Subsea Oil Terminal Pipelines 3D Integrity Assessment

Project Context

BM was engaged to support an oil terminal operator abroad in the preliminary stage of a structured Fitness-for-Service (FFS) assessment of its offshore subsea pipelines.

The scope focused on exposed pipeline sections requiring geometric baseline establishment and condition documentation prior to analytical evaluation under API 579-1 / ASME FFS-1.

Objective

The campaign aimed to:

• Establish a geo-referenced geometric baseline of exposed pipeline sections

• Document surface condition and degradation features

• Support FFS component segmentation and thickness measurement planning

• Perform an initial free-span screening assessment

This phase formed the foundation of a staged FFS methodology.

Technical Approach

The inspection was performed using an instrumented ROV equipped with ultra-high-resolution imaging, calibrated scaling references and integrated navigation sensors for spatial referencing.

Multi-angle image acquisition enabled structured photogrammetric reconstruction of exposed pipeline segments, including field joints and coating transition zones.

3D Photogrammetric Methodology

A controlled acquisition protocol was applied to generate a geo-referenced, metrology-oriented 3D model of the pipeline geometry.

The reconstruction was tied to the project coordinate system, enabling spatial traceability and repeatable re-inspection.

The resulting model supported:

• Local deformation verification

• Coating breakdown and corrosion mapping

• Spatial anomaly referencing for FFS component definition

Initial Free-Span Screening Assessment

Using the geo-referenced 3D model and visual data:

• Unsupported sections were identified and geo-located

• Span lengths and clearances were measured

• Seabed interaction conditions were documented

This constituted a geometric screening stage. Detailed hydrodynamic or fatigue verification was planned for the subsequent analytical phases (ongoing project).

Engineering Output

The campaign produced:

• Geo-referenced defect mapping (in 3D)

• FFS-relevant component segmentation

• Identification of candidate locations for targeted thickness measurements

• Preliminary free-span dataset

All outputs were structured for direct integration into subsequent FFS and structural assessment.

FFS Integration

The 3D assessment supported Level 1 screening and structured planning for Level 2 analytical evaluation. It optimized the follow-up NDT campaign without replacing formal thickness measurement or structural verification.

Outcome

A traceable, geo-referenced geometric and condition baseline was established, enabling progression toward systematic thickness measurement, corrosion rate formation and formal Fitness-for-Service assessment.