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Dimensions: L=length, m=mass, q=electrical charge, t=time, T=temperature, M=money, and n=amount of substance.
Letter Symbol | 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 projection) in a row | L |
aE | FaE | air requirement, unit, in laboratory experimental run, volumes of air per unit mass of pack | L3/m |
aR | FaR | air requirement, unit, in reservoir, volumes of air per unit bulk volume of reservoir rock | |
A | amplitude | various | |
A | S | area | L2 |
A | atomic weight | m | |
A | S | cross section (area) | L2 |
A | F | helmholtz function (work function) | mL2/t2 |
Ac | amplitude, compressional wave | various | |
Ar | amplitude, relative | various | |
As | amplitude, shear wave | various | |
b | W | breadth, width, or (primarily in fracturing) | various |
thickness | |||
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 (primarily in fracturing) thickness | L |
bg | fg,Fg | reciprocal gas formation volume factor | |
bgb | fgb,Fgb | reciprocal gas formation volume factor at bubblepoint conditions | |
bo | fo,Fo | reciprocal oil formation volume factor (shrinkage factor) | |
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 | |
Bg | Fg | formation volume factor, gas | |
Bgb | Fgb | bubblepoint formation volume factor, gas | |
Bgb | Fgb | formation volume factor at bubblepoint conditions, gas | |
Bo | Fo | formation volume factor, oil | |
Bob | Fob | bubblepoint formation volume factor, oil | |
Bob | Fob | formation volume factor at bubblepoint conditions, oil | |
Bt | FT | formation volume factor, total (two-phase) | |
Bw | Fw | formation volume factor, water | |
c | k,κ | compressibility | Lt2/m |
cf | kf,κf | compressibility, formation or rock | Lt2/m |
cg | kg,κg | compressibility, gas | Lt2/m |
co | ko,κo | compressibility, oil | Lt2/m |
cpr | kpr,κpr | compressibility, pseudoreduced | |
cw | kw,κw | compressibility, water | Lt2/m |
C | capacitance | q2t2/mL2 | |
C | Ct | capital investments, summation of all | M |
C | coefficient of gas-well backpressure curve | L3–2nt4nm2n | |
C | nC | components, number of | |
C | c,n | concentration | various |
C | σ | conductivity (electrical logging) | tq2/mL3 |
C | K | conductivity, other than electrical (with subscripts) | various |
C | c,n | salinity | various |
C | c | specific heat (always with phase or system subscripts) | L2/t2T |
C | waterdrive constant | L4t2/m | |
Ca | σα | conductivity, apparent | tq2/mL3 |
CC1 | cC1 | concentration, methane (concentration of other paraffin hydrocarbons would be indicated similarly, CC2, C¬C3, etc.) | various |
CfD | conductivity, fraction, dimensionless | ||
Ci | capital investment, initial | M | |
Ck | capital investment in period k | M | |
CL | cL,nL | content, condensate or natural gas liquids | various |
CL | waterdrive constant, linear aquifer | L4t2/m | |
Cm | cmnm | fuel concentration, unit (see symbol m) | various |
CO2 | cO2 | concentration, oxygen (concentration of other elements or compounds would be indicated similarly, CCO2, CN2, etc.) | |
Cpv | investment at present value | M | |
Cwg | cwg,nwg | content, wet-gas | various |
d | decline factor, effective | ||
d | D | diameter | L |
d | Ld,L2 | distance between adjacent rows of injection and production wells | L |
dh | dH,Dh | diameter, hole | L |
di | dl,Di | diameter, invaded zone (electrically equivalent) | L |
dp | Dp | diameter, mean particle | L |
D | deliverability (gas well) | L3/t | |
D | depletion, depreciation, or amortization (all nonreal account entries) | various | |
D | y,H | depth | L |
D | µ,δ | diffusion coefficient | L2/t |
e | i | encroachment or influx rate | L3/t |
eg | ig | encroachment or influx rate, gas | L3/t |
eo | io | encroachment or influx rate, oil | L3/t |
eO2 | EO2 | oxygen utilization | |
ew | iw | encroachment or influx rate, water | L3/t |
ez | exp z | exponential function | |
E | η,e | efficiency | |
E | V | electromotive force | mL2/t2q |
E | U | energy | mL2/t2 |
E | expense, total (except income taxes) | M | |
E | modulus of elasticity (Young’s modulus) | m/Lt | |
EA | ηA,eA | efficiency, areal (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 |
ED | ηD,eD | efficiency, displacement: volume of hydrocarbons (oil or gas) displaced from individual pores or small groups of pores divided by the volume of hydrocarbon in the same pores just prior to | |
EDb | ηDb,eDb | efficiency, displacement, from burned portion of in-situ combustion pattern | |
EDu | ηDu,eDu | efficiency, displacement, from unburned portion of in-situ combustion pattern | |
EI | ηI,eI | efficiency, invasion (vertical): hydrocarbon pore space invaded (affected, contacted) by the injection fluid or heat front divided by the hydrocarbon pore space enclosed in all layers behind the injected fluid or heat front | |
Ek | Φk | electrokinetic component of the SP | mL2/t2q |
Ek | kinetic energy | mL2/t2 | |
En | Euler’s number | ||
EpSP | ΦSP | pseudo-SP | mL2/qt2 |
Ep | ηP,eP | efficiency, pattern sweep (developed from areal efficiency by proper weighting for variations in net pay thickness, porosity, and hydrocarbon saturation): hydrocarbon pore space enclosed behind the injected fluid or heat front divided by total hydrocarbon pore space of the reservoir or project | |
ER | ηR,eR | efficiency, overall reservoir recovery: volume of hydrocarbons recovered divided by volume of hydrocarbons in place at start of project (ER=EPEIED=EVED) | |
ESP | ΦSP | SP (measured SP) (self-potential) | mL2/t2q |
ESSP | ΦSSP | SSP (static SP) | mL2/t2q |
Eu | expense per unit | M | |
EV | ηV,eV | efficiency, volumetric; product of pattern sweep and invasion efficiencies | |
EVb | ηVb,eVb | efficiency, volumetric, for burned portion only, in-situ combustion pattern | |
−Ei(−x) | exponential integral, dt, x positive | ||
Ei(x) | 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 | |
fg | Fg | fraction gas | |
fg | Fg | mole fraction gas, V/(L+V) | |
fL | FL,fℓ (script ℓ) | fraction liquid | |
fL | FL,fℓ (script ℓ) | mole fraction liquid, L/(L+V) | |
fs | Q,x | quality (usually of steam) | |
fV | fVb, Vbf | fraction of bulk (total) volume | |
fsØh | Øigfsh | fraction of intergranular space ("porosity") occupied by all shales | |
fØshd | Øimfshd | fraction of intermatrix space (“porosity”) occupied by nonstructural dispersed shale | |
fØw | Øigfw | fraction of intergranular space (“porosity”) occupied by water | |
F | degrees of freedom | ||
F | f | fluid (generalized) | various |
F | Q | force, mechanical | mL/t2 |
F | ratio or factor in general (always with identifying subscripts) | ||
FaF | air/fuel ratio | various | |
FB | factor, turbulence | ||
FR | formation resistivity factor—equals R0/Rw (a numerical subscript to F indicates the value Rw) |
||
Fs | Fd | damage ratio or condition ratio (conditions relative to formation conditions unaffected by well operations) |
|
FwF | water/fuel ratio | various | |
Fwo | water/oil ratio, producing, instantaneous | ||
Fwop | water/oil ratio, cumulative | ||
FWV | γ | specific weight | mL2/t2 |
g | acceleration of gravity | L/t2 | |
g | γ | gradient | various |
gc | conversion factor in Newton’s second law of motion | ||
gG | gg | gradient, geothermal | T/L |
G | F | free energy (Gibbs function) | mL2/t2 |
G | g | gas (any gas, including air) always with identifying subscripts | various |
G | g | gas in place in reservoir, total initial | L3 |
G | fG | geometric factor (multiplier) (electrical logging) | |
G | Es | shear modulus | m/Lt2 |
Gan | fGan | factor, geometric (multiplier), annulus (electrical logging) | |
Gan | fGan | geometric factor (multiplier), annulus (electrical logging) | |
Ge | ge | gas influx (encroachment), cumulative | L3 |
GFi | gFi | free-gas volume, initial reservoir (=mNBoi) | L3 |
GFp | gFp | free gas produced, cumulative | L3 |
Gi | gi | gas injected, cumulative | L3 |
Gi | fGi | geometric factor (multiplier), invaded zone (electrical logging) | L3 |
GL | gL | condensate liquids in place in reservoir, initial | L3 |
GLp | gLp | condensate liquids produced, cumulative | L3 |
Gm | fGm | geometric factor (multiplier), mud (electrical logging) | L3 |
Gp | gp | gas produced, cumulative | L3 |
Gp | fGp | geometric factor (multiplier), pseudo (electrical logging) | L3 |
Gpa | gpa | gas recovery, ultimate | L3 |
GpE | gpE | gas produced from experimental tube run | L3 |
Gt | fGt | geometric factor (multiplier), true (noninvaded zone) (electrical logging) | |
Gwgp | gwgp | wet gas produced, cumulative | L3 |
Gxo | fGxo | geometric factor (multiplier), flushed zone (electrical logging) | |
h | d,e | bed thickness, individual | L |
h | i | enthalpy, specific | L2/t2 |
h | hh,hT | heat-transfer coefficient, convective | m/t3/T |
h | d,e | height (other than elevation) | L |
h | hyperbolic decine constant (from equation) | ||
q=qi | |||
h | d,e | thickness (general and individual bed) | L |
hmc | dmc,emc | thickness, mud cake | L |
hn | dn,en | thickness, net pay | L |
ht | dt,et | thickness, gross pay (total) | L |
H | I | enthalpy (always with phase or system subscripts) | mL2/t2 |
Hs | Is | enthalpy (net) of steam or enthalpy above reservoir temperature | mL2/t2 |
i | discount rate | ||
i | injection rate | L3/t | |
i | interest rate | 1/t | |
ia | injection rate, air | L3/t | |
ig | injection rate, gas | L3/t | |
iR | rate of return (earning power) | ||
iw | injection rate, water | L3/t | |
I | I (script i), i | current, electric | q/t |
I | I (script i), i | electric current | q/t |
I | IT,Iθ | heat transfer coefficient, radiation | m/t3T |
I | income (net revenue minus expenses) | M | |
I | i | index (use subscripts as needed) | |
I | i | injectivity index | L4t/m |
I(z)(script I) | imaginary part of complex number z | ||
Ibt | income before taxes | M | |
If | if,IF,iF | fracture index | |
IFf | iFf | free fluid index | |
IH | iH | hydrogen index | |
Ipwk | income at present value in period k | M | |
IR | iR | hydrocarbon resistivity index Rt/R0 | |
Is | is | injectivity index, specific | L3t/m |
IshGR | ishGR | shaliness gamma ray index, (γlog–γcn)/(γsh–γcn) | |
IΦ | iΦ | porosity index | |
IΦ1 | iΦ1 | porosity index, primary | |
IΦ2 | iΦ2 | porosity index, secondary | |
J | ω | reciprocal permeability | 1/L2 |
J | j | productivity index | L4t/m |
Js | js | productivity index, specific | L3t/m |
K | κ | magnetic susceptibility | mL/q2 |
K | K | permeability, absolute (fluid flow) | L2 |
K | r,j | reaction rate constant | L/t |
kg | Kg | effective permeability to gas | L2 |
kg/ko= | Kg/Ko | gas/oil permeability ratio | |
kh | λ | thermal conductivity (always with additional phase or system subscripts) | |
ko | Ko | effective permeability to oil | L2 |
krg | Krg | relative permeability to gas | |
kro | Kro | relative permeability to oil | |
krw | Krw | relative permeability to water | |
kw | Kw | effective permeability to water | L2 |
kw/ko | Kw/Ko | water/oil permeability ratio | |
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) | |
K | M | multiplier or coefficient | various |
Kani | Man | anisotropy coefficient | |
Kc | Mc,Kec | electrochemical coefficient | mL2/t2q |
KR | MR,a,C | formation resistivity factor coefficient (FRΦm) | |
ln | natural logarithm, base e | ||
log | common logarithm, base 10 | ||
loga | logarithm, base a | ||
L | s,ℓ (script l) | distance, length, or length of path | L |
L | s,ℓ (script l) | distance, path length, or distance | L |
L | nL | liquid phase, moles of | |
L | s,ℓ (script l) | path length, length, or distance | L |
Lf | xf | fracture half-length (specify "in the direction of" when using xf) | L |
Ls | s,ℓ (script l) | spacing (electrical logging) | L |
Lv | λv | heat of vaporization, latent | L2/t2 |
L (y) (script L) | transform, Laplace of y, y(t)e-stdt | ||
m | cementation (porosity) exponent (in an empirical relation between FR and Φ | ||
m | FF | fuel consumption | various |
m | mass | m | |
m | FFo,Fgo | ratio of initial reservoir free-gas volume to initial reservoir oil volume | |
m | A | slope | various |
mE | FFE | fuel consumption in experimental tube run | m/L3 |
mEg | FFEg | fuel consumption in experimental tube run (mass of fuel per mole of produced gas) | m |
k | amortization (annual write-off of unamortized investment at end of year k) | M | |
mR | FFR | fuel consumption in reservoir | m/L3 |
M | I | Magnetization | m/qt |
M | Fλ | mobility ratio, general (λdisplacing/λdisplaced) | |
M | Fλ | mobility ratio, sharp-front approximation (λD/λd) | |
M | molecular weight | m | |
M | m | number of compounding periods (usually per year) | m |
M | mθD | slope, interval transit time vs. density (absolute value) | tL2/m |
Mf | Magnetization, fraction | ||
ML | molecular weight of produced liquids, mole-weighted average | m | |
M | MDd,Msu | mobility ratio, diffuse-front approximation [(λD+λd)swept/(λd)unswept]; mobilities are evaluated at average saturation conditions behind and ahead of front | |
Mt | Fλt | mobility ratio, total, [(λt)swept/(λt)unswept]; "swept" and "unswept" refer to invaded and uninvaded regions behind and ahead of leading edge of displacement front | |
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, or components, or steps, or increments, etc.) | |
n | N | number (quantity) | |
n | number of compounding periods | 1/t | |
n | saturation exponent | ||
nj | Nj | moles of component j | |
nN | density (number) of neutrons | 1/L3 | |
npj | Npj | moles of component j produced, cumulative | |
nt | Nt | number of moles, 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 | n | pump strokes, number of, cycles per unit of time | |
N | mθND | slope, neutron porosity vs. density (absolute value) | L3/m |
Ne | oil influx (encroachment), cumulative | L3 | |
NGR | Nγ,CG | gamma ray count rate | 1/t |
Ni | ni | oil in place in reservoir, initial | L3 |
NN | Nn,CN | neutron count rate | 1/t |
Np | np | oil produced, cumulative | L3 |
Npa | npa | oil recovery, ultimate | L3 |
NR | NF | fuel deposition rate | m/L3t |
NRe | Reynolds number (dimensionless number) | ||
p | P | pressure | m/Lt2 |
p | price | M | |
pa | Pa | pressure, atmospheric | m/Lt2 |
pb | ps,Ps,Pb | pressure, bubblepoint (saturation) | m/Lt2 |
pbh | Pbh | pressure, bottomhole | m/Lt2 |
pc | Pc | pressure, critical | m/Lt2 |
pcf | Pcf | pressure, casing flowing | m/Lt2 |
pcs | Pcs | pressure, casing static | m/Lt2 |
pd | Pd | pressure, dewpoint | m/Lt2 |
pD | PD | pressure, dimensionless | |
pe | Pe | pressure, external boundary | m/Lt2 |
pext | Pext | pressure, extrapolated | m/Lt2 |
pf | Pf | pressure, front or interface | m/Lt2 |
pgk | price of gas in period k | M | |
pi | Pi | pressure, initial | m/Lt2 |
piwf | Piwf | pressure, bottomhole flowing, injection well | m/Lt2 |
piws | Piws | pressure, bottomhole static, injection well | m/Lt2 |
pk | price in period k | M | |
ppc | Ppc | pressure, pseudocritical | m/L2 |
ppc | Ppc | pseudocritical pressure | m/Lt2 |
ppr | Ppr | pressure, pseudoreduced | |
pr | Pr | pressure, reduced | |
psc | Psc | pressure, standard conditions | m/Lt2 |
psp | Psp | pressure, separator | m/Lt2 |
ptD | PtD | pressure function, dimensionless, at dimensionless time tD | |
ptf | Ptf | pressure, tubing flowing | m/Lt2 |
pts | Pts | pressure, tubing static | m/Lt2 |
pw | Pw | pressure, bottomhole general | m/Lt2 |
pwf | Pwf | pressure, bottomhole flowing | m/Lt2 |
pws | Pws | pressure, bottomhole static | m/Lt2 |
pws | Pws | pressure, bottomhole, at any time after shut-in | m/Lt2 |
p | P | average pressure | m/Lt2 |
p | P | pressure, average or mean | m/Lt2 |
pR | PR | pressure, reservoir average | m/Lt2 |
P | phases, number of | ||
P | profit | M | |
Pc | PC,pC | capillary pressure | m/Lt2 |
Ppvat | profit at present value after tax | M | |
Ppvatk | profit at present value after tax in period k | M | |
q | Q | production rate or flow rate | L3/t |
qa | Qa | production rate at economic abandonment | L3/t |
qdh | qwf,qDH,Qdh | volumetric flow rate downhole | L3/t |
qD | QD | production rate, dimensionless | |
qg | Qg | production rate, gas | L3/t |
qgD | QgD | production rate, gas dimensionless | |
qi | Qi | production rate at beginning of period | L3/t |
qo | Qo | production rate, oil | L3/t |
qoD | QoD | production rate, oil, dimensionless | |
qp | Qp | production rate or flow rate at mean pressure | L3/t |
qs | Qs | segregation rate (in gravity drainage) | L3/t |
qsc | qσ,Qsc | surface production rate | L3/t |
qs | qσ,Qsc | volumetric flow rate, surface conditions | L3/t |
qw | Qw | production rate, water | L3/t |
qwD | QwD | production rate, water, dimensionless | |
production rate or flow rate, average | L3/t | ||
Q | Q | charge | q |
Q | q,Φ | heat flow rate | mL2/t3 |
Qi | qi | pore volumes of injected fluid, cumulative, dimensionless | mL2/t3 |
QLtD | QℓtD (script l) | influx function, fluid, linear aquifer, dimensionless | |
Qp | QℓtD (script l) | fluids, cumulative produced (where Np and Wp are not applicable) | |
Qp | produced fluids, cumulative (where Np and Wp are not applicable) | L3 | |
QtD | fluid influx function, dimensionless, a dimensionless time tD | ||
QV | ZV | cation exchange capacity per unit pore volume | |
r | R | radius | L |
r | R | resistance | ML2/tq2 |
r | royalty | various | |
rd | Rd | drainage radius | L |
rD | RD | radius, dimensionless | |
re | Re | external boundary radius | L |
rH | RH | hydraulic radius | L |
rR | royalty rate | various | |
rs | Rs | radius of well damage or stimulation (skin) | L |
rw | Rw | well radius | L |
rws | Rwa | radius of wellbore, apparent or effective (includes effects of well damage or stimulation) | L |
R | ρ,r | electrical resistivity (electrical logging) | mL3/tq2 |
R | gas constant, universal (per mole) | mL2/t2T | |
R | Fg,Fgo | gas/oil ratio, producing | |
R | N | molecular refraction | L3 |
R | reaction rate | m/L2 | |
R | revenue | M | |
R(z)(script R) | real part of complex number z | ||
Ra | ρa,ra | apparent resistivity | mL3/tq2 |
RF | FgF, FgoF | free gas/oil ratio, producing (free-gas volume/oil volume) | |
Ri | ρi, ri | invaded zone resistivity | mL3/tq2 |
Rm | ρm ,rm | mud resistivity | mL3/tq2 |
Rmc | ρmc ,rmc | mudcake resistivity | mL3/tq2 |
Rmf | ρmf ,rmf | mud-filtrate resistivity | mL3/tq2 |
Rp | Fgp,Fgop | cumulative gas/oil ratio | |
Rs | Fgs,Fgos | solution gas/oil ratio (gas solubility in oil) | |
Rsb | Fgsb | solution gas/oil ratio at bubblepoint conditions | |
Rsh | ρsh,rsh | shale resistivity | mL3/tq2 |
Rsi | Fgsi | solution gas/oil ratio, initial | |
Rsw | gas solubility in water | ||
Rt | ρt,rt | true formation resistivity | mL3/tq2 |
Rw | ρw,rw | water resistivity | mL3/tq2 |
Rxo | ρxo,rxo | flushed-zone resistivity (that part of the invaded zone closest to the wall of the hole, where flushing has been maximum) | mL3/tq2 |
Rz | ρz,rz | apparent resistivity of the conductive fluids in an invaded zone (caused by fingering) | mL3/tq2 |
R0 | ρ0,r0 | formation resistivity when 100% saturated with water of resistivity Rw | mL3/tq2 |
S | Laplace transform variable | ||
S | L | displacement | L |
S | Σ | entropy, specific | L2/t2T |
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 | |
S | s, σ | storage or storage capacity | various |
SfD | SD | dimensionless fracture storage capacity | |
Sg | ρg,sg | gas saturation | |
Sgc | ρgc,sgc | gas saturation, critical | |
Sgr | ρgr,sgr | gas saturation, residual | |
Sh | ρh,sh | saturation, hydrocarbon | |
Shr | ρhr,shr | residual hydrocarbon saturation | |
Siw | ρiw,siw | irreducible (interstitial or connate) water saturation | |
SL | ρL,sL | liquid saturation, combined total | |
So | ρo,so | oil saturation | |
Sog | ρog,sog | gas-cap interstitial-oil saturation | |
Sor | ρor,sor | residual oil saturation | |
Sw | ρw,sw | water saturation | |
Swc | ρwc,swc | critical water saturation | |
Swg | ρwg,swg | interstitial-water saturation in gas cap | |
Swi | ρwi,swi | initial water saturation | |
Swo | Swb | interstitial-water saturation in oil band | |
Swr | ρwr,swr | residual water saturation | |
T | τ | time | t |
t (script t) | Δt | interval transit time | t/L |
td | τd | time, delay | t |
tdN | decay time, neutron (neutron mean life) | t | |
tD | τD | time, dimensionless | |
tDm | τDm | time, dimensionless at condition m | |
tma (script t) | Δtma | matrix interval transit time | t/L |
tN | τN,tn | neutron lifetime | 1/t |
tp | τp | time well was on production prior to shut-in, equivalent (pseudotime) | t |
tpoat | payout time, after tax | t | |
tpypobt | payout time, before tax at present value | t | |
ts | τs | time for stabilization of a well | t |
tsh (script t) | Δtsh | shale interval transit time | t/L |
t1 | τ1 | relaxation time, proton thermal | t |
t½ | half-life | t | |
t2 | τ2 | relaxation time, free-precession decay | t |
T | Θ | period | t |
T | tax on income | various | |
T | Θ | temperature | T |
T | T | transmissivity, transmissibility | various |
Tbh | θBH | bottomhole temperature | T |
Tc | θc | critical temperature | T |
Tf | θf | formation temperature | T |
Tk | tax in period k | various | |
Tpr | θpr | pseudoreduced temperature | T |
Tr | θr | reduced temperature | |
TR | θR | reservoir temperature | T |
TR | tax rate | various | |
Tsc | θsc | temperature, standard conditions | T |
u | Ψ | flux | various |
u | Ψ | flux or flow rate, per unit area (volumetric velocity) | L/t |
u | Ψ | superficial phase velocity (flux rate of a particular fluid phase flowing in pipe; use appropriate phase subscripts) | |
U | UT,Uθ | heat transfer coefficient, overall | m/t3T |
v | V,u | acoustic velocity | L/t |
v | vs | specific volume | L3/m |
v | value (economic) | M | |
v | V,u | velocity | L/t |
vb | Vb,ub | burning-zone advance rate (velocity of) | L/t |
vp | net present value (NPV) | M | |
V | nv | moles of vapor phase | |
V | U | potential difference (electric) | mL2/qt2 |
V | v | volume | L3 |
V | fvFv | volume fraction or ratio (as needed, use same subscripted symbols as for volume; note that bulk volume fraction is unity and pore volume fractions are ø) | various |
Vb | vb | bulk volume | L3 |
VbE | vbE | bulk volume of pack burned in experimental tube run | L3 |
Vbp | vbp | volume at bubblepoint pressure | L3 |
Ve | Vpe,ve | volume, effective pore | L3 |
Vgr | vgr | volume, grain (volume of all formation solids except shales) | L3 |
Vig | vig | volume, intergranular (volume between grains; consists of fluids and all shales)(Vv−Vgr) | |
Vim | vim | volume, intermatrix (consists of fluids and dispersed shale) (Vb-Vma) | L3 |
VM | vm | molal volume (volume per mole) | L3 |
Vma | vma | matrix (framework) volume (volume of all formation solids except dispersed clay or shale) | L3 |
Vma | vma | volume, matrix (framework)(volume of all formation solids except dispersed shale) | L3 |
Vp | vp | pore volume (Vb−Vs) | L3 |
VpD | vpD | pore volume, dimensionless | |
Vpoat | vpD | payout volume, after tax | L3 |
VRb | volume of reservoir rock burned | L3 | |
VRu | volume of reservoir rock unburned | L3 | |
Vs | vs | volume, solids(s) (volume of all formation solids) | L3 |
Vsh | vsh | volume, shale(s)(volume of all shales: structural and dispersed) | L3 |
Vshd | vshd | volume, shale, dispersed | L3 |
Vshs | vshs | volume, shale, structural | L3 |
w | z | Arrhenius reaction-rate velocity constant | L3/m |
w | m | mass flow rate | m/t |
w | m | rate, mass flow | 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 |
We | we | water influx (encroachment), cumulative | L3 |
Wi | wi | water injected, cumulative | L3 |
Wp | wp | water produced, cumulative | L3 |
x | mole fraction of a component in liquid phase | ||
vector of x | |||
tensor of x | |||
mean value of a random variable, x, estimated | |||
X | reactance | ML2/tq2 | |
y | f | 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 a vapor phase | ||
z | Z | gas compressibility factor (deviation factor) (z=pV/nRT) | |
z | mole fraction of a component in mixture | ||
Zp | Zp | gas deviation factor (compressibility factor) at mean pressure | |
Z | atomic number | ||
Z | D,h | elevation referred to datum | |
Z | D,h | height, or fluid head or elevation referred to a datum | |
Z | impedance | various | |
Za | impedance, acoustic | m/L2t |
Greek
Letter Symbol | Reserve SPE Letter Symbol | Quantity | Dimensions |
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 |
αSPsh | reduction ratio, SP, caused by shaliness | ||
β | γ | bearing, relative | |
β | b | thermal cubic expansion coefficient | 1/T |
γ | gamma ray [usually with identifying subscript(s)] | various | |
γ | s,Fs | specific gravity (relative density) | |
γ | k | specific heat ratio | |
γ | εs | strain, shear | |
shear rate | 1/t | ||
γg | sg,Fgs | specific gravity, oil | |
γw | sw,Fws | specific gravity, water | |
δ | Δ | decrement | various |
δ | deviation, hole (drift angle) | ||
δ | Fd | displacement ratio | |
δ | drift angle, hole (deviation) | ||
δ | rs | skin depth (logging) | L |
δob | Fdob | displacement ratio, oil from burned volume, volume per unit volume of burned reservoir rock | |
δou | Fdou | displacement ratio, oil from unburned volume, volume per unit volume of unburned reservoir rock | |
δwb | Fdwb | displacement ratio, water from burned volume, volume per unit volume of burned reservoir rock | |
Δ | difference or difference operator, finite (Δx=x2−x1 or x1−x2) | ||
ΔGe | Δge | gas influx (encroachment) during an interval | L3 |
ΔGi | Δgi | gas injected during an interval | L3 |
ΔGp | Δgp | gas produced during an interval | L3 |
ΔNe | Δne | oil influx (encroachment) during an interval | L3 |
ΔNp | Δnp | oil produced during an interval | L3 |
Δr | ΔR | radial distance (increment along radius) | L |
Δtwf | Δτwf | drawdown time (time after well is opened to production) (pressure drawdown) | t |
Δtws | Δτws | buildup time; shut-in time (time afterwell is shut in) (pressure buildup, shut-in time) | t |
ΔWe | Δwe | water influx (encroachment) during an interval | L3 |
ΔWi | Δwi | water injected during an interval | L3 |
ΔWp | Δwp | water produced during an interval | L3 |
ε | dielectric constant | q2t2/mL3 | |
ε | e,εn | strain, normal and general | |
η | hydraulic diffusivity (k/øcμ or λ/øc) | L2/t | |
θ | β,γ | angle | |
θ | θV | strain, volume | |
Ө | αd | angle of dip | |
Өa | αda | dip, apparent angle of | |
Өc | Гc,γc | contact angle | |
λ | C | decay constant(1/τd) | 1/t |
λ | mobility (k/μ) | L3t/m | |
λ | wavelength(1/σ) | L | |
λg | mobility, gas | L3t/m | |
λo | mobility, oil | L3t/m | |
λt | Λ | mobility, total, of all fluids in a particular region of the reservoir [e.g., (λo+ λg+ λw)] | L3t/m |
λw | mobility, water | L3t/m | |
μ | M | azimuth of reference on sonde | |
μ | m | magnetic permeability | mL/q2 |
μ | mean value of a random variable | ||
μ | υ,σ | Poisson’s ratio | |
μ | η | viscosity, dynamic | m/Lt |
μa | ηa | viscosity, air | m/Lt |
μc | chemical potential | ||
μg | ηg | viscosity, gas | m/Lt |
μga | ηga | viscosity, gas, at 1 atm | m/Lt |
μo | ηo | viscosity, oil | m/Lt |
μp | ηp | viscosity at mean pressure | m/Lt |
μw | ηw | viscosity, water | m/Lt |
ν | N | kinematic viscosity | L2/t |
ν | N | viscosity, kinematic | L2/t |
ρ | D | density | m/L3 |
ρ | R | resistivity, electrical (other than logging) | mL3tq2 |
ρa | Da | density, apparent | m/L3 |
ρb | Db | density, bulk | m/L3 |
ρf | Df | density, fluid | m/L3 |
ρF | DF | density, fuel | m/L3 |
ρg | Dg | density, gas | m/L3 |
ρma | Dma | density, matrix (solids, grain) | m/L3 |
ρo | Do | density, oil | m/L3 |
ρsE | DsE | density of solid particles making up experiment pack | m/L3 |
ρt | Dt | density, true | m/L3 |
ρw | Dw | density, water | m/L3 |
ρxo | Dxo | density, flushed zone | m/L3 |
L | L | density of produced liquid, weight-weighted average | m/L3 |
σ | γ | conductivity, electrical (other than logging) | various |
σ | cross section, microscopic | 1/L | |
σ | s | cross section of a nucleus, microscopic | L2 |
σ | y,γ | interfacial surface tension | m/t2 |
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 |
Σ | summation (operator) | ||
τ | ss | stress, shear | m/Lt2 |
τ | τc | time constant | t |
τd | td | decay time (mean life) (1/λ) | t |
τd | tdt | mean life (decay time) (1/λ) | t |
τe | tortuosity, electric | ||
τH | hydraulic tortuosity | ||
τH | tortuosity, hydraulic | ||
τ | t | lifetime, average (mean life) | t |
φ | f,ε | porosity (Vb−Vs)/Vb | |
φa | fa,εa | porosity, apparent | |
φe | fe,εe | porosity, effective (Vpe/Vb) | |
φE | fE,εE | porosity of experimental pack | |
φh | fh,εh | porosity, hydrocarbon-filled, fraction or percent of rock bulk volume occupied by hydrocarbons | |
φig | fig,εig | "porosity" (space), intergranular(Vb−Vgr)/Vb | |
φim | fim ,εim | “porosity” (space), intermatrix (Vb−Vma)/Vb |
|
φne | fne,εne | porosity, noneffective (Vpne)/Vb | |
φR | fR,εR | porosity of reservoir or formation | |
φt | ft,εt | porosity, total | |
Φ | βd | dip, azimuth of | |
Φ | f | potential of potential function | various |
ψ | dispersion modulus (dispersion factor) | ||
Ψ | stream function | various | |
ψ | dispersion modulus (dispersion factor) | ||
ω | angular frequency (acentric factor) | 1/t |
Math
Letter Symbol | Reserve SPE Letter Symbol | Quantity | Dimensions |
proportional to | |||
– | average or mean (overbar) | ||
< | smaller than | ||
≤ | equal to or smaller than | ||
> | larger than | ||
≥ | equal to or larger than | ||
~ | asymptotically equal to | ||
≈ | approximately equal to or is approximated by | ||
del (gradient operator) | |||
divergence operator | |||
Laplacian operator | |||
curl | |||
erf | error function | ||
erfc | error function, complementary | ||
lim | limit | ||
b | γ | intercept | various |
En | Euler’s number | ||
Ei(x) | exponential integral, modified, x positive | ||
–Ei(–x) | exponential integral, , x positive | ||
ez | exp z | exponential function | |
F | ratio | ||
f | F | fraction | |
ς(z) | imaginary part of complex number z | ||
L (y) | Laplace transform of y, y(t)estdt | ||
ln | logarithm, natural, base e | ||
log | logarithm, common, base 10 | ||
loga | logarithm, base a | ||
m | A | slope | various |
N | number, dimensionless | ||
n | number (of variables, or steps, or increments, etc.) | ||
P(z) | real part of complex number z | ||
s | Laplace transform variable | ||
s | standard deviation of a random variable, estimated | ||
s2 | variance of a random variable, estimated | ||
x | mean value of a random variable, x, estimated | ||
vector of x | |||
tensor of x | |||
α | β,γ | angle | |
γ | Euler’s constant=0.5772 | ||
Δ | difference (Δx=x2–x1 or x1–x2) | ||
Δ | difference operator, finite | ||
μ | mean value of a random variable | ||
σ | standard deviation of a random variable | ||
σ2 | variance of a random variable | ||
Φ | f | potential or potential function | various |
Ψ | stream function | various |
See also
Recommended SI units and conversion factors
Nomenclature for SI metric conversion tables