Field Development & Construction
Michael Cowie Technical Director Ecosse Subsea Systems Ltd
Ambient Lifting: A Real Alternative to Heavy Lift Vessels 4 th 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 Te 250Te In-water structural weight Buoyancy in receptacle designed to ensure structure is neutrally buoyant Neutrally Buoyant 250Te 250Te 12
Structure FOUNDATION Example Te In-water weight increased by adding ballast material Structure sinks to floor in a very controlled manner 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 14 250Te 250Te
Structure FOUNDATION Example 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 Te 250kg 3 x Wt =600Te 15 250Te 250Te
Structure FOUNDATION Example Reverse process for recovery Fluid replaces heavy fluid Te 16
Structure FOUNDATION Example Te Structure is neutrally buoyant Structure is returned to surface in a very controlled manner 17
Structure FOUNDATION Example Te Structure on surface Can be towed to quayside for recovery Neutrally Buoyant 250Te 18
Structure INSTALLATION / RECOVERY Example Te Structure is designed to be buoyant when flooded with fluid Structure is positioned over structure to be recovered 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 Fluid in receptacle is replaced by gas Structure is recovered to surface in a very controlled manner 300Te 21
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 1 st 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 mcowie@ecosse-subsea.com