Drill String Buoyancy Calculator: Hook Load and Buoyed Weight

How It Works

1. Enter Mud Weight

   Input the current drilling fluid density in ppg. Confirm the value against mud balance readings and the drilling program.

2. Enter Total String Weight

   Enter the total drill-string air weight from the tally or drilling program. The app does not build a multi-component pipe tally.

3. Add Optional WOB or Overpull

   Enter WOB or overpull in klbs only when you want the simplified hook-load screen to include those terms.

4. Review Caveats Before Use

   Use the result as a static reference. Operational limits require torque-and-drag modeling, connection and pipe-body checks, rig limits, and qualified review.

Built For

• Drillers checking a static buoyed-weight estimate against a planned trip sheet
• Drilling engineers reviewing a quick free-hanging weight screen before detailed torque-and-drag work
• Rig crews comparing rough expected hook load with weight-indicator behavior while keeping drag and hole condition caveats visible
• Well planners documenting the buoyancy factor basis used in preliminary planning notes
• Fishing or stuck-pipe discussions where the first step is separating buoyed weight from any proposed overpull term

Features & Capabilities

Steel BF Formula

Uses BF = 1 - MW / 65.44 for a steel-density basis of 489.5 lb/ft3.

Total Air-Weight Input

Accepts total string weight in klbs or pounds and normalizes results to klbs.

Static Hook-Load Screen

Applies Hook Load = Buoyed Weight - WOB + Overpull with clear warnings about what the simplification omits.

Overpull Caveats

Flags overpull as a value requiring pipe, connection, rig, slip, jar, and stuck-pipe-plan checks.

Reference Table

Shows local buoyancy-factor rows from freshwater through 18.5 ppg for quick context.

PDF Export

Exports the calculation with source warnings, assumptions, and source pointers for planning records.

Assumptions

• Steel density basis is 65.44 ppg, based on 489.5 lb/ft3.
• Mud weight is uniform over the relevant interval.
• Buoyancy factor BF = 1 - MW / 65.44 is applied as a static screening formula.
• Pipe is treated as free-hanging with no wall contact, friction, bending, or dynamic forces.
• WOB and overpull are entered in klbs and applied after buoyed weight.

Limitations

• Does not model drag and friction in deviated or horizontal wellbores.
• Does not calculate or verify connection ratings, pipe-body limits, slip crushing, burst, collapse, torsion, fatigue, or dogleg severity.
• Does not model internal fluid differences, multi-fluid columns, ECD, riser gas, cuttings beds, surge/swab, or dynamic hoisting loads.
• Does not build a drill-pipe, HWDP, collar, BHA, casing, or landing-string tally.
• Does not approve stuck-pipe overpull, weight on bit, rig capacity, top-drive limits, or operational procedures.

References

• API RP 7G and related API 7G series source pointer for drill stem design and operating limits.
• IADC Formulas and Calculations for Drilling, Production and Workover source pointer.
• ISO 10407-2 source pointer for drill stem inspection and classification context.
• Current drilling program, pipe tally, connection data, rig specifications, survey, torque-and-drag model, and qualified drilling engineering review.

Frequently Asked Questions