Nexus Deepwater Engineering

IWOCS & CWOR

We have experience in Innovative Intervention Systems. IWOCS stands for Installation Workover Control System. Our company has the expertise in both; Riser-based and Riser-less Systems.

The Riser-Based system is a rig dependent system. It is clamped to the the marine riser or drill pipe, depending on the completion and testing campaign. As a minimum, the following equipment is used for running a rig based IWOCS:

• Hydraulic Power Unit (HPU)
• Umbilical integrated to a pnuematic driven Reel
• Chemical Injection Unit; typically for methanol
• Electrical Power & Control Unit - for power and communication to the Tree mounted SCM
• Subsea Distribution Units - IWOCS "Box"
• Hydraulic & Electrical Flying Leads
• Annulus Umbilical and Reel

Availability of rigs has become a challenge, especially when demand exceeds the supply. Open water subsea tree installationsusing DSV - tree on wire - has become an increasingly popular method for installation. Moreover, operators discover that a lot of rigs they have contracted tend to have space limitations especially when the rig is required to drill, install wellheads, complete the well and install Subsea Christmas Trees. The alternative that meets these challenges is what is known as AWOCS / RWOCS.

The enabling technology, otherwise known as Riser-Less IWOCS operates independent of the rig. The Riser-Less system utilizes a self-supporting umbilical system that can be deployed on diver support vessels (DSV) or a vessel (with AHC Crane) to provide intervention, subsea testing and workover control. The AWOCS is typically a rental system and allows flexibility that the riser-based system can not offer.

RISER-BASED IWOCS

The IWOC system is riser-based and depends on the marine riser / drill pipe. This system is deployed during well completions and workover to provide control fluid pressure to SCSSV and various Subsea Christmas Tree valves. Installation and Workover Control System (IWOCS) provides:
 

• Hydraulic Power Unit: Hydraulic Low and High Pressure Regulated supply

• Surface Controlled Power & Electrical Test Unit (SCPET)

• The PETU provides Electrical Power / Communications for Subsea Control Module (SCM)

• Topside Umbilical Reel Assembly

• Subsea Distribution Units - Mounted on the LMRP and BOP

• Hydraulic Flying Lead & Electrical Flying Leads

• Hydraulic & Electrical Disconnect System (HEDS)

• Umbilical Clamps for running umbilical to Marine Riser / Drill pipe

• Chemical Injection Unit (CIU)

 

The Installation and Workover Control System (IWOCS) typically supports the upper completions campaign. When landing and locking the tubing hanger the umbilical provides the fluid power to lock, test and keep the SCSSV open. In some configurations an IWOCS box is used when a BOP on Tree option is used.

Gumusut utilized the following on Atwood Falcon for its IWOCS System:

- Hydraulic Power Unit utiling low pressure (LP) and high pressure (HP) water-glycol based dynex pumps.
- The main umbilical Reeler provided the conduit for testing seal integrity and controls to the depthstar SCSSV.
- Well Dynamics control system connected via the Main Umbilical electrical junction box.
- Various sheeves and clamps were utilized to run the main umbilical over to the derrick and down-through the rotary.

 

 

RISER-LESS IWOCS

The Alternate Workover Control System (AWOCS) is riser-less and is considered a stand alone system. This system can be deployed during well completions and workover to provide control fluid pressure to SCSSV and various Subsea Christmas Tree valves. Since, AWOCS is not rig dependent, any vessel of opportunity, for example DSV (diver-support vessel) can be used to run this system. With more subsea equipment being installed unused for 1yr (or more), the AWOCS provides the flexible solution for post-installation testing of subsea trees, manifolds and controls systems.

The Alternate IWOCS provides:
 

• Hydraulic Power Unit: Hydraulic Low and High Pressure Regulated supply

• Surface Controlled Power & Electrical Test Unit (PETU)

• The PETU provides Electrical Power and Communications for Subsea Control Module (SCM)

• Topside Umbilical Reel Assembly

• Subsea Distribution Units - Mounted on the LMRP and BOP

• Hydraulic Flying Lead & Electrical Flying Leads

• Hydraulic & Electrical Disconnect System (EQD)

• Umbilical Clamps for running umbilical on wireline winch

• Chemical Injection Unit (CIU)

 

 

CWOR SYSTEM

CWOR stands for Completion Workover Riser system., Nexus has knowledge in running upper completion operations. Using the IWOCS Hydraulic Power Unit, Main Umbilical Reeler and Annulus Umbilical Reeler the completions campaign relies on the EDP (Emergency Disconnect Package) and LRP (Lower Riser Package) for light well intervention.

Operation Assurance (OA) using rig layouts and detailed planning, coupled with time-saving techniques; we can help you reduce CAPEX and OPEX.