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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 | F_{a} | air requirement | various |
a | decline factor nominal | ||
a | L_{a}, L_{1} | distance between like wells (injection or production) in a row | L |
A | amplitude | various | |
A | atomic weight | m | |
A | F | Helmboltz function (work function) | mL^{2}/t^{2} |
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 | Lt^{2}/m |
C | capacitance | q^{2}t^{2}/mL^{2} | |
C | capital costs or investments | M | |
C | coefficient of gas-well backpressure curve | L^{3−2n}t^{4n}/m^{2n} | |
C | n_{C} | components, number of | |
C | c,n | concentration | various |
C | σ | conductivity (electrical logging) | tq^{2}/mL^{3} |
C | c,n | salinity | various |
C | c | specific heat capacity (always with phase or system subscripts) | L^{2}/t^{2}T |
C | waterdrive constant | L^{4}t^{2}/m | |
C_{ƒD} | fracture conductivity, dimensionless | ||
C_{L} | c_{L},n_{L} | condensate or natural gas liquids content | various |
d | decline factor, effective | ||
d | D | diameter | L |
d | L_{d},L_{2} | distance between adjacent rows of injection and production wells | L |
D | deliverability (gas well) | L^{3}/t | |
D | y,H | depth | l |
D | µ,δ | diffusion coefficient | L^{2}/t |
e | i | influx (encroachment) rate | L^{3}/t |
e_{O}_{2} | E_{O}_{2} | oxygen utilization | |
e^{z} | exp z | exponential function | |
E | η,e | efficiency | |
E | V | electromotive force | mL^{2}/t^{2}q |
E | U | energy | mL^{2}/t^{2} |
E | Y | modulus of elasticity (Young’s modulus) | M/Lt^{2} |
E_{A} | η_{A},e_{A} | areal efficiency (used in describing results of model studies only): area swept in a model divided by total model reservoir area (see E_{p}) | |
E_{c} | Φ_{c} | electrochemical component of the SP | mL^{2}/t^{2}q |
E_{k} | Φ_{k} | electrokinetic component of the SP | mL^{2}/t^{2}q |
E_{n} | Euler number | ||
E_{SP} | Φ_{SP} | SP (measured SP) (self potential) | mL^{2}/t^{2}q |
−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/Lt^{2} | |
f_{s} | 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 |
F_{R} | formation resistivity factor—equals R_{0}/R_{w} (a numerical subscript to F indicates the value R_{w}) | ||
F_{WV} | γ | specific weight | mL^{2}/t^{2} |
g | γ | gradient | various |
g | gravity, acceleration of | L/t^{2} | |
g_{c} | conversion factor in Newton’s second law of Motion | ||
G | g | gas in place in reservoir, total initial | L^{3} |
G | g | gas (any gas, including air), always with identifying subscripts | various |
G | ƒ_{G} | geometrical factor (multiplier)
(electrical logging)|| | |
G | E_{s} | shear modulus | m/Lt^{2} |
G_{L} | g_{L} | condensate liquids in place in reservoir, initial | L^{3} |
h | i | enthalpy, specific | L^{2}/t^{2} |
h | h_{h},h_{T} | heat transfer coefficient, convective | m/t^{3}T |
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) | mL^{2}/t^{2} |
i | injection rate | L^{3}/t | |
i | interest rate | 1/t | |
i_{R} | rate of return (earning power) | ||
I | income (net revenue minus expenses) | ||
I | i (script i), i | current, electric | q/t |
I | I_{T},I¬_{θ} | heat transfer coefficient, radiation | m/t^{3}T |
I | i | index (use subscripts as needed) | |
I | i | injectivity index | L^{4}t/m |
ς (z)(script I) | imaginary part of complex number z | ||
I_{R} | i_{R} | resistivity index (hydrocarbon)—equals R_{t}/R_{0} | |
j | i_{R} | reciprocal permeability | 1/L^{2} |
J | j | productivity index | L^{4}t/m |
k | κ | magnetic susceptibility | mL/q^{2} |
k | K | permeability absolute (fluid flow) | L^{2} |
k | r,j | reaction rate constant | L/t |
k_{h} | λ | thermal conductivity (always with additional phase or system subscripts) | mL/t^{3}T |
K | K_{b} | bulk modulus | m/Lt^{2} |
K | coefficient in the equation of the electrochemical component of the SP (spontaneous electromotive force) | mL^{2}_{/t}^{2}q | |
K | M | coefficient or multiplier | various |
K | d | dispersion coefficient | L^{2}/t |
K | k,F_{eq} | equilibrium ratio (y/x) | |
K_{ani} | M_{ani} | anisotropy coefficient | |
K_{c} | M_{c}, K_{ec} | electrochemical coefficient | mL^{2}/t^{2}q |
K_{R} | M_{R},a,C | formation resistivity factor coefficient (F_{R} Φ^{m}) | |
ln | natural logarithm, base e | ||
log | common logarithm, base 10 | ||
log_{a} | logarithm base a | ||
L | n_{L} | moles of liquid phase | |
L_{f} | x_{f} | fracture half-length (specify "in the direction of" when using x_{f}) | L |
L_{s} | s_{s},l_{s} (script l) | spacing (electrical logging) | L |
L_{v} | λ_{v} | latent heat of vaporization | L |
L (y) (script L) | Laplace transform of y, y(t)e-stdt | ||
m | F_{F} | fuel consumption | various |
m | mass | m | |
m | porosity exponent (cementation) (in an empirical relation between FR and ) | ||
m | F_{Fo},F_{go} | ratio of initial reservoir free-gas volume to initial reservoir oil volume | |
m | A | slope | various |
M | I | magnetization | m/qt |
M | F_{λ} | mobility ratio, general (λ_{displacing}/λ_{displaced}) | |
M | molecular weight | m | |
M | m_{θD} | slope, interval transit time vs. density (absolute value) | tL^{2}/m |
M | volumetric heat capacity | m/Lt^{2}T | |
n | N | density (indicating "number per unit volume") | 1/L^{3} |
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 | |
n_{}t | N_{t} | 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) | L^{3}/m |
N_{GR} | N_{γ},C_{G} | gamma ray count rate | 1/t |
N_{R} | N_{F} | fuel deposition rate | m/L^{3}t |
O | operating expense | various | |
p | P | pressure | m/Lt^{2} |
p | price | M | |
P | phases, number of | ||
P | profit total | M | |
P_{c} | P_{c} ,p_{c} | capillary pressure | M/Lt^{2} |
q | Q | production rate or flow rate | L^{3}/t |
Q | q | charge (current times time) | q |
Q | q,Φ | heat flow rate | mL^{2}/t^{3} |
Q_{i} | q_{i} | pore volumes of injected fluid, cumulative dimensionless | |
Q_{LtD} | Q_{l tD} (script l) | fluid influx function, linear aquifer, dimensionless | |
Q_{p} | Q_{l tD} (script l) | fluids, cumulative produced (where N_{p} and W_{p} are no applicable) | |
Q_{tD} | fluid influx function, dimensionless, at dimensionless time t_{D} | ||
Q_{V} | Z_{V} | cation exchange capacity per unit pore volume | |
r | R | radius | L |
r | R | resistance | mL^{2}/tq^{2} |
R | ρ,r | electrical resistivity (electrical logging) | ml^{3}tq^{2} |
R | gas constant, universal (per mole) | mL^{2}/t^{2}T | |
R | Fg,Fgo | gas/oil ratio, producing | |
R | N | molecular refraction | L^{3} |
R(z) (script R) | real part of complex number z | ||
s | L | displacement | L |
s | σ | entropy, specific | L^{2}/t^{2}T |
s | Laplace transform variable | ||
s | S, σ | skin effect | various |
s | standard deviation of a random variable, estimated | ||
s^{2} | variance of a random variable, estimated | ||
S | σt | entropy, total | mL^{2}/t^{2}T |
S | ρ,s | saturation | |
t | τ | time | t |
t_{ma}(script t) | Δt_{ma} | matrix interval transit time | t/L |
t_{½} | 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/t^{3}T |
v | V,u | acoustic velocity | L/t |
v | νs | specific volume | L^{3}/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) | mL^{2}/q^{2} |
V | v | volume | L^{3} |
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 | L^{3}/m |
w | m | mass flow rate | m/t |
W | w | water (always with identifying subscripts) | various |
W | w | water in place in reservoir, initial | L^{3} |
W | w,G | weight (gravitational) | mL/t^{2} |
W | w | work | mL^{2}/t^{2} |
x | mole fraction of a component in liquid phase | ||
vector of x | |||
tensor of x | |||
xD | dimensionless quantity proportional to x | ||
X | reactance | mL^{2}/tq^{2} | |
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 | L^{2/}t |
α | reduction ratio or reduction term | ||
α | a,ηh | thermal or heat diffusivity | L^{2/}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=x_{2}−x_{1} or x_{1}−x_{2}) | ||
Δ r | Δ R | radial distance (increment along radius) | L |
ε | dielectric constant | q^{2}t^{2}/mL^{3} | |
ε | e,εn | strain, normal and general | |
η | hydraulic diffusivity (k/Φcμ or λ/Φc) | L^{2}/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) | L^{3}t/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/q^{2} |
ν | N | kinematic viscosity | L^{2}/t |
ρ | D | density | m/L^{3} |
ρ | R | electrical resisivity (other than logging) | mL^{3}/tq^{2} |
σ | γ | electrical conductivity (other than logging) | various |
Letter Symbol Greek | |||
σ | microscopic cross section | L^{2} | |
σ | standard deviation of a random variable | ||
σ | s | stress, normal and general | M/Lt^{2} |
σ | y, γ | surface tension, interfacial | m/t^{2} |
σ | wave number (1/λ) | 1/L | |
σ^{2} | variance of a random variable | ||
Σ | S | cross section, macroscopic | 1/L |
τ | s_{s} | stress, shear | m/Lt^{2} |
τ | τ_{c} | time constant | t |
τ | tortuosity | ||
lifetime, average (mean life) | t | ||
τ_{d} | t_{d} | decay time (mean life) (1/ λ) | t |
ø | f, ε | porosity (Vb−Vs)/Vb | |
Φ | β_{d} | dip, azimuth of | |
Φ | f | potential or potential function | various |
ψ | dispersion modulus (dispersion factor) | ||
Ψ | stream function | various | |
ω | angular frequency | 1/t |