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3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
COLLAPSE OF IN SERVICE DEEPWATER PIPELINES
JOINT INDUSTRY PROJECT PROPOSAL
(CSDP JIP PROPOSAL)
Adilson C. Benjamin (PETROBRAS R&D Center)
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
PRESENTATION TOPICS
BACKGROUND
CORROSION IN CARBON STEEL PIPELINES
DEEPWATER SCENARIO
CHARACTERISTICS OF THE PROBLEM
CSDP JIP PROPOSAL
INTRODUCTION
OBJECTIVE
SCOPE OF WORK
REFERENCES
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
PRESENTATION TOPICS
BACKGROUND
CORROSION IN CARBON STEEL PIPELINES
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(1)
As the oil and gas fields discoveries are moving into deeper waters
far from the coast, the use of large diameter export pipelines is
increasing in the offshore industry.
Due to economic reasons lengthy export pipelines have to be made
of carbon steel.
CORROSION IN CARBON STEEL PIPELINES
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(2)
Despite being the most cost effective option of pipeline material,
carbon steel has a major drawback: the susceptibility to corrosion.
Therefore sooner or later a carbon steel pipeline will be corroded.
Even when the transported fluid is dry gas, after some time in
operation it is not uncommon that corrosion begins to occur
because corrosive water does enter the pipeline occasionally as a
result of upsets in the gas processing facility.
CORROSION IN CARBON STEEL PIPELINES
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(3)
In submarine pipelines it is generally accepted that the major threat
is internal corrosion rather than external corrosion which is
generally quite well addressed using good cathodic protection and
coatings.
The mitigation of internal corrosion requires attention throughout
the life cycle of the pipeline.
Besides the corrosion allowance that is established in the design
phase several techniques are employed during the operation phase
in order to mitigate internal corrosion.
CORROSION IN CARBON STEEL PIPELINES
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(4)
Recognizing that it is almost impossible to preclude the occurrence
of internal corrosion in submarine pipelines, operators perform
periodically inline inspections using smart pigs to detect corrosion
defects.
After the detection of the corrosion defect the submarine pipeline
must have its structural integrity checked in at least two loading
conditions:
dominant internal pressure (pi > pe) and
dominant external pressure (pi < pe).
CORROSION IN CARBON STEEL PIPELINES
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(5)
Due to the high cost of repairing deepwater pipelines the service
life of the corroded pipeline segments must be maximized.
In order to achieve this maximization it is necessary that the
assessment of the corrosion defects detected in the inline
inspection is performed using an accurate and experimentally
validated method.
CORROSION IN CARBON STEEL PIPELINES
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(6)
The literature on corroded pipelines subjected to dominant internal
pressure is extensive and several experimentally validated
assessment methods are currently available.
The literature on corroded pipelines subjected to dominant external
pressure is limited and experimentally validated assessment
methods are not available.
CORROSION IN CARBON STEEL PIPELINES
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
PRESENTATION TOPICS
BACKGROUND
CORROSION IN CARBON STEEL PIPELINES
DEEPWATER SCENARIO
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(1)
Ever since the first pipeline was installed offshore, pipeline
developments have been moving into ever deeper waters.
While in the early days of the offshore industry 100 m water depth
was considered as deep, now pipelines are being installed in 2500 m
water depth or more.
Herein, water depths equal to or greater than 1000 m (3281 feet) are
considered deep.
DEEPWATER SCENARIO
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(2)
As a pipeline is installed in deeper water, the external pressure that
the pipe have to be able to withstand increases.
Consequently the pipe becomes thicker.
Submarine pipelines usually have De / t ratios smaller than 30 while
deepwater pipelines usually have De / t ratios smaller than 20.
DEEPWATER SCENARIO
During installation the pipeline is empty and its portion that is
resting on the seabed is subjected to an external overpressure
(external pressure alone).
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(3)
Corrosion is a time dependent phenomenon that usually requires
several years to produce a corrosion defect sufficiently large to
cause a significant reduction in the collapse pressure of the
pipeline.
Consequently during installation it is considered that the pipeline is
free of any metal loss due to corrosion.
In service, if the transported fluid is gas, an external overpressure
occurs when there is a shutdown of operation (scheduled or not).
DEEPWATER SCENARIO
If the transported fluid is oil, an external overpressure occurs when
after a shutdown of operation the line is evacuated (emptied).
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(4)
For large diameter, heavy walled linepipe, the UOE pipe
manufacturing process is the general method applied by pipe mills.
The name UOE stems from the initials of three mechanical steps
which are carried out during the process:
U for U-ing cold forming from the plate,
O for O-ing cold forming from the Ushape,
and E for cold expansion to meet the geometric tolerances
DEEPWATER SCENARIO
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(5)
Out-of-roundness (ovality) of the pipe cross section is one of the
imperfections introduced during the UOE pipe manufacturing
process.
Typical deep water pipelines can have an initial out-of-roundness of
at most 1%.
Another side effect of the UOE process is the reduction of the tube
compressive yield stress in the hoop direction.
DEEPWATER SCENARIO
As a result of the cold deformation caused by forming operation,
the transverse compressive yield strength measured on the pipe
may be lower than that measured on the plate.
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(6)
However extensive research has shown that the de-rating of the
compressive yield strength can be compensated for by a heat
treatment at a moderately elevated temperature (about 200°C to
220°C).
This heat treatment is analogous to what the linepipe experiences
during the application of the anticorrosive coating (polyethylene or
polypropylene).
DEEPWATER SCENARIO
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(7)
It is anticipated that over the next 20 years, deepwater field
developments will increase substantially in number and water
depth.
Potential areas of developments around the world include:
Gulf of Mexico;
Offshore Brazil;
West Africa;
UK Atlantic Frontier and
Norwegian sector.
DEEPWATER SCENARIO
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(8)
The figure below presents a map in which oil and gas fields located
off the Brazilian coast are shown.
DEEPWATER SCENARIO
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
PRESENTATION TOPICS
BACKGROUND
CORROSION IN CARBON STEEL PIPELINES
DEEPWATER SCENARIO
CHARACTERISTICS OF THE PROBLEM
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(1)
From a structural point of view an empty pipeline resting on the
seabed is a long circular tube subjected to an external hydrostatic
pressure.
Depending on its external diameter to thickness ratio (De / t) the
pipeline is classified as a thick tube (De / t less than 20) or as a thin
tube (De / t equal to or greater than 20).
CHARACTERISTICS OF THE PROBLEM
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(2)
Submarine pipelines usually have external diameter to thickness
ratios (De / t) that range from 10 to 30.
In this range of De / t ratio the failure behavior of a non corroded
pipeline subjected to an external pressure is characterized by the
interaction between plasticity and geometric instability.
That is, yielding of the pipeline cross section begins before the
collapse by geometric instability is attained.
CHARACTERISTICS OF THE PROBLEM
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(3)
The failure behavior of a non corroded pipeline subjected to an
external pressure is sensitive to initial imperfections introduced by
the manufacturing process, as for example:
Out-of-roundness (ovality) of the pipe cross section and
reduction of the tube compressive yield strength.
CHARACTERISTICS OF THE PROBLEM
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(4)
The failure behavior of a corroded pipeline subjected to an external
pressure is sensitive not only to initial imperfections but also to the
dimensions of the corrosion defect, that is,
the defect depth (d),
the defect length (L) and
the defect width (w).
CHARACTERISTICS OF THE PROBLEM
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(5)
The corrosion defect can be seen as a geometric imperfection
whose dimensions grow with time.
The detrimental effect of the corrosion defect on the pipeline
strength varies in function of its position in relation to the ovality of
the pipe cross section.
Depending on its relative position the corrosion defect intensify or
lessen the pipe ovalization.
CHARACTERISTICS OF THE PROBLEM
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(6)
Due to the complexity of the problem, the Nonlinear Finite Element
Method is the best method to calculate the collapse pressure of a
corroded pipeline subjected to an external hydrostatic pressure.
However a method composed of closed form equations,
experimentally validated, is more adequate to perform the collapse
check of the great quantity of defects detected in the periodical
inline inspections.
CHARACTERISTICS OF THE PROBLEM
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
PRESENTATION TOPICS
BACKGROUND
CORROSION IN CARBON STEEL PIPELINES
DEEPWATER SCENARIO
CHARACTERISTICS OF THE PROBLEM
CSDP JIP PROPOSAL
INTRODUCTION
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(1)
The literature about the problem of hydrostatic collapse of
corroded pipelines is limited.
Until now little research on corroded pipelines subjected to
external pressure has been carried out.
So far only nine full scale tests of tubular specimens containing
single corrosion defects have been performed.
INTRODUCTION
And research on pipelines containing closely spaced corrosion
defects subjected to external pressure has not been undertaken.
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(2)
The problem of corroded pipelines subjected to external pressure
is much more complex than two correlated problems:
corroded pipelines subjected to internal pressure and
non-corroded pipelines subjected to external pressure.
However the literature about these two problems is extensive
and the number of full scale tests already performed is large.
INTRODUCTION
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(3)
The assessment of corroded pipelines subjected to external
pressure is in an incipient stage of development.
More research projects are needed.
And much more full scale collapse tests must still be performed.
INTRODUCTION
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(4)
Due to the high cost of repairing deepwater pipelines it is
anticipated that soon the oil companies will be highly interested in
the development of cutting edge methods for the assessment of
corrosion defects in pipelines subjected to dominant external
pressure.
Being aware that, in their early stage of development, several of the
key technologies in the petroleum industry were developed through
group sponsored projects, PETROBRAS decided to propose a joint
industry project (JIP) to address the problem of corroded pipelines
subjected to external pressure.
INTRODUCTION
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(5)
This JIP, named Collapse of in Service Deepwater Pipelines Joint
Industry Project (CSDP JIP), will be conducted by Catholic
University of Rio de Janeiro (PUC-Rio).
Besides paying the JIP share fee PETROBRAS will have an active
participation in the project.
INTRODUCTION
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
PRESENTATION TOPICS
BACKGROUND
CORROSION IN CARBON STEEL PIPELINES
DEEPWATER SCENARIO
CHARACTERISTICS OF THE PROBLEM
CSDP JIP PROPOSAL
INTRODUCTION
OBJECTIVE
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
The objective of the CSDP JIP is to develop an extensive
experimental program in which full scale tubular specimens
containing internal single corrosion defects will be submitted to
external hydrostatic pressure up to collapse.
These defects will be generated using spark erosion.
Sound experimental foundations for the development and/or
validation of methods for the assessment of the hydrostatic
collapse of corroded deepwater pipelines will be established in the
experimental program that will be undertaken.
OBJECTIVE
A broad range of parameters, such as the defect depth (d), the
defect length (L) and the defect width (w) will be covered.
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
PRESENTATION TOPICS
BACKGROUND
CORROSION IN CARBON STEEL PIPELINES
DEEPWATER SCENARIO
CHARACTERISTICS OF THE PROBLEM
CSDP JIP PROPOSAL
INTRODUCTION
OBJECTIVE
SCOPE OF WORK
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(1)
Twelve participants will be necessary to perform the full scope of
work of the CSDP JIP.
However a minimum of three participants will be sufficient to start
the project.
The CSDP JIP is composed of four modules.
SCOPE OF WORK
Fifteen tests will be performed in each of these modules.
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
(2)
If the project starts with less than 12 participants the project
activities will have to be reduced to fit the available financial
resources (see table below).
SCOPE OF WORK
60 tests12
55 tests11
50 tests10
45 tests9
40 tests8
35 tests7
30 tests6
25 tests5
20 tests4
15 tests3
Number of full scale tests performedNumber of Participants
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
PRESENTATION TOPICS
BACKGROUND
CORROSION IN CARBON STEEL PIPELINES
DEEPWATER SCENARIO
CHARACTERISTICS OF THE PROBLEM
CSDP JIP PROPOSAL
INTRODUCTION
OBJECTIVE
SCOPE OF WORK
REFERENCES
3rd COPEDI Forum / 2013 – April 15, 2013 – CSDP JIP Proposal
The main references of this presentation are listed below.
1. Benjamin, A. C. and Cunha, D. J. S., “Assessment of the Hydrostatic Collapse of Corroded Submarine Pipelines: Current Status and Research Needs”, Proceedings of the Rio Oil & Gas Expo and Conference 2012, Paper IBP2124_12, 2012.
2. Cosham, A., “Assessment Methods for Corrosion in Pipelines”, A report to the Pipeline Defect Assessment Manual (PDAM) Joint Industry Project, Report NR99012/4238.1.72, Revision 3, September 2002.
3. Benjamin, A. C. and Cunha, D. J. S., “Assessment of Hydrostatic Collapse of Submarine Pipelines: An up-to-date Literature Review”, Proceedings of the Rio Oil & Gas Expo and Conference 2012, Paper IBP2132_12, 2012.
REFERENCES
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