drilling · directional
Turn Rate
click formula to derive ↑
Inputs
°
°
ft
ft
Description
Computes the rate of azimuth (turn) change between two adjacent survey stations, normalized to a standard interval — the azimuth-only counterpart to Build Rate. Distinct from Dogleg Severity, which combines both inclination and azimuth change into a single total curvature rate; Turn Rate isolates the azimuth (walk) component alone.
Variables
| Symbol | Unit | Description |
|---|---|---|
| TR | °/100ft | Turn Rate |
| A₁ | ° | Azimuth at the upper (shallower) survey station, measured clockwise from north. |
| A₂ | ° | Azimuth at the lower survey station, measured clockwise from north. |
| MD₁ | ft | Measured depth of the upper survey station. |
| MD₂ | ft | Measured depth of the lower survey station. Must exceed MD₁. |
Assumptions
- Survey stations are accurate (verified gyro or properly corrected MWD survey)
- Azimuth change between stations reflects intentional or formation-driven walk, not magnetic interference or tool-face control noise
- Station spacing is short enough that a constant turn rate between the two stations is a reasonable approximation
Limitations
- Does not capture inclination change — a station pair with high dogleg severity but zero net azimuth change will show a turn rate of zero despite significant total curvature; use dogleg_severity for total curvature
- Near-vertical wellbores (low inclination) can show large, physically insignificant azimuth swings from small positional noise — turn rate is most meaningful once the well has built meaningful inclination
- Magnetic interference or poor gyro calibration can produce spurious azimuth changes that inflate apparent turn rate
Use Cases
- → Directional drilling walk tendency QC: Screen MWD surveys against the planned turn profile to catch unplanned formation-driven walk during rotary drilling.
- → Build-and-turn trajectory design: Isolate the azimuth (turn) component when planning a curve section that both builds inclination and turns azimuth simultaneously.
- → Tool-face performance review: Compare achieved turn rate against the RSS or motor's rated turning capability for a given interval.
Related Calculations
Region Notes
Permian Basin
Build-and-turn curve designs targeting a specific lateral azimuth on multi-well pads commonly plan turn rates of 1-3°/100ft alongside the primary build rate.
Global
Turn rate is most useful once inclination exceeds roughly 10-15° — at very low inclination, small survey noise in azimuth can produce turn-rate values with little physical meaning.
References
Primary source
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