Mud weight from the pore pressure
Equivalent density of the pore pressure and the mud weight that keeps the hydrostatic pressure above it by the margin of the Kazakhstan industrial safety rules (item 85-2), with the depth-dependent cap on the overbalance.
ρ_e = P_p / (g · H)ΔP = min(k · P_p, ΔP_max)ρ = (P_p + ΔP) / (g · H)ΔP_max = 1.5 MPa (H ≤ 1200 m), 2.5 MPa (H ≤ 2500 m), 3.5 MPa (H > 2500 m)The margin is a percentage of the pore pressure and may not exceed 1.5, 2.5 or 3.5 MPa depending on depth — the cap is applied automatically. The rule does not apply where wellbore stability sets the mud weight. The equivalent density in g/cm³ equals the pressure anomaly coefficient. The circulating mud weight may deviate by at most ±0.02 g/cm³ (item 85-3).
Source: Industrial safety rules for hazardous production facilities of the oil and gas industries of Kazakhstan (order of the Minister for Investment and Development No. 355 of 30.12.2014), item 85-2
Inputs
You can change a field's unit: the value is converted to the formula's units automatically.
Top of the formation to be drilled; it sets the interval of the rules.
Rules: 10–15 % down to 1200 m, 5–10 % from 1200 to 2500 m, 4–7 % below 2500 m.
Unit converter for this formulaPressure · Length · Density and °API · Pressure gradient and equivalent density · Fraction and percent
- MPa1
- kPa1,000
- bar10
- atm9.86923
- kgf/cm²10.1972
- mmHg7,500.62
- MPa(g)0.898675
- barg8.98675
- psi145.038
- psia145.038
- psig130.342
- ksi0.145038
psi and psia are absolute pressure; gauge units (barg, MPa(g), psig) are above atmospheric (101.325 kPa = 14.696 psi). Pressure differences in the formulas do not depend on this.
- ΔP — Overbalance–
- ΔP_max — Overbalance cap of the rules at this depth–
- ρ_e — Pore pressure equivalent density–
More in Pressures and drilling fluid
Pressure of a column of drilling or kill fluid at a true vertical depth, and its gradient (equivalent density).
Kill mud weight from the shut-in drill pipe pressure, and the initial and final circulating pressures for the driller's and the wait-and-weight methods.
The density equivalent to the bottomhole (or shoe) pressure while circulating: the static mud column plus the annular friction loss above that point.
Fracture (leak-off) equivalent density and pressure at the shoe from a LOT or FIT, and the maximum allowable annular surface pressure (MAASP) for the current mud weight.
How much weighting material (barite, hematite, calcium carbonate), water or another fluid to add to bring the mud to the required density, and the final 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.