Subsea Wells Tie-back to Onshore Plant (Subsea + Offshore Flow line + Pigging Line Infrastructure) at Anchois -1 Field.

1. 1 OFF550 SUBSEA TECHNOLOGY Project Report / ANCHOIS – 1 Field
! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!By!Jose!V.Taboada!//!Stud.nr:!217961!
!
Project Overview
The “Anchois – 1” is part of the Production Tanger-Larache
blocks (47, 48, and 49 in Offshore Morocco), the overall of the
area is around 2744 m2
, being located at 40Km off the Morocco
shoreline to South West (SW). The project operator is lead by
Repsol YPF SA (36%), and operated the consortium with:
Gas Natural Exploration SL→ 24%
Dana Petroleum (D&P) LTD→ 15%
ONHYM→ 25%
The “Anchois – 1” includes encountering reservoir with 90 m of
Gross Gas Column in Two sections (100Bcf = 2.8Bcm
=2.779MMSm3). Potential restriction with “Gas-Bearing Sands”
detected. The “Anchois – 1” reservoir is a discovery from March
2009.
The Field Development contains a Subsea, Offshore Flowline
and Pigging Line infrastructure. The concept selection carry out
is a Subsea System tied back and exported to Onshore Plant
(“Subsea Wells Tie-back to Onshore Plant”) via flow lines and
control umbilical.
The field itself shall be designed with flexibility for new tie-in of
the new discoveries further in the area. Prospection phase has
been development in 2009, and Exploration was during 2011 and
the Drilling phase along 2013.
The water depth is around 387m.The field representation and
existing subsea infrastructure, shown on the Annexes.
Subsea Concept
First at all, to reach up a determination of a Subsea Concept, to
carry out and be implement, shall be base on the ‘‘Objectives of
the Design’’, are listed below:
! Efficient Interface coordination (between Drilling
&Well, Subsurface, Downstream Facilities).
! Cover all design premises for the facilities concept
development process, and successive development
steps.
! Have into account, future operational objectives and
functional requirements for field.
! Establish coalition between services companies and
operator.
In based on previous objectives cited above, the Concept selected
shall be a “Subsea Wells Tie-back to Onshore Plant” through
“Subsea Wells + Multi-Manifold”.(See Annexes representation).
Which one, has been determined through a survey of couple
number of parameters and requirements to satisfy. As main
requirement of the concept, shall allow for tie-in of the future
prospects in the area, for more Subsea Templates, in addition to
possible future Low-pressure production. Which one, we concept
selected allows that. In terms of production rate, using Multi-
Manifold (with Gas Condensate Pumps) will increase
considerable high, due to two pumps in parallel position
integrated.
(QOutLetFlow=QA+ QB → ↑"$ ↑), this particular dimensioning
allows to decrease the pressure rate at the outlet in the Multi-
Manifold (HOutLetFlow=HA- HB → POutLetFlow↓↓). See next
representation below;
.
Figure 1. Pumps production system into the Multi-Manifold.
In contrast, using this type of dimensioning is going to demand
more consuming Energy Supply.
Sand detectors and Gas meters will be installed at the Wellhead
on each well. Such as, Salt detection will be installed as part of
the wet gas meters.
The objective of this subsea solution is to keep up affordable to a
manageable level of activity within a reasonable time frame, and
balancing the full lifecycle with the benefits of production from
the field.
Subsea Features and Key Equipment
The whole Subsea installation begins from Subsea satellite wells,
to ending of the Flow lines and Cables to Onshore plant.
The key pieces equipment, could the two VXTree for each well,
have the next characteristic bellow;
• Simple installation from Vessel, as result a decrease of
Cost Installation.
• Save Energy Supply, only is needed one time to run
each BOP from shore.
As second key part of the installation, could be the Mult-
Manifold (with Gas Condensate Pumps), being classified as key
element for the whole installation, for the next reason below;
• Allows flexibility for new tie-in of the new discoveries
further in the area (new Infield Flow lines into the same
Multi-Manifold).
• Rise up the caudal Flow production, from each column
of Gas, due to two pumps, as having also safety effect
to avoid the formation of ‘Gas Hydrates’, where the
pumps will draw down wellhead pressure and increase
considerably the Flow line Inlet pressure and the caudal
Flow from wells increase as well. (VFlow↑→ Ta↑↑ and
Pressure↓).

2. 1 OFF550 SUBSEA TECHNOLOGY Project Report / ANCHOIS – 1 Field
! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!By!Jose!V.Taboada!//!Stud.nr:!217961!
!
• A considerable reduction of the CAPEX, due to a minor
controls requirements and the installation Cost, in
contrast the Net increases in Oil production (QFlow↑=
$↑↑).
Therefore, using a Multi-Manifold will increase the Control
Capacity, Flexibility, Reservoir Management and Production.
As third key component, shall be cited the Subsea Control
Module, which one shall be capable of management and
controlling each VX-Tree with associated sensors, valves, and
flow control system, in addition to downhole applications.
Other Options and Solutions
We could carry out two main types of subsea solutions;
1. Deepwater Platform to Onshore Plan
(“Offshore stand-alone development”).
2. “Subsea Wells Tie-back to Onshore Plant” through
“Template”.
For the first one, the impact of this conceptual development has
high cost of implementation for Facilities Offshore, which ones
will increase the Cost of Production phase, that means shall raise
considerable the Reduced Costs during cited phase, as result that
Equipment is not designed for the entire project life, having
interchangeable phases.
In the second one, to consider this conceptual idea, could be
carry out and satisfactory to implement for this Well-Stream
Composition in particular. The Template is a large steel structure
which is used as a base of a global integration for wells, subsea
trees and manifolds.
This subsea well configuration has better global integration of
the subsea equipment and productive structures covering, to
prevent damage from fishing activities. But breaks down the
further concept develop in the area (“Flexibility for new tie-in of
the new discoveries”).
Optimal Solution
As was stated above, the solution to execute might be a “Subsea
Wells Tie-back to Onshore Plant” through “Subsea Wells +
Multi-Manifold”.
Knowing that reservoir is close to shore and located between
shallow to transitional waters (D=387m), due to using this
concept selection will contribute to avoid the huge cost of
displacement a Platform dry/wet wells and FSU or even high
Risk levels during the Production(“Offshore stand-alone
development”).
By other hand, according to the estimates reserves provided
(100Bcf = 2.8Bcm =2.779MMSm3
=16.479MM BOE) consider
this Input information given, could be classified as big field, that
means, installing of this concept selection (“Subsea Wells Tie-
back to Onshore Plant”) will contribute for a long period of life
cycle Production, reducing costs during the Production phase.
From OPEX perspective, exist less leak possibilities, less risk of
mal-operations, and simplified operational procedures.
Although, having into account the needs of the Field itself (Big
reservoir + Two columns of gas), the most optimal philosophy
design to carry out (“Subsea Wells + Multi-Manifold”) for this
Well-Stream Composition, looking to keep open new
possibilities for new subsea wells located around further, that
means using Multi-Manifold (with Gas Condensate Pumps) is
going to allow us, more Infield Flowlines into the same Multi-
Manifold, as well was explained previously.
The magnitude of Pipeline Export system (L=40Km) will have a
better contribution during the production phase for this solution,
rather than “Offshore stand-alone development” solution, which
one is suitable for small fields.
In summary, the Facilities (Risers, Export Pipeline rises, Subsea
System, Topside Production Facilities or Mooring lines) will be
avoided to install and mobilize that Equipment.
A balance between Economical, Technical and Strategic issues
had been found for an optimal solution.
Risk and Lessons Learned
Focus on the “Offshore stand-alone development”, in case to
implement this concept development, is going to originate more
Risk Levels during the Production Phase, due to is necessary to
mobilized and implement more Equipment Supply Offshore,
rather than the concept determined above.(“Subsea Wells Tie-
back to Onshore Plant”).
For the Optimal solution, the formation of Span and Buckling
along 40Km of pipeline to shore, are quite likely to happen these
types of Risk, as consequence of the conditions and properties
(Sand = Soft Friction) on Seabed, as well as high dimensioning
requirement for the legs/foundations of the Multi-Manifold. Such
as, a Corrosion distribution along the pipeline, shall be expected
to happen.
As main Risk of Flow Assurance, obviously is the Gas-Bearing
Sand formation that might be gives the chance to originated
Slugg Effect, or even sand screen failure. The mitigation of this
harms, shall be prevent through as first barrier, a Sand Control
System (Active Sand Control is needed!), and with second
barrier on the Terminal Plant (Onshore), through Slugg Catchers.
From the Economical perspective, the installation along pipeline
to shore (40Km) will rise up the CAPEX investment, and also
reduced the controls requirements and given more flexibility.
As Risk induced by the Owner (Repsol YPF) might not be
willing to invest enough money for O&M while Wells were
producing profitably.
Concerning to the Environmental Risk, the Concept selected as
Optimal, will have a major impact on the Sea bottom nature or
even a limitation area for fishing activities.

3. 1 OFF550 SUBSEA TECHNOLOGY Project Report / ANCHOIS – 1 Field
! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!By!Jose!V.Taboada!//!Stud.nr:!217961!
!
References
[1]http://www.onhym.com/Default.aspx?alias=www.onhym.com
/EN
[2]Leslie Adriaansen, Jens Henrik Neuenkirchen, Jim Cattanach,
Sigurd Moe, Carl Eriksen and Huge Clayton. Subsea Control and
Data Acquisition. Professional Engineering Publishing(June -
2002).
[3]API RP 17A, Recommended Pratice 17A, Design and
Operation of Subsea Production Systems.Second Edition(Sept –
1996).
[4]http://www.repsol.com/es_en/corporacion/prensa/notas-de-
prensa/ultimas-
notas/descubrimiento_gas_aguas_marruecos.aspx
[5]http://www.tekna.no/ikbViewer/Content/22993/Nils%252520
Arne%25252 0S%2525C3%2525B8lvik.pdf
[6] http://www.subseaworld.com/fields/dana-petroleum-makes-
gas-discovery- offshore-marocco-02913.html
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4. OFF550 SUBSEA TECHNOLOGY ANNEXES Project Report /ANCHOIS – 1 Field
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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Ref:!ONYM(www.onhym.com).Ac5vity!Report!2009.Office!Na5onal!Des!Hydrocarbures!et!des!mines.!Kingdom!of!Morocco.!2009.!
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! !Ref:!ONYM(www.onhym.com).Ac5vity!Report!2009.Office!Na5onal!Des!Hydrocarbures!et!des!mines.!Kingdom!of!Morocco.!2009.!
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Annexes!
NGL!
Compressor!
Sta5on!

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!! Project(Overview(
N Objec.ve:(To!transport!Rich!Gas!from!Blocks!(47,!48,!
and!49)!to!Onshore!Plant!Facili5es.!
N Field(Development:(Subsea!+!Offshore!Flowline!+!
Pigging!Line.(“Subsea'to'Shore'–'S2S”)!
N Concept(Selected:!“Subsea!Wells!TieNback!to!Onshore!
Plant”!through!“Subsea!Wells!+!Mul5NManifold”.!!
N Drive(Mechanism:!Rich!Gas!+!Condensate!shall!be!
Recovered!by!Deple2on!and!later!by!Gas'
Compression.!
N Loca.on(:(From!“Anchois!1”!wells!to!the!Onshore!
Facili5es!at!40Km!off!the!Morocco!shoreline!to!South!
West(SW).!
N Owner:(Repsol!YPF!(36%)!
N Shareholders(:(Gas!Natural!Explora5on!SL!(24%),!
Dana!Petroleum!(D&P)!LTD!(15%)!and!ONHYM!(25%).!
N Capacity:!100Bcf!=!2.8Bcm!=2.779MMSm3(High!
Volume!of!Rich!Gas!moved).!
N Target!Depth!(TD)!Points!for!each!Column!of!Gas,!are!
depth.!!(Greater!Depth!Reservoir!=!High!Pressure)!!
! Schedule(&(Phases(
N Prospec.on:(during!2009!(Discovery!in!March!2009).!
N Explora.on:(during!2011.!
N Drilling:(during!2013.!
N Produc.on:(Forward!2014.!
! Challenges(
N!!!!!!Flow!Assurances.!
N Well!Stream!Composi5on.!
N Remote!Control.!
N Corrosion!Control!&!Corrosion!Monitoring.!
N GasNBearing!Sand!forma5on.(demanded%acousSc%%%
Sand%Control).!
N Gas!Hydrates!forma5on.(avoid%through%MEG'flow%
control).!
N Pipelines!Rou5ng.(Against!Wave!Impact!&!Abrasion!
from!moving!Sand!and!Gravel).!
! Design(Objec.ves(
N Be!available!to!produce!as!much!as!possible!from!
Reservoir.[QOutLetFlow!=↑$!↑!]/Max(Produc.vity!/!
N LowNCost!Pumping!for!both!Gas!Wells!to!recovery!
more!Gas./Minimize(Energy(Consump.on/!
N The!whole!system!must!be!FailESafe.!
N Marine!Systems/Subsea!Technology!for!Improved(
Operability(and!CAPEX/OPEX(Op.miza.on.!
N Reservoir!Proper5es!on!a!wide!range!of!Inlet!
composi5ons.!(Flow(Assurance)!
N Environmental(Impact!Considera5ons.(HSE)!