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Overview of subsea production systems


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Overview of main components of subsea production / injection systems, including:
­ Wellhead
­ Subsea tree (Vertical, Horizontal, or Drill-thru)
­ Structural foundation / Template / Manifold /Jumpers
­ Subsea processing equipment
­ Chemical injection system
­ Umbilical with electrical power and signal cables
­ Risers
­ Production Control and Monitoring System

Published in: Technology

Overview of subsea production systems

  1. 1. Overview of Subsea Production Systems G. Moricca Senior Petroleum Engineer Main Sources: API 17 TR 13 Jan 2015, GE, DNV GL, Aker Solutions
  2. 2. April 2017 G. Moricca 2 Subsea Production and Injection System A subsea production or injection system can include one or more of the following main elements:  Wellhead  Subsea tree (Vertical, Horizontal, or Drill-thru)  Structural foundation / Template / Manifold /Jumpers  Subsea processing equipment  Chemical injection system  Umbilical with electrical power and signal cables  Risers  Production Control and Monitoring System
  3. 3. April 2017 G. Moricca 3 All Segments of a Subsea Production System The subsea production system associated with the overall process and all the equipment involved in drilling, field development and field operation, is shown. Subsea distribution systems in operation Field development Drilling
  4. 4. April 2017 G. Moricca 4 Typical subsea production system Sources: Statoil
  5. 5. April 2017 G. Moricca 5 Sources: GE Oil and Gas
  6. 6. April 2017 G. Moricca 6 Subsea Wellhead  A wellhead with associated casing strings to provide a basic foundation structure and pressure-containment system for the well Subsea wellhead Subsea wellhead Subsea wellhead
  7. 7. April 2017 G. Moricca 7 Subsea Xmas Tree  A subsea Xmas tree (Vertical, Horizontal, or Drill-thru) incorporating flow and pressure-control valves
  8. 8. April 2017 G. Moricca 8 Christmas Tree Systems Onshore Tree Offshore Tree Subsea Tree DNV GL © 2013
  9. 9. April 2017 G. Moricca 9 Xmas Tree Overview Xmas Tree features:  Control, monitor and condition either produced or injected media. (Designs for either 5000, 10000 or 15,000 psi wp)  Provides normal and failsafe methods of shutting the well at the mudline  Provides a interface to re-enter the well at any time during the life of the field  Provides a platform/interface from which to monitor down hole pressure temperature or ‘smart well’ systems & applications  Provides a platform/interface from which to inject chemicals either down hole or at the Xmas Tree
  10. 10. April 2017 G. Moricca 10 Xmas Tree Overview  There are two basic types of subsea trees: - vertical trees (VXT) - horizontal trees (HXT). The defining differences between the two basic tree types are as follows:  in a VXT, the master valve is located directly above the tubing hanger in the vertical run of the flowpath, while in an HXT the master valve is in the horizontal run adjacent to the wing valve, i.e. there are no tree valves in the vertical portion of the flowpath, unless a ball valve is incorporated into the internal tree cap;  in a VXT configuration, the tubing hanger and downhole tubing are run prior to installing the tree, while in an HXT the tubing hanger is typically landed in the tree, and hence the tubing hanger and downhole tubing can be retrieved and replaced without requiring removal of the tree. By the same token, removal of an HXT normally requires prior removal of the tubing hanger and completion string;  VXT systems are run on a dual-bore completion riser (or a monobore riser with bore selector located above LRP and a means to circulate the annulus; usually via a flex hose from surface). TH of HXT are typically run on casing tubular joints, thereby saving the cost of a dual-bore completion riser, however a complex landing string is required to run the TH. The landing string is equipped with isolation ball valves and a disconnect package made specially to suit the ram and annular BOP elevations of a particular BOP. Subsequent rig change requires certain components of the landing string to be changed out to suit the new BOP ram and annular BOP elevations.
  11. 11. April 2017 G. Moricca 11 Vertical Tree (VXT) Systems  In VXT systems, the tubing hanger is typically installed inside the wellhead and the tree is then installed on top of the wellhead.  The tubing hanger forms the connection between the production/injection tubing and the tree via extension subs which seal between the base of the tree and the matching seal bores in the top of the tubing hanger.  The tree consists of a valve block with bores and valves configured in such a manner that fluid flow and pressure from the well can be controlled for both safety and operational purposes.  The tree includes a connector for attachment to the wellhead (or tubing hanger spool if used).  The connector forms a pressure-sealing connection to the wellhead, while bore extension subs from the tree to the tubing hanger form pressure- sealing conduits from the main bore and annulus of the well to the tree.
  12. 12. April 2017 G. Moricca 12 Example of a typical vertical tree
  13. 13. April 2017 G. Moricca 13 Horizontal Subsea Tree (HXT) Systems  The HXT consists of a valve block with bores and valves configured in such a manner that fluid flow and pressure from the well can be controlled for both safety and operational purposes. The tree includes a connector for attachment to the wellhead.  The connector forms a pressure-sealing connection to the wellhead, while annular seals on the tubing hanger (TH) seal between the main bore and annulus of the well to the tree.  A completion stab seal extending from the bottom of the XT penetrates and seals into the upper casing hanger. The completion stab seal features a helix to passively orientate the TH during landing.  External piping provides fluid paths between the bores of the tree and the flowline connection points. The flowline(s) may be connected either directly to the tree, or via piping on a production guidebase.  A plug is usually installed inside the top of the TH to seal the vertical bore through the TH, and then an internal tree cap is installed inside the top of the tree to provide a second pressure-retaining barrier.
  14. 14. April 2017 G. Moricca 14 Example of a typical horizontal tree
  15. 15. April 2017 G. Moricca 15 Horizontal Subsea Tree (HXT) Systems  Use of HXT was initially aimed at ESP applications where frequent full bore workovers were expected, but has now gained acceptance for use even in natural drive wells. They were also of interest due to the ability to run the TH on standard tubing joints rather than a dual-bore completion riser, but similar systems are now available for VXT systems.  The fact that the TH can be retrieved without disturbing the XT makes this type of tree of considerable interest for installations using downhole equipment deemed to require frequent retrieval (i.e. submersible pumps, intelligent completions, etc.).  The use of VXTs with ESP in a deepwater marginal development, for instance, can prove to be uneconomical purely on account of the frequent costly workover operations.  HXT designs are also of interest for use on high production-rate wells or water injection wells, particularly in template or clustered configurations. In these cases, only one HXT might be needed, instead of perhaps two VXT types.
  16. 16. April 2017 API 17 TR 13 Xmas Tree Components Key 1 SCSSV control line 2 tubing hanger (TH) 3 conductor housing 4 casing hangers and seal assemblies 5 guideposts (optional) 6 XT cap 7 Xmas tree (XT) 8 DHPTT monitoring line 9 flowline connector 10 XT connector 11 guidebase 12 flowline/tie-in spool connector 13 wellhead 14 drilling guidebase or template slot Vertical Xmas Tree (VXT) Horizontal Xmas Tree (HXT) Key 1 horizontal stroking couplers/connectors 2 SCSSV and DHPTT lines 3 wellhead 4 XT connector 5 TH orientation helix 6 completion stab sleeve 7 conductor housing 8 casing hangers and seal assemblies 9 XT cap 10 guideposts (optional) 11 internal tree cap (ITC) 12 ITC plug 13 tubing hanger (TH) 14 TH plug 15 Xmas tree (XT) 16 flowline connector 17 guidebase 18 flowline/tie-in spool connector 19 wellhead 20 drilling guidebase or template slot 16G. Moricca
  17. 17. April 2017 G. Moricca 17 Dual Bore Tree Diverless Xmas Tree Overview Dual Bore Tree Deepwater Mono Bore Tree Deepwater Horizontal Tree Deepwater Vertical Shallow Water Dual-Bore Subsea Tree Systems
  18. 18. April 2017 G. Moricca 18 Horizontal vs Conventional Tree Gate Valve
  19. 19. April 2017 G. Moricca 19 Horizontal vs Conventional Tree Horizontal tree Vertical tree Production master valve (PMV) in horizontal bore Production master valve (PMV) in vertical bore Single, concentric bore Dual bore (production + annulus) Production bore up to 7” Production bore up to 5” Must pull the production tubing to retrieve the tree Must pull the tree to retrieve the production tubing Workover riser on tree Requires landing string to secure well before workover Both barriers fail if the tree is accidentally removed Primary barrier is maintained if the tree is accidentally removed Designed to take the load from a BOP (increased weight) Not designed to take the load from a BOP Must run the BOP twice during completion Only needs one BOP run during completion DNV 2015
  20. 20. April 2017 G. Moricca 20 Selection Criteria Horizontal vs Conventional Tree DNV 2015  The cost of an HXT is much higher than that of a VXT; typically the purchase price of an HXT is five to seven times more.  A VXT is larger and heavier, which should be considered if the installation area of the rig is limited.  Completion of the well is another factor in selecting an HXT or VXT. If the well is completed but the tree has not yet been prepared, a VXT is needed. Or if an HXT is desired, then the well must be completed after installation of the tree.  An HXT is applied in complex reservoirs or those needing frequent workovers that require tubing retrieval, whereas a VXT is often chosen for simple reservoirs or when the frequency of tubing retrieval workovers is low.  An HXT is not recommended for use in a gas field because interventions are rarely needed.
  21. 21. April 2017 G. Moricca 21 Structural Foundation/Template  A template is a seabed-founded structure that consists of a structural framework and a foundation (driven/suction piles or gravity-based), arranged so as to provide support for various subsea equipment such as: - subsea wellheads and trees, - piping manifolds (for production, injection, well testing and/or chemical distribution systems), - control system components, e.g. SCMs, hydraulic piping, electrical cabling, - drilling and completion equipment, - pipeline pull-in and connection equipment, - production risers. Aker Solutions Mini Suction Piles Template Aker Solutions Hinged Manifold / Template
  22. 22. Structural Foundation/Template photo gallery (1) 15 slot Claxton subsea drilling template-Statoil Pre-drill template in place - Statoil Seabed Wellheads Template - Statoil Subsea Gas Compression - StatoilApril 2017 G. Moricca 22
  23. 23. April 2017 G. Moricca 23 Structural Foundation/Template photo gallery (2) Work in progress
  24. 24. April 2017 G. Moricca 24 Manifold Module  A manifold is a system of headers, branched piping and valves used to gather produced fluids or to distribute injected fluids. The manifold should provide sufficient piping, valves and flow controls to safely gather produced fluids or distribute injected fluids such as gas, water or chemicals. - The Manifold Module provides the interface between the production pipeline, flowline and well. - Pipelines or flexibles normally interconnect the manifold. - Collecting produced fluids from individual subsea wells. - Distributing production fluids, inject gas, inject chemicals and control fluids. - Distribute the electrical and hydraulic system. - Several XT can be connected to the manifold. - Satellite modules (if required) will be connected to the manifold via a flow line.
  25. 25. April 2017 G. Moricca 25  A manifold module for controlled gathering/distributing of various fluid streams Manifold Module
  26. 26. April 2017 G. Moricca 26  In subsea oil/gas production systems, a subsea jumper is a short pipe connector that is used to connect manifold systems to wells, sleds to wells and/or manifolds to sleds.  Another word the subsea jumper is used to transport production fluid between two subsea components, for example, a tree and a manifold, a manifold and another manifold, or a manifold and an export sled.  Commonly, subsea jumper is classified into two categories which are flexible and rigid jumpers. The flexible jumper systems provide versatility, unlike rigid jumper systems, which limit space and handling capability. Jumpers Subsea Rigid Jumper [Aker Solution].
  27. 27. April 2017 G. Moricca 27 Subsea Processing equipment  Subsea processing equipment, including fluid separation devices and/or pumps/compressors and associated electrical power distribution equipment Subsea Processing System
  28. 28. April 2017 G. Moricca 28 Chemical injection system – Umbilical - Flowlines  A chemical injection system;  An umbilical with electrical power and signal cables, as well as conduits for hydraulic control fluid and various chemicals to be injected subsea into the produced fluid streams;  One or more flowlines to convey produced and/or injected fluids between the subsea completions and the seabed location of the host facility;
  29. 29. April 2017 G. Moricca 29 The primary function is to provide :  chemical injection for flow assurance,  electrical signals for valve control and monitoring,  hydraulic pressure for valve actuation,  electrical power for subsea pumping,  fibre optics for data acquisition and monitoring Umbilical systems for offshore application
  30. 30. April 2017 G. Moricca 30 A riser is a pipe that connects an offshore Floating Production Structure or a Drilling Rig to a sub-sea system either for production purposes such as drilling, production, injection and export, or for drilling, completion and workover purposes. Riser Flexible Riser Production Risers
  31. 31. April 2017 G. Moricca 31 Production Risers  The portion of a pipeline extending from the seafloor to the surface is termed a riser.  The function of a riser is to provide conduit(s) for the conveying of produced fluids and/or injection fluids between the seafloor equipment and the production host. Such risers are generally known as production risers in order to distinguish them from other types of risers such as marine drilling risers and completion/workover risers.  Production risers can be grouped according to the type of production host facility to which the subsea production system is tied back, i.e. either a fixed, bottom-founded structure (e.g. a steel-piled jacket or a concrete gravity structure) or a floating structure, i.e. either a tension-leg platform or a floating production system (e.g. a ship, semisubmersible or spar).  Production risers tied back to floating structures are inherently more complex than those tied back to fixed structures, since they need to be able to accommodate the motion of the floating structure. For this reason such risers are commonly referred to as dynamic risers. Production Risers
  32. 32. April 2017 G. Moricca 32 Completion/workover Riser Systems  Completion/workover riser systems are used for the initial installation of the subsea completion equipment and during major well workovers.  These systems typically require the use of a mobile offshore drilling vessel equipped with full-wellbore-diameter pressure control equipment.  A drilling marine riser has a large diameter, low pressure main tube with external auxiliary lines that include high pressure choke and kill lines for circulating fluids to the subsea BOP, and usually power and control lines for the BOP.  A completion riser is a riser that is designed to be run through the drilling marine riser and subsea BOP stack, and is used for the installation and recovery of the downhole tubing and tubing hanger in a subsea well.  Since the completion riser is run inside a drilling marine riser, it is not exposed to environmental forces such as wind, waves and current. drilling marine riser
  33. 33. April 2017 G. Moricca 33 Completion/workover Riser Systems Completion/workover riser systems are used for the initial installation of the subsea completion equipment and during major well workovers. These systems typically require the use of a mobile offshore drilling vessel equipped with full-wellbore-diameter pressure control equipment. It is essential that, at the conceptual design phase of any subsea field development, the intervention philosophy, both for installation and through the life-cycle, is established. Intervention should be accomplished in a reliable manner that minimizes potential damage to the intervention/operating personnel, the environment, the subsea equipment and the intervention tooling.  A secondary requirement is that the equipment be designed to perform the intended purpose effectively and efficiently, given the environmental operating conditions in which it is to work.
  34. 34. April 2017 G. Moricca 34 Production Control and Monitoring System  The Production Control and Monitoring System provides the means to control and monitor the operation of a subsea production or injection facility from a remote location.  The Production Control and Monitoring System consists of both surface and subsea equipment  Depending on system design and field-specific requirements, the design of the surface equipment can range from simple hydraulic power-packs with integrated control panels, through to more advanced systems including signal multiplexing, with the operator interface integral with the control system for the surface-processing equipment.  The control system may interface with the actuated subsea equipment directly or via a subsea control module. The subsea control module(s) may be configured to operate/monitor functions on each or several subsea XTs, downhole functions and/or manifold functions.
  35. 35. April 2017 G. Moricca 35 Surface equipment  Typical surface components can include: - Topside Umbilical Termination Unit (TUTU) - Hydraulic Power Unit (HPU) - Electrical Power Unit (EPU) - Subsea Control Unit (SCU) - -Master Control Station (MCS) Subsurface equipment  Typical systems components can include: - Umbilical Termination Assembly (UTA) - Subsea Distribution Assembly (SDA) - Subsea Distribution Unit (SDU) - Communications Interface Unit (CIU) - Subsea Electrical Junction Box - Subsea Control Module (SCM) - Subsea Electronics Module (SEM) Production Control and Monitoring System
  36. 36. April 2017 G. Moricca 36 Characteristics of Different Types of Control Systems  According to API 17 TR 13 recommendations, because of the large number of variables and the high degree of operator preference in choosing control systems, only relative comparisons of systems are possible. The following is proposed. API 17 TR 13 - Characteristics of Different Types of Control Systems
  37. 37. April 2017 G. Moricca 37 Control Systems: Choice of system  According to DNV GL, the following system selection matrix, could be adopted.
  38. 38. Thank You for Your Attention G. Moricca Senior Petroleum Engineer April 2017 G. Moricca 38