Petroleum industry maintains two primary measurement unit systems: Oil Metric (based on SI units) and Oil Field (based on Imperial units).
Both Oil Metric and Oil Field unit systems have deviations from their original base systems.
Some companies historically maintain customized unit systems at corporate level which are usually a slight variation of one of the two primary systems.
| Symbol | Dimension | SI | Oil Metric | Oil Field | Additional | |
|---|---|---|---|---|---|---|
| Time | t | T | s | d = 86,400 s | d = 86,400 s | hr = 3,600 s |
| Length | L | L | m | m = 3.281 ft | ' = ft = 0.3048 m | |
| Area | A | L2 | m2 | m2 | ||
| Volume | V | L3 | m3 | m3 = 6.289811 bbl | ||
| Mass / Weight | M, m | M | kg | kg | lb = 0.45359237 kg | g = 10-3 kg |
| Pipe Diameter | d, ø | L | m | m = 39.37 in | " = in = 0.0254 m | mm = 0.001 m= 0.0393701 in |
| Temperature | T | Θ | K | °C = K - 273 | °F = 9/5 T [°C] + 32 | K = 273 °C |
| Pressure (absolute) | P | M L-1 T-2 | Pa | psi = 6894.76 Pa = 6.89476 kPa | ||
| Pressure (gauge) | Pgauge | M L-1 T-2 | Pa | kPa(g) = kPa(abs) - 101,325 kPa | psi(g) = psi(abs) - 14.6959 psi | |
| Volumetric flow rate (oil & water) | q, Q | L3 T-1 | m3/s | cmd = m3/d = 1.16 · 10-5 m3/s | bpd = 0.184 · 10-5 m3/s = 0.159 cmd | |
| Volumetric flow rate (gas) | qg, Qg | L3 T-1 | m3/s | cmd = m3/d = 35.3147 scf/d | scf/d = ft3/d = 0.0283168 cmd | |
| GOR | Yg | – | m3/m3 | m3/m3 = 5.615 scf/bbl | scf/bbl = 0.1781 m3/m3 | |
| Density (solids) | ρ | M L-3 | kg/m3 | g/cc = 103 kg/m3 | g/cc = 103 kg/m3 | |
| Density (oil) | ρo | M L-3 | kg/m3 | g/cc = 103 kg/m3 | °API = (141.5/ γo) - 131.5 | |
| Specific gravity (oil) | γ | – | – | 1 = 103 kg/m3 | 1 = g/cc | γ = ρ / ρw |
| Compressibility | c | L T2 M-1 | Pa-1 | psi-1 = 0.145 · 10-3 Pa-1 = 0.145 kPa-1 | ||
| Permeability | k | L2 | m2 | md = 9.869233 · 10−16 m2 | md = 9.869233 · 10−16 m2 | D = 9.869233 · 10−13 m2 |
| Dynamic Viscosity | μ | M L-1 T-1 | Pa⋅s | cp = 10−3 Pa⋅s | cp = 10−3 Pa⋅s | 1 P = 100 cp |
| Productivity | J | L4 T M-1 | m3/(Pa·s) | cmd /kPa = 10-3 m3/(Pa·s) | bpd/psi = 0.0231 cmd /kPa | cmd /atm = 101.325 cmd /kPa = 4.394 · 103 bpd/psi |
| Transmissibility | σ | L4 T M-1 | m3/(Pa·s) | (md·m)/cp = 9.87 · 10-13 m3/(Pa·s) | (md·ft)/cp = 0.3048 (md·m)/cp | |
| Pressure diffusivity | χ | L2 T-1 | m2/s | (md·kPa)/cp = 9.869233 · 10−10 m2/s | (md·psi)/cp = 6.89476 (md·kPa)/cp | (md·atm)/cp = 101.325 (md·kPa)/cp |
| Wellbore storage | WBS, CS | L4 T2 M-1 | m3/Pa | m3/kPa = 0.001 m3/Pa | bbl/psi = 0.0231 m3/kPa | |
| Thermal conductivity | λ | M L T-3 Θ-1 | W/(m·K) | W/(m ·°C) = W/(m·K) | BTU/(hr⋅ft⋅°F) = 1.73 W/(m ·°C) | |
| Specific heat capacity | cp | M L2 T-2 Θ-1 | J/K | kJ/°C = 1,000 J/K | kJ/°F = 1,800 J/K | |
| Thermal diffusivity | a | L2 T-1 | m2/s | m2/s = 0.0929 ft2/s |