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Neuralog Well Geodetics


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Well Geodetics and the importance of Geodesy in Master Data Management

Well Geodetics and the importance of Geodesy in Master Data Management

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  • 1. NeuralogWell Geodetics in Master Data ManagementRobert E. BestDean C. Mikkelsen
    Turning Paper Into Petroleum
  • 2. Outline
    What is Well Geodetics?
    Why is it Important in MDM?
    Geodesy Concepts
    Implementation in MDM
  • 3. What is Well Geodetics?
    The science of locating a well’s surface and bottom locations.
    Location with respect to other features:
    Other wells
    Geopolitical boundaries
    Hydrocarbon targets
    Geological features
  • 4. Why is it Important?
    When combining well data of different ‘vintages’, different systems may have been used.
    In order to accurately map your wells, geologic features and boundaries together, the same Coordinate Reference System (CRS) must be used.
  • 5. Dramatic example of what might happen
    Lake Peigneur, Louisiana, USA 1980.
    Well drilled a little too close to salt dome.
  • 6. Result
    Lake drained in 2 days.
    Rig and several barges lost (no life lost)
    Freshwater lake became a saltwater lake
  • 7. Bottom Line : Check the CRS
    Failing to account for these differences can create errors of 100’s of meters.
    A wells report from the 1951 may have a completely different CRS than one from 2001.
    The main factors are the CRS used
    Datum - Ellipsoid
    Projection - North Reference
  • 8. Reference Systems and Coordinates
    Depth Reference
    Measured Depth
    True Vertical Depth
    Inclination Reference
    Vertical Reference
    Direction Measurement
    Azimuth Reference
    Quadrant Bearings
  • 9. Depth Reference Points – Land and Offshore Rigs
    Elevation: Kelly Bushing, Ground Level, Elevation above Mean Sea Level (MSL), MSL
    Land Rig
    Offshore Rig
    Elevation: Platform, Seabed, MSL, Kelly Bushing
    Vertical Component of well location is vital to integrity of the data set. Correctly referenced height data (ellipsoid, elevation or z). May prove challenging for legacy data.
  • 10. Map Projections
    Map projections display the earth on a ‘developable’ surface
    Distortion will be a result
  • 11. Universal Transverse Mercator
    Widely used internationally
    Zone/Grid system
    60 Zones, 6deg width
  • 12. UTM Grid
    Positive Easting and Northing coordinates
    Grid Convergence (difference between true/grid north) zero at equator and central meridian
  • 13. North Reference
    Azimuth measurements, such as in a well deviation survey, require a North Reference.
    ‘North’ can be referenced to one of the following:
    True North
    Direction of the Earth’s Northern Geographic Pole
    Grid North
    Map North (North Direction of the Y-Axis of a Cartesian Grid)
    Magnetic North
    Direction of the Earth’s Northern Magnetic Pole
  • 14. True North
    Parallel to lines of Longitude
  • 15. Grid North Reference
    North direction parallel to Y Axis of map
  • 16. Grid North Reference - UTM
    True North
    Grid North
    Angle between the two is the Grid Convergence Angle
  • 17. Application in Well Deviation Surveys
    3 basic measurements
    Azimuth (with respect to a North Reference)
    Deviation Angle (from vertical)
    Measured Depth
    Standards vary for North Reference but some basic rules of thumb:
    International/Onshore USA – True North
    Offshore USA – Grid North
  • 18. Application in Well Deviation Surveys
    Q: What happens if the wrong North Reference is used?
    A: The well bottom hole location will be in the wrong place!
    In UTM, the issue is more acute the farther you get from the equator and central meridian.
  • 19. Datums and Ellipsoids
    The earth is usually modeled as a ellipsoid.
    Regional maps frequently employ a datum to better match the area by employing an ellipsoid shift
  • 20. Common Ellipsoid & Datums
    North American Datum
    Clarke 1866
    WGS Datum
    Tokyo Datum
    South American Datum
    Arc Datum
    Clarke 1880
  • 21. Horizontal Datums
    Many nations established their own datum
    Standards and procedures vary widely
    Coordinates from different datums are completely incompatible
    Relative to Initial Point of Datum
    Will vary as a function of Ellipsoid parameters
  • 22. Datum Transformation – 7 Parameter – One Method
    • To translate one datum to another we must know the relationship between the chosen ellipsoids in terms of position and orientation. The relationship is defined by 7 constants.
    • 23. 3 - Distance of the ellipsoid center from the center of the earth (X, Y, Z)
    • 24. 3 - Rotations around the X, Y, and Z of the Cartesian Coordinate System Axes (, , )
    • 25. Scale change (S) of the survey control network
  • Transformation between 2 Horizontal Datums
    The two ellipsoid centers called  X,  Y,  Z
    The rotation about the X,Y, and Z axes in seconds of arc
    The difference in size between the two ellipsoids
    Scale Change of the Survey Control Network S
  • 26. What does this mean?
    Longitude and Latitude are not unique for a given location.
    Must know the associated datum
    f1 ¹f2
  • 27. Units of Measurement
    Several different units of measurement have been used in location of wells and seismic.
    Unambiguous identity and correct knowledge and application of units of measurement are required.
    Eg. “Foot” might be any of the following:
    International Foot
    US Survey Foot
    British Foot (Sears 1922)
    British Foot (Benoit 1895 A & B, 1865, 1936)
    Indian Foot (1937, 1962, 1975)
    Gold Coast Foot
  • 28. What magnitude of errors could happen?
    • Wrong geodetic datum:
    • 29. Several hundreds of meters : 100’s m
    • 30. Incorrect ellipsoid:
    • 31. Horizontally: 10’s m
    • 32. Height: 0-100’s m
    • 33. Wrong map projection:
    • 34. Entirely the wrong projection: 100-1000’s m
    • 35. Partly wrong (i.e. one or more parameters are wrong): 100-1000’s m
    • 36. No geodetic metadata  meaningless coordinates
    • 37. Datum
    • 38. Ellipsoid
    • 39. Prime meridian
    • 40. Map Projection
  • Standards – OGP/EPSG/UKOOA
    The OGP Geomatics Committee is now the custodian of upstream geodesy information for international E&P
    Was born from the European Petroleum Survey Group (EPSG) and UKOOA Standards.
  • 41. EPSG Database
    Comprehensive database of ellipsoids, datums, projections and coordinate reference systems used worldwide
  • 42. Standards - APSG
    Formed in 1998 to promote exchange of ideas and issues encountered in worldwide E&P. Individuals come from within the oil and gas industry, from majors to service companies.
    Definitions of multiple Horizontal Datums
  • 43. Implementing Geodetics in MDM
    Given the previous discussion, a Master Data Management Solution should be able to:
    Support grid and Lat/Lon coordinates
    Support individual CRS for an entity (well, seismic navigation, etc)
    Support the storage of the geodetic metadata to specify the CRS
  • 44. Example MDM Model - PPDM
    Professional Petroleum Data Management Association
    International Data Modeling consortium
    Members companies include Oil & Gas and Technology Firms
    Model refined over 20 years
  • 45. CRS Tables in PPDM
  • 46. Transformations in PPDM
  • 47. Well CRS in PPDM
  • 48. Well Deviation Survey in PPDM
  • 49. PPDM Implementation
    Each entity (well, seismic, etc) has individual CRS specification for pertinent locations.
    Datum, Ellipsoid and Transformation parameters stored and tied to CRS.
    Full parameters needed for transformation to any system stored.
  • 50. Conclusions and Recommendations
    Gather and store all the geodetic meta-data available for your wells and seismic.
    Be aware of how missing or incorrect information can effect your mapping.
    Employ a MDM strategy to account for these factors at the outset.
  • 51. Thank You!We appreciate your spending time with us today.
    Turning Paper Into Petroleum