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ENGINEERING GEOLOGY EVALUATION

Image credit: Arup

PRODUCT DESCRIPTION

Category

Component products

Integrated Product

  • Elevation
  • Slope, curvature, aspect
  • Geomorphology mapping
  • Lithology and surficial geology
  • Faults and discontinuities
  • Slope stability
  • Floodplain mapping
  • Waterbody extent
  • Coastline Monitoring

Uses

  • Seismic planning - areas of poor coupling
  • Seismic planning - identification of adverse terrain for trafficability
  • Surface geology mapping – mapping geological features
  • Surface geology mapping – structural interpretation
  • Surface geology mapping – lithological discrimination
  • Surface geology mapping – terrain evaluation and geo-morphology characterization
  • Surface geology mapping – engineering geological evaluation
  • Subsidence monitoring - infrastructure monitoring
  • Environmental monitoring - baseline historic mapping of environment and ecosystems
  • Logistics planning and operations – facility siting, pipeline routing and roads development

Geo-information requirements

  • Lithology, geology and structural properties of the near surface
  • Surface and ground motion
  • Terrain information
  • Topographic information

Description

Engineering geological evaluations are typically undertaken in a staged approach, as follows:

  • Desk based studies;
  • In-field reconnaissance and terrain studies;
  • Ground investigation(s) - intrusive (e.g., drilling) and non-intrusive (e.g., geophysics);
  • Interpretation and ground model development;
  • Development of risk register; and
  • Input to design / mitigation.

Evaluations vary in focus according to the geographic, topographic and tectonic settings of project areas and provide assessments of the hazards posed by the ground and groundwater conditions, slope instability, erosion, seismicity, volcanism, flooding, etc.

The engineering geological evaluation product identifies and delineates engineering geological features that have the potential to impact on oil and gas facilities and infrastructure, at various stages of project lifecycles.  The product will also assist the planning of mitigation measures which could include avoidance (re-siting), protection, monitoring, appropriate design, maintenance and remediation.

This product is based on specialist interpretation of the various input datasets. EO data may be complimented by other inputs, such as published maps or memoirs.  A range of scales can be used depending on the project type and the stage of development; for example DEM analysis can be undertaken with data ranging from 90 or 30 m resolution (SRTM) data for the regional scale up to 1 m resolution (from stereo VHR1 data) for the more detailed studies required for facility site selection and infrastructure pipeline routing.

The type of features that can be mapped by geomorphological analysis includes slope instability, river alignments and wadi courses, coastal erosion, flooding, playa lakes and sabkha, karst terrain, mobile sands, active faulting and volcanic landforms. Potential locations of springs, seepages and shallow groundwater table can also be obtained.

Multi-temporal image/DEM analysis with archive and recent datasets allows landform changes to be evaluated – including coastal erosion, river migration, sand dune mobility, subsidence and slope instability.

Product outputs include PDF maps or vector digital files that delineate and identify engineering-geological themes, such as:

  • Engineering-geology and geomorphology maps;
  • Terrain unit maps (incorporating lithology with terrain classes);
  • Shaded-relief maps; slope maps; aspect maps (raster); and
  • Hazard (geohazard) maps – unified and thematic (e.g., landslide, dune-mobility).

Known restrictions / limitations

Geographies with dense vegetation such as tropical regions reduce the accuracy of interpretation, although larger features may still be visible even where the canopy is dense and continuous.  Use of radar imagery can mitigate these limitations to some extent. Airborne techniques such as LiDAR can also help mitigate these issues.

Lifecycle stage and demand

Pre-license

Exploration

Development

Production

Decommissioning

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Exploration: Information on engineering geological evaluation to support decision-making on a prospect with relation to cost estimation for exploration and development costs associated with access and geohazards.

Exploration: Information to support geomorphological mapping, terrain analysis and hazard identification, in particular to assist panning of seismic surveys and other field work and provide data to support interpretation of seismic data.

Development: Knowledge of risk potential will influence development decisions regarding asset and infrastructure placement and emergency protocols. Information for planning and design of infrastructure, to support site selection and pipeline routing to determine hazards and risks in a proposed development area.

Production: May be required to be updated to monitor hazards within project area that may affect operations e.g., slope instability, river erosion, dune migration, subsidence.

Decommissioning: Not typically required unless ongoing monitoring is required.

Geographic coverage and demand

Demand and coverage is global.

Demand is in all terrain areas.

Challenges Addressed

OTM:008   Determine historical ground movement for infrastructure planning

OTM:009   Determine historical ground movement for pipeline routing

OTM:014   Forecasting sand dune migration

OTM:015   Geological and terrain base maps for development of environmental baseline

OTM:023   Enabling survey to understand structural properties of the sub-surface for infrastructure planning

OTM:036   Geohazard exposure analysis

OTM:052   Identify the cause of geological movement

OTM:059   Understanding outcrop mineralogy

OTM:073   Identifying sources of building resources

OTM:074   Estimating ground bearing capacity

HC:1102    Identify rock-strewn areas to avoid point loading

HC:1103    Identify soft and hard ground as areas of potentially poor source and receiver coupling

HC:1203    Identify areas with soft sediments to plan access and assess hazards

HC:1206    Identify steep slopes to assess potential constraints to access

HC:1207    Identify claypan surfaces to be avoided

HC:1212    Identify sabkhas / salt lake areas

HC:2102    Understanding hydrogeology

HC:2201    Identify geological structure through landform

HC:2301    Identify discreet lithology

HC:2401    Identify geohazards and landscape change rates

HC:2501    Characterization of surface/near-surface structural geological properties for infrastructure planning

HC:2502    Identification of problem soils

HC:2503    Assessment of duricrusts and rock excavability

HC:2504    Identification of slope instability

HC:4303    Understand extent of lakes and wet areas for hazard assessment

HC:5301    Planning and assessing borrow pits as source of aggregate material

HC:5302    Terrain stability for route planning

PRODUCT SPECIFICATIONS

Input data sources

Optical: VHR1, VHR2, HR1, HR2, MR1

Radar: HR1, HR2

Supporting data:

  • Geological maps
  • Topographic maps
  • Published literature and reports
  • Digital elevation models (DEM)
  • Air photo interpretation
  • Field mapping and ground investigations

Archive data has considerable value for detection of multi-temporal changes over decades to help identify and quantify active geomorphic processes such as river migration, coastal erosion, slope instability, flooding, etc.

Spatial resolution and coverage

Varies depending on input imagery used and client needs.

Low resolution DEM, HR2 and MR1 for basin wide exploration studies, higher resolution DEM and optical imagery (HR2 to VHR1) for development and infrastructure planning and design.

Minimum Mapping Unit (MMU)

N/A

Accuracy / constraints

Varies depending on input imagery and user requirements.

Accuracy assessment approach & quality control measures

Professional judgment by comparison with any published geological mapping or reports and ground truth data. Field reconnaissance mapping.

Frequency / timeliness

Varies depending on input imagery and user requirements.

Observation frequency: Typically uses archive data. New and/or repeat data collection subject to project requirements e.g., monitoring of active geo-hazard processes.

Timeliness of delivery: Usually off-the-shelf data can be utilised. Commissioned data may be required in some cases e.g., for collection of VHR1 stereo data for very high resolution DEM and ortho production.

Availability

On-demand availability for most component products from commercial suppliers.

New acquisitions can be requested globally.

Delivery / output format

Data type:

  • Raster
  • Vector
  • Digital or paper maps

File format:

  • Geotiff, .ecw
  • Shapefile or any other OGC standard file formats
  • PDF files or plots

 

 Download product sheet.

 

Lead Author:

Hatfield consultants

Peer reviewer:

 

Author(s):

Jason Manning

Document Title:

Engineering geology evaluation

# of Pages:

6

Circulation:

Internal – Project consortium and science partners

 

External – ESA

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