Offshore Produced Water Disposal Relocation Concept Select & PreFEED

Objective

A Middle Eastern offshore operator engaged io consulting to conduct a concept select and PreFEED study for the relocation of produced water disposal (PWD) infrastructure at a mature offshore oil field. The project aimed to develop a cost-effective and technically viable solution to address increasing produced water volumes and the limitations of existing disposal wells.

The study focused on defining a subsea disposal system that minimises project schedule risks while integrating with future offshore infrastructure developments. The selected concept would allow for phased implementation, with an initial standalone system that could later be expanded to tie into a larger offshore network.

Project Scope

The study covered:

1. Produced Water Disposal System Optimisation – Evaluating offshore subsea wells vs. platform-based disposal solutions.
2. Infrastructure Re-use vs. Greenfield Development – Assessing opportunities to leverage existing pipelines, risers and platform modifications.
3. Pipeline & Subsea Layout – Determining the optimal routing and expansion strategy for a new produced water pipeline.
4. Phased Development Plan – Designing a standalone Phase 1 system with the option for a future tie-in to an offshore processing hub.
5. Economic & Risk Assessment – Conducting techno-economic evaluations to identify the most commercially attractive development pathway.

Findings & Recommendations

Findings

• Produced Water Disposal Strategy: The existing disposal wells had limited remaining capacity, necessitating a new disposal solution to sustain long-term production.
• Concept Selection & Phased Implementation: A standalone subsea system (Phase 1) offered the fastest path to implementation, while a future connection to an offshore processing hub (Phase 2) could improve long-term system efficiency.
• Pipeline & Subsea Infrastructure Design: A 26” pipeline was required to transport produced water to the new disposal wells, with a subsea manifold designed for future expansion.
• Integration with Existing Infrastructure: The re-use of existing risers and platform tie-ins could provide cost savings but required further structural modifications.
• Economic & Risk Evaluation: The subsea disposal approach provided the lowest CAPEX and operational risk, while minimising dependencies on other projects.
• Advanced System Modelling & Flow Assurance: Pipeline hydraulics and pigging strategies were critical to system reliability, requiring detailed flow assurance studies.
  • io consulting utilised OLGA dynamic simulation modelling to assess flow stability, injection pressure requirements, and the impact of temperature and fluid properties on long-term operability.

Recommendations

1. Produced Water Disposal Strategy: Implement a new subsea disposal centre with disposal wells located near a future offshore drilling platform, avoiding platform construction delays.
2. Concept Selection & Phased Implementation: Adopt a two-phase approach, allowing for rapid implementation of subsea wells in Phase 1, with an extension pipeline to the future platform in Phase 2.
3. Pipeline & Subsea Infrastructure Design: Optimise pipeline routing to minimise crossings, incorporate pigging capability in Phase 2, and ensure long-term operational flexibility.
4. Integration with Existing Infrastructure: Proceed with brownfield modifications to integrate with existing facilities while ensuring long-term reliability.
5. Economic & Risk Evaluation: Prioritise subsea disposal for Phase 1, progressing to a full offshore disposal network in Phase 2.
6. Advanced System Modelling & Flow Assurance: Implement a robust pigging strategy and pipeline depressurisation protocol to mitigate risks of scaling, hydrate formation, and flow instabilities.