Thermal Expansion & Helical Buckling of

Pipe-in-Pipe Flowline System2012 SIMULIA Community Conference

Genesis – A “New” Brand within Technip

• The Keynote Talk by Jim O’Sullivan illustrates how advanced engineering simulations

allow Technip, across the globe and across brands & products, to Take it Further.

• Genesis is a wholly owned Technip subsidiary. Originally acquired by Technip in the early

2000s. The Genesis HQ is in London.

• Genesis professionals provide services from conceptual field studies to the detailed

engineering design and analysis of offshore oil and gas production systems from the

seafloor to the host facilities, whether on land or at the water surface.

• Today Genesis staff, which number about 1100, represent a little more than1/30th of the

Technip’s worldwide workforce.

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System2

Heating cables

Carrier

pipe

Centraliser

Flowline

Optical fibre

Passive insulation

Design of Subsea Flowline Systems

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System3

Flow Assurance

•Hydrocarbon Behavior

•Operational Targets

•Nonlinear Thermal Transient Modeling

Pipeline Design

•Flow Rates

•Wellhead Pressures

•Temperature

•Wall Thickness

•Insulation Performance

Pipeline Performance

•Installation

•Thermal Expansion Loading

•Pipe-Soil Interaction

•ECA

Actively Heated Pipe-in-Pipe (PiP) Systems

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System4

Hydrocarbon fluids flow within the

inner pipe of the system

Hot liquid is pumped down the

PiP annulus

Heating liquid in the active PiP system can

return to the production platform via an external

flowline (not shown here)

Engineering Design of Decentralized Pipe-in-Pipe System

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System5

• Genesis has considerable experience in using advanced engineering simulations to guide

the development of deepwater pipeline designs.

• Wet insulated pipeline systems

• Passive Pipe-in-Pipe systems (Centralized)

• Electrically heated Pipe-in-Pipe systems (Centralized)

• Over a decade had passed since

the last decentralized pipe-in-pipe

design (with circulating hot fluid)

had been developed.

• Numerous engineering design

challenges with decentralized PiP

design

• Flow Assurance Tools

• Thermal Expansion & Helical

Buckling of Pipe

• Installation of Decentralized

Pipe-in-Pipe Design

Nonlinear FEA of Decentralized Pipe-in-Pipe System

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System6

• Challenges to the structural design of a decentralized Pipe-in-Pipe System

• Complex, nonlinear contact between inner and outer pipes

• Pipe-Seabed contact

• Temperature dependent material properties for the steel pipes

• Initial stress state for both pipelines

• Complex thermal and internal pressure loading

• Structural instabilities (buckling of both pipelines)

6-inch pipe

12-inch pipe

ITT31 Elements for Pipe-

to-Pipe Contact

FRIC subroutine for outer

pipe-to-Seabed Contact

Nonlinear FEA of Decentralized Pipe-in-Pipe System

Objectives of the Study

• Develop robust methodology to control the various types of structural instability

that could arise during nonlinear FEA of this decentralized PiP system

• Attempt to validate the FEA with published analytical expressions critical

loading necessary for the helical buckling of pipe in pipe systems.

– Y.C. Chen, Y.H. Lin and J.B. Cheatham, “An Analysis of Tubing and Casing

Buckling in Horizontal Wells”

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System7

r

EIwFcs 2

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System8

Buckling Instability in Decentralized Pipe-in-Pipe System

Energy balance from unstable pipeline bucking model

Rotational Instability in Decentralized Pipe-in-Pipe System

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System9

Time history plot of

nodal rotations in the

inner pipeline

of the PiP system

Techniques for FEA Simulations with Instabilities

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System10

• Include the inertial terms (*DYNAMIC) in the equilibrium equations

• Use global solution methods (i.e. RIKS)

• Include viscous damping terms

– DASHPOT elements for every displacement & rotational DOF

– Automated volume-proportional viscous damping (Abaqus version 6.3 and later)

– Drag forces (Abaqus/Aqua)

• Convert loads from “Load Control” to “Displacement Control”

Results from Helical Buckling Study

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System11

Results from Helical Buckling Study

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System12

Analysis Method/Model mFcs

(MN)

Fc

(MN)Comments

Analytical 0.0 0.675 0.954 Assumes horizontal, frictionless wellbore.

FEA / Horizontal Model 0.35 1.46 1.46Transition from sinusoidal to helical

buckling occurs immediately

FEA / Horizontal Model 0.22 1.21 1.22

FEA / Horizontal Model 0.15 1.06 NA Loading never reached Fc level

FEA / Horizontal Model 0.1 0.944 NA Loading never reached Fc level

FEA / Horizontal Model 0.08 0.894 NA Loading never reached Fc level.

FEA / Horizontal Model 0.01 0.72 NA Loading never reached Fc level

FEA / Horizontal Model w.

nearly Frictionless Contact~0.0 0.680 NA Friction Coefficient is 0.005.

FEA/ Single 0.75 m Sleeper

with flat Seabed 0.35 0.90 NA

Inner pipeline does not reach Fc loads.

Pipe-Sleeper Friction Coefficient: 0.3

PiP Geometry 8” x 12”

Helical Buckling Study – Summary & Conclusions

Thermal Expansion & Helical Buckling of Pipe-in-Pipe Flowline System13

• FEA methodology developed to simulate the complex deformation associated with helical

buckling of the inner pipe of a PiP system

• Predicted values for Fcs and Fc that are very similar to those calculated using published

analytical expression

• The magnitude of Fcs increases as the friction coefficient between the two pipes of the PiP

system is increased.

• Sinusoidal buckling of the inner pipeline creates enough lateral loads on the outer pipe to

cause a global lateral buckle in the PiP system.

• Global buckling of the PiP system reduces the probability that helical buckles will form, by

reducing the effective axial force in the inner pipe.