Petroleum industry maintains two major measurement unit systems: Oil Metric (based on SI units) and Oil Field (based on Imperial units).
Both Oil Metric and Oil Field have deviations from their original basement 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 | m3/d = cmd = 1.16 · 10-5 m3/s | bpd = 0.184 · 10-5 m3/s = 0.159 m3/d | |
| Volumetric flow rate (gas) | qg, Qg | L3 T-1 | m3/s | m3/d = cmd = ??? | scf/d = ft3/d = ??? | |
| GOR | Yg | – | m3/m3 | m3/m3 = ??? | scf/bbl = ??? | |
| 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 | 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 · 10−7 m2 | md = 9.869233 · 10−7 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) | m3/(d·kPa) = 10-3 m3/(Pa·s) | bpd/psi = ??? | m3/(d·atm) = ??? |
| Transmissibility | σ | L4 T M-1 | m3/(Pa·s) | (md·m)/cp = 9.87 · 10-4 m3/(Pa·s) | (md·ft)/cp = ??? | |
| Pressure diffusivity | χ | L2 T-1 | m2/s | (md·kPa)/cp = ??? | (md·psi)/cp = ??? | (md·atm)/cp = ??? |
| Wellbore storage | WBS, CS | L4 T2 M-1 | m3/Pa | m3/kPa = ??? | bbl/psi = ??? | |
| Thermal conductivity | λ | M L T-3 Θ-1 | W/(m·K) | W/(m·°C) = ??? | BTU/(hr⋅ft⋅°F) = ??? | |
| Specific heat capacity | cp | M L2 T-2 Θ-1 | J/K | kJ/°C = ??? | kJ/°F = ??? | |
| Thermal diffusivity | a | L2 T-1 | m2/s | m2/s |