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I Tieback of the Future

Crondall Energy approached the challenge of the ‘Tie-back of the Future’ initiative from The Net Zero Technology Centre  (NZTC) by proposing either a mechanically connected steel flowline or a composite flowline laid directly on the seabed, with a new technology internal coating to manage flow assurance.  Potential advantages of this arrangement are reduced cost on first use and suitability for re-use, resulting in greater cost savings and meeting the ‘Plug & Play’ & ‘Circular Economy’ criteria.    

However, this approach is not feasible with current technology.  Consequently Crondall Energy undertook a study to assess the feasibility, identify the technology gaps and the work required to deliver such a system.  The work divides into two parts, namely Pipeline Re-use and Flow Assurance.  

Pipelines on the seabed

Key Technologies:

I Reusable Pipe

In developing technology to reduce the cost of tiebacks, flowline re-use is attractive as it allows the capital cost of a flowline to be amortised over a number of developments.   However, to make re-use a reality it is necessary to challenge our technical and commercial approaches. 

We must consider:

  • On-bottom design - protection from fishing gear interaction, pipeline stability and lateral buckling.

  • Alternative flowline technologies - mechanical connectors or composite pipe.

  • Commercial - there will be significant commercial challenges associated with this initiative.

I Flow Assurance

A significant proportion of the cost of conventional subsea tie-backs is due to flow assurance mitigations, which may demand high levels of insulation, chemical injection systems and heat input.  Potentially new technologies could reduce the cost and complexity of flow assurance issues and enhance the flow assurance performance.

We must consider:

  • An academic understanding of the commercial products available.

  • Development of coating materials, application techniques and testing requirements to meet industry needs. 

  • Generic independent testing of coatings against specific flow assurance challenges, with focus on the most relevant North Sea challenges of hydrate and wax management.  

  • Development of industry guidance on the application and use of internal coatings specifically for flow assurance mitigation. 

I Internal Coatings

Long distance oil and gas systems can be blocked by various deposits originating from the unprocessed production stream.  Conventionally, subsea flow assurance problems are addressed by pipeline insulation, heating and/or chemical inhibitor injection.  Complex and costly operating procedures including depressurisation, displacement or frequent cleaning may also be required. 

Crondall Energy are currently leading a detailed study looking at alternatives to conventional flow assurance solutions, in an effort to significantly reduce the capital and operating costs of subsea tiebacks.  The study is focused on the interface between the fluid and pipeline where deposits adhere and build up to cause blockages.  The study is being supported by both The Oil & Gas Innovation Centre (OGIC) and The Net Zero Technology Centre (NZTC) and is being executed within the Institutes of Chemical Sciences and Petroleum Engineering at Heriot-Watt University.

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