Permeability and transmissibility from the semilog slope
Transmissibility kh/μ, flow capacity kh and permeability from the slope of the semilog straight line of a build-up or drawdown (radial flow).
kh/μ = ln 10 / (4π) · q · B / m = 0.1832 · q · B / mk = 2.149 · q · B · μ / (m · h)Infinite homogeneous reservoir, radial flow of a slightly compressible single-phase liquid; the straight line lies after wellbore storage and before the boundaries. The constant 2.149 is for mD, m³/d, mPa·s, MPa/cycle and m (21.49 with bar/cycle, 162.6 in field units: psi, bbl/d, cP, ft). Gas wells use pseudo-pressure or P².
Source: Earlougher, Advances in Well Test Analysis, SPE Monograph 5 (1977), ch. 3 and 5; Lee, Well Testing (1982): k = 162.6 · q · B · μ / (m · h)
Inputs
You can change a field's unit: the value is converted to the formula's units automatically.
Pressure change per log cycle of time, the sign does not matter; for a build-up take it from the Horner or MDH plot.
At standard conditions; B converts it to reservoir conditions.
About 1 for water.
Unit converter for this formulaSemilog slope · Liquid rate · Oil formation volume factor · Viscosity · Length · Permeability · Flow capacity kh, kf·w · Transmissibility kh/μ
- MPa/cycle1
- kPa/cycle1,000
- bar/cycle10
- (kgf/cm²)/cycle10.1972
- psi/cycle145.038
Pressure change per log cycle of time.
- kh — Flow capacity kh–
- kh/μ — Transmissibility–
More in Build-up and drawdown
Skin factor from the semilog straight line of a pressure build-up curve.
Skin factor from the semilog straight line of a pressure drawdown curve.
Slope m of the semilog straight line of a pressure build-up (+) or drawdown (−) curve, in psi per log cycle.
Slope m of the semilog straight line of a pressure build-up (+) or drawdown (−) curve, in bar per log cycle.
Effective producing time before a build-up from the cumulative production and the last rate, the Horner time ratio (t_p + Δt)/Δt for the plot axis, and Agarwal's equivalent time.
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.