Underwater Operations

1.1 Offshore platform type

Offshore Platforms for Jack-up, semi-submersible and drillships

  • Before a jack-up reaches location, buoys are normally dropped off to mark the centre and leg positions. Marex’s divers are required to do a circular search of these position to ensure that the legs will be clear of debris
  • Marex measure de depth of penetration of the legs using an air probe
  • in area of strong currents, our divers will have to check for scour around the legs and, if necessary, fill scour holes with sandbags and build a protective wall around the base of the legs
  • Marex inspecting and repairing the hull
  • Checking anchor rack and fairleads
  • Marex checking for debris and penetration of the pontoons (if resting on the seabed) when in shallow water
  • Inspecting Thrusters, pontoons and all underwater parts of the structures
  • Assisting with the rigging of anchor pendant wires
  • Assisting with the recovery of any lost or damaged equipment
  • Inspect, maintain and repair ship’s accessory structures such as moonpool doors
  • Inspect all the ship’s thrusters and keep them clear of fouling
1.3 pipelay barge 1

Pipelay barges

  • Shallow, surface-oriented air diving task on the stinger to check and maintain its efficient operation. When diving on stingers divers should have a means if indicating their position day and night.
  • Deeper, work on the seabed associated with the pipe and work on the laydown head ad pipeline connections.
  • Camera or light replacement
  • Testing valve to flood or dewater the pipe
  • Stinger valve operation to adjust buoyancy and catenary
  • Operation on wire of pulling head’s pipe
  • Install hyperbaric welding habitat
  • Bolt tensioning
  • Operate A-frames
  • Line Up pipeline/risers, measure spoolpiece requirements
1.6 pipeline connection

Pipeline connections

  • Metrology: Measurements for spoolpiece fabrication and installation
  • All types Flanging connections and alignment operations
  • Flange pulling or spitter operation
  • Hyperbarically welding
  • Mechanical connections
  • Bolt tensioning procedures
  • Cameron, flexiforge, Morgrip, smart flange connecting operation
  • Weldball operation
  • pigs and pigging
  • pipeline brends and lateral connection
  • pipeline valve
1.2 BOP 1

Drilling Support

  • Assistance with de guiding/lowering of the BOP (Blow Out Preventer) onto de Guidebase
  • BOP stack inspection
  • Checking and connection
  • Trouble-shooting any electrical, hydraulic and mechanical malfunctions
1.4 trenching barge

Trenching Barges

  • Checking Depth of trench and seabed
  • Checking rollers, position and clear of debris
  • Check leaks on hose connections
1.5 DP Vessel

Dynamically positioned Vessels operations

1.7 stab

Pipeline stabilisation

  • Ground anchor systems
  • Concrete or bitume mattress
  • Saddle block
  • Gravel dump
1.8 prod syst

Offshore production systems

  • Tie-back: installation and maintenance
  • Sky hook: transfer to crane
  • Subsea manifold operation
1.10 pipeline

Pipeline inspection

  • IRM for crack, concrete losses, surface deposits, construction features and defects
  • Offshore standard reporting
  • Pipeline damaged by anchor cables repair operating
1.9 SPM 2

Single Point Mooring systems expertise

  • Expert on all types: CALM, SALM, VALM, SPMT, ELSBM, ALP: IRM (Inspection, Repair and maintenance)
  • Inspection programme at regular interval operating
  • Marine tasks
  • All non-diving, diving and surfaces maintenance tasks
  • Underbuoy hose change operation
  • All Seabed diving work
1.11 Shipping

Shipwork

  • Preparing work before operation
  • Rudder, stock and bearing inspection
  • Propeller and shafting inspection
  • Hull cleaning and prop polishing
1.12 dock

Dock and harbours

  • Inspection of damage to dock walls, gates and sills
  • Debris removal
  • Video inspection of ship propellers
  • Maintenance of sluices including replacement of spear rods in sluice pits
  • Recovery of lost cargo and containers
  • recovery of miscellaneous lost item including various vehicles
1.13 lock

Weirs & Lock

  • Tasks on weirs
    • Visual inspection of abutment and foundation structure up and down-stream of the gates
    • Check for any damage caused by scouring on downstream side. Identify any damage found
    • Repair as necessary, eg filling voids with grout or welding re-enforcing plates over any separated piles
    • Visual inspection of the gates
    • Metal thickness measurements on gates using ‘D’ meters
    • Visual inspection of lifting gear. Replace any part as necessary
    • Removal of obstruction and/or debris from under gates
    • Replacement of seals
    • Fitting a dam where work has to be carried out in dry conditions
    • Replacement of damaged or missing ‘stop’ on buck weirs
  • Locks: Diver tasks similar on weirs, plus:
    • Removal of silt from around gates using air-lift.
    • Repair of sluice gear as necessary: eg, broken iron-work or sluice doors
    • Repair hydraulic systems as necessary
    • Inspect and repair gates and damage to sills as necessary
1.17 wind farm

Offshore wind farm

  • J-tube or I-tub Installation
  • Cable route surveys
  • Fitting of bellmouths to mono piles
  • Cable span rectification
  • IRM
  • Monopile Marine growth cleaning
  • Cathodic protection systems and anodes
  • Subsea inspection and NDT to towers
  • Export and inter-array cable installation and cable pull-ins
  • Shore end beach landings
  • Trenching, jetting and burial machine support (loading and unloading etc)
  • Scour protection and stabilisation
  • Mattress and rock placement
  • Articulated cable protection installation
  • Fitting of bend restrictors and restraining clamps
  • Cable location and tracking
  • Debris and unexploded ordnance clearance
  • Cable route clearance
  • Video surveys
1.14 dam

Spillways, reservoir and dams

  • Repair and inspection of pumps and control gear
  • Inspection and repair of structural elements
  • Silt and debris clearance within control structures and from debris screens
  • IRM within culvert systems including gate valves
  • Inspection of dam faces to check for localised leakages or seepage flows
  • Guiding placement of gabion baskets and mattresses for scour protection
  • Connecting, monitoring and disconnecting concrete supply hose to anti-scour mattresses
1.16 sheet

Sheet piles

  • Cleaning of sheet piling prior to pouring of concrete.
  • Attaching drilling tube to prepare for grouted anchors
  • Visual inspection, Ultrasonic thickness measurement, cathodic electrical potential levels
  • Diving in bentonite
1.15 outfall

Outfalls

  • Check structural integrity
  • Survey of outfall for later extension or modification
  • Check of hydraulic performance