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Case Study • Hydrographic, Geophysical, and Geotechnical Survey for a Subsea Pipeline in the Eastern Mediterranean Sea • Lighthouse

Snapshot
Project
Pipeline Reconnaissance Survey
Role
Contractor
Client
Confidential
Year
2015-2016
Location
Eastern Mediterranean Sea
Environment
Offshore
Region
Europe
Details

Introduction

Lighthouse carried out a pipeline reconnaissance survey for a 112km long gas pipeline route in the Eastern Mediterranean Sea in 2015-2016. The purpose of the hydrographic, geophysical and geotechnical site investigation was to establish the engineering feasibility of two proposed pipeline routes along a pre-defined 2,220km² wide corridor.

Scope of Work

  • The scope of work comprised bathymetric, seabed, and sub-seabed data acquisition, processing and interpretation, performed from Lighthouse's DP1 Odin Finder Geotechnical and Survey Vessel, including:
  • Pre-survey route centreline survey
  • Post-survey route centreline and two wing lines 500m offset each side of centreline survey
  • Pre-defined corridor survey
  • Geotechnical characterisation by means of box core sampling, piston coring, and geotechnical laboratory testing and analysis
  • Data processing, interpretation, and integrated hydrographic/geophysical/geotechnical reporting

Hydrographic & Geophysical Survey

The pre-survey route centreline was investigated by means of multibeam echosounder (MBES) and sub-bottom profiler (SBP) to detect and assess any geohazards or potential issues for the proposed pipeline installation. The survey data was processed onboard simultaneously and provided to the Client in order to facilitate survey optimisation and acquisition of additional data if required. Once the post-survey route was defined, the survey was extended to cover a wider corridor. The geophysical survey was subsequently continued to cover the pre-defined corridor area.

Geotechnical Sampling Operations

Following the successful completion of the hydrographic and geophysical survey, Lighthouse carried out the geotechnical sampling phase of the campaign. This is included shallow sub-seabed sampling using box corers and piston corers to provide adequate and representative soil samples for further laboratory testing and analysis, such as soil identification and classification, bulk and dry density, particle size distribution (PSD), and photography for input into the Client's engineering design.

Equipment & Instrumentation
  • Primary Positioning system: DGPS C-Nav 3050
  • Secondary Positioning system: DGPS C-Nav 1010R
  • Underwater Positioning: Sonardyne Ranger 2 6G
  • Transponders (Beacon): Sonardyne WSM 8170 6G
  • Gyrocompass/Motion Reference Unit (MRU): GEM Polaris FOG-200
  • Gyrocompass/Motion Reference Unit (MRU): Teledyne TSS MAHRS
  • SVP Probes: Valeport Mini SVP – Mini SVS
  • Navigation Software: QPS QINSy 8.0
  • Bathymetric System: L3 ELAC Nautik Seabeam 3030
  • Sub-Bottom Profiler System: Teledyne Benthos Chirp III
  • Mini Air Gun: Sercel 20cu.inch
  • Seabed Sampling Systems: 1,000cm² Box Corer
  • Nioz Passive Acoustic Monitoring (PAM) System: TLS MK2 PAM
 
Vessels
IMO:
7031761
MMSI:
247048200
Vessel Operator:
Lighthouse
Flag:
Italy
Related Case Studies
Introduction Lighthouse performed a pre-engineering marine survey for 280km long gas pipeline route in the Atlantic Ocean offshore Cameroon in 2014. The purpose of the hydrographic, geophysical and geotechnical site investigation was to determine the suitability of the proposed pipeline routes and to identify any geological and bathymetric conditions ... Morewhich could impair pipeline installation and associated burial operations.

Scope of Work

The scope of work comprised bathymetric, seabed, and sub-seabed data acquisition, processing and interpretation, performed from Lighthouse's DP1 Odin Finder Geotechnical and Survey Vessel, including:

2D ultra high resolution (UHR) seismic survey

Pipeline routes corridor bathymetric and geophysical survey by means of multibeam echosounder (MBES), singlebeam echosounder (SBES), side scan sonar (SSS), sub-bottom profiler (SBP), and magnetometer

Pipeline routes geotechnical characterisation by means of shallow vibrocorer sampling and subsequent geotechnical laboratory testing

Pipeline routes environmental survey to characterise biologic chemical and physical properties of the seabed and seawater.

Data processing, interpretation, final charting, and reporting

Initial 2D UHR Seismic Geophysical Survey

The 2D UHR seismic survey was performed to detect possible hazard in the shallow stratigraphy for the pipelines routes. The main challenge was to provide the Client and engineering consultant with the necessary engineering data within the expected deadlines in order to proceed with the following phases of the survey. All the acquired geophysical data passed through a rigid Quality Control (QC) procedure, and was processed and finally interpreted onboard the survey vessel. A preliminary interpretation was provided before the start of the geophysical survey (24 hours after the end of the last acquired line), and the final interpretation was provided to the Client at the end of the geophysical survey.

Pipeline Routes Corridor Bathymetric and Geophysical Survey

Once the optimal pipeline routes were determined by the Client, the whole corridor was investigated in order to detect any possible hazard for the future pipeline installation and construction. The main challenge was to provide the Client with information and warning of any potential geohazards in advance of any critical milestones which may have impacted route optimisation or design. The results of the bathymetric and subsequent geophysical survey facilitated the scope for the geotechnical and environmental surveys.

Geotechnical and Environmental Sampling Operations
Following the successful completion of the hydrographic and geophysical survey, Lighthouse carried out the geotechnical and environmental sampling phase of the campaign. This is included shallow sub-seabed sampling using a vibrocorer to provide adequate and representative soil samples for further laboratory testing and analysis, such as soil identification and classification, bulk and dry density, particle size distribution (PSD), and photography for input into the Client's engineering design. 

Equipment & Instrumentation

Primary Positioning System: DGPS C-Nav 3050

Secondary Positioning System: DGPS C-Nav 1010R

Gyrocompass/Motion Reference Unit (MRU): GEM Polaris FOG-200

Gyrocompass/Motion Reference Unit: Teledyne TSS MAHRS

Sound Velocity Probe (SVP): Valeport

Navigation Software: QPS QINSy 8.0

Bathymetric System: R2 Sonic 2024

Bathymetric System: L3 ELAC Nautik Seabeam3030

Sub-Bottom Profiler (SBP) System: Teledyne Benthos Chirp III

Underwater Positioning System: Applied Acoustics-Easytrak Lite

Singlebeam Echosounder (SBES): NAVISOUND 215 (hull mounted)

Hydrofone Array: Sercel SEAL Streamer

Recording System: Sercel SEAL 408 Recording System

Seismic Source: Sercel Ming G Gun

QC and Processing System: Promax 2D

Water Sampling: NISKIN

Multi-parameter probe: Idronaut Probe

Vibrocorer: Geo Vibro Corer 6000

Seabed Grab Sampling: Van Veen Grab
Keywords
Bathymetric SurveyEngineeringGeophysical SurveyGeotechnicalMultibeam EchosounderMBESOffshoreOffshore Oil & GasSeismic SurveySide Scan SonarSSSSite InvestigationSub-Bottom ProfilerSBPSubsea Engineering
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