Equivalent circulating density (ECD)
The density equivalent to the bottomhole (or shoe) pressure while circulating: the static mud column plus the annular friction loss above that point.
ECD = ρ + ΔP_a / (g · H)P_c = ρ · g · H + ΔP_aECD at the shoe and in the open hole must stay below the fracture (loss) equivalent density. Cuttings loading, temperature and mud compressibility are not included; tripping adds surge and swab pressures.
Source: API RP 13D, Rheology and Hydraulics of Oil-well Fluids; Bourgeois et al., Applied Drilling Engineering (SPE, 1986), ch. 4
Inputs
You can change a field's unit: the value is converted to the formula's units automatically.
Above the point considered: from the hydraulics program or a PWD reading.
The bottom or the casing shoe.
Unit converter for this formulaDensity and °API · Pressure · Length · Pressure gradient and equivalent density
- kg/m³850
- g/cm³0.85
- t/m³0.85
- rel. (water 4 °C)0.850024
- lb/ft³53.0638
- lb/gal (ppg)7.09359
- SG (60/60 °F)0.850837
- °API34.8068
°API and SG refer to the density at 60 °F (15.6 °C) relative to water at 60 °F, relative density to water at 4 °C. The oil's thermal expansion between the measurement temperatures is not included. °API = 141.5 / SG − 131.5.
- P_c — Circulating pressure at depth H–
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.
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.
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.