Analysis of different griddingmethods using “Surfer7”
MichiganTechnological
Universitypresentation byFehmi Kamcili
February 10, 2001
Fig.: Shaded Relief and Contour map
Analysis of different griddingmethods using “Surfer7”
Table of content
• Introduction• Grid Files• Grid Methods
1. Inverse Distance to a Power; 2. Kriging;3. Minimum Curvature; 4. Modified Shepard’s Method;5. Natural Neighbor; 6. Nearest Neighbor;7. Polynomial Regression; 8. Radial Basis Function;9. Triangulation w/ linear Interpolation
• Best Results• Conclusion
Introduction
• Surfer 7; Feb. 2000Surface mapping systemGolden Software, Inc.
• Differences in createdgrid-files visualized byoverlaying wireframeand contour mapsFig.: Wireframe and Contour Map
• Vernon/Rosebuch oilfields in Isabella county, Michiganwith 245 well Data-Points (Lat-Long of Top Dundee)
Analysis of different griddingmethods using “Surfer7”
Grid Files
• gridding by specifingsource file-Spreadsheets (Excel)-manually in Surfer (Worksheet)
• gridding method
• accuracy of grid
• faults and breaklines
• creates “file.grd”Fig.: Contour and Post Map
Analysis of different griddingmethods using “Surfer7”
Grid Methods
• Inv. Distance to power
• Kriging
• Minimum curvature
• Modified shepard’s
• Natural neighbor
• Nearest neighbor
• Polynomial regression
• Radial basis function
• Triangulation w/ linearinterpolation
Fig.: Wireframe Map
Analysis of different griddingmethods using “Surfer7”
Inverse Distance to aPower
• weighting averageinterpolator
• Power parameterbetween 1E-38 & 38“0” = planar surface;great weighting power= less effect on pointsfar from the grid nodeduring interpolation
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Fig.: Power: 0.00001
Fig.: Power: 2
Analysis of different griddingmethods using “Surfer7”
Inverse Distance to aPower
• exact or smoothinginterpolator
• generate "bull's-eyes”-smoothing reducethis effect
• very fast method forgridding-till 500 Datapoints
Fig.: withsmoothing: 0.01
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Analysis of different griddingmethods using “Surfer7”
Kriging
• express trendssuggested in your data
• Point or Block-Block is usingaverage values-smoother; not perfect
• specify & add asmany variogram-components as wished
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Fig.: Point Kriging
• by entering path & filename production estimatedstandard deviation grid
Analysis of different griddingmethods using “Surfer7”
Minimum Curvature
• smooth but not exact
• recalculation of gridnode values untilreached less of max.Residual value, ormax. Iteration
• Set Internal andBoundary Tension
• Relaxiation Factor
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Fig.: default
Analysis of different griddingmethods using “Surfer7”
Modified Shepard’sMethod
• Like IDP Method
• exact or smoothing
• Weighting andQuadratic Neighborsparameters specifiessize (number) of localneighborhood
• Fig.1: Q13/W19;Fig.2: Q40/W60
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Fig.: 1
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Analysis of different griddingmethods using “Surfer7”
Natural Neighbor
• Natural Neighborinterpolationalgorithm uses aweighted average ofneighboringobservations, wherethe weights areproportional to newadded polygons
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Analysis of different griddingmethods using “Surfer7”
Nearest Neighbor
• assigns value of thenearest point to eachgrid node
• useful when data arealready evenlyspaced
• this method iseffective for fillingmissing values
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Fig.: default
Analysis of different griddingmethods using “Surfer7”
PolynomialRegression
• used to define large-scale trends &patterns
• not real interpolator(does not predictunknown Z values)
• Fig.1: Simple planarsurface; Fig.2: Bi-linear saddle
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Fig.: 1
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Analysis of different griddingmethods using “Surfer7”
Radial BasisFunction
1. Inverse Multiquadric
2. Multilog
3. Multiquadric
4. Natural Cubic Spline
5. Thin plate Spline
• 1.; 2.; 4.- error
• 5.- good; 3.- best
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Fig.: 5. Thin plate spline
Analysis of different griddingmethods using “Surfer7”
Radial BasisFunction
• all exactinterpolators+ smoothing factor
• = variogram in K.(mathematicallyspecifies spatialvariability of data set& resulting grid fileFig.: 3. Multiquadric
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Analysis of different griddingmethods using “Surfer7”
Triangulation w/linear Interpolation
• creates triangles bydrawing linesbetween data points
• exact interpolator
• for evenly distributeddata over grid area-sparse areas result indistinct triangularfacets on map
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Analysis of different griddingmethods using “Surfer7”
Best Results
zKriging is exact, has many options & modifications,but needs knowledge
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Fig.: Point Kriging
Analysis of different griddingmethods using “Surfer7”
Best Results
zRadial Basis Function is exact, shows nice views& is uncomplicated
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Analysis of different griddingmethods using “Surfer7”
Conclusion
• I did not consider all aspects & details
• Surfer is very powerful for the 3D-Visualization
• Surfer 7 works:-fast & without consuming much disk space-uncomplicated with Object manager
• All processes (gridding, mapping) can be automatedwith writing programs in Visual Basic
• Help content is very useful & describes also backgroundinformation
Analysis of different griddingmethods using “Surfer7”