header
A568_P1
Left Header
A568_P2
A9_P2 &
A456_P2
A4_P1 & A123_P4
A123_P3
Right Header
D_P2 & A68_P1
A689_P1 &
EF_P2
Left Header
A9_P1
B_P2 & G_P2
Right Header
D_P1
EF_P1
Left Header
D_P3
G_P1
P20
Right Header
Left Header
P30
P40
First
End
A simplified drawing of the above table wells arrangement per loop is given below :
Genesis France
February 2006
A123_P1 &
A123_P2
A456_P1
B_P1
Total Upstream Nigeria Limited
AKPO Field Development Project
Project
J12126-RT-001 Rev 0
Page 13 / 45
3.3
Akpo
Production Lines Bathymetry
The production line profile including SCR profile and the total length is as follows.
P10 Production Loop
Water Depth below MSL
0
-200 0
1000
2000
3000
4000
5000
6000
7000
7000
8000
-400
-600
-800
-1000
-1200
-1400
-1600
Production Line Length (m)
P20 Production Loop
Water Depth below MSL
0
-200 0
1000
2000
3000
4000
5000
6000
-400
-600
-800
-1000
-1200
-1400
-1600
Production Line Length (m)
P30 Production Loop
Water Depth below MSL
0
-200 0
1000
2000
3000
4000
5000
6000
-400
-600
-800
-1000
-1200
-1400
-1600
Production Line Length (m)
P40 Production Loop
Water Depth below MSL
0
-200 0
1000
2000
3000
4000
5000
6000
7000
-400
-600
-800
-1000
-1200
-1400
-1600
Production Line Length (m)
Genesis France
February 2006
Akpo
Total Upstream Nigeria Limited
AKPO Field Development Project
Project
J12126-RT-001 Rev 0
Page 14 / 45
Pipe lengths with elevation are shown in the table below.
P10
Length (m)
P20
Water Depth
Well
(m)
Connections
Length (m)
P30
Water Depth
Well
(m)
Connections
Length (m)
P40
Water Depth
Well
(m)
Connections
Length (m)
Water Depth
Well
(m)
Connections
0
20
0
20
0
20
0
20
25
-5
30
-10
33
-13
30
-10
113
-89
118
-94
121
-97
118
-94
444
-405
449
-410
452
-413
449
-410
713
-655
718
-660
721
-663
718
-660
934
-852
939
-857
942
-860
939
-857
1116
-1004
1121
-1009
1124
-1012
1121
-1009
1269
-1120
1274
-1125
1277
-1128
1274
-1125
1400
-1205
1405
-1210
1408
-1213
1405
-1210
1515
-1262
1520
-1267
1523
-1270
1520
-1267
1621
-1296
1626
-1301
1629
-1304
1626
-1301
1721
-1307
1726
-1312
1729
-1315
1795
-1307
1800
-1312
1803
-1315
1895
-1307
1900
-1312
1903
-1315
1995
-1308
2000
-1315
2003
-1315
2381
-1310
2197
-1315
2330
-1320
TDP = 930m
Flowline/Riser
Transition
TDP = 930m
Flowline/Riser
Transition
TDP = 930m
Flowline/Riser
Transition
A689-P1, A9P1, EF-P2
1726
-1312
1800
-1312
1900
-1312
2000
-1313
2093
-1315
3015
-1310
2739
-1320
2996
-1325
2548
-1320
4191
-1315
3477
-1325
3566
-1330
2792
-1322
4855
-1320
4018
-1330
4042
-1335
3071
-1325
5263
-1325
4215
-1335
4516
-1340
3525
-1330
5826
-1330
4658
-1335
4992
-1345
3981
-1335
6081
-1335
5150
-1340
5230
-1350
4435
-1340
6235
-1337
Genesis France
658-P1 & A658-P
A123-P1, A123P2, A123-P4,
A4-P1
A68-P1, A456P2, A9-P2, DP2
B-P1, B-P2, GP2
5415
-1345
4696
-1345
5574
-1350
4858
-1350
5786
-1355
5312
-1353
5997
-1360
6221
-1355
6209
-1365
6645
-1358
6474
-1370
6686
-1375
6845
-1380
7004
-1385
7110
-1390
5370
-1355
456-P1 & 123-P3
February 2006
TDP = 930m
Flowline/Riser
Transition
D-P1, D-P3
EF-P1, G-P1
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 15 / 45
3.4
Akpo
Project
J12126-RT-001 Rev 0
SCR Description
The Steel Catenary Riser (SCR) is the base case on AKPO project. Therefore, all
thermo-hydraulic calculations consider this technology, with a mainly up sloping
shape from the far end manifold to the FPSO.
The next graph shows the typical profile for the steel catenary riser to be used for
OLGA simulations. The values are detailed in the following table.
The developed length of the riser is 2000 m up to the riser / flowline transition.
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 16 / 45
3.5
Singular Geometries
3.5.1
Wellhead / Jumper Input in OLGA simulation
Akpo
Project
J12126-RT-001 Rev 0
The jumpers will be designed with a nominal distance of 30 m from the trees to the
manifold and a positioning tolerance of ± 10 m for the wells and ± 5 m on manifold
position. This could result in a jumper distance of 45 m maximum or 15 m as a
minimum.
In order to obtain the maximum pressure and temperature drop through the jumpers,
the longest distance will be considered for flow assurance simulations (45 m).
Additional length is added in order to take into account the length of tree piping from
production choke to tree connector interface and the dilatation lire (+ 5 m).
The following layout will be input in OLGA. It does respect the distance and the top
and low points. However, the exact elevation is not reproduced to limit the minimum
pipe length which is time consuming for simulations (see sketch below):
The modelled total length of a jumper is 70.7 m.
It has to be noted that the subsea choke is considered +5 m above the mud level
(i.e. the water depth).
Moreover, it has to be noted that the connection tie-in (from the wellhead to the
jumper) is located 4m above the mudline.
The jumper layout changes during the detail phase, but the modifications are not yet
been agreed on its shape, but should not have any significant impact on the thermohydraulic calculations. Indeed, its length contributes to less than 2% of the flowline
and riser length.
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 17 / 45
3.5.2
Akpo
Project
J12126-RT-001 Rev 0
Manifold / Spool / Sled Input in OLGA simulation
Manifold assembly drawing is given in refs [7, 9 & 12]. The valves of the manifold
should not induce any pressure drop, but manifold header valves and dual block
valve might be required to be operated from the OTS.
The manifold and the flowline spool modelled in OLGA are schematised as follows.
One 10-inch production branch of the manifold is represented only.
For the manifolds furthest from the FPSO; manifold+spool model in OLGA will
extend from the well jumper tie-in to the flowline tie-in. No pigging loop will be
modelled.
3.5.3
Valves
The following table gives the characteristics of the subsea and topside choke valves
that will be used in the simulation.
At end of life, a topside 6-inch choke valve will generate acceptable pressure drops.
For start-up a 2” choke is also available topside, but currently no Cv curve is
available.
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 18 / 45
Akpo
Project
J12126-RT-001 Rev 0
It has to be noted that the subsea choke is considered +5 m above the mud level
(i.e. the water depth).
3.6
Topside Process
3.6.1
Separator Train
In order to obtain optimum oil production, the oil and gas processing is based on a
four stage separation scheme. The oil, associated gas and produced water from the
wells are separated in a production train consisting of two 1st Stage Separators, a 2nd
Stage Separator, a 3rd Stage Separator and a 4th stage Separator, operating
respectively at 80 bara, 23.5 bara, 9 bara and 2 bara. Each 1st stage separator is
dedicated to one production manifold and is designed for 60% of the inlet production.
The oil stream from the 2nd Stage Separator is heated to about 90 °C in order to
achieve the Reid Vapour Pressure (RVP) specification of crude oil-to-storage (10
psia). The liquid hydrocarbon stream is then routed to the Electrostatic Dehydrator
for final water removal to meet the BS&W specification. The oil is then routed to the
4th Stage Separator for final stabilisation and is then cooled in the Crude Oil Coolers
before being sent to the cargo tanks that are located in the hull for storage. The
crude oil cooler are designed to provide a margin of 5 °C below the crude oil bubble
point at atmospheric pressure in order to avoid any degassing in the storage tank.
3.6.2
Temperature required at first stage separator
The minimum temperature at the inlet of the first stage separator is 50°C for the mix
of the four production loops. The maximum is 92°C. A minimum of 48°C is required
at riser choke to ensure that the 14 hours preservation sequence can be achieved as
per plan.
Genesis France
February 2006
Akpo
Total Upstream Nigeria Limited
AKPO Field Development Project
Project
J12126-RT-001 Rev 0
Page 19 / 45
3.7
Production Lines Characteristics
3.7.1
Insulation Thermal Properties
The following table summarises the characteristics of the insulation materials to be
considered for the OLGA simulations (average values for the operating conditions of
AKPO field). They are in line with the values given from SAIBOS. But as final design
is not yet frozen, the thickness of the insulation (~550mm for the flowlines and risers,
~80mm for the jumpers) should be worked out to obtain a U value of 3.2 W/m²/K.ref.
ID. The final description of the insulation will be made when the contractor will have
frozen its choice.
3.7.2
Pipe Wall Thickness
The following table gives the steel thickness based on preliminary UFR calculations;
the following steel thickness will be used for OLGA simulations:
Production
Jumper
Diameter
Riser
(mm)
Clad
(mm)
Flowline
(mm)
10-inch ID
6-inch OD
27
No
3
No
24.7
14.3
Currently, the clad section is proposed at two locations for production lines:
• at the touch down point, over ± 100 m upstream and downstream the nominal
touch down point (TDP)
• at the riser top, over 50 m below the flexible joint.
Genesis France
February 2006
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Page 20 / 45
3.7.3
Akpo
Project
J12126-RT-001 Rev 0
Pipe Roughness
The following hydraulic roughness will be considered for the flow assurance
calculations:
• Roughness of the production tubing: 1.52e-5 m (15 µm)
• Roughness of the jumper: 4.6e-5 m (46 µm)
• Roughness of the production flow line and the riser: 4.6e-5 m (46 µm)
4 RESERVOIR AND WELL DATA
4.1
Well Architecture
Ten wells architectures have been selected for AKPO field development. The
architecture is summarised in the excel file: WellProgramm-december05.xls, ref [13]
It has been agreed that all the 22 well profiles will not be modelled and that generic
well profiles will be used for pre-defined groups of wells. These generic well profiles
and corresponding groups of wells are defined as follows :
Two generic well profiles for the horizontal wells :
- D_P1 (to be used for wells D_P1, D_P2, D_P3, EF_P1 and EF_P2)
- A9_P1
And Four generic well profiles for the vertical wells :
- G_P1 (to be used for G_P1, A4_P1 and A123_P2)
- G_P2 (to be used for G_P2, A568_P1, A689_P1, B_P2,)
- A456_P1 (to be used for A456_P1, A456_P2, A9_P2, A123_P3)
- B_P1 (to be used for B_P1, A568_P2, A123_P1, A123_P4 and A68_P1)
The curves below show the well profiles for vertical and horizontal wells and highlight
the above groups with corresponding generic well :
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 21 / 45
Genesis France
Akpo
Project
J12126-RT-001 Rev 0
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Akpo
Project
J12126-RT-001 Rev 0
Page 22 / 45
The table hereafter summarizes the generic well profiles that will be used in the
OLGA model, reference being see surface level :
D_P1
x
y
0
-1359
0
-1429
37.02702
-2114
475.8345
-2721
1451.012
-3396
2380.648
-3422
G_P2
x
y
0
-1354
0
-1424
0
-2034
184.1195
-2584
628.1071
-3730
A9_P1
x
y
0
-1330
0
-1400
0
-1993
184.8107
-2494
674.1828
-2956
1467.208
-3012
A456_P1
x
y
0
-1392
0
-1462
0
-2130
441.1632
-2846
702.0464
-3220
G_P1
x
y
0
-1360
0
-1430
0
-2050
46.51881
-2590
128.1828
-3700
B_P1
x
y
0
-1354
0
-1424
34.94281
-2034
463.8484
-2591
833.4495
-3189
Description of well layers as a function of well True Measured depths are
summarized in APPENDIX A.
The well drain and the associated sand control will not be described in OLGA.
It is simply modelled by production index and a reservoir pressure.
4.2
Material Characteristics
The following table summarises the thermal characteristics of the materials to be
used in the well description (from the bottom hole to the wellhead).
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Akpo
Project
J12126-RT-001 Rev 0
Page 23 / 45
The casing architecture of each well will be modelled in OLGA. To maximise the heat
loss through the casing, the surrounding soil will be modelled by a heat transfer
coefficient of 10000 W/m2/°C.
4.3
Reservoir Pressures
The following table gives the initial reservoir pressures that will be used in the OLGA
model :
Reservoirs
Reservoir
True Vertical
Pressure
Depth TVD (m)
(in bara)
A /B
303
3108
D / EF
357
3436
G
422
3770
4.4
Reservoir Temperatures
The initial reservoir temperature depends essentially on the burial depth of the well.
A model with a liner regression was used to perform this evaluation (see memo
“AKPO_Fluid_temperature_Dec04.doc”):
Table 1 Initial reservoir temperatures for reservoir A
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Akpo
Project
J12126-RT-001 Rev 0
Page 24 / 45
Table 2 Initial reservoir temperatures for reservoir B, D, EF & G
4.5
Well Productivity Indexes
The values of productivity index of each well are given in the tables below. This well
PI is a result of ECLIPSE software. For the vertical well (all A wells) the PI are
between 250 blpd/bar to 13 000 blpd/bar but in horizontal wells (B D & EF wells) the
PI could achieved 30 000 blpd/bar.
Tables of Well Productivity Index
Genesis France
February 2006
Akpo
Total Upstream Nigeria Limited
AKPO Field Development Project
Project
J12126-RT-001 Rev 0
Page 25 / 45
4.6
Results Of reservoir Simulations
Summary of the reservoir results per well is given in the tables below.
Location
Res
A123
Res
A456
Res
A458
Res
A678
9
A123_P
1
A123_P
2
A123_P
3
A123_P
4
M 12
A4_P1
A456_P
1
A456_P
2
A568_P
1
A568_P
2
M 12
M 12
M 22
M 12
Res
B
Res
D
Loop
P10
P20
P30
P40
WC >
80% after
Maximum
WC at the
end of
well life
(%)
Associated
liquid
flowrate
(blpd)
Associated
GOR
(Sm3/m3)
16500
8200
350
year 6
-
80
13000
420
15000
7000
400
year 5
-
50
5300
300
year 8
year 11
year 8
21000
10000
320
year 3
year 5
95
1400
310
End of field
life
18500
9000
390
year 5
year 11
87
6300
380
480
year 7
-
70
7000
450
6000
year 18
End of field
life
Year 4
22500
12500
330
year 1
year 6
95
8000
320
M 21
M 11
15000
9000
520
year 7
-
50
6200
370
9000
-
585
-
-
-
-
-
M 11
Year 1
Year 3
M 21
Year 1
17500
21000
8800
8200
330
330
year 2
year 5
year 3
year 14
95
82
16000
4200
310
340
M 31
Year 2
End of field
life
Year 3
13500
5000
480
year 8
-
25
8000
400
M 31
Year 7
16000
8800
540
year 5
year 8
92
3200
410
M 21
Field startup
Year 1
Year 8
14000
9500
340
year 4
-year 5
94
9000
360
M 32
Year 2
End of field
life
Year 18
18700
9000
1090
year 14
-
50
2000
320
19700
-
-
start up
year 12
94
6600
350
29200
-
-
start up
-
33
2000
9000
25300
-
-
start up
-
50
3000
11000
B_P1
B_P2
D_P1
M 32
Year 4
M 21
D_P2
M 42
D_P3
M 42
Field startup
Field startup
Field startup
Year 5
End of field
life
End of field
life
End of field
life
End of field
life
End of field
life
End of field
life
End of field
life
EF_P1
M 43
Year 5
EF_P2
Res
G
Water
break
through
11500
M 31
Res
EF
Field startup
Field startup
Field startup
Field startup
GOR
peak
before
water
break
through
(Sm3/m3)
year 8
A9_P1
A9_P2
End of
Production
Minimum
flowrate
for water
cut - 0
Year 1
Field startup
Field startup
Year 2
M 22
A68_P1
A689_P
1
Start of
Production
Maximum
peak
flowrate
(blpd)
G_P1
M 43
G_P2
M 32
Field startup
Field startup
14200
1000
-
start up
-
0
1000
5500
29000
10000
1080
year 8
year 11
95
22000
750
28300
5000
910
start 8
year 11
95
22000
900
35100
20000
660
year 4
year 10
90
28000
580
37300
17000
600
start 3
start 5
95
15000
560
Well
EF
Well G
Loops Nominal
flow
Right
Header
Left Header
0
0
50200
15000
35200
NA
NA
6
3
3
0
61000
21000
40000
START UP
Well A
Flow rate (blpd)
50200
0
0
Nb of wells
6
NA
NA
Flow rate (blpd)
46000
0
15000
0
Well B
Well D
Nb of wells
5
NA
1
NA
NA
6
3
3
Flow rate (blpd)
16000
7000
0
0
18400
41400
8000
33400
Nb of wells
2
1
NA
NA
1
4
1
3
Flow rate (blpd)
0
0
17500
0
18400
35900
10000
25900
Nb of wells
NA
NA
2
NA
1
3
1
2
Genesis France
February 2006
Akpo
Total Upstream Nigeria Limited
AKPO Field Development Project
Project
J12126-RT-001 Rev 0
Page 26 / 45
Loop
P10
P20
P30
P40
FULL FIELD
Well A
Flow rate (blpd)
44500
0
0
Nb of wells
6
NA
NA
Flow rate (blpd)
28900
0
7500
Nb of wells
5
NA
1
Flow rate (blpd)
7000
12000
0
Nb of wells
2
2
NA
Well B
Well
EF
Well D
Well G
Loops Nominal
flow
Right
Header
Left Header
0
0
44500
26500
18000
NA
NA
6
3
3
0
0
36400
12700
23700
NA
NA
6
3
3
14000
10000
43000
24000
19000
1
1
6
3
3
Flow rate (blpd)
0
0
7500
22500
25000
55000
27000
28000
Nb of wells
NA
NA
2
1
1
4
2
2
The following profile for each loop is revised based on new field layout and on
reservoir management with a design plateau of 185 kbopd for the produced oil and
235 kblpd for the produced liquid. The production rate from each reservoir is given in
these tables with the number of producing wells on each loop considered frozen.
Further details of the field production profiles of the oil, the water and the gas are
given for each well and each loop is given on Appendix 1 to 4 of ref [4].
4.6.1
All Production Loops
Production rate, WC, and GOR per branch is given on the table below. See ref [4],
appendix1 for details.
Loop
4.6.2
P10
P20
P30
P40
Year
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Average
Flow Rate
(blpd)
50200
44500
35500
61000
36400
28400
41400
43000
42500
35900
55000
35750
Water Cut
WC (%)
15
60
75
30
65
75
7
25
80
5
70
60
GOR
(Sm3/m3)
480
340
340
500
1200
2500
580
650
650
450
2000
4000
Production Loop P10
Loop P10
Right Header
Well
Year
Average
Flow Rate
(blpd)
Water Cut
WC (%)
GOR
(Sm3/m3)
Total flow
rate per
branch
A568-P1
Left Header
A123-P1
A123-P2
A568-P2
A4-P1
A123-P4
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
6000
6500
6500
1000
5000
4000
8000
15000
10000
10000
9000
7200
15200
8000
6800
10000
1000
1000
45
85
95
0
55
90
0
10
60
5
60
90
0
60
85
0
85
85
530
370
370
330
310
320
430
320
310
400
400
400
380
350
350
380
340
340
Genesis France
15000
26500
20500
35200
18000
February 2006
15000
Akpo
Total Upstream Nigeria Limited
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Project
J12126-RT-001 Rev 0
Page 27 / 45
4.6.3
Production Loop P20
Loop P20
Right Header
Well
A9-P2
Year
Average
Flow Rate
(blpd)
Water Cut
WC (%)
GOR
(Sm3/m3)
Total flow
rate per
branch
4.6.4
A456-P1
D-P2
A68-P1
A123-P3
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
5000
3200
2000
6000
2000
1000
10000
7500
6500
15000
7500
3500
15000
8500
8000
10000
7700
7400
20
90
90
0
45
70
35
70
90
0
7
7
5
70
85
40
88
90
350
360
360
450
370
370
380
370
370
600
2500
3700
350
350
350
350
350
350
21000
12700
9500
40000
23700
18900
Production Loop P30
Loop P30
Right Header
Well
EF-P2
Year
Average
Flow Rate
(blpd)
Water Cut
WC (%)
GOR
(Sm3/m3)
Total flow
rate per
branch
4.6.5
Left Header
A456-P2
Left Header
A689-P1
B-P1
A9-P1
B-P2
G-P2
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
0
14000
27000
8000
2000
2000
0
8000
5000
8000
5000
2000
7000
4000
2000
18400
10000
4500
0
0
85
0
50
90
0
40
70
0
53
70
0
15
30
15
90
90
0
900
800
480
350
350
0
330
320
1000
380
380
600
550
350
580
580
580
8000
24000
34000
33400
19000
8500
Production Loop P40
Loop P40
Right Header
Well
Left Header
D-P1
Year
Average
Flow Rate
(blpd)
Water Cut
WC (%)
GOR
(Sm3/m3)
Total flow
rate per
branch
10000
Note:
Genesis France
EF-P1
D-P3
G-P1
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
Early
Mid
Late
10000
4500
2500
0
22500
12250
7500
3000
1000
18400
25000
20000
0
0
0
0
70
95
0
0
0
0
65
80
500
4500
5500
0
800
800
480
5000
20000
580
580
580
27000
Early
14750
Mid
25900
28000
21000
Late
February 2006
Akpo
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 28 / 45
Project
J12126-RT-001 Rev 0
5 FLUID COMPOSITION
A first model will consider an average composition consistent to the HYSYS model
for topside simulations. Same composition will be attributed to all wells and is given
below (from ref 16):
Average well fluid composition used in HYSYS simulations
Genesis France
February 2006
Akpo
Total Upstream Nigeria Limited
AKPO Field Development Project
Project
J12126-RT-001 Rev 0
Page 29 / 45
Below is given the hypothetical component data:
Name
C6*
C7*
C8*
C9*
C10*
C11*+
C12*
C13*
C14*
C15*
C16*
C17*
C18*+
C19*
CN2*
CN3*
NBP (°C)
69.11
99.25
126.3
151.9
174.3
188.7
204.6
217.6
233
253.1
269.7
287.9
300.9
313.5
370.6
498.3
Genesis France
Mol Wt
85.11*
98.40*
111.7*
125.2*
137.8*
149.0*
163.0*
176.0*
191.0*
207.0*
221.0*
237.0*
249.0*
261.0*
320.0*
475.0*
Liq
Density
(kg/m3)
685.0*
722.0*
745.0*
764.0*
778.0*
789.0*
800.0*
811.0*
822.0*
832.0*
839.0*
847.0*
852.0*
857.0*
877.0*
914.0*
Tc (°C)
240.0*
280.0*
310.0*
345.0*
385.0*
390.0*
402.0*
417.0*
435.0*
452.0*
467.0*
480.0*
470.0*
480.0*
644.0*
800.0*
Pc (bar)
Vc
Acentricity
(m3/kgmole)
32.73*
30.97*
28.42*
27.24*
26.50*
24.82*
23.42*
22.24*
21.09*
19.93*
19.05*
18.20*
17.30*
16.80*
16.70*
14.25*
0.3800*
0.4300*
0.5000*
0.5300*
0.5600*
0.6269*
0.6858*
0.7405*
0.8036*
0.8710*
0.9299*
0.9972*
1.048*
1.098*
1.141*
1.565*
0.2590*
0.2790*
0.3250*
0.3440*
0.3780*
0.3960*
0.4140*
0.4320*
0.4590*
0.4770*
0.5040*
0.5220*
0.5400*
0.5490*
0.7700*
0.9200*
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 30 / 45
Akpo
Project
J12126-RT-001 Rev 0
In addition to that typical case, a more accurate model will be built based on true
composition per well.
Throughout the lifetime of the AKPO field, the compositions of the different reservoirs
evolve significantly see ref [8]. This is particularly true for the reservoir panels
supported by gas injection, where the GOR varies from around 300 Sm³/Sm³ to
around 8000 Sm³/Sm³ over the field life.
In order to perform representative characterisation of flowing conditions throughout
the lifetime of the AKPO field, three compositions were selected for each well type
(A; B; D; EF; G) to represent early, mid and late field life.
The reservoir fluid is complex, varying from gas/condensate at the top of the
reservoir to light oil at the base. During field life, the fluids produced from the
reservoir panels supported by water injection will become heavier with time
(hydrocarbon produced from the top, with water injected at the base). On the
contrary fluids produced from reservoir panels supported by gas injection will
become lighter with time, with a high potential for gas breakthrough to occur.
• For reservoirs supported by water injection, compositions were taken from the Top,
Middle and Bottom of the reservoir to represent Early, Mid and Late Life.
• For reservoirs supported by gas injection (D type wells), compositions were taken
from the Bottom of the reservoir for Early Life. For Mid Life, the composition was
taken from a reservoir depth yielding a GOR of around 3000 Sm³/Sm³. For Late Life,
the composition was provided with a corresponding GOR of around 8000 Sm³/Sm³,
as this period covers operation following gas breakthrough and the composition
cannot be directly derived from the PVT analysis.
The molar compositions (on a dry basis) for each well type are provided in the
following table, completed with the corresponding GORs.
Note:
The water cut of the produced fluid is determined from the production profiles of
each well (see chapter above).
Regarding the GOR, it is important to note that the average GOR value for A wells
(<500 Sm3/m3) resulting from this composition is largely below the one issued from
the reservoir simulation that reaches up to 970 Sm3/m3 for some A wells.
Genesis France
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Page 31 / 45
Akpo
Project
J12126-RT-001 Rev 0
For reservoir A and G, latest reservoir shall be used and the fluid composition for
these two wells are summarized hereafter :
Genesis France
February 2006
Akpo
Total Upstream Nigeria Limited
AKPO Field Development Project
Project
J12126-RT-001 Rev 0
Page 32 / 45
Well type A
Depth
Early
Mid
Later
mSL
-3040
-3160
-3300
N2
0.105
0.100
0.095
CO2
C1
C2
C3
IC4
NC4
IC5
NC5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
0.135
62.544
7.704
4.360
1.609
2.066
1.393
0.982
2.867
3.367
2.653
2.008
1.769
1.088
0.885
0.858
0.726
0.535
0.440
0.344
0.277
0.258
0.120
59.633
6.880
4.463
1.647
2.115
1.521
1.073
3.130
3.676
2.896
2.372
2.090
1.285
1.045
1.013
0.902
0.665
0.546
0.427
0.344
0.320
0.106
56.928
6.036
4.522
1.669
2.142
1.625
1.146
3.344
3.927
3.094
2.701
2.379
1.463
1.190
1.154
1.068
0.787
0.646
0.506
0.407
0.379
CN2
0.593
0.928
1.337
CN3
0.432
0.809
1.349
Total
100
100
100
Table 3 Fluid composition for reservoir A
Genesis France
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Project
J12126-RT-001 Rev 0
Page 33 / 45
Wel type G
Depth
Early
Mid
Later
mSL
-3644
-3674
-3694
N2
0.078
0.077
0.075
CO2
C1
C2
C3
IC4
NC4
IC5
NC5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
0.918
64.063
8.500
5.134
1.692
1.955
1.420
0.983
2.737
3.153
1.819
1.805
1.403
0.787
0.609
0.600
0.427
0.344
0.275
0.224
0.217
0.167
0.915
62.507
8.479
5.200
1.713
1.980
1.494
1.034
2.880
3.318
1.914
1.980
1.540
0.863
0.668
0.658
0.482
0.389
0.310
0.252
0.245
0.188
0.913
61.449
8.458
5.237
1.726
1.994
1.542
1.068
2.973
3.425
1.976
2.100
1.633
0.915
0.708
0.698
0.520
0.420
0.335
0.273
0.264
0.203
CN2
0.434
0.555
0.650
CN3
0.260
0.361
0.447
Total
100
100
100
Table 4 Fluid composition for reservoir G
Note:
The above compositions have been extracted from the PVT Synthesis report of Jan
2006, for different reservoir depths, in order to obtain compositions corresponding to
Early, Mid and Late Life operation.
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 34 / 45
Akpo
Project
J12126-RT-001 Rev 0
6 SCOPE OF WORK
The main objectives of this first study are to build a dynamic model using the design
basis described previously, and to perform several OLGA runs in steady state and
transient conditions to ensure that the model is working correctly and give results
similar to what was found during Basic Engineering.
6.1
Software
The following software will be used:
PVTsim version 4.15.0 in order to characterise the fluids and create the PVT tables
OLGA 2000 standard version 3.02 was used during basic engineering. But the new
release 4.16 was bench mark during FA impact due to the new layout [4]. This
revision as well as 4.17.3 can be used for the multiphase flow dynamic simulations.
Compositional and slug tracking options will have to be available when required.
6.2
OLGA Model
Four OLGA models will be built, one for each production loop P10, P20, P30 and
P40. Hence the all production network will be modelled.
Each OLGA model will include wells, jumpers, manifolds, spools, flowlines, risers,
subsea chocke valves at each wellhead and topsides choke valves at each riser top.
All the production wells will be modelled with the WELL keyword in OLGA by using
the following parameters : reservoir Static Bottom Hole Pressures, reservoir
temperatures and reservoir productivity indexes. In the simulations, the required
flowrate per well will be obtained by adding a controller at wellhead that will act on
the subsea choke opening. Topside pressure will be fixed at 80 bara at the FPSO
(pressure at the first stage separator at early field life).
The model will be built to allow easy update/modification of most critical parameters
which are likely to change during the project phase :production modification, well
allocation to branches, branches allocation to manifolds (production or test), etc…
For that purpose it is proposed to provide a detailed description of the OLGA input
files in order to quickly identify where the required modifications need to be
performed.
The PVT tables needed to perform the simulations described in § 6.3 will be built
based on the reservoir composition given in the design premise. Equation of state
Peng Robinson with Peneloux volume correction will be used, and Corresponding
States (CSP) for viscosity correlation. The fluid GOR and water cut will be tuned to
meet the values given in the production profile per well.
Genesis France
February 2006
Akpo
Total Upstream Nigeria Limited
AKPO Field Development Project
Project
J12126-RT-001 Rev 0
Page 35 / 45
It is also highlighted that all the required modifications to be performed on the OLGA
subsea modelling prior to its link to the topside HYSYS model will be performed by
the topside dynamic simulation contractor (modification/addition of OLGA output
variables, modification of topside arrangement…). It is not considered part of this
scope to prepare the model to take these changes into considerations.
6.3
OLGA 2000 Simulations
Aim of the simulations presented below is to ensure that the OLGA models are
working correctly in typical steady state and transient scenarios. Sequences and
timing of the simulations have been fixed arbitrary and do not correspond necessarly
to the AKPO preservation and operating procedures. Review and optimisation of
these procedures could be further addressed in a separated scope.
The following simulations will be performed with the models :
6.3.1
Steady State Runs
The following steady state cases will be performed, selected to be representative of
early field life:
Loop P10
Right Header
Left Header
Well
A568-P1
A123-P1
A123-P2
A568-P2
A4-P1
A123-P4
Year
Average Flow Rate
(blpd)
Early
Early
Early
Early
Early
Early
6000
1000
8000
10000
15200
10000
Water Cut WC (%)
45
0
0
5
0
0
GOR (Sm3/m3)
530
330
430
400
380
380
Loop P20
Right Header
Left Header
Well
A9-P2
A456-P2
A456-P1
D-P2
A68-P1
A123-P3
Year
Average Flow Rate
(blpd)
Early
Early
Early
Early
Early
Early
5000
6000
10000
15000
15000
10000
Water Cut WC (%)
20
0
35
0
5
40
GOR (Sm3/m3)
350
450
380
600
350
350
Loop P30
Right Header
Left Header
Well
EF-P2
A689-P1
B-P1
A9-P1
B-P2
G-P2
Year
Average Flow Rate
(blpd)
Early
Early
Early
Early
Early
Early
0
8000
0
8000
7000
18400
Water Cut WC (%)
0
0
0
0
0
15
GOR (Sm3/m3)
0
480
0
1000
600
580
Loop P40
Right Header
Left Header
Well
D-P1
EF-P1
D-P3
G-P1
Year
Average Flow Rate
(blpd)
Early
Early
Early
Early
10000
0
7500
18400
Water Cut WC (%)
0
0
0
0
GOR (Sm3/m3)
500
0
480
580
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 36 / 45
Akpo
Project
J12126-RT-001 Rev 0
After presenting the results for the early field life, TOTAL may require results for Mid
and Later field life. In a first approach these cases are considered optional and will
be the subject for a variation.
Results of these simulations will be compared against results of the Basic
Engineering. Acceptance criteria for this benchmark exercise will be further
discussed with TOTAL once results are available.
6.3.2
Branch Packing
The branch packing simulations will be performed from a restart of the above steady
state cases.
The simulation sequence for the branch packing will be to close the topsides choke
valves over 30 seconds allowing the wells to continue flowing by keeping the
production wing and production choke valve open. This caused the wells to pack the
branch.
For these simulations, controlers will be removed from the model and wellhead valve
opening will be set at the one defined by the controllers in the steady state runs.
6.3.3
Cooldown
The cooldown simulations will be performed from a restart of the above branch
packing cases.
The simulations will allow the pipeline to settle out and cooldown for a duration fixed
at 14 hours.
6.3.4
Depressurisation
The depressurisation simulations will be performed from a restart of the above
cooldown cases.
Target pressure of this depressurisation will be fixed at 20 bara at topside and
depressurisation rate will be adjusted in order to depressurise each loop in one hour.
However depressurisation of each loop is initiated in sequence. The depressurisation
sequence of all loops will last less than 3 hours.
The simulations will utilise the LEAK function of OLGA with a fixed size orifice.
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 37 / 45
6.3.5
Akpo
Project
J12126-RT-001 Rev 0
Start-up sequence
Start-up simulations will be performed from a restart of the above depressurisation
cases.
Wells will be started-up in sequence with a ramp-up time of 3 hours to reach the well
nominal flowrates defined in § 6.3.1 (steady state nominal flowrates at early field
life). As for steady state cases, topsides pressure will be fixed at 80 bara.
Usually this kind of simulations, where several wells with different fluid compositions
are brought into production, require the use of OLGA compositional tracking module
(fluid composition not constant in the production loop).
However as this start-up sequence is just simulated to ensure that the model is
working correctly, it is proposed that PVT files of steady state simulations (§6.3.1)
are used to simulate the start-up sequence. Use of compositional tracking module
could be considered in a separate scope if review and optimisation of operating
procedures is requested afterwards.
6.3.6
Slugging analysis
Simulations will be performed to determine the extent of slugging in the production
flowlines and risers.
In addition to assessing slugging at production profile rates at early field life (§ 6.3.1),
the minimum turndown rate that avoid slugging issues will be established for the four
production loops.
In the OLGA model, wells and jumpers will be removed and flowrates will be applied
at manifolds. OLGA slugtracking option will be used for these simulations.
It is highlighted that only early field life will be studied within the scope of this study.
Mid and late field life will have to be studied separately.
This model may be used by others (OCWR contractor) to investigate the slug control
aspect.
6.4
Deliverables
The deliverables of this study will be :
Four models of the subsea production network : P10, P20, P30, and
P40
A list of the available runs with a description and potential case
associated
File descriptions
Genesis France
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Project
J12126-RT-001 Rev 0
Page 38 / 45
6.5
Akpo
Schedule
This study could be started as soon as both parties agree on this design premise.
The OLGA model should be made available to Topside simulation sub-contractor to
be interfaced with topside simulations, and also to support the OTS (Operator
Training Simulator) scope.
Planned duration for this scope of work :
Genesis France
9 weeks
February 2006
Akpo
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 39 / 45
Project
J12126-RT-001 Rev 0
APPENDIX A
Generic Well Layer Descriptions
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February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 40 / 45
Genesis France
Akpo
Project
J12126-RT-001 Rev 0
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 41 / 45
Genesis France
Akpo
Project
J12126-RT-001 Rev 0
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 42 / 45
Genesis France
Akpo
Project
J12126-RT-001 Rev 0
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 43 / 45
Genesis France
Akpo
Project
J12126-RT-001 Rev 0
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 44 / 45
Genesis France
Akpo
Project
J12126-RT-001 Rev 0
February 2006
Total Upstream Nigeria Limited
AKPO Field Development Project
Page 45 / 45
Genesis France
Akpo
Project
J12126-RT-001 Rev 0
February 2006