Deepwater production remains an essential part of the global energy mix and economically viable projects continue to progress and subsea processing systems are increasingly being considered as a cost-effective solution for both brownfield and greenfield developments. In this regard, an advisory by ABS seeks to support the offshore industry in advancing the development of subsea processing technologies and their implementation.
The benefits of an SPRS include the potential for reducing CAPEX and OPEX associated with topside facilities, increased design flexibility, improved recovery and production rates, extended field life, reduction of flow assurance problems, debottleneck of topside water treatment constraints, reduction of energy consumption for produced water, and minimization of manual operation associated with a topside facility.
As the industry increases reliance on these systems, there are still some technical challenges that need to be overcome before wider adoption is possible. Some of these challenges include the effects of external pressure on SPRS design, long-distance power transmission/distribution, and optimized monitoring and control systems. While the industry is actively addressing these challenges, near-term field applications primarily focus on subsea boosting systems and components for enhanced oil recovery, increasing tie-back distances and extending field life.
Key technology challenges
- Subsea pressure vessels design in deep water application: Increased water depth and external pressure reduces their feasibility in deep water because thick wall designs are typically required which make such pressure vessels difficult and expensive to manufacture and install. Similar concerns also apply to other types of pressure vessel equipment, such as subsea transformers, variable speed drives (VSDs), and switchgears. One possible solution is the adoption of a pressure compensation-based design that balances the pressure differential. Several manufacturers are working towards this solution.
- Long distance power transmission and distribution: As many targeted fields have extremely long tie-backs, they require increased power for operation and accordingly more efficient power supply solutions are needed. Subsea switchgears, distributors, VSDs, and uninterrupted power systems (UPSs) are emerging technologies aimed at remediating those issues with respect to current spike and damaging harmonics due to the long tie-backs. This concept is undergoing verification and validation processes by power solution vendors. The reliability issues have the potential to limit the economic viability.
- Monitoring and control challenges: With the increased complexity and additional equipment located on the seafloor, the requirements for subsea monitoring and control systems have become more demanding. This includes bandwidth increase, real-time monitoring, prompt control response, processing equipment automation, and safety system/equipment design.
- Verification and validation strategy for new technology: The effort and expense associated with developing a new SPRS technology is still quite high. It requires long term and complex qualification programs to demonstrate the technology readiness levels (TRLs) of both components and the system overall. The selected verification and validation strategy can affect projects with respect to both cost and schedule. Standardizing and optimizing technology qualification programs may improve cost effectiveness.
Feasibility Assessment
Tasks associated with performing this assessment include but are not limited to:
- Development of conceptual block flow diagram (BFD) and process flow diagram (PFD) as relevant
- Evaluation of risks involved with economic, legal, environmental, and operational conditions
- Performance of high level flow assurance analysis
- Completion of preliminary risk assessments
- Estimation of CAPEX/OPEX, schedule, and profit.
System Design Basis
Key elements of a design basis include, but are not limited to:
- Project requirements
- Process, operating and environmental parameters
- Applicable design standards/codes
- Design and operational constraints
Once the design basis is determined, the next critical task is the development of a system architecture which can satisfy all aspects of the design basis. To confirm an optimal system configuration can meet project requirements, the following requirements should be met:
- Oil and gas product specifications
- Recovery rate and production rate
- Produced water/sand handling
- Electrical power consumption
- System integrity and reliability
- CAPEX and OPEX.
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