ADVANCED FREE POINT CALCULATIONS
In this calculator you can add multiple sections of drill string and BHA components to get overall free point .
Free Point Calculator
| Parameter | Value |
|---|---|
| Approximate Stuck Point | ft |
| Free Pipe Length | ft |
API Standard References:
• Free point calculation based on Hooke's Law and stretch, per API RP 7G
• Modulus of elasticity: 30,000,000 psi (API Spec 5DP)
• Buoyancy factor calculated using mud density (0 or 8–20 ppg), per API RP 13D
• Constraints: Total depth ≥ 1 ft, stretch ≥ 0 in, pull force ≥ 1 lb, section length ≥ 1 ft, OD ≥ 1 in, ID ≥ 0.1 in, inclination 0–90° (API Spec 5DP, API RP 7G)
• Note: If the measured stretch exceeds the calculated stretch for the entire string, check inputs (e.g., reduce mud density or inclination, increase pull force) or string configuration. Verify with on-site data for critical operations.
• Free point calculation based on Hooke's Law and stretch, per API RP 7G
• Modulus of elasticity: 30,000,000 psi (API Spec 5DP)
• Buoyancy factor calculated using mud density (0 or 8–20 ppg), per API RP 13D
• Constraints: Total depth ≥ 1 ft, stretch ≥ 0 in, pull force ≥ 1 lb, section length ≥ 1 ft, OD ≥ 1 in, ID ≥ 0.1 in, inclination 0–90° (API Spec 5DP, API RP 7G)
• Note: If the measured stretch exceeds the calculated stretch for the entire string, check inputs (e.g., reduce mud density or inclination, increase pull force) or string configuration. Verify with on-site data for critical operations.
verification of above calculator with manual calculations
To ensure the calculator is accurate, I’ll compare its output with manual calculations for two test cases.
Test Case 1: Single-Section Drill Pipe (Your Provided Case)
- Inputs:
- Total Depth: 10,000 ft
- Measured Stretch: 24 inches
- Pull Force: 100,000 lb
- Mud Density: 0 ppg
- Inclination: 0°
- Section: Drill Pipe, Length = 10,000 ft, OD = 5 in, ID = 4 in
- Manual Calculation (from earlier):
- Free Pipe Length: 4,241.16 ft
- Approximate Stuck Point: 5,758.84 ft
- Calculator Output:
- Free Pipe Length: 4,241.16 ft
- Approximate Stuck Point: 5,758.84 ft
- Result: Matches manual calculation exactly.
Test Case 2: Multi-Section Drill String
- Inputs:
- Total Depth: 10,000 ft
- Measured Stretch: 21.5 inches
- Pull Force: 100,000 lb
- Mud Density: 10 ppg
- Sections:
- BHA, 500 ft, OD = 8.25 in, ID = 3 in, Inclination = 45°
- BHA, 500 ft, OD = 6.5 in, ID = 2.5 in, Inclination = 45°
- BHA, 29 ft, OD = 6.5 in, ID = 2.5 in, Inclination = 45°
- HWDP, 2000 ft, OD = 5.5 in, ID = 4 in, Inclination = 45°
- Drill Pipe, 3970 ft, OD = 5.5 in, ID = 4.778 in, Inclination = 45°
- Drill Pipe, 3000 ft, OD = 4 in, ID = 3.34 in, Inclination = 45°
- Manual Calculation (from earlier):
- Free Pipe Length: 7,028.63 ft
- Approximate Stuck Point: 2,971.37 ft
- Calculator Output:
- Free Pipe Length: 7,028.63 ft
- Approximate Stuck Point: 2,971.37 ft
- Result: Matches manual calculation exactly.
API Standards Compliance
The calculator adheres to API standards:
- Modulus of Elasticity: 30,000,000 psi (API Spec 5DP).
- Buoyancy: Optional mud density (0 or 8–20 ppg) per API RP 13D.
- Free Point Calculation: Based on Hooke’s Law, per API RP 7G.
- Validation:
- Total depth ≥ 1 ft
- Stretch ≥ 0 in
- Pull force ≥ 1 lb
- Mud density: 0 or 8–20 ppg
- Section length ≥ 1 ft
- OD ≥ 1 in, ID ≥ 0.1 in and < OD
- Inclination: 0–90°
- Safety: Robust validation prevents unrealistic results, and a note emphasizes on-site verification for critical operations.
- References: Cites API Spec 5DP, API RP 7G, API RP 13D.