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Mapping and Prediction of Near surface features

Image credit: BGP (Pakistan) International

PRODUCT DESCRIPTION

Category

Component products

Integrated Product

 

  • § Land cover characterisation
  • § Urban area/ settlement map
  • § Surficial geology/ soil type
  • § Elevation
  • § Slope, curvature, aspect
  • § Soft ground map
  • § Terrain roughness

Uses

  • Surface geology mapping - mapping geological features
  • Surface geology mapping - Lithological discrimination
  • Surface geology mapping - Engineering geological evaluation
  • Subsidence monitoring - land motion relating to fault lines or other causes
  • Subsidence monitoring - Areas of poor coupling

Geo-information requirements

  • Lithology, geology and structural properties of the near surface
  • Precision ortho-images
  • Terrain information
  • Topographic Information
  • Detailed land use information
  • Detailed land cover information
  • Distribution and status of infrastructure
  • Distribution and status of assets

Description

Having an understanding of both surface and near surface features can be a benefit throughout the project cycle.

Seismic operations

For seismic operations, delineating areas where a poor seismic signal may emanate or a weak signal may return could influence line positioning and impact on source and receiver configurations in particular locations. Hard and soft areas have different impacts on a seismic survey. Hard areas may point to considerably increased drilling effort for dynamite source locations, as will areas with high amounts of aggregates present in the near surface strata. These areas may also result in difficulty in coupling of receivers resulting in the need for geophones to be drilled. Soft areas may require a larger and more concentrated source output. One example would be a historic river bed that may not be obvious from recent satellite imagery alone. Receivers in softer ground, like the leeward side of a sand dune, may also experience coupling issues.

From a logistics perspective, delineating surface and near surface conditions helps estimate potential clearance effort required, for example excessive rocks on the earth surface for a vibrator based operation or excessive vegetation for all operation types. In addition, understanding surface conditions will help in establishing all-weather access routes for both shifting of equipment and people and for emergency response planning.

Both surface and sub-surface identification of existing pipelines and other buried and above ground services will aid safe distance offset planning of seismic sources. At present, positioning information for services can be difficult to get from relevant authorities in certain countries and effort is dedicated to man portable underground detection methods along already planned and surveyed seismic lines.

Having a better understanding of the nature of the near surface weathering layer can benefit seismic processing when introducing static correction techniques.

Infrastructure planning and logistics

Further along the value chain, pipeline planning will benefit from sub-surface information as proposed routes can take into account near surface geology, soil consistency and existing services in place, in addition to the usual considerations, well before any ground activity (such as scouting) occurs.

Overall, a near-surface product delivers an integrated assessment of factors impacting seismic survey, pipeline location, and infrastructure planning. Outputs include delineation of potential problem areas coded to indicate the nature of the concern (e.g., surface roughness/hardness/softness, dense vegetation, buried hazards, etc.).

Known restrictions / limitations

Ground-penetrating imaging, thermal and magnetic-derived products:

No operational satellite EO data sources are available. Airborne systems can be used.

Radar-derived products:

Very high resolution DEM data would be required to identify the subtleties of elevation changes signifying a potential old or currently dry water course.

Optical-derived products:

Density of vegetation and distribution of infrastructure and assets may limit optical derived products. These factors may affect the utility and reliability of visual detection of any surface qualities.  

Lifecycle stage and demand

Pre-license

Exploration

Development

Production

Decommission

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*

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Pre-License: A rough idea of what may be experienced during a typical asset lifecycle to establish potential budgets in the asset bidding process.

Exploration: Current and historical information to support effective and safe land seismic surveys. Good information will help acquire a consistent quality seismic product by identifying locations with good and poor receiver coupling potential, pre-adopting appropriate and differing source configurations in defined areas to suit near surface conditions and avoid potential HSE incidents from inadequate safe distance offsetting from unknown buried services.

Development: Current and historical information for planning and design of infrastructure. Pipeline and other development planning needs to consider near surface buried objects and surface and near surface lithology and geology.

Production: Buried services and potential soil stability need to be considered for ongoing development infrastructure planning as the asset develops.

Decommissioning: Useful as a baseline record of what has been left in place.

Geographic coverage and demand

Demand is global.

Challenges Addressed

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

OTM:053  Understanding the near-surface for explosive charge placement

OTM:054  Understanding the near-surface for anticipating seismic signal absorption properties

hc:2101  Lineament mapping

hc:3101  Baseline and monitoring of areas with active faults and subsidence

PRODUCT SPECIFICATIONS

Input data sources

Optical: VHR1, VHR2, HR2, HR1

Radar: VHR2

Supporting data:

  • Digital elevation models (DEM)
  • Existing  GIS data such as topographic maps, infrastructure, and assets

Spatial resolution and coverage

High resolution data is required to identify subtle and small objects.

Minimum Mapping Unit (MMU)

N/A

Accuracy / constraints

Thematic accuracy: To be determined for mapping sub-surface features on a case-by-case basis.

Spatial accuracy: the goal would be 1 pixel, but depends on reference data.

Accuracy assessment approach & quality control measures

Accuracy assessment or the value of the EO-derived information would be determined based on the benefits derived from more efficient and effective field operations.

Frequency / timeliness

Observation frequency: Unless this was an area with regular ongoing development there is no requirement for regular data delivery. A baseline product should be generated for the start of operations and potentially an updated product for comparison use further down the value chain as development projects start.

Timeliness of delivery: Delivery time is not critical as the risk is generally already in place and not changing.  Delivery needs to be in line with the project planning requirements. Typically, a 4 week turn around period should easily be sufficient.

Availability

On-demand availability from commercial suppliers.

New acquisitions can be requested globally.

Archived products available for public search. Availability may be limited for specific dates and locations.

Delivery / output format

Data type:

  • Raster
  • Vector (depending on customer needs)

File format:

  • Geotiff
  • Shapefile or any other OGC standard file formats

 

 Download product sheet.

 

Lead author:

Hatfield consultants/RPS

Peer reviewers:

OTM/WesternGeco

Author(s):

Nolan

Document Title:

Mapping and Prediction of Near Surface Features

# of Pages:

4

Circulation:

Internal – Project consortium and science partners

 

External – ESA

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