1、 Guidance Notes on Drilling Riser Analysis GUIDANCE NOTES ON DRILLING RISER ANALYSIS JULY 2017 American Bureau of Shipping Incorporated by Act of Legislature of the State of New York 1862 2017 American Bureau of Shipping. All rights reserved. ABS Plaza 16855 Northchase Drive Houston, TX 77060 USA Fo
2、reword Foreword These Guidance Notes are intended to assist users of the ABS Guide for the Classification of Drilling Systems (CDS Guide) to deal with the drilling riser analysis to meet ABS CDS Guide requirement. These Guidance Notes provide the latest recommended practices for typical types of ana
3、lyses that may be required for a drilling riser. The actual types and scopes of analyses that will be required for a particular drilling riser will be decided on a project specific basis. In addition, considerations and suggestions are also provided in these Guidance Notes on important features of t
4、hese analyses with sufficient details including evaluation parameters, approaches, procedure, modeling, and sample figures of results, etc. The design acceptance guideline of a drilling riser is based on API RP 16Q, while the detail analysis process is provided in these Guidance Notes. In these Guid
5、ance Notes, the word “Unit” is used in general to refer to the structure from which the drilling riser is deployed. In an actual case, that structure can be a Mobile Offshore Drilling Unit, Floating Production Installation, or other type of structure as considered in the CDS Guide. These Guidance No
6、tes become effective on the first day of the month of publication. Users are advised to check periodically on the ABS website www.eagle.org to verify that this version of these Guidance Notes is the most current. We welcome your feedback. Comments or suggestions can be sent electronically by email t
7、o rsdeagle.org. Terms of Use The information presented herein is intended solely to assist the reader in the methodologies and/or techniques discussed. These Guidance Notes do not and cannot replace the analysis and/or advice of a qualified professional. It is the responsibility of the reader to per
8、form their own assessment and obtain professional advice. Information contained herein is considered to be pertinent at the time of publication, but may be invalidated as a result of subsequent legislations, regulations, standards, methods, and/or more updated information and the reader assumes full
9、 responsibility for compliance. This publication may not be copied or redistributed in part or in whole without prior written consent from ABS. ii ABSGUIDANCE NOTES ON DRILLING RISER ANALYSIS .2017 Table of Contents GUIDANCE NOTES ON DRILLING RISER ANALYSIS CONTENTS SECTION 1 Summary of Drilling Ris
10、er Analyses . 1 1 Riser Space-out and Stability Calculations . 1 3 Storm Hang-off Analysis . 1 5 Operability Analysis 1 7 Deployment/Retrieval Analysis . 1 9 Vortex Induced Vibration (VIV) fatigue Analysis . 1 11 Wave Fatigue Analysis . 1 13 Drift-off/Drive-off Analyses 2 15 Recoil Analysis 2 17 Wea
11、k Point Analysis . 2 19 Abbreviations 2 21 Symbols 2 FIGURE 1 Typical Drilling Riser Analysis Procedure . 3 SECTION 2 Drilling Riser System Components 4 1 Overview of Riser System . 4 3 Top Tensioning System 5 5 Diverter System 5 7 Flex and Ball Joints . 5 9 Telescopic Joint 5 11 Riser Joints . 5 11
12、.1 Typical Riser Joint . 5 11.3 Riser Couplings . 5 11.5 Auxiliary Lines . 5 11.7 Buoyancy Module 6 11.9 Pup Joints 6 13 Other Special Riser Joints 6 13.1 Spider and Gimbal . 6 13.3 Landing Joint . 6 13.5 Subsea Fill-up Joint . 6 13.7 Various Adapters . 6 15 Lower Marine Riser Package (LMRP) 6 17 Bl
13、owout Preventer (BOP) Stack . 6 FIGURE 1 Typical Drilling Riser System and Components 4 ABSGUIDANCE NOTES ON DRILLING RISER ANALYSIS .2017 iii SECTION 3 Riser Analysis Evaluation Considerations . 7 1 General . 7 3 Riser Design Guidelines . 7 5 Other Analysis Evaluation Considerations 9 SECTION 4 Ris
14、er System Modeling 10 1 Required Information 10 1.1 Information about the Riser String . 10 1.3 Information about the Unit . 12 1.5 Information of the Site 13 3 Riser String . 13 3.1 Riser Joints 13 3.3 Load Sharing from Auxiliary Lines . 14 3.5 Telescopic Joint . 15 3.7 Ball/Flex Joint 15 3.9 Condu
15、ctor and Casings . 15 5 Boundary Conditions . 15 5.1 Top Boundary Condition 15 5.3 Top Tensioning System . 16 5.5 Bottom Boundary Condition . 17 5.7 Soil Restraint . 17 FIGURE 1 Example of Riser Main Pipe Load Sharing Factor 15 SECTION 5 Riser Space-out and Stability Calculation 18 1 Required Inform
16、ation 18 3 Riser Space-out 18 5 Riser Stability Calculation . 19 5.1 Minimum Top Tension . 19 5.3 Maximum Top Tension 19 5.5 Riser Space-out and Stability Calculation Procedure 20 SECTION 6 Storm Hang-off Analysis 21 1 Required Information 21 3 Types of Riser Hang-off 21 5 Considerations in Modeling
17、 . 22 5.1 Riser Fluid . 22 5.3 Time Domain Riser Dynamic Simulation for Hard Hang-off . 22 5.5 Time Domain Riser Dynamic Simulation for Soft Hang-off 22 5.7 Added Mass and Damping in Hang-off Analysis 22 7 Analysis Procedure . 23 7.1 Time Domain Riser Dynamic Simulation for Hard Hang-off . 23 7.3 Ti
18、me Domain Riser Dynamic Simulation for Soft Hang-off 24 9 Mitigation for Riser Axial Dynamics 24 FIGURE 1 Spring Length versus Tension Curve for a Wire Tensioner 23 iv ABSGUIDANCE NOTES ON DRILLING RISER ANALYSIS .2017 SECTION 7 Operability Analysis . 25 1 Required Information 25 3 Operating Modes 2
19、5 5 Considerations in Modeling. 25 7 Analysis Procedure . 25 FIGURE 1 Typical Riser Operability Plot for Drilling 26 SECTION 8 Deployment and Retrieval Analysis 27 1 Required Information 27 3 Operation Stages 27 5 Considerations in Modeling. 27 7 Analysis Procedure . 28 7.1 Time Domain Simulation .
20、28 SECTION 9 VIV Fatigue Analysis 29 1 Required Information 29 3 Analysis Approach 29 3.1 S-N Curve 29 3.3 VIV Analysis Method and Software . 30 5 Modeling Considerations 30 7 Analysis Procedure . 31 9 Mitigation Options for Riser VIV 31 SECTION 10 Wave Fatigue Analysis 32 1 Required Information 32
21、3 Analysis Methods 33 3.1 S-N Curve 33 3.3 Frequency Domain Analysis Method: Spectral-based . 33 3.5 Time Domain Analysis Method 34 5 Considerations in Modeling. 34 7 Analysis Procedure . 35 9 Mitigation Options for Riser Wave Fatigue Damage 35 SECTION 11 Drift-off/Drive-off Analysis . 36 1 Required
22、 Information 36 3 Analysis Approach 37 3.1 Drift-off Simulation . 37 3.3 Drive-off Simulation . 37 5 Considerations in Modeling. 37 7 Analysis Procedure . 38 7.1 Drift-off Analysis 38 7.3 Drive-off Analysis . 38 FIGURE 1 Typical Watch Circle Plot for Drift-off/Drive-off . 39 ABSGUIDANCE NOTES ON DRI
23、LLING RISER ANALYSIS .2017 v SECTION 12 Recoil Analysis . 40 SECTION 13 Weak Point Analysis 41 1 Required Information 41 3 Analysis Approach 41 5 Considerations in Modeling . 41 7 Analysis Procedure . 41 SECTION 14 References 42 vi ABSGUIDANCE NOTES ON DRILLING RISER ANALYSIS .2017 Section 1: Summar
24、y of Drilling Riser Analyses SECTION 1 Summary of Drilling Riser Analyses The types of analyses typically required for a drilling riser may include those listed below. Section 1, Figure 1 depicts the general sequence of the analyses and gives the primary purpose of each analysis type. The actual ana
25、lyses types and scopes, which will be required in ABSs review of the riser for Classification in accordance with the ABS Guide for the Classification of Drilling Systems (CDS Guide), will depend on the specifics of an individual project. The information given in these Guidance Notes is meant to give
26、 an indication of the possible scope for the listed types of analyses which may apply. 1 Riser Space-out and Stability Calculations This is often the first step in the drilling riser analyses. The purpose of this analysis is to establish feasible riser space-out (i.e., layout or arrangement) configu
27、rations based on the water depth and available types of riser joints and to determine whether the top tensioning system has sufficient capacity to support the riser space-out and anticipated mud weight. 3 Storm Hang-off Analysis The purpose of this analysis is to determine the limiting sea states (e
28、nvironmental window), in which the riser can be hung-off without damaging the riser. This analysis is especially important for a deep water riser, since the natural period of the risers axial dynamic response may fall in the frequency range of highly energetic waves. 5 Operability Analysis The purpo
29、se of this analysis is to determine, for each mud density, the operating envelopes that define the required top tension range and the allowable Unit offsets for normal drilling operation and/or for keeping the riser connected to well but no drilling. 7 Deployment/Retrieval Analysis This analysis is
30、performed when the Unit moves to a site that is in deepwater or is sensitive to the environment (e.g., high current). The purpose of this analysis is to determine the environmental window for running/pulling the riser. 9 Vortex Induced Vibration (VIV) fatigue Analysis This analysis is often required
31、 when the Unit is operating in an area of strong current with riser either connected or hung off for long duration. The purpose of the analysis is to predict the fatigue damage induced by vortex induced vibration due to currents and to identify critical locations for regular inspection. 11 Wave Fati
32、gue Analysis The purpose of the analysis is to predict the fatigue damage induced by sea waves. Because drilling riser joints are in general considered robust and can be often inspected between deployments, this analysis may not be required. However, if the Unit is in high waves with the riser conne
33、cted to a well or hung off in storm waves for long duration and/or multiple times, such analysis is often warranted to verify that no excessive fatigue damage is sustained by the riser joints. ABSGUIDANCE NOTES ON DRILLING RISER ANALYSIS .2017 1 Section 1 Summary of Drilling Riser Analyses 13 Drift-
34、off/Drive-off Analyses These two analyses are specifically for dynamically positioned (DP) Units. The purpose of the analyses is to define the radius of the “yellow” and “red” watch circles for emergency disconnection when the Unit suffers a black-out or DP system malfunction. 15 Recoil Analysis Thi
35、s analysis is typical performed for DP Units. The purpose of this analysis is to determine the requirements of the recoil system on a DP Unit for safe emergency disconnection. 17 Weak Point Analysis This analysis is to identify the weak points in a drilling riser/well system under extreme Unit offse
36、ts due to drive-off/drift-off or mooring line failure. The focus of this analysis is on well integrity. Extreme offsets can lead to overloading of various components in the drilling riser/well system such as connectors, BOP stack, wellhead, and casing, etc. The maximum load predicated from the weak
37、point analysis can be used for design/selection of the drilling riser and well system components or compatibility check between riser and existing well system. This analysis is often required before the Units first deployment or before an important drilling campaign by the Operator. 19 Abbreviations
38、 BOP Blow Out Preventer C and it is also used to control the shape of the riser when subjected to environmentally-induced load effects. The tensioning system is normally composed of a number of “tensioners”. The number and rating of the tensioner units will determine the total capacity of the tensio
39、ning system. There are two types of tensioner designs (i.e., wireline tensioners and direct-acting tensioners). A wireline tensioner unit uses a hydraulic ram with a large volume air-filled accumulator to maintain near constant tension on the tensioner wires. One end of the wire is attached at the t
40、ensioner and the other is attached to the outer barrel of the telescopic joint through sheaves underneath the drill floor. A direct-acting tensioner has a hydraulic rod and piston assembly, which are attached directly to the drill floor structure and the outer barrel of the telescopic joint. 5 Diver
41、ter System The purpose of a diverter system is to direct mud returns to processing and to divert any low pressure gas in the riser away from the drill floor, and to discharge it to a safe area. The diverter is mounted in the housing directly below the drill floor. The upper flex/ball joint is typica
42、lly attached below the diverter. 7 Flex and Ball Joints Flex or ball joints are used at the top and bottom of the riser to allow for angular displacement thus reducing the bending stresses at both ends of the riser string. Intermediate flex or ball joint may also be fitted below the telescope joint.
43、 Typically flex joints have a rotational stiffness which makes them more effective in controlling riser angles. 9 Telescopic Joint The basic function of the telescopic joint is to accommodate the relative translational movement between the Unit and the riser due to heave, tidal changes, Unit offset,
44、 and riser shape. A telescopic joint has an outer barrel which is connected to the riser string and an inner barrel which is connected to the drilling Unit. The telescopic joint also has brackets for the goosenecks which connects to the drape hoses for auxiliary lines. The tensioning system is conne
45、cted to the outer barrel of the telescopic joint, normally through a tensioner ring, to provide tension to the riser string. 11 Riser Joints 11.1 Typical Riser Joint A riser joint is typically an assembly of riser pipe, coupling box and pin, choke and kill lines, auxiliary lines, choke/kill/auxiliar
46、y line support brackets, and other devices for guidance and/or supporting buoyancy modules. A typical full length riser joint has length ranging from 50 to 90 feet. 11.3 Riser Couplings Riser couplings are the connectors at each end of the riser joint that link one joint to another. The riser joint
47、coupling rating often controls the maximum allowable tension that can be applied to the riser string. 11.5 Auxiliary Lines Auxiliary lines typically include Choke/Kill lines to carry fluid along the length of the riser. C or Soil undrained shear strengths, submerged unit weights and strains at 50% o
48、f the maximum stress on laboratory undrained compression tests at different penetration depths 3 Riser String 3.1 Riser Joints In the riser system analysis, riser joints is generally modeled as homogenous pipes. Since the drilling riser joints normally have auxiliary lines attached and with coupling
49、s at the ends, the modeled homogenous pipe should be equivalent to the riser joint in the following aspects: i) Mass and buoyancy, including the riser fluid in main tube and auxiliary lines The mass should include the mass of the whole riser joint and the mass of the fluids in the auxiliary lines. The modeled pipe OD and ID should provide the same buoyancy and submerged weight as the riser joints in water. ABSGUIDANCE NOTES ON DRILLING RISER ANALYSIS .2017 13 Section 4 Riser System Modeling ii) Hydrodynamic added mass and drag The equivalent added mass and inertia coefficients
