Calculator Input
Use a single straight segment or a multi-station survey table.
Example Data Table
This sample survey demonstrates increasing inclination and azimuth across depth stations.
| Station | Measured Depth | Inclination (°) | Azimuth (°) |
|---|---|---|---|
| 1 | 0 | 0 | 0 |
| 2 | 500 | 8 | 40 |
| 3 | 1000 | 15 | 55 |
| 4 | 1500 | 22 | 60 |
| 5 | 2000 | 30 | 65 |
Formula Used
Single straight segment
TVD = MD × cos(I)
North = MD × sin(I) × cos(Az)
East = MD × sin(I) × sin(Az)
HD = √(North² + East²)
Directional survey, minimum curvature
Dogleg = arccos[cos(I1)cos(I2) + sin(I1)sin(I2)cos(Az2 - Az1)]
Ratio Factor = 2 / Dogleg × tan(Dogleg / 2)
ΔTVD = (ΔMD / 2) × (cos(I1) + cos(I2)) × RF
Vertical Section = North × cos(CA) + East × sin(CA)
How to Use This Calculator
- Choose single segment for one straight interval, or directional survey for multiple stations.
- Select the length unit and enter closure azimuth for projected vertical section.
- Add optional reference elevation when you also need TVD subsea.
- For survey mode, paste one station per line as measured depth, inclination, and azimuth.
- Press Calculate TVD to show summary values, graph, and station table above the form.
- Use the CSV and PDF buttons to export the current results for reports, planning, or field review.
FAQs
1. What does true vertical depth measure?
True vertical depth is the straight vertical distance from the reference point to the current downhole position. It differs from measured depth, which follows the actual well path.
2. Why is TVD smaller than measured depth in deviated wells?
Measured depth traces the drilled path, including deviation and horizontal movement. TVD keeps only the vertical component, so it becomes smaller whenever inclination moves the path away from vertical.
3. When should I use the single segment mode?
Use single segment mode when the interval can be treated as one straight path with one inclination and azimuth. It is ideal for simple checks, estimates, and short planning runs.
4. When is directional survey mode better?
Directional survey mode is better when inclination or azimuth changes across depth. It handles multiple stations and computes a more realistic TVD using minimum curvature across each interval.
5. What is vertical section?
Vertical section is the horizontal projection of the well path onto a chosen closure azimuth. It helps compare path progress in the target direction instead of using raw northing and easting only.
6. What does dogleg severity show?
Dogleg severity expresses how sharply the path changes direction over a selected basis length. Higher values indicate stronger curvature, which matters for drilling limits, torque, drag, and completion planning.
7. How is TVD subsea calculated here?
This page calculates TVD subsea by subtracting TVD from the reference elevation you enter. Leave that field blank when you only need TVD without an elevation-based depth reference.
8. Can I export the result table for reporting?
Yes. After calculation, use the CSV button for spreadsheets or the PDF button for report-ready output. Both exports include summary values and the visible station table.