Determine the linear weight, cross-sectional area, and steel volume for oilfield casing operations.
Casing Weight Calculator (Imperial)
Common sizes: 5.5, 7, 9.625, 13.375, 20
Please enter a valid positive diameter.
Typically ranges from 0.2 to 1.0 inches based on grade/pressure.
Thickness must be positive and less than half of OD.
Standard Steel: 0.2833.
Please enter a valid density.
Calculated Weight Per Foot (Plain End)
42.70 lb/ft
Formula: 10.68 × (OD – t) × t
Inner Diameter (ID):8.755 in
Cross-Sectional Area:12.56 in²
Internal Capacity:0.0744 bbl/100ft
Graph: Casing Weight (lb/ft) vs. Wall Thickness (in) for selected OD.
Wall Thickness (in)
Weight (lb/ft)
Inner Diameter (in)
Drift Diameter (approx -0.125)
Comparison of different wall thicknesses for the selected Outer Diameter.
What is Calculate Weight Per Foot Petroleum Casing?
When engineers plan a drilling program, one of the most critical mechanical properties to determine is the mass of the tubulars being run into the wellbore. To calculate weight per foot petroleum casing is to determine the linear mass density of the steel pipe used to line the borehole. This metric is fundamental for designing the drill string, calculating hook loads, determining shipping logistics, and ensuring the rig's hoisting system is not overloaded.
This calculation is primarily used by drilling engineers, rig managers, and procurement specialists. A common misconception is that the "nominal weight" printed on a pipe tally is exactly the same as the physical weight of every foot of pipe. In reality, the plain-end weight (the pipe body without threads) differs slightly from the nominal weight, which accounts for the added mass of threaded connections and couplings (like BTC or LTC connections). This calculator focuses on the plain-end weight derived from physical dimensions, which is the baseline for all engineering load calculations.
Casing Weight Formula and Mathematical Explanation
The industry standard for these calculations comes from the American Petroleum Institute (API) Specification 5CT. To accurately calculate weight per foot petroleum casing, we treat the casing as a hollow cylinder. The formula determines the volume of steel per linear foot and multiplies it by the density of the material.
The standard API formula for plain-end weight ($w_{pe}$) is:
Weight (lb/ft) = 10.68 × (OD – t) × t
Where 10.68 is a constant derived from the density of steel (0.2833 lb/in³). If you are using a non-standard material density, the generalized physics formula is:
$$ W = 12 \times \rho_{steel} \times \frac{\pi}{4} \times (OD^2 – (OD – 2t)^2) $$
Variables used to calculate weight per foot petroleum casing
Variable
Meaning
Unit
Typical Range
OD
Outer Diameter
Inches (in)
4.5″ to 20″
t
Wall Thickness
Inches (in)
0.2″ to 1.0″
ID
Inner Diameter
Inches (in)
OD – 2t
$\rho$ (Rho)
Density of Material
lb/in³
0.2833 (Steel)
Practical Examples (Real-World Use Cases)
Example 1: Surface Casing String
Scenario: A drilling engineer needs to run a 13 3/8″ surface casing to protect shallow aquifers. The available pipe has a wall thickness of 0.480 inches.
Interpretation: If the well is 3,000 feet deep, the total air weight of the string is $3,000 \times 66.1 = 198,300$ lbs. The rig's hoisting system must be rated to handle this load plus a safety margin.
Example 2: Production Liner
Scenario: For a deep high-pressure well, a 7-inch liner with extra thick walls (0.500 in) is required.
Interpretation: This is significantly heavier than standard 7″ casing (often ~26 lb/ft), affecting the buoyancy factor and the tension applied to the liner hanger.
How to Use This Casing Weight Calculator
Identify the Outer Diameter: Enter the nominal OD of your pipe in inches (e.g., 9.625 for 9 5/8″ casing).
Enter Wall Thickness: Input the specific wall thickness. This can be found on the mill certificate or API 5CT tables.
Verify Density: Leave as 0.2833 for standard carbon steel. Change this only if you are using exotic alloys (e.g., Titanium or heavy wall Chrome).
Read the Result: The large blue number is your Plain End Weight per foot.
Analyze Intermediates: Check the Inner Diameter (ID) to ensure your drill bits or subsequent casing strings can pass through (drift).
Use the chart to visualize how increasing wall thickness (for higher burst pressure ratings) linearly increases the weight per foot, helping you optimize your casing design for both strength and weight efficiency.
Key Factors That Affect Casing Weight Results
When you calculate weight per foot petroleum casing, several factors influence the final engineering decision:
Wall Thickness vs. Burst Pressure: Thicker walls increase weight but provide higher burst and collapse resistance. Engineers often balance weight to reduce hook load against the need for pressure integrity.
Steel Grade (Yield Strength): While grade (e.g., N80, P110) does not significantly change density or weight per foot, it allows for thinner walls to carry the same pressure, effectively reducing string weight.
Coupling Type: This calculator provides Plain End weight. Premium connections or API couplings (Buttress vs. Short Round) add varying amounts of mass at the joints, typically increasing the average string weight by 1-3%.
Buoyancy (Archimedes Principle): The calculated weight is "air weight." Once submerged in drilling fluid (mud), the effective string weight decreases. Heavy casing in heavy mud weighs significantly less on the hook.
Manufacturing Tolerances: API 5CT allows for a tolerance in wall thickness (often -12.5%). Real-world pipe may be slightly lighter or heavier than the theoretical calculation.
Cost Implications: Steel is sold by weight (tonnage). Accurately estimating the total tonnage of a casing program is vital for accurate AFE (Authorization for Expenditure) budgeting.
Frequently Asked Questions (FAQ)
Why does the calculated weight differ from the "Nominal Weight"?
Nominal weight is a class designation that roughly approximates the weight including couplings. The calculator provides the exact theoretical plain-end weight based on geometry.
Can I use this for Drill Pipe?
Yes, the geometric formula works for drill pipe tubes, but drill pipe has heavy tool joints (upsets) that add significant weight not captured by a simple cylinder formula.
Does this account for buoyancy?
No, this tool calculates air weight. To find the hook load in mud, you must multiply this result by the Buoyancy Factor ($BF = 1 – \frac{MW}{65.5}$).
What is the standard density of API casing?
API standards use 0.2833 lbs per cubic inch ($7843 kg/m^3$) for carbon steel calculations.
How does diameter affect weight compared to thickness?
Weight increases linearly with diameter, but the relationship with thickness is slightly more complex as it reduces the ID. Generally, increasing OD adds weight faster than increasing thickness.
Is this calculator valid for stainless steel or chrome casing?
Yes, provided you adjust the density. High chrome alloys have densities very close to carbon steel, so the standard 0.2833 is usually sufficient for estimation.
What is "Drift Diameter"?
Drift diameter is the verified minimum diameter that a mandrel can pass through. It is typically the ID minus 1/8 inch (0.125″) for standard casing sizes.
Why is accurate weight calculation critical for deep water?
In deep water, the sheer weight of the riser and casing strings can approach the tensile limits of the landing string. Accurate weight-per-foot calculations prevent catastrophic structural failures.
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