Symbols in alphabetical order

English

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

SI metric conversion factors

Nomenclature for SI metric conversion tables