Post on 18-Jul-2016
description
Services
Services
■■ Subsea■Production■Systems
■■ Subsea■Mechanical■Integrity■
■■ Flow■Assurance■for■Subsea■Production■Systems
■■ Pipelines,■Flowlines■and■Risers
Subsea SystemsConsulting Services
2
2 Subsea Systems
Source: FMC Technologies
3Subsea Systems
Subsea Production Systems
With the depletion of onshore and offshore
shallow water hydrocarbon reservoirs, the
exploration and production of oil in deep
water has become a challenge to the offshore
industry. Since these subsea developments
are moving further offshore and into deeper
waters, the technical challenges of such pro-
jects are continuously increasing.
For deep water developments a wide range
of subsea layouts and production systems,
greatly differing in complexity, are utilized.
A subsea production system consists of a
subsea completed well, subsea Christmas
trees and wellhead systems, subsea tie-in to
flowline system, jumpers, umbilical and riser
system and subsea equipment to operate
the well. The single or clustered well can be
connected through the flowline to a fixed
platform, FPSO (Floating Production, Storage
and Offloading) or onshore facilities. Alterna-
tively, an existing subsea production system
can be connected to a newly operated pro-
duction well by means of a subsea tie-back,
that have become popular in the develop-
ment of new oil and gas reserves.
Due to the high pressures, potentially large
temperature gradients and the harsh envi-
ronment in deep-water, the subsea systems
and equipment are subjected to complex and
critical load cases. Therefore in all offshore
pipeline systems the transportation of fluids
including the flow of oil, gas, water and mix-
tures thereoff should be analyzed to optimize
performance and minimize the operational
risks.
Subsea Flow Assurance
The flow in subsea transportation pipelines
and tie-backs are often governed by risers.
Both risers and flowlines are located on the
DRG■provides■consulting■services■for■Subsea■Engineering■problems■related■to■Subsea■Flow■Assurance■and■Subsea■Structures,■Equipment,■Risers■and■Flowlines
Subsea Engineering
4 Subsea Systems
seabed, such that these typical components
may be subject to thermal and mechanical
problems. In particular, transient heat and
mass transfer phenomena are often present
in specific components and need to be ana-
lyzed and/or simulated in order to achieve a
proper system design.
The deliverability of hydrocarbon products
from the reservoir to the end user is essential
to the success of oil and gas developments,
but often turns out to be the bottleneck of
the system. Pipelines, either onshore or off-
shore, play a vital role in ensuring a reliable
production process, which provides a mana-
geable and profitable flow of fluids from the
subsea wellhead to the fixed platform, FPSO
or onshore facilities.
Hydrocarbons are rarely found in single-
phase flow during transport from a reservoir
to production platform. It is these multiphase
flows that form the most serious hazard in
the production process. In subsea operati-
ons, controlling multiphase flows is of the up-
most importance, as these can have adverse
effects on the often long riser lines that are
used to surface hydrocarbon products from
the subsea production system.
Multiphase Flows
There are several critical problems that can
be attributed to the occurrence of multi-
phase flows, which typically consists of wa-
ter, oil and gas. For instance, a mixture of
water and hydrocarbons can form hydrates
that block pipelines obstructing the flow.
Additionally, slugs may be formed within the
pipelines, which can cause severe damage to
downstream processing facilities. It is there-
fore of high importance to be able to predict
and control the slugging in the subsea pro-
duction system.
OLGA®, a widely used software tool to simula-
te multiphase transport of oil, water and gas-
es is often used for multiphase flow analysis,
together with PVTsim®. When necessary, full
CFD (Computational Fluid Dynamics) simula-
tions are performed to make detailed flow
assessments of all kinds of equipment like
separators, slug catchers etc. and connecting
“DRG assists the client to in-crease their perfomance and reduce the risks of subsea production”
5Subsea Systems
flowlines between the subsea well head and
fixed platform, FPSO or onshore facilities.
Using the broad knowledge and wide ranging
expertise in multiphase flows, DRG is able to
interprete the complex multiphase flow re-
sults in order to assist the client to increase
the performance and reducing the risks of
subsea production.
Subsea Structures and Pipelines
Since subsea flowlines are subjected to high
external pressure, collapse and buckling cri-
teria are very important. These criteria de-
pend on the diameter to wall thickness ratio,
pipe imperfections and load conditions such
as axial tension, bending stress and external
pressure. A good knowledge of these criteria
is required to come to a sufficiently robust
flowline design. Using a fully validated sui-
te of design tools DRG is capable of solving
some of the oil industry’s most difficult pro-
blems such as detailed lateral buckling and
pipeline walking issues.
The increased activities in subsea processing,
such as separation or compression, requi-
res more advanced structures. The nozzles
of subsea vessels are differently loaded in
the subsea regime, on account of the high
pressure and low temperature, than their
counterparts in onshore installations. Dyna-
flow Research Group has broad experience
in performing FEA (Finite Element Analyses)
simulations of various types of equipment,
which might be loaded due large pressures
and critical thermal effects in accordance
with many international codes such as ASME,
EN, BS, etc.
Dynaflow Research Group
We believe it is important not only to have
a sound grasp of the physics behind these
phenomena but also to have a very hands-
on and pragmatic approach to your real life
problems.
Due to our highly qualified staff and expe-
rience in this field, DRG is often required to
solve problems involving subsea production
systems, subsea flowlines from wellhead to
fixed platform, FPSO or onshore facilities,
and attached equipment like separators and
slugcatchers.
DRG provides engineering services in all pha-
ses of a subsea system design.
Source: FMC Technologies
6 Subsea Systems
Source: Aker Kvaerner
7Subsea Systems
Manifold Design and Analysis
Subsea manifolds have been used in the de-
velopment of oil and gas fields to simplify the
subsea system, minimize the use of subsea
pipelines and risers and optimize the fluid
flow production sytem. The manifold con-
sists of an arrangement of piping and valves
designed to combine, distribute, control and
often monitor fluid flow. Subsea manifolds
are installed on the seabed connected to se-
veral wells to collect the product or to inject
gas or water into the well. The most common
subsea manifold is a PLEM (PipeLine End
Manifold) which is directly connected to the
pipelines.
The subsea manifold should be designed to
provide sufficient piping, valves and control
equipment to collect all produced oil and gas
or to inject fluids like gas, water or chemicals.
Dynaflow Research Group assists its clients
DRG■provides■consulting■services■and■engineering■solutions■to■improve■and■verify■the■mechanical■integrity■of■subsea■systems
Subsea Structures and Equipment
to improve their manifold design and to ve-
rify its structural integrity. Manifold modules
belong to subsea structures and therefore,
their structural integrity should follow rele-
vant standards for subsea structures such
as ISO 13819-1 and ISO 13819-2. The piping
of the subsea manifold should be designed
to comply with the ASME code. DRG has an
indepth knowledge of these codes.
Mechanical Response Analysis
Any structure will have a number of mechani-
cal resonance (natural) frequencies. If these
frequencies coincide with those of external
Source: FMC Technologies
8 Subsea Systems
excitatons, for example those due to produc-
tion pumps or the fluid flow within a pipe,
then any small pipe deflection caused by the
excitation mechanism at these frequencies,
could be amplified and may result in vibrati-
ons in the mechanical structure.
These mechanical vibrations, if persistent,
could result in problems due to LCF (Low
Cycle Fatigue) or HCF (High Cycle Fatigue).
As a result of a surge analysis or multiphase
flow analysis (using OLGA® or BOSfluids®),
for each pipe section, the magnitude of the
unbalanced forces are calculated and used in
the mechanical response analysis. This me-
chanical analysis is performed by means of
a pipe stress software package with dynamic
harmonic capabilities. In addition to the flow
transients inside the pipe, the effects of tidal
waves and currents are incorporated.
Subsea separator vessel design
Performing a part of the required separa-
tion process at the seabed, enables a more
effective production. Additionally, the need
for processing facilities on the fixed platform,
FPSO or onshore facility can be significantly
reduced. Dynaflow Research Group assists
its clients in optimizing their in-line subsea
separator technology.
Multiphase (subsea) flow separator vessels
often encounter slugs. The parts of the se-
parator that is most vulnerable to slug loads
are the internals to promote gravity separa-
tion, sand removal, demisting internals and
cyclone scrubbers.
The effects of slug forces working on the in-
ternals can be analyzed using dedicated CFD
(Computational Fluids Dynamics) and FEA
(Finite Element Analysis) techniques. The
numerical results should be combined and
compared with analytical multiphase flow
calculation. It is also possible to assess the
flow (detailed structure and medium proper-
ties) for a three-phase flow, which is difficult
to predict. Common analytical theories can
be used to predict the flow regimes based
upon the process conditions supplied by the
client.
When the kind of flow structure is known and
what the average flow velocities are for the
different flow phases, the slug loads can be
determined. Based on the determined slug
loads and the geometry and configuration of
the internals, a detailed FEA (Finite Element
Analysis) analysis can be performed to assess
the fatigue performance.
Source: FMC Technologies
9Subsea Systems
Subsea wellheads and trees
In the subea production system the wellhead
and Christmas trees are the most vital pieces
of equipment. The subsea wellhead system
has the same functions as a conventional
surface wellhead. It needs to seal the casing
strings in the well, supports the BOP (Blow
Out Preventer) during drilling and supports
the tree during production. The primary
function of the subsea Christmas tree is to
ensure a structural and pressure containing
anchoring point on the seabed for drilling
and production. All internal components of
the subsea tree to support the casing strings
and provide guidance and mechanical sup-
port need to be designed conform the rele-
vant code and regulations.
Depending on the project and field develop-
ment, DRG assists its clients designing their
subsea tree to comply with codes like API
6A, API 17D, API RP 17H, ASME B31.3, ASME
B31.8, ASME BPVC VIII, among others. Detai-
led dedicated FEA (Finite Element Analysis)
techniques will be employed to satisfy the
main subsea tree requirements like sealing
of the casing strings, interface between tree
system and BOP and to accept all loads on
the subsea wellhead system from drilling and
production (including thermal expansion).
Dynaflow Research Group is often involved
with the design and verification of a subsea
structure, including:
■ Analysis of the mechanical integrity of
the subsea manifold, including detailed
mechanical response analysis and mul-
tiphase flow behavior,
■ Proper design of subsea equipment like
separators, subsea wellheads and trees
to increase drilling and production effi-
ciency.
Source: FMC Technologies
10 Subsea Systems
Source: Emerson
11Subsea Systems
The deliverability of hydrocarbon products
from the reservoir to the end user is essential
to the success of oil and gas developments,
but often turns out to be the bottleneck of
the system. Especially in subsea systems, ri-
sers and flowlines play a vital role to ensure
a production that generates a reliable, mana-
geable and profitable flow of fluids from the
subsea well and tree up to the fixed platform,
FPSO or onshore facilities. The most signifi-
cant challenge of subsea flow assurance is
prevention and control of solid deposits that
could potentially block the flow of product.
Steady state hydraulic and thermal performance analysis
Using software like OLGA® or BOSfluids® a
steady state flow model can be generated
which is basically the first step in the analy-
sis of the subsea flowline performance. The
relationship between flow rate and pressure
DRG■provides■consulting■services■and■engineering■solutions■of■Flow■Assurance■of■Subsea■Systems■in-cluding■steady■state,■transient■multiphase■flows,■heat■transfer■and■erosion■modelling
Subsea Flow Assurance
drop along the subsea flowline, tie-back and
riser is determined, leading to maximum and
minimum allowable flow rates.
Subsequently, the temperature and pressure
distributions along the subsea flowlines are
obtained to ensure that the conditions in
the flowline are such to avoid the formation
of hydrates during steady-state conditions.
When the temperature distibution is ob-
tained, an insulation combination is chosen
that prevents the temperature at the riser
base of a tie-back subsea system from fal-
ling below the minimum value for cooldown
at the maximum range of production rates.
Using dedicated software solutions, the
maximum flow rate in the system can be ob-
tained to ensure that arrival temperatures do
not exceed any upper limits defined by the
separation or dehydration processes or by
equipment design.
12 Subsea Systems
Transient flow behavior and ther-mal performance analysis
Water temperatures at the sea bottom can
be very low, almost at freezing point. When
the flow in a pipeline on the seabed comes
to a standstill, the temperature of the hydro-
carbon pipe content can quickly decrease.
Low temperature in a pipeline can lead to
the formation of paraffin, asphaltenes and
hydrates, which can cause significant, even
catastrophic, operational issues.
The transient subsea flowline analysis typi-
cally include start-up, shutdown and blow
down scenarios as well as pigging and slug-
ging occurances. During these scenarios, it is
important to maintain the fluid temperature
above the hydrate dissociation temperature
corresponding to the pressure at every loca-
tion. To meet this important requirement, it
may be necessary to incorporate a combina-
tion of an insulated pipeline and the injection
of chemical inhibitors into the transient simu-
lation to prevent hydrate formation.
BOSfluids® and OLGA®
Successful design and operation of multi-
phase production systems rely on detailed
understanding of the fluid flow behaviour.
BOSfluids® is the engineering software packa-
ge that analyzes fluid transients in piping sys-
tems and relates this information back to the
mechanical system transferring the fluid.
Additionally, Dynaflow Research Group is
experienced in the use of OLGA®, a widely
used software tool to simulate multip-
hase transport of oil, water and gases.
For complex and sensitive systems, it
can necessary to investigate the three-
dimensional flow field. This can be obtained
by performing a full Computational Fluid Dy-
namics (CFD) analysis.
Flow regime prediction
Multiphase flow can take many different
forms. The most severe multiphase flow
regime is slug flow, subsea flowline or riser
sections completely filled up with liquid and
holding up the gas flow. Slugging can cause
large pressure transients or potentially lead
to flooding of liquid at the receiving end at
the platform. Slugs can also result in an in-
creased volume of solid deposits, corrosion
and erosion.
“DRG assists in improving thermal and pressure control to increase subsea produc-tion rates”
13Subsea Systems
It is, however, extremely difficult to predict
the detailed structure of a multiphase flow
and therefore to determine the medium
properties. Several theories are often used
to predict the type of flow regime for a mul-
tiphase flow, sometimes even supported by
measurements. With these theories it beco-
mes possible to estimate what flow structure
is likely to occur and what the actual average
velocities are for the different phases.
Erosion assessment of subsea flowlines and structures
The integrity of the subsea system and
structures is of upmost importance during
the production life of a field. Sand particles
in the produced hyrdrocarbon can lead to
erosion as it is transported from the well to
the platform or onshore facilities through
various subsea structures. Therefore it is
necessary to obtain good knowledge about
the particle travels, which can be a good
indication where erosion might occur over
time. Prior understanding of erosion in
a subsea system can help assure system
integrity by taking measures as cladding
of the subsea structures or incorporate
predictive devices to monitor erosion rates.
Dynaflow Research Group uses advanced
CFD (Computational Fluid Dynamic)
techniques in combination with several
recent erosion correlations, to reliably predict
erosion rates in subsea systems. The regions
where maximum erosion (“hot spots”) is
likely to occur under complex flow behavior,
i.e. several multiphase flow regimes can be
highlighted.
CFD is often used as well for various multip-
hase flow problems related to subsea pro-
duction systems like slug catchers, separa-
tors, mixing vessels among others.
DRG is able to assist you using all of the above
mentioned techniques to verify and improve
the performance of the subsea production
system related to flow assurance issues.
14 Subsea Systems
15Subsea Systems
Pipelines, flowlines and risers are crucial in
production of oil and natural gas. Unreliable
fluid flow can affect the productivity of the
whole production process. Particularly since
flowlines and risers often deal with complica-
ted multiphase flow conditions, a sound ana-
lysis and thorough understanding of the riser
design is of vital importance to keep produc-
tion high and to minimize losses.
Structural integrity of rigid and flexible risers
A subsea production system consists of con-
ductor pipes connected to floaters on the
surface on one end and to the wellhead at
the seabed. There are essentially two types of
subsea risers: rigid risers and flexible risers.
Alternatively, an hybrid riser is constructed
by combining the two.
The rigid risers forms an extension from the
flowline that is hung from the platform in a
Using■a■broad■Subsea■Engineering■experience,■DRG■provides■high■quality■support■for■the■design■verification■of■subsea■risers■and■flowlines
simple catenary, SCR (Steel Catenary Riser).
The rotational movement between riser and
the platform is equiped with flexible joints to
cope with the movement. The second type of
rigid riser is called TTR (Top Tensioned Riser)
and consists of a long circular cylinders con-
necting the seabed to the platform. These
risers are subject to steady currents with va-
rying intensities and oscillating wave flows. At
the top, these TTRs are equiped with tensio-
ners to maintain the angles of the riser pipes.
Flexible risers are constructed using multiple
layer composite pipes with relative bending
stiffness. Layers of different types of steel
(stainless and carbon) are used to provide
sufficient strength, while adding enough
flexibility. Flexible risers are successfully ap-
plied in deep and shallow water flowline sys-
tems.
For the preparation of FEED (Front End En-
gineering Design) documentation, detailed
Subsea Risers and Flowlines
16 Subsea Systems
strength and fatigue assessments of both
rigid and flexible risers are performed to ve-
rify:
■ Extreme response satisfying API 2RD
and extreme rotation for the flexible
joints,
■ Fatigue life related to Vortex Induced
Vibrations and oscillating Wave loading,
■ Interference with the floater constructi-
ons.
Prevent risers slugging
The very nature of risers, vertical lines with
multiphase flow conditions, makes riser lines
and the connecting flowlines highly suscepti-
ble for slugging. The slugs in a riser or vertical
part of a pipeline are often created near the
lowest point of the line when the liquid in a
gas-liquid flowline fills the complete cross-
section of the pipe. Consequently, the gas
pressure will drastically increase behind the
liquid, such that the liquid slug is blown out
of the riser.
The slugs, developed in a riser, have the ten-
dency to grow in size when travelling up the
riser. These slugs can grow as long as many
hundreds of meters with periods in the or-
der of hours. The slugs can grow even longer
than the riser itself, a condition called severe
slugging. Liquid carryover or problems rela-
ted to liquid- and pressure-control problems
might occur when long liquid slugs and gas
surges are processed.
DRG assists its clients to avoid or minimize
slug problems by accommodating your riser
design, for example by applying choked flow,
or with the design verification of separator
vessels.
Critical transient flow scenarios
Considering a riser line landing on a platform
with the riser exposed to slug flow. A valve
protects the platform from pressures excee-
ding a designed maximum. Different critical
scenarios need to be defined of to pressure
surges due to sudden valve closure related to
the characteristic time and thus the length of
the slug and hence the slug volume.
For valve closure times longer than the cri-
tical closure time the valve is called “slow
closing” and the reflected pressure wave
reaches the valve before it is fully closed. For
times shorter than the critical closure time
the valve is “fast closing”. The resulting pres-
sure surges can be calculated by considering
the deceleration of the fluid. Additionally,
Source: Total
17Subsea Systems
very high pressures are able to develop when
an amount of gas is trapped and compressed
in between the slug and the valve.
DRG assists its clients by performing compre-
hensive riser studies. Often corrugated pipes
are susceptible for excitation of the longitu-
dinal acoustic modes of the pipe due to the
multiphase flow, so called ‘singing risers’.
Sometimes, a full CFD analysis is required to
study vortex shedding and slug build-up in
flexible risers and transportation lines.
Collapse, buckling and fatigue of pipelines and risers
Buckling is a failure mode characterized by
structural instability in a compressive stress
field. Since subsea flowlines are subjected
to high external pressure, special attention
should be given to collapse and buckling cri-
teria.
These criteria depend on the diameter to wall
thickness ratio, pipe imperfections and load
conditions such as axial tension, bending
stress and external pressure. A good know-
ledge of these criteria is required to arrive at
a robust pipeline design, which exhibits suf-
ficient safety against buckling.
Flowline stability design from sub-sea tree to processing facility
In subsea production it is vital to ensure that
hydrocarbons are transported in stable pipe-
lines. Here vertical and lateral stability may
be critical. Regarding vertical stability, not
only floatation problems of the pipeline are
to be considered, but also sinking problems.
When a pipeline is running over a sandy se-
afloor, liquefaction of the soil might result in
too deep settling of the pipeline in the seaf-
loor sediment.
A lateral stability analysis is performed in all
waters subjected to large current and waves,
DRG perfoms these analyses often in compli-
ance with the appropriate codes (i.e. DNV-
RP-F109) to perform an absolute lateral stabi-
lity analysis, a the generalized lateral stability
analysis or a full dynamic lateral stability ana-
lysis.
Source: FMC Technologies
18 Subsea Systems
19Subsea Systems
DRG■provides■consulting■services■and■engineering■solutions■to■improve■Subsea■Production■Systems
What can we do for you?
What can we do for you?
Due to our highly qualified staff and expe-
rience in this field, DRG is often required to
solve problems involving subsea production
systems, subsea flowlines from wellhead to
fixed platform, FPSO or onshore facilities,
and attached equipment like separators and
slugcatchers.
Dynaflow Research Group can assist you with
the following engineering assignments:
1. Analytical multiphase flow regime and
heat transfer assessment,
2. Pressure drop calculations,
3. Transient multiphase and thermal flow
analysis of subsea flowlines and risers,
4. Predicting hydrodynamic and terrain/
riser induced slugs,
5. Development of the operating envelope
cold and hot start-up, cooldown blow-
down and warm-up,
6. Detailed flow studies using Computati-
onal Fluids Dynamics of slug catchers,
separators and multiphase subsea flow-
lines and equipment,
7. Analysis of the mechanical integrity of
the subsea manifold, including detailed
mechanical response analysis and mul-
tiphase flow behavior,
8. Proper design of subsea equipment like
separators, subsea wellheads and trees
to increase drilling and production effi-
ciency.
Communication
To us communication with our clients during
a project is of upmost importance. For each
project the client is updated regularly with
the progress of our work. We liaise with the
client to ensure we have the most accurate
information to conduct our analyses and to
ensure the clients remain closely involved.
20 Dynaflow Research Group
At■Dynaflow■Research■Group■(DRG)■we■support■our■clients,■solve■their■most■complex■and■critical■technical■issues
Dynaflow Reseach Group
Consulting services
We provide engineering consulting services
in all aspects of design and analysis for the
Petro- chemical industry. Our work often re-
quires a multi-disciplinary approach where
we combine expertise in fluid flow behaviour,
dynamic oscillations, FEM and stress analysis
with sophisticated analysis software to pre-
dict system performances.
Training
DRG offers a wide range of training courses
such as software training, fiberglass training,
dynamics and stress training. Most of these
training courses are offered on a regular ba-
sis during the year. We also develop custo-
mised training programs with our customers
fit to their specific needs.
Products
DRG has been developing software for many
years, which has resulted in several commer-
cially available software packages such as
BOSfluids®, BOSpulse®, Jive and Hades. We
also provide technical consulting services,
and develop numerical software that can be
used in computer simulations and other ty-
pes of scientific computations.
Research
DRG conducts research on different aspects
of pipe-system design and pressure vessels.
Most of this research is done in close collabo-
ration with Paulin Research Group and their
Houston test facilities (www.paulin.com).
Dynaflow Research Group provides support
to clients with their R&D to help them conti-
nuously improve their products.
21Dynaflow Research Group
Topic specific brochures:
• Consulting Service Series• Software Product Series• Training Series
Visit our website www.dynaflow.com or send an e-mail to info@dynaflow.com
Houtsingel 95 2719 EB Zoetermeer The NetherlandsReg nr. 27320315
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+31 79 361 5150+31 79 361 5149info@dynaflow.comwww.dynaflow.com