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Page 1: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,
Page 2: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Guidelines for Drilling Riser Joint Integrity

GUIDELINES FOR DRILLING RISER JOINT INTEGRITY

by Dr Hugh Howells

2H Offshore Inc

Fry Road, Houston

Presented at the Deepwater Riser System Management Forum, Pennwell, League City, Texas, June 2000

ABSTRACT The characteristics of deepwater drilling riser systems that influence integrity requirements and loss of integrity are as follows: • Higher tensions, placing increased importance on wall thickness and which may accelerate fatigue crack growth

in the riser; • Larger curvatures, promoting the possibility of wear from drill string rotation; • Vortex induced vibrations due to severe currents, which can generate high levels of fatigue damage in short

periods of time; • Longer drill string having increased tension, increasing wear at the top of the riser; • Longer and heavier riser joints, more difficult to handle with increased scope for damage during riser running

and retrieval; • Greater internal pressures from mud head placing increased importance on wall thickness for hoop load

resistance; • Greater external pressures from water column, placing increased importance on wall thickness and dimensional

tolerances for collapse resistance; • Load sharing between riser tube and choke and kill lines placing increased importance on integrity of choke and

kill lines for overall structural integrity. The potentially greater rates of wear and fatigue damage accumulation and increased importance of wall thickness integrity for deepwater indicate that traditional inspection practices used for shallow water operations may need to be revised for deepwater drilling. When initiating a drilling programme in deep water or harsh environments, the riser inspection strategy must therefore be re-evaluated to take account of the severity of the operating conditions. As part of an industry initiative for developing guidance for drilling riser usage in deepwater, 2H Offshore Inc were contracted to develop guidelines for drilling riser joint integrity. This work consisted of the following activities: • Review of current practice for monitoring riser usage; • VIV fatigue analysis of 2 case study drilling riser; • Fracture analysis and inspection methods assessment; • Requirements for riser record keeping. The findings of this work, which form the basis of the integrity assessment guidelines being developed, are reported in this paper.

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Page 3: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

GUIDELINES FOR DRILLINGRISER JOINT INTEGRITY

by

Dr Hugh Howells

2H Offshore Inc

Presented at the Deepwater Riser System ManagementForum,

League City, Texas, June 2000Learn more at www.2hoffshore.com

Page 4: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Introduction

• Characteristics of deepwater drillingrisers

• VIV - effects and implications

• Wear - reasons for concern

• Deepwater drilling riser joint inspection– Objectives, difficulties, rationalisation

• Usage logging requirements

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Page 5: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Deep Water v Shallow Water

• Larger tensions

• Larger internal and external pressures

• Longer, heavier riser joints

• Exposure to severe currents

• Subject to vortex induced vibrations

• Larger curvature

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Page 6: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Deepwater 1 Year ReturnPeriod Currents

0

500

1000

1500

0 1 2

Current Speed (m/s)

Ele

vati

on

Ab

ove

Sea

bed

(m

)

WoS

Brazil

GoM Loop

West Africa

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Page 7: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Effects of VIV

• High rates of fatiguedamage

• Increased dragloading

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Page 8: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

6000ft Drilling RiserVIV Fatigue (1)21 INCH Drilling Riser - 6000ft - 12 ppg Mud

F2 CLASS WELD AND SCF 1.3

0.00E+00

2.00E-04

4.00E-04

6.00E-04

8.00E-04

1.00E-03

1.20E-03

1.40E-03

1.60E-03

1.80E-03

2.00E-03

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Location Along Riser (x/L)

Fat

igu

e D

amag

e (1

/Yea

rs)

Bin 7 Bin 9 Bin 11 Bin 13 Bin 15 Bin 17 Bin 19 Bin 21 Bin 23

Bin 25 Total

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Page 9: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

6000ft Drilling RiserVIV Fatigue (2)

21 INCH Drilling Riser - 6000ft - 16.5 ppg MudF2 CLASS WELD AND SCF 1.3

0.00E+00

3.50E-03

7.00E-03

1.05E-02

1.40E-02

1.75E-02

2.10E-02

2.45E-02

2.80E-02

3.15E-02

3.50E-02

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Location Along Riser (x/L)

Bin 7 Bin 9 Bin 11 Bin 13 Bin 15 Bin 17 Bin 19 Bin 21 Bin 23

Bin 25 Total

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Page 10: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

6000ft Drilling RiserVIV Drag Amplification21 INCH Drilling Riser - 12 ppg Mud - Operational Top Tension

F2 CLASS WELD AND SCF 1.3

1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2

2.1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Location Along Riser (x/L)

Cd

Am

plif

icat

ion

Bin 7 Bin 9 Bin 11 Bin 13 Bin 15 Bin 17 Bin 19 Bin 21 Bin 23 Bin 25

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Page 11: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Wear in Deep Water

• Larger mean angles

• Larger tensions

• Higher external pressures– 2667/4445psi at 6,000/10,000ft

• Higher internal pressures– 4393/7321psi 14ppg mud, 6,000/10,000ft

• Integrity of wall more important

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Page 12: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Wear Hotspots

BOP

LMRP

LowerFlex-Joint

Casing

ConductorFirmSoil

SoftSoil

LOWERRISER

UPPERRISER

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Page 13: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Wear Control

• Flex joint angle limits– 2 degrees mean, 4 degree max (API)

• Criteria based on historical performance

• Deepwater limits?– 1 degree mean used by some drilling

contractors

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Page 14: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Deepwater Integrity Issues

• Increased fatigue damage from severecurrents

• Increased wear from riser curvature

• Increased susceptibility to handlingdamage from the use of longer, heavierriser joints

• Increased wall thickness integrityrequired to accommodate higher tensionsand pressures

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Page 15: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Purpose of Riser JointInspection

• Detect and quantify deterioration inintegrity

• Sources of deterioration:– fatigue damage accumulation

– impact / handling damage

– wear from drill string rotation

– corrosion

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Page 16: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Status of Drilling RiserInspection

• Shallow water– total kip-days

– 1 year usage

• Deep water– increased wear and fatigue

– limited long term experience

– strategies need to be defined

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Page 17: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Deepwater InspectionDifficulties

• Joint length - 75-90ft

• Joint weight - 60-70kips

• Difficult to handle - damage to buoyancy

• More remote - longer turn around

• More joints

• More expensive

• Need to rationalise

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Page 18: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Riser Joint Access

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Page 19: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Riser Joint Rack (1)

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Page 20: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Deepwater InspectionDifficulties

• Joint length - 75-90ft

• Joint weight - 60-70kips

• Difficult to handle - damage to buoyancy

• More remote - longer turn around

• More joints

• More expensive

• Need to rationalise

Learn more at www.2hoffshore.com

Page 21: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

How to Rationalise?

• In-place inspection– Calipers, pigging

• On-deck inspection– Space, equipment, personnel

• On-deck screening– Magnetostrictive method

• Selective onshore inspection

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Page 22: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Rationalization by Selection

• Fatigue based approach:– Severity of operating conditions

– Time in service

– Inspection detail

– Inspection frequency

– Inspection coverage

• Wear– Joint position

– Time in service

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Page 23: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Fatigue Crack GrowthLower Riser - Through-Thickness Crack Growth

0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

0 10 20 30 40 50 60 70 80 90 100

Time (years)

Cra

ck D

epth

, a (

mm

)

Initial a/c = 1.0Initial a/c = 0.5Initial a/c = 0.2a = t

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Page 24: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Rationalization by Selection

• Fatigue based approach:– Severity of operating conditions

– Time in service

– Inspection detail

– Inspection frequency

– Inspection coverage

• Wear– Joint position

– Time in service

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Page 25: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Influence of OperationalPractices

• Tension and tension variation– reduced VIV, vessel capacity may limit,

increased wellhead loading

• Joint rotation– spread fatigue damage

– scope may be limited

• Flex-joint angle limits– reduced limits give less wear

– more downtime

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Page 26: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

VIV Fatigue at Riser Base

21 INCH Drilling Riser - 6000ft - 12 ppg MudF2 CLASS WELD AND SCF 1.3

0.00E+00

2.00E-04

4.00E-04

6.00E-04

8.00E-04

1.00E-03

1.20E-03

1.40E-03

1.60E-03

1.80E-03

2.00E-03

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Location Along Riser (x/L)

Fat

igu

e D

amag

e (1

/Yea

rs)

Bin 7 Bin 9 Bin 11 Bin 13 Bin 15 Bin 17 Bin 19 Bin 21 Bin 23

Bin 25 Total

Learn more at www.2hoffshore.com

Page 27: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Riser Joint Rack (2)

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Page 28: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Deepwater InspectionFramework

• Use time in service approach as basis

• Account for increased wear and fatigue

• Account for operational practices

• Adjust intervals with experience

• Practice can vary from contractor tocontractor and vessel to vessel

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Page 29: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Variables to Accommodate

• Drilling in different water depths

• Different usage of different joints– lower rated joints used more often

• Actual operating conditions– may be more or less severe than predicted

• Requires rigorous usage logging

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Page 30: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Usage Logging Requirements

• Operations log– riser history

• Riser stack-ups– joint position and dates

– basis for selective inspection

• Operating conditions– tension, mud-weight, drill string tension,

current and wave

– verify operation and identify extreme events

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Page 31: Guidelines for Drilling Riser Joint Integrity...Guidelines for Drilling Riser Joint Integrity GUIDELINES FOR DRILLING RISER JOINT INTEGRITY by Dr Hugh Howells 2H Offshore Inc Fry Road,

Summary

• Current inspection practices must beextended for long term deepwater drilling

• Rationalisation dependent on:– depth and environmental conditions– time in service of each joint– operational practices

• Logging necessary to verify correctoperation and enable selective coverage

• Experience will enable refinement

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