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Basic symbols in alphabetical order
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Letter Symbol English | Reserve SPE Letter Symbol | Quantity | Dimensions |
a | activity | ||
a | Fa | air requirement | various |
a | decline factor nominal | ||
a | La, L1 | distance between like wells (injection or production) in a row | L |
A | amplitude | various | |
A | atomic weight | m | |
A | F | Helmboltz function (work function) | mL2/t2 |
b | Y | intercept | various |
b | f,F | reciprocal formation volume factor, volume at standard conditions divided by volume at reservoir conditions (shrinkage factor) | |
b | w | width, breadth, or thickness (primarily in fracturing) | L |
B | C | correction term or correction factor (either additive or multiplicative) | |
B | F | formation volume factor, volume at reservoir conditions divided by volume at standard conditions | |
c | k, κ | compressibility | Lt2/m |
C | capacitance | q2t2/mL2 | |
C | capital costs or investments | M | |
C | coefficient of gas-well backpressure curve | L3−2nt4n/m2n | |
C | nC | components, number of | |
C | c,n | concentration | various |
C | σ | conductivity (electrical logging) | tq2/mL3 |
C | c,n | salinity | various |
C | c | specific heat capacity (always with phase or system subscripts) | L2/t2T |
C | waterdrive constant | L4t2/m | |
CƒD | fracture conductivity, dimensionless | ||
CL | cL,nL | condensate or natural gas liquids content | various |
d | decline factor, effective | ||
d | D | diameter | L |
d | Ld,L2 | distance between adjacent rows of injection and production wells | L |
D | deliverability (gas well) | L3/t | |
D | y,H | depth | l |
D | µ,δ | diffusion coefficient | L2/t |
e | i | influx (encroachment) rate | L3/t |
eO2 | EO2 | oxygen utilization | |
ez | exp z | exponential function | |
E | η,e | efficiency | |
E | V | electromotive force | mL2/t2q |
E | U | energy | mL2/t2 |
E | Y | modulus of elasticity (Young’s modulus) | M/Lt2 |
EA | ηA,eA | areal efficiency (used in describing results of model studies only): area swept in a model divided by total model reservoir area (see Ep) | |
Ec | Φc | electrochemical component of the SP | mL2/t2q |
Ek | Φk | electrokinetic component of the SP | mL2/t2q |
En | Euler number | ||
ESP | ΦSP | SP (measured SP) (self potential) | mL2/t2q |
−Ei (−x) | exponential integral, , dt, x positive | ||
Ei (x) | exponential integral, modified, x positive | ||
f | F | fraction (such as the fraction of a flow stream consisting of a particular phase) | |
f | v | frequency | 1/t |
f | friction factor | ||
f | fugacity | m/Lt2 | |
fs | Q,x | quality (usually of steam) | |
F | degrees of freedom | ||
F | A,R,r | factor in general, including ratios (always with identifying subscripts) | various |
F | ƒ | fluid (generalized) | various |
FR | formation resistivity factor—equals R0/Rw (a numerical subscript to F indicates the value Rw) | ||
FWV | γ | specific weight | mL2/t2 |
g | γ | gradient | various |
g | gravity, acceleration of | L/t2 | |
gc | conversion factor in Newton’s second law of Motion | ||
G | g | gas in place in reservoir, total initial | L3 |
G | g | gas (any gas, including air), always with identifying subscripts | various |
G | ƒG | geometrical factor (multiplier)
(electrical logging)|| | |
G | Es | shear modulus | m/Lt2 |
GL | gL | condensate liquids in place in reservoir, initial | L3 |
h | i | enthalpy, specific | L2/t2 |
h | hh,hT | heat transfer coefficient, convective | m/t3T |
h | d,e | height (other than elevation) | L |
h | hyperbolic decline constant (from equation) | ||
q=qi/ | |||
h | d,e | thickness (general and individual bed) | L |
H | I | enthalpy (always with phase or system subscripts) | mL2/t2 |
i | injection rate | L3/t | |
i | interest rate | 1/t | |
iR | rate of return (earning power) | ||
I | income (net revenue minus expenses) | ||
I | i (script i), i | current, electric | q/t |
I | IT,I¬θ | heat transfer coefficient, radiation | m/t3T |
I | i | index (use subscripts as needed) | |
I | i | injectivity index | L4t/m |
ς (z)(script I) | imaginary part of complex number z | ||
IR | iR | resistivity index (hydrocarbon)—equals Rt/R0 | |
j | iR | reciprocal permeability | 1/L2 |
J | j | productivity index | L4t/m |
k | κ | magnetic susceptibility | mL/q2 |
k | K | permeability absolute (fluid flow) | L2 |
k | r,j | reaction rate constant | L/t |
kh | λ | thermal conductivity (always with additional phase or system subscripts) | mL/t3T |
K | Kb | bulk modulus | m/Lt2 |
K | coefficient in the equation of the electrochemical component of the SP (spontaneous electromotive force) | mL2/t2q | |
K | M | coefficient or multiplier | various |
K | d | dispersion coefficient | L2/t |
K | k,Feq | equilibrium ratio (y/x) | |
Kani | Mani | anisotropy coefficient | |
Kc | Mc, Kec | electrochemical coefficient | mL2/t2q |
KR | MR,a,C | formation resistivity factor coefficient (FR Φm) | |
ln | natural logarithm, base e | ||
log | common logarithm, base 10 | ||
loga | logarithm base a | ||
L | nL | moles of liquid phase | |
Lf | xf | fracture half-length (specify "in the direction of" when using xf) | L |
Ls | ss,ls (script l) | spacing (electrical logging) | L |
Lv | λv | latent heat of vaporization | L |
L (y) (script L) | Laplace transform of y, y(t)e-stdt | ||
m | FF | fuel consumption | various |
m | mass | m | |
m | porosity exponent (cementation) (in an empirical relation between FR and ) | ||
m | FFo,Fgo | ratio of initial reservoir free-gas volume to initial reservoir oil volume | |
m | A | slope | various |
M | I | magnetization | m/qt |
M | Fλ | mobility ratio, general (λdisplacing/λdisplaced) | |
M | molecular weight | m | |
M | mθD | slope, interval transit time vs. density (absolute value) | tL2/m |
M | volumetric heat capacity | m/Lt2T | |
n | N | density (indicating "number per unit volume") | 1/L3 |
n | exponent of backpressure curve, gas well | ||
n | μ | index of refraction | |
n | N | number (of variables, components, steps, increments, etc.) | |
n | n | number (quantity) | |
n | saturation exponent | ||
n | number of compounding periods | 1/t | |
nt | Nt | moles, number of, total | |
N | n,C | count rate (general) | 1/t |
N | neutron [usually with identifying subscript(s)] | various | |
N | number, dimensionless, in general (always with identifying subscripts) | ||
N | n | oil (always with identifying subscripts) | various |
N | m ND | slope, neutron porosity vs. density (absolute value) | L3/m |
NGR | Nγ,CG | gamma ray count rate | 1/t |
NR | NF | fuel deposition rate | m/L3t |
O | operating expense | various | |
p | P | pressure | m/Lt2 |
p | price | M | |
P | phases, number of | ||
P | profit total | M | |
Pc | Pc ,pc | capillary pressure | M/Lt2 |
q | Q | production rate or flow rate | L3/t |
Q | q | charge (current times time) | q |
Q | q,Φ | heat flow rate | mL2/t3 |
Qi | qi | pore volumes of injected fluid, cumulative dimensionless | |
QLtD | Ql tD (script l) | fluid influx function, linear aquifer, dimensionless | |
Qp | Ql tD (script l) | fluids, cumulative produced (where Np and Wp are no applicable) | |
QtD | fluid influx function, dimensionless, at dimensionless time tD | ||
QV | ZV | cation exchange capacity per unit pore volume | |
r | R | radius | L |
r | R | resistance | mL2/tq2 |
R | ρ,r | electrical resistivity (electrical logging) | ml3tq2 |
R | gas constant, universal (per mole) | mL2/t2T | |
R | Fg,Fgo | gas/oil ratio, producing | |
R | N | molecular refraction | L3 |
R(z) (script R) | real part of complex number z | ||
s | L | displacement | L |
s | σ | entropy, specific | L2/t2T |
s | Laplace transform variable | ||
s | S, σ | skin effect | various |
s | standard deviation of a random variable, estimated | ||
s2 | variance of a random variable, estimated | ||
S | σt | entropy, total | mL2/t2T |
S | ρ,s | saturation | |
t | τ | time | t |
tma(script t) | Δtma | matrix interval transit time | t/L |
t½ | half-life | t | |
T | Θ | period | t |
T | θ | temperature | T |
T | T | transmissivity, transmissibility | various |
u | ψ | flux | various |
u | ψ | flux or flow rate, per unit area (volumetric velocity) | L/t |
U | UT,Uθ | heat transfer coefficient, overall | m/t3T |
v | V,u | acoustic velocity | L/t |
v | νs | specific volume | L3/m |
v | V,u | velocity | L/t |
V | R,Vt,Rt | gross revenue ("value"), total | M |
V | nν | moles of vapor phase | |
V | U | potential difference (electric) | mL2/q2 |
V | v | volume | L3 |
V | ƒV,FV | volume fraction or ratio (as needed, use same subscripted symbols as for "volumes"; note that bulk volume fraction is unity and pore volume fractions are Φ) | various |
w | z | Arrhenius reaction-rate velocity constant | L3/m |
w | m | mass flow rate | m/t |
W | w | water (always with identifying subscripts) | various |
W | w | water in place in reservoir, initial | L3 |
W | w,G | weight (gravitational) | mL/t2 |
W | w | work | mL2/t2 |
x | mole fraction of a component in liquid phase | ||
vector of x | |||
tensor of x | |||
xD | dimensionless quantity proportional to x | ||
X | reactance | mL2/tq2 | |
y | ƒ | holdup (fraction of the pipe volume filled by a given fluid: yo is oil holdup; yw is water holdup; sum of all holdups at a given level is one) | |
y | mole fraction of a component in vapor phase | ||
z | Z | gas compressibility factor (deviation factor) (z=pV/nRT) | |
z | mole fraction of a component in mixture | ||
z | valence | ||
Z | atomic number | ||
Z | D,h | elevation (height or fluid head) referred to datum | L |
Z | impedance | various | |
Greek | |||
α | β, γ | angle | |
α | mα | attenuation coefficient | 1/L |
α | a,ηh | heat or thermal diffusivity | L2/t |
α | reduction ratio or reduction term | ||
α | a,ηh | thermal or heat diffusivity | L2/t |
β | γ | bearing, relative | |
β | b | thermal cubic expansion coefficient | 1/T |
γ | Euler’s constant=0.5772 | ||
γ | gamma ray [usually with identifying subscripts(s)] | various | |
γ | s,Fs | specific gravity (relative density) | |
γ | k | specific heat ratio | |
γ | εs | strain, shear | |
ė | shear rate | 1/t | |
δ | Δ | decrement | various |
δ | deviation, hole (drift angle) | ||
δ | Fd | displacement ratio | |
δ | rs | skin depth (logging) | L |
Δ | difference or difference operator, finite
(Δx=x2−x1 or x1−x2) | ||
Δ r | Δ R | radial distance (increment along radius) | L |
ε | dielectric constant | q2t2/mL3 | |
ε | e,εn | strain, normal and general | |
η | hydraulic diffusivity (k/Φcμ or λ/Φc) | L2/t | |
θ | β,γ | angle | |
θ | θV | strain, volume | |
θ | αd | angle of dip | |
θ c | Γc,γc | contact angle | |
λ | C | decay constant (1/τd) | 1/t |
λ | mobility (k/μ) | L3t/m | |
λ | wave length (1/σ) | L | |
μ | v, σ | Poisson’s ratio | |
μ | m | azimuth of reference on sonde | |
μ | m | magnetic permeability | mL/q2 |
ν | N | kinematic viscosity | L2/t |
ρ | D | density | m/L3 |
ρ | R | electrical resisivity (other than logging) | mL3/tq2 |
σ | γ | electrical conductivity (other than logging) | various |
Letter Symbol Greek | |||
σ | microscopic cross section | L2 | |
σ | standard deviation of a random variable | ||
σ | s | stress, normal and general | M/Lt2 |
σ | y, γ | surface tension, interfacial | m/t2 |
σ | wave number (1/λ) | 1/L | |
σ2 | variance of a random variable | ||
Σ | S | cross section, macroscopic | 1/L |
τ | ss | stress, shear | m/Lt2 |
τ | τc | time constant | t |
τ | tortuosity | ||
lifetime, average (mean life) | t | ||
τd | td | decay time (mean life) (1/ λ) | t |
ø | f, ε | porosity (Vb−Vs)/Vb | |
Φ | βd | dip, azimuth of | |
Φ | f | potential or potential function | various |
ψ | dispersion modulus (dispersion factor) | ||
Ψ | stream function | various | |
ω | angular frequency | 1/t |