Field Development &
Construction
Michael Cowie
Technical Director
Ecosse Subsea Systems Ltd
Ambient Lifting:
A Real Alternative to Heavy Lift Vessels
4th February 2016, AECC, Michael Cowie
Presentation Overview
• Ecosse Subsea Systems
• ESS Ethos
• Installation and Recovery of Subsea Structures Without the Use of
Heavy Lift Vessels
• Ambient Lifting Technology – theory and examples
• Current Project Status
• Summary
Ecosse Subsea Systems
ESS is a Technology Based Company:
•
Established in 1996
•
100% Scottish owned
•
Initially O & G focused, diversified into Offshore Renewables
•
Core business:
 Subsea engineering consultancy
 Offshore contracting
 SCAR Seabed System
 Route clearance, pre-cut trenching, backfilling
 Technology development and implementation
ESS Ethos
Provision of Subsea Services that are focused on being:
• Safe
• Simple
• Robust
• Cost-effective
 Off-the Shelf Components
 Installable by local people and vessels
 Recoverable, recyclable
 Negate the requirement for specialist vessels
Installation and Recovery of Subsea Structures
Without the Use of Heavy Lift Vessels
• Image installing a 400Te Foundation utilising Multicat Vessels in
extreme environmental conditions……
• Imagine recovering a 600Te+ structure using an Anchor Handler
vessel in remote locations……
This can be achieved with Ambient Lifting and Ballast
Technology where:
 Spread cost is more than halved
 Weather risk is significantly reduced
 Vessel choice is increased
Ambient Lifting
Ambient Lifting – General Overview
• Ambient lifting is a flexible mechanism that allows you
to control the ascent, descent and underwater
positioning of offshore structures.
• Utilisation of off-the-shelf pressure containment
vessel/receptacle and a mechanism to accurately
control ballast/buoyancy.
• Ambient lifting can be used in a variety of industries
including Oil & Gas, Decommissioning, Offshore Wind,
Wave & Tidal Energy.
• Innovative subsea lifting without use of heavy-lift
vessels.
Ambient Lifting:
Theory Examples
Structure FOUNDATION Example
Te
• In air structural weight
250Te
Liquid
Gas
Low Friction Gel Pig
0kg
11
Structure FOUNDATION Example
• In-water structural weight
• Buoyancy in receptacle
designed to ensure structure is
neutrally buoyant
Te
250Te
Neutrally Buoyant
250Te
250Te
12
Structure FOUNDATION Example
• In-water weight increased by adding
ballast material
• Structure sinks to floor in a very
controlled manner
Te
250Te
0-200Te
250Te
250Te
13
Structure FOUNDATION Example
• Gas is replaced or compressed by
fluid
• Now in-water structural weight plus
weight generated by water in
receptacle
• Design ensures sufficient for
temporary stability
Te
250Te
200Te
250Te
250Te
14
Structure FOUNDATION Example
•
•
•
•
Te
250kg
3 x Wt
=600Te
250Te
250Te
15
Fluid is be replaced by denser fluid
Fluid has SG = 3.0 and is pump-able
On-bottom weight is trebled
Structure is fit for extreme environmental
loading
Structure FOUNDATION Example
• Reverse process for recovery
• Fluid replaces heavy fluid
Te
16
Structure FOUNDATION Example
Te
17
• Structure is neutrally buoyant
• Structure is returned to surface in a
very controlled manner
Structure FOUNDATION Example
• Structure on surface
• Can be towed to quayside for recovery
Te
Neutrally Buoyant
250Te
18
Structure INSTALLATION / RECOVERY Example
• Structure is designed to be buoyant
when flooded with fluid
• Structure is positioned over structure
to be recovered
Te
Neutrally Buoyant
300Te
19
Structure INSTALLATION / RECOVERY Example
• Structure is neutrally buoyant
• Structure encloses over top of structure
and is locked in
Te
300Te
20
Structure INSTALLATION / RECOVERY Example
Te
300Te
21
• Fluid in receptacle is replaced by gas
• Structure is recovered to surface in a
very controlled manner
Foundation Installation/Recovery Example
Ambient Lifting – Typical Configuration
Steel Frame (Lower Section)
Lower pipework section
First pipe section loaded to Steel Frame on
quayside and secured
Lower section steelwork and pipework
loaded in to water
Mass
Buoyancy
Net Uplift
Second pipework section loaded into Steel
Frame in Quayside water
Mass
Buoyancy
Net Uplift
Third pipework section loaded into Steel
Frame in Quayside water
Mass
Buoyancy
Net Uplift
Upper steelwork attached to Steel Frame in
Quayside water
Mass
Buoyancy
Net Uplift
Bottom third of ABL pipework filled with SG
3.0 fluid prior to tow out.
Mass
Buoyancy
Net Uplift
External ballast added to frame prior to
tow out.
Mass
Buoyancy
Net Uplift
Second vessel arrives in the
field to assist in ballasting
operations.
ABL unit is attached to both vessel winches.
The unit is ballasted via the control umbilical
until it has a negative buoyancy and both
winches are showing a weight of 5-10Te.
Vessels simultaneously pay
out on winches to lower the
foundation to the seabed.
Upon laydown on the
seabed, the ABL unit can be
fully water ballasted and
then disconnected.
On bottom weight when fully
water ballasted with bottom third
filled with SG 3.0 fluid
For recovery of unit the
removal of heavy fluid from
top two HDPE sections gives
a net uplift for tow back to
port. Reverse Process to
installation.
Subsea Structure Recovery Example
Two AHTS vessels are implemented
for the removal of the subsea
Structure
19m
4m
600Te
Lift
connection
points to be
located in
Structure
The ABL unit is constrained by tow
chains from the vessels.
The ABL unit ballasted down to
connect to the Structure.
ABL attached to the Jacket
Footing using the
mechanical connectors
shown on following slide.
Ambient Lifting – Innovative Mechanical Connection Option
Male portion
attached to
underside of
Ambient Lifting
frame
Female portion to
be placed on the
foundation.
Upon connection, buoyancy is
added to ABL unit to lift Structure
from the seabed.
The unit can be towed by a single
vessel to port for decommissioning.
Ambient Lifting – Current Status
• Prototype constructed, 1:10 model
• Test tank procured for ESS Workshop
• Successful prototype trials undertaken
• Trials witnessed by potential Clients
• Secured 1st Project
•
Installation of gravity based foundation
•
400Te foundation – on-bottom weight
•
Detailed design complete Q4 2015
•
Installation Q1/Q2 2016 – using multi-cats in extreme currents
• Evaluating and implementing feedback on system e.g. contingency measures
Ambient Lifting – Detailed Design Renewables
Summary
• Overview of Ecosse Subsea Capabilities
• Ambient Lifting theory has been summarised along with lifting and
foundation examples
• Ambient lifting is shown to be a cost effective way of
install/recover/relocate small to large subsea structures using:
• simple construction methods
• local companies/people
• local vessels,
• Current status of Ambient Lifting presented for most recent project
• Had hoped to show Case Study of 450Te foundation installation
without the use of Heavy Lift Vessel – installation will hopefully be
in 2016
Thank you.
Michael Cowie – Technical Director
[email protected]