seabed surveys at ormen lange & draugen: challenges …€¦ · - iceberg ploughmarks - varying...

Copyright of A/S Norske Shell

SEABED SURVEYS AT ORMEN LANGE & DRAUGEN: CHALLENGES AND ACHIEVEMENTS

Ian Douglas: Head Offshore Surveys, Shell Projects & Technology

Authors: P. Riddell, J. Erwin, J. Garrard, I. Douglas

29 May 2014 1


1. Seabed Surveys: AUV and ROV

2. Ormen Lange Surveys

- Deep water, Extreme topography, Erratic temperatures

- Matching DTMs for new cable/pipeline routes

3. Draugen Surveys

- Iceberg Ploughmarks

- Varying Soils

- Corals

4. General Data Processing & QC

5. Summary / Learnings

OVERVIEW

229 May 2014


SEABED SURVEYS: AUV AND ROV

1.0

329 May 2014


INTEGRATED SENSORS FOR EFFECTIVE SURVEYING

429 May 2014

Images source: www.km.kongsberg.com

Image source: Subsea 7


AUVS AND ROVS FOR SEABED SURVEYS

Designed to run multiple survey sensors simultaneously

Sharp clean data possible

More coverage in less time

Accurate positioning is a challenge over extreme topography

529 May 2014

Not designed to run full survey sensor spread simultaneously

Very high resolution data possible

More time for less coverage: expensive for large areas

Greater control on subsea positioning

Greater flexibility for close inspection or changing survey plan

Image source: www.mbari.org


ORMEN LANGE SURVEYS

2.0

629 May 2014

Copyright of INSERT COMPANY NAME HERE

ORMEN LANGE - FAST FACTS

Discovered :1997– Production start: 2007

Four subsea templates tieback to onshore gas treatment plant on Nyhamna, Aukra

Gas export via Langeled to UK, representing almost 30% of UK’s gas consumption in 2012.

First deep sea project in Norway, 800-1000 m waterdepth

Challenges:

- Reservoir in slide area

- Steep incline to shore

- Rugged seabed

- Distance to control centre

- Minus 1.2oc on the sea bed

Licence partners: Shell, Petoro, Statoil, Dong Energy, ExxonMobil

7


ORMEN LANGE – STOREGGA SLIDE

829 May 2014

Ormen Lange Gas Field

Storegga Slide upper headwall

North Sea Fan

Storegga Slide

From P. Bryn et al. 2005, Explaining the Storegga Slide

N


SEABED SURVEYS AT ORMEN LANGE

Seabed surveys required primarily for new subsea development: – New

pipelines and wells for increased production

Field development (construction) activities:

Structure Design & Installation

Pipeline & cable routing design & installation

Seabed intervention (rock placement, trenching, dredging)

New data required: i) Bathymetry ii) Seabed features iii) Shallow soils

929 May 2014

Inherited ROV & AUV based data. Good data but lacked coverage for new areas, insufficient resolution for new, higher accuracy engineering requirements.


ORMEN LANGE SEABED

OLMN Production Lines

1029 May 2014


OL SEABED SURVEY CHALLENGES

Focus for Ormen Lange

Environmental challenges – Storegga slide:

Deep water

Seabed topography

Erratic temperature affecting sound velocity (and thus

positioning)

Solutions:

High accuracy USBL, INS, DVL

Multiple water column SV profiles, real-time SV measurement

AUV and ROV. ROV for detailed site areas, AUV for larger

mapping

1129 May 2014


OL SEABED SURVEY CHALLENGES

Focus for Ormen Lange

Technical Challenges:

Acquire new data effectively and accurately – find the quality /

cost balance

Sonar data: Side swipe and Transmission pulse

Merge Datasets into one baseline DTM

Solutions:

Testing height of acquisition. ROV and tow height affect

coverage, resolution, reverberation (noise)

Close co-operation with engineers offshore and onshore

Complete ROV single baseline DTM for route centrelines

1229 May 2014


STOREGGA SLIDE AT ORMEN LANGE

1329 May 2014


STOREGGA SLIDE BATHYMETRY – GOOD DATA

1429 May 2014


BUT....MBES RESOLUTION IS NOT EVERYTHING

1529 May 2014

2m x 2m cell size bathymetry data Newer AUV 1m x 1m cell size bathymetry data


SIDE SCAN SONAR DATA EXAMPLE

29 May 2014 16


SUB BOTTOM PROFILER - SHALLOW WATER

1729 May 2014


SUB BOTTOM PROFILER – DEEP WATER

1829 May 2014


DRAUGEN SURVEYS

3.0

1929 May 2014


DRAUGEN FAST FACTS

20

Discovered :1984. Production start:1993

Located in the Norwegian Sea, 150km north of Kristiansund. 250m water depth

The first Norwegian field to commence operations north of the 62° latitude

Top hydrocarbon recovery rate on the Norwegian Shelf

New platform and subsea developments in order extend the original life span significantly

Licence partners: Shell, Petoro, Chevron

DRAUGEN

ORMEN LANGE

Kristiansund


SEABED SURVEYS AT DRAUGEN

New subsea tie-back developments to enhance field hydrocarbon production (multiple new wells)

Seabed Surveys required in support of this:

i) rig site hazard surveys

ii) pipeline route surveys

ii) structure pre-installation

Focus for Draugen:

a. Iceberg Ploughmarks from Bathymetry

b. Detailed Soil Verifications via Geotechnical sampling

c. Cold Water Coral Assessments using Sidescan Sonar & Bathymetry data plus ROV visual inspection

2129 May 2014


DRAUGEN – ICEBERG PLOUGHMARKS

2229 May 2014

Iceberg

Ploughmarks across

Draugen area

Can be 160m wide

and 12m deep

Flowline routing design altered to accomodate iceberg ploughmark


DRAUGEN - SOILS

Varying soil conditions

Regional and localised variations

2329 May 2014

Draugen Platform


DRAUGEN - SOILS

Localised soil variations – manifold installation example

2429 May 2014


COLD WATER CORALS

Abundance of Cold Water Corals (CWCs) in the Norwegian Sea,

north of 62° parallel

‘Red-listed’ CWCs are rare and protected by Government

Strict Rules implemented to protect them

It is responsibility of Operator to ensure, and prove, there is no harm

to corals within their concession area.

2529 May 2014


DRAUGEN – COLD WATER CORALS

2629 May 2014



Need to prove no damage to

corals as a result of operator’s

activities

Requires separate ROV

inspection pre and post rig move

All findings recorded, mapped

and reported

2729 May 2014

Potential Coral identified for ROV inspection

ROV visual inspection



2829 May 2014


DATA PROCESSING & QC

4.0

2929 May 2014


DATA ACQUISITION QUALITY CONTROL

3029 May 2014

Tidal checks CMG

Track / DGPS Phins/ Octans


DTM CROSS PROFILE QUALITY QC

3129 May 2014


FINAL DATA QC - MBES

3229 May 2014


SUMMARY & LEARNINGS

5.0

3329 May 2014


SUMMARY IN ONE SLIDE!

Understand engineering objectives – balance cost with fit-for-purpose

quality (accuracy, resolution etc)

Consider the survey accuracy requirements and assess vessel, AUV

and ROV survey options. Consider combinations

Plan for sufficient start-up testing time to find optimum acquisition

configuration

Focus on processing QC and reporting as much as acquisition. Good

raw data can still be processed badly

Consider unique factors at your location e.g. Corals at Draugen

3429 May 2014


LEARNINGS

Schedule time required at start-up to find optimum acquisition

altitude: start-up evaluation of data Coverage, Resolution, Noise

Engineer designers understanding of more than one version of the

truth.

Establish one baseline DTM for routes, provides QC for overlapping

surveys

Seabed shape and relative differences can be more important than

absolute values for construction installation

Data QC during acquisition (offshore) and at regular data processing

intermediate stages – do not leave until final product

3529 May 2014

seabed surveys at ormen lange & draugen: challenges …€¦ · - iceberg ploughmarks - varying...

Documents