Introduksjon til gassløftbrønner for
risikoanalytikere
ESRA seminar, September 3, 2014, Stavanger
Per Holand, ExproSoft
No gas lift
Gas lifted well, without ASV
Gas lifted well, with ASV
P
P
PT TT
Platform deck
PT TT
Platform deck
Seabed
Volume above
ASV: 5 m3
Gas volume:
80 m3
Gas lift gas
Reservoir fluid
Volume below
ASV: 75 m3
Gas lift valves (GLVs, typical
1500 - 3000m MD)
Gas lift valves (GLVs, typical
1500 - 3000m MD)
Gas lifted well, No ASV with
ASCV and MSAS/HSAS
Gas lifted well, No ASV with ASCV
P
P
Blind flange
Blind flange
SWAB
(manual)
SWAB
(manual)
PT TT
PT TT
Choke (No barrier)
Choke (No barrier)
B-area
B-area
AFV (manual)
AFV (manual)
HMV
HMV
Hydraulic line (SCSSV)
Hydraulic line (SCSSV)
MMV (manual)
MMV (manual)
Manual gate valve
Hydraulic failsafe
closed gate valve
Hydraulic failsafe
closed gate valve
ACSV
ACSV
P
Blind flange
MSAS/HSAS
Platform deck
Platform deck
Seabed
Seabed
SCSSV
SCSSV
Gas volume:
80 m3
Gas volume:
80 m3
Gas lift valves (GLVs, typical
1500 - 3000m MD)
Production packer
Gas lift valves (GLVs, typical
1500 - 3000m MD)
Production packer
Retrofit, with GLV in straddle and H-ASCV in
wellhead
Base case: Conventional gas lift
with ASV, 1 - 4 GLVs
P
To flare
P
To flare
PT TT
From gas
lift manifold
PT TT
From gas
lift manifold
FCV
HV (normally
closed, fail as is)
PT
Wing valve
(hydraulic)
Hydraulic
Master Valve
HV (normally
closed, fail as is)
Hydraulic line (WR-SCSSV)
Scale inhibitor line
Hydraulic line (ASV)
X-mas tree
connector
seal
C-area
VR-plug
Blind flange
PT
FCV
PT
Hydraulic
Master Valve
X-mas tree
connector
seal
H-ASCV in dedicated block
PT
HV (failsafe
closed)
ESV (fail-safe
closed)
Continuous monitoring
PT
P
PT
HV (failsafe ESV (failclosed)
safe closed)
P
Platform deck
Key factors, both
designs:
Platform deck
• Permanent annulus
blowdown system
Wing valve
(hydraulic)
• The second outlet from
the wellhead will be
blinded off
• The B-annulus will be
VR-plug
continuously monitored
Blind flange
• Relatively small annulus
Continuous monitoring
volumes compared to
other gas lifted wells
P
P
Seabed
Seabed
WR-SCSSV (typical depth 280 m RKB)
WR-SCSSV
SCASV (typical depth 300m RKB)
Annulus volume typical
24 m3 (14 - 42 )
Gas lift valves (GLVs, typical 1500 3000m MD, up to 4 valves)
Annulus volume
typical 24 m3 (14
- 42 )
GLV in straddle
Scale inhibitor line w/check valve
13 3/8” csg, 72 lb/ft,
non gas tight threads
13 3/8” csg, 72 lb/ft,
non gas tight threads
Production packer (2000 m - 6000m
MD, Typical 3400 m MD)
Production packer (2000 m - 6000m
MD, Typical 3400 m MD)
Reservoir fluid
Reservoir fluid
Gas lift gas
Gas lift gas
Closed during
production
Closed during
production
Open during
production
Open during
production
Corrosion cap
(no barrier)
Annulus Wing
Valve (GLV)
Workover
valve
(WOV)
2" line gas lift line
Upper
crown plug
(THUCP)
Lower
crown plug
(THLCP)
Crossover
Valve (XOV)
AWV
TT PT
PT
Production Wing Valve (PWV)
TT
Annulus Master Valve (AMV)
PT
TT PT
Tubing hanger
Production Master Valve (PMV)
Production Wing Valve (PWV)
TT
Tubing hanger
Wellhead connector w/gasket
Production Master Valve (PMV)
Wellhead connector w/gasket
9.5 m3 Gas lift gas above ASV
7" TR-SCSSV,
TR SCSSV flapper (600 m TVD=MD)
TVD MD)
ASV (optional, approximately 650 m TVD = MD)
41 m3 Gas lift gas in annulus
Production fluids
7" tubing (32 lbs/ft CrS-110 )
7" tubing (32 lbs/ft CrS-110 )
A-annulus fluids
Normally open valve
Normally closed valve
31 m3 Gas lift gas below ASV
GLV (Gas lift valve)
PBR
DIACS Assembly
Production packer
GLV (Gas lift valve)
7" TR-SCSSV, flapper (just above packer)
PBR
Production packer
All depths related to MSL
• Base Case: Gas lifted subsea
production wells with ASV and shallow
set TR-SCSSV
• Case III: Gas lifted subsea production
wells with no ASV and deep set TRSCSSV
Annulus gas volumes
Field
Ekofisk typical
Ekofisk M
Statoil Retrofit
Brage
Skinfaks/Rimfaks
Norne
Tyrihans
Fossekall
Dompap
Hyme
Havis
Skrugard
Maria
Ivar Aasen
•
Typical volumes of gas lift gas (m3)
Above ASV Below ASV
Total
4,3
72,0
76,3
4,2
153,0
157,2
2,5
24,0
26,5
13,0
104,0
117,0
9,5
31,0
40,5
2,6
33,4
36,0
2,8
44,0
46,8
3,0
26,0
29,0
3,0
29,0
32,0
2,5
20,5
23,0
2,3
8,2
10,5
2,3
5,0
7,3
10,0
95,0
105,0
6,6
26,6
33,2
Inlet gas
pressure (bar)
125
125
130
130
245
200
310
295
295
200
186
150
330
150
Note that other, not well related, volumes of gas can be much higher
•
Export risers
•
Gas lift flowlines subsea
IN COMMERCIAL CONFIDENCE
•
Gas injection flowlines subsea
Platform or
subsea
Platform
Platform
Platform
Platform
Subsea
Subsea
Subsea
Subsea
Subsea
Subsea
Subsea
Subsea
Subsea
Platform
6
Leak rate vs. time and volume in annulus (equivalent hole size
2.67 mm)
0.16
80 m3 (original study)
0.14
Typical time dependant
leak rates associated to
typical failures, example
from platform completed
wells
5 m3 (original study M design)
153 m3 (M well design)
Leak rate (kg/s)
0.12
0.1
0.08
0.06
0.04
0.02
0
0
10
20
30
40
50
60
Time (minutes)
Leak rate vs. time and volume in annulus (equivalent hole size
12.5 mm)
Leak rate vs. time and volume in annulus (equivalent hole size
37.5 mm)
2.5
25
80 m3 (original study)
5 m3 (original study & M design)
80 m3 (original study)
153 m3 (M well design)
5 m3 (original study & M design)
20
153 m3 (M well design)
Leak rate (kg/s)
Leak rate (kg/s)
2
1.5
1
0.5
15
10
5
0
0
10
20
30
Time (minutes)
40
50
60
0
0
10
20
30
Time (minutes)
40
50
60
ASV closing time
IN COMMERCIAL CONFIDENCE
Key elements in risk analyses
•
•
•
•
•
•
•
•
•
•
•
•
•
Annulus volumes - above and below ASV
Annulus pressures
Annulus barriers wellhead, gas inlet side
Annulus barriers wellhead, monitoring side
ASV or not in the well
ASV closing time
Surface leak rates and associated probabilities
Gas lift valve reliability (scale affected)
No. of GLVs
Water depth for subsea completions
ASV related workover risk
DHSV below GLVs or not
Blowout risk through annulus
IN COMMERCIAL CONFIDENCE
10