well directional survey processing in fme
TRANSCRIPT
Well Directional Survey Processing in FME
Jerrod StutzmanDevon Energy
Directional Survey for a WellIn geoscience, a directional survey is a collection of data points recorded along a wellbore.
Magnetic and/or gyroscopic instruments are sent down the wellbore to record the 3D wellbore location with high precision. These instruments record measured depth, inclination, and azimuth values.
Spherical Coordinate System?Measured Depth (MD), Azimuth (Az), and Inclination (I) specify a 3D point in space.
This is essentially a spherical coordinate system where:MD = rAz = φ (clockwise from North)I = θ (+z is defined as downward)
Problem: Raw Surveys “Unmappable”Azimuth, Inclination, and Measured Depth are all measured with reference to an origin – that being the surface location of the well.
Obviously, this can’t be used for storing multiple wells in a geodatabase because they need to have a common origin, coordinate reference system, etc.!
Therefore, we must convert the survey stations to XYZ coordinates. The most accurate method for calculating northing and easting offsets is known as the minimum curvature method.
Considerations- Azimuth angle can be recorded in terms of True, Grid, or
Magnetic North. Must correct for convergence! There are equations for this, but there is also a Custom FME Transformer.
- Surface Hole location must be known for well to convert ΔN/ΔE to ΔLon/ΔLat
- Geoscience database stores both sets of coordinates: - ΔN/ΔE and ΔLon/ΔLat- ΔN/ΔE needs directional indicators (N,S,E,W)- ΔLon/ΔLat requires +/- to indicate direction
http://os.is/gogn/unu-gtp-report/UNU-GTP-2013-27.pdf
Minimum Curvature Method
This math is all replicated in FME!
Workbench Overview
Screenshots of FME workbench math
Minimum CurvatureCalculations happen here
Retrieve Well Header & Survey Data
Use Surface Latitude to calculate feet per degree conversion factor.
Test Azimuth North reference
Convergence CorrectionIf azimuth is referenced to grid north, apply convergence correction.
Must know grid north coordinate system!
“Multiple Feature Attribute Support” is the magic behind this process. Without it, this would not be possible.
This allows us to use attribute values from previous (or subsequent) features!
Workbench: Minimum Curvature Calculations
Math Translation to FME - Example
No, it’s not pretty, but it is effective!!
feature[-1].Inc refers to the Inclination value from the previous featurefeature[-1].Azi is the Azimuth value from the previous feature
becomes (via ExpressionEvaluator):
Store Processed SurveysWell Surveys that have been processed using this method are then written back to the geoscience database with XY offsets and lat/lon offsets for each station.
These processed surveys can then be used to map all directional surveys in the database, in 2 and 3-dimensions! (TVD is used as absolute z value for 3D)
Data points are converted from azimuth, inclination, and depth values to X/Y Offsets and Lat/Lon Offsets. These can be used to map data in standard coordinate systems (and even in 3 dimensions!)
Summary
Directional Survey Points Mapped in 2D and 3D
3D view2D (top-down) view
