Casing Depth Calculator

Work out casing depth instantly with clear inputs, formula shown and shareable results.

About Casing Depth Calculator

Casing depth is chosen so the shoe can withstand the mud weight needed to reach the next target plus a kick margin. Working from the bottom up, the shoe must sit deep enough in competent rock that its fracture gradient exceeds the required mud weight by the safety margin.

Formulas

Casing shoe depth

Shoe depth = required mud weight x target depth / (fracture gradient at shoe - kick margin)

Mud weight

Required mud weight = pore pressure gradient + trip margin

Worked example

With the default values below, Casing Depth Calculator returns Minimum Casing Shoe Depth of 10,431.4. Change any input above and every figure here is recalculated in your browser.

Inputs used

Target Depthminimum 0.01 ft: 12,000 ft
Pore Pressure Gradient At Targetminimum 0.01 ppg: 13 ppg
Fracture Gradient At Candidate Shoeminimum 0.01 ppg: 15.8 ppg
Required Kick Marginminimum 0 ppg: 0.5 ppg

Results

Minimum Casing Shoe Depth: 10,431.4
Mud Weight Needed For Target: 13.300
Available Margin At Shoe: 2.500
Casing Point Assessment: Casing point acceptable

Step by step

1Values used
2Casing shoe depth
3Mud weight
4Minimum Casing Shoe Depth= 10,431.4
5Mud Weight Needed For Target= 13.300
6Available Margin At Shoe= 2.500
7Casing Point Assessment= Casing point acceptable

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Casing design is a safety-critical engineering activity governed by regulation. It must be carried out by qualified well engineers using verified geopressure data.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Casing design is a safety-critical engineering activity governed by regulation. It must be carried out by qualified well engineers using verified geopressure data.

Frequently Asked Questions

Why design from the bottom up?

Because the deepest objective sets the mud weight, which sets the strength needed at the shoe above it, which in turn sets the next casing point. Designing top-down usually produces an infeasible string.

What else constrains casing points?

Isolating loss zones, unstable shales, shallow gas and freshwater aquifers, plus regulatory requirements for surface casing depth and cement coverage.