Drilling and Intervention Riser Tensioner Load Modelling ... gallagher.pdf · Drilling and Intervention Riser Tensioner Load Modelling and its ... Accumulator Air ... Anti-Recoil

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


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


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


Wellhea d a nd C onduc tor S ys tem


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


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


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)


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.


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


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


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


1275 kips

725 kips

75 kips

1590 kips


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)




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


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


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


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


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


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


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?

Documents

Drilling and Intervention Riser Tensioner Load Modelling ... gallagher.pdf · Drilling and Intervention Riser Tensioner Load Modelling and its ... Accumulator Air ... Anti-Recoil