drilling and intervention riser tensioner load modelling and
TRANSCRIPT
E xperienc e that Delivers
Drilling and Intervention Riser Tensioner Load Modelling and its Impact on Wellhead Fatigue and Riser Loading Subsea 2012 Exhibition & Conference 8th Feb
Dr illing & Wells Divis ion
Conor Gallagher
1 E xperienc e that Delivers
Introduc tion
• Wellhead & conductor fatigue loading key importance in offshore well design • Deepwater oil and gas exploration (>10,000ft) – Modern vessels • Modern tensioning systems - Complex hydro-pneumatic systems • Detailed tensioner model - Includes individual hydraulic and pneumatic
components (DeepRiser TM)
• Existing modelling and API recommended practices • Accurate assessment of expected fatigue damage and riser loading
2 E xperienc e that Delivers
P res entation Outline
• Description of Riser, Wellhead and Conductor Systems • Overview of Marine Riser Direct Acting Tensioners (DAT) • Existing Industry Modelling Techniques for Wellhead Fatigue/Riser Loading • Case Study #1 - Offshore Brazil (7,000ft Water depth) – Riser Loading
• Case Study #2 - North Sea (4,000ft Water Depth) – Wellhead Fatigue
3 E xperienc e that Delivers
Wellhea d a nd C onduc tor S ys tem
Conductor Connector
(Weld & Body)
Low Pressure Wellhead Housing (LPWHH)
Conductor Weld
High Pressure Wellhead (HPWH)
Wellhead Weld
Rigid Lock Down 36” Conductor
20” Casing
4 E xperienc e that Delivers
Wellhea d a nd C onduc tor S ys tem
5 E xperienc e that Delivers
Direc t A c ting Tens ioner S ys tem (DAT )
• Slip Ring – Direct Connection • Trip Saver • Up to 5,000,000 lbs Capacity • 50ft Stroke Capacity • Manufacturer – NOV N-Line, Aker
MH • Vessels – 5th & 6th Generation
6 E xperienc e that Delivers
Direc t A c ting Tens ioner S ys tem (DAT )
LP NitrogenAccumulator
Air Pressure Vessels(APVs)
HP Air/OilAccumulator
Anti-RecoilValv e
Shackle Connection toVessel
Shackle Connection toTension Ring
Tensioner Piston and Rod
Tensioner Cy linder- HP Side
Tensioner Cy linder- LP Side
PLC
Flexible Hose
Flexible Hose
TensionerStrokeSignal
1
2
3
4
5 5
6 7
8
7 E xperienc e that Delivers
Dyna mic C ha ra c ter is tic s – DAT S ys tem
xF ix - cy lsupportp - cy loilsideF - cy lsupportv F ix - cy lsupportm/s
-3
-2
-1
0
1
2
3
kN
1000
0
-1000
-2000
-3000
-4000
bar
0
20
40
60
80
100
120
140
160
180
200
m
-8
-6
-4
-2
0
2
4
6
8
15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60
s
Piston Stroke (m) Piston Velocity (m/s)
Cylinder Load (KN)
Cylinder Pressure (bar)
8 E xperienc e that Delivers
C a s e S tudy #1 – Offs hore B ra zil, 7,000ft Water Depth
• Location – Offshore Brazil • Water Depth – (approx 7,000ft) • Max Connected Seastate – (based on 8m
allowable vessel heave) • Max Drilling Seastate – (based on 5m allowable
heave) • Mud weight – Max 12ppg • Tensioning System – 6 Cylinder DAT System
rated to 3600 kips • Key Requirements – Maintain positive riser
tension and keep wellhead loading to a minimum.
9 E xperienc e that Delivers
C a s e S tudy #1 – Top Tens ion Methodology
API RP 16Q
Tmin = TSRmin N/[Rf (N-n)]
Tension (kips) 1515
Mud (ppg) 10
TSRmin (kips) 1200
N 6
n 1
Rf 0.95
Detailed Tensioner Model
Seastate – Max Connected
Tension (kips) 1920
Mud (ppg) 10
TSRmin (kips) 1200
N 6
n 1
Rf
Detailed Tensioner Model – Iterate on top tension for given seastate to achieve positive tension at base of riser (factored up by 1.2 to account for 1 tensioner failure)
0.75
10 E xperienc e that Delivers
C a s e S tudy #1 – Top Tens ion V Wellhea d Tens ion
-500
0
500
1000
1500
2000
2500
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Tens
ion
(kip
s)
Hs (m)
Recommended Top Tension 8.56ppg Recommended Top Tension 9ppg Recommended Top Tension 10ppgRecommended Top Tension 11ppg Recommended Top Tension 11.7ppg Wellhead Tension 8.56ppgWellhead Tension 9ppg Wellhead Tension 10ppg Wellhead Tension 11ppgWellhead Tension 11.7ppg
Wellhead Tension occurs when Top Tension > Weight Riser + LMRP + BOP
11 E xperienc e that Delivers
C a s e S tudy #1 – Wellhea d Tens ion Va r iations
0 10 20 30 40 50 60 70 80 90Time (s)
-500
-250
025
050
075
010
0012
5015
00Ef
fect
ive
Tens
ion
(kip
s)
Max Connected, Top Tension= 1920 kips
Max Drilling, Top Tension= 1920 kips
Max Drilling, Top Tension= 1690 kips
1275 kips
725 kips
75 kips
1590 kips
12 E xperienc e that Delivers
C a s e S tudy #1 – R is er S tres s C ompa r is on
0 10 20 30 40 50Von Mises Stress Envelope (ksi)
010
0020
0030
0040
0050
0060
0070
0080
00Di
stan
ce a
long
the
Rise
r (ft)
Max Drilling, Top Tension= 1920 kips
Max Drilling, Top Tension= 1690 kips
13 E xperienc e that Delivers
C a s e S tudy 1# – Deta iled Tens ioner Model With A P I Top Tens ion
0 10 20 30 40 50 60 70 80 90Time (s)
-100
0-5
000
500
1000
1500
Effe
ctiv
e Te
nsio
n (k
ips)
-500 0 500 1000 1500 2000 2500 3000Effective Tension Envelope (kips)
010
0020
0030
0040
0050
0060
0070
0080
00Di
stan
ce a
long
the
Rise
r (ft)
Max Connected, Top Tension=1920 kips, 7000ft
Max Connectd, API Top Tension=1515 kips, 7000ft
Compression
14 E xperienc e that Delivers
C a s e S tudy #1 – S ha llow Water (1,000ft) - Wellhea d Tens ions
0 10 20 30 40 50 60 70 80 90Time (s)
-100
0-5
000
500
1000
1500
Effe
ctiv
e Te
nsio
n (k
ips)
Max Connected, Top Tension= 1920 kips, 7000ft
Max Connected, Top Tension= 1050 kips, 1000ft
1590 kips
1125 kips
15 E xperienc e that Delivers
C a s e S tudy #2 – Nor th S ea , 4200ft Water Depth
• Location – North Sea • Water Depth – 4,200ft • Vessel – 6th Generation • Tensioning System – 6 Cylinder DAT System
rated to 3600 kips • Wellhead Stick-up – 12ft • Conductor System – 36” x 20” – 200ft BML • Soil Type – Soft • Objective – Assess Fatigue Damage –
Detailed V Simplified Tensioner
16 E xperienc e that Delivers
C a s e S tudy #2 – E ffec t of Tens ioner Model on Fatigue L ife (yrs )
• Riser: SCF=1.3, DnV E Curve Conductor: SCF=5.0, DnV B1 Curve
• Unfactored Fatigue Life
Location Detailed Tensioner model Simplified Tensioner model
0m offset
6.5m offset
13m offset
0m offset
6.5m offset
13m offset
Drilling Riser 124.5 117.6 123 112.5 115.3 118.7
LPWHH Weld 2.5 0.74 0.10 4.2 0.72 0.15
36-inch Conductor 9.3 2.2 1.9 3.7 2.2 1.8
17 E xperienc e that Delivers
C a s e S tudy #2 – E ffec t of Tens ioner Model on Fatigue L ife (yrs )
1
10
100
1000
10000
100000
1000000
10000000
0 500 1000 1500 2000 2500 3000 3500 4000 4500
Fati
gue
Lif
e (y
rs)
Distance Above Mudline (ft)
Riser Fatigue Life
1300m-Base Case-Default Tensioner
1300m-0.5% offset-Default Tensioner
1300m-1% Offset-Default Tensioner
1300m-Base Case-Detailed Tensioner
1300m-0.5% offset-Detailed Tensioner
1300m-1% Offset-Detailed Tensioner
-60
-50
-40
-30
-20
-10
0
10
110100100010000100000100000010000000
Elev
atio
n w
.r.t
. Mud
line
(ft)
Fatigue Life (yrs)
Conductor Connector Fatigue Life
1300m-0.5% offset-Default Tensioner
1300m-1% Offset-Default Tensioner
1300m-Base Case-Default Tensioner
1300m-Base Case-Detailed Tensioner
1300m-0.5% offset-Detailed Tensioner
1300m-1% Offset-Detailed Tensioner
Telescopic Joint Location
60% Reduction
18 E xperienc e that Delivers
K ey C onc lus ions
• Accurate Fatigue & Riser modelling must incorporate tensioner load variations – Drilling & Intervention Fatigue Budgets
• Modern tensioning systems - Large wellhead tensions and stress ranges
for large seastates • Existing API top tension recommendations – Riser compression • Accurate seastate forecasting – Reduce top tensions and risk of
wellhead fatigue issues • Tension primarily dependent on stroke velocity - Independent of water
depth
19 E xperienc e that Delivers
A c k nowledgements
• Dara Williams (MCSK) • Donogh Lang (MCSK) • John Greene (MCSK)
E xperienc e that Delivers
Thank you
Any questions?
Thank You
Any Questions?