Balanced cement plug
Slurry volume for a plug of a given length, the slurry height with the pipe in the hole, the spacer volume behind the cement that balances the columns, and the displacement volume.
V_c = π/4 · D² · L · (1 + k)C_a = π/4 · (D² − d_o²); C_p = π/4 · d_i²L_p = V_c / (C_a + C_p)V_b2 = V_b1 · C_p / C_aV_d = C_p · (H − L_p) − V_b2The spacer behind is sized so that its height in the pipe equals the height of the spacer ahead in the annulus — then the columns balance (same spacer and displacement fluid on both sides). Heights use the nominal capacities; the excess only increases the slurry volume. The displacement is often reduced slightly so the pipe pulls dry.
Source: Lapeyrouse N. J., Formulas and Calculations for Drilling, Production and Workover (Gulf Professional Publishing): balanced cement plug; Nelson, Guillot, Well Cementing (Schlumberger, 2006)
Inputs
You can change a field's unit: the value is converted to the formula's units automatically.
For open hole; 0 inside casing.
Tubing or drill pipe used to pump the cement.
Unit converter for this formulaLength · Liquid volume · Fraction and percent
- m1
- cm100
- mm1,000
- km0.001
- ft3.28084
- in39.3701
- 1/32 in1,259.84
- 1/64 in2,519.69
- mile0.000621371
- L_p — Slurry height with the pipe in the hole–
- V_b2 — Spacer behind the cement–
- V_d — Displacement volume–
- H_t — Top of the plug after pulling out–
More in Cementing
Slurry volume for a single-stage casing job: the open-hole annulus with excess, the overlap with the previous casing, the shoe track and the rat hole, plus the displacement volume down to the float collar.
Slurry density and yield from the water-cement ratio, and the dry cement mass and mix water volume for a given slurry volume.
Results are engineering estimates from standard formulas; for design decisions check them against the codes, project documents and specialists' calculations. The formulas carried over from the original set are unchanged, and their errors are described in the notes.