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Subscript symbols in alphabetical order
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| Letter Subscript | Reserve SPE Subscript | Subscript Definition |
| Greek and Numerical | ||
| ε | E | strain |
| η | diffusivity | |
| θ | angle, angular, or angular coordinate | |
| λ | M | mobility |
| ρ | density | |
| Φ | f,ε | porosity |
| Φ | f,ε | porosity data, derived from tool-description subscripts: see individual entries such as "amplitude log," "neutron log," etc. |
| 0 (zero) | zr | formation 100% saturated with water (used in R0 only) |
| 1 | p,pri | primary |
| 1,2,3, etc. | location subscripts; usage is secondary to that for representing times or time periods | |
| 1,2,3, etc. | numerical subscripts (intended primarily to represent times or time periods; available secondarily as location subscripts or for other purposes) | |
| 1,2,3, etc. | times or time periods | |
| ½ | half | |
| 2 | s,sec | secondary |
| ∞ | conditions for infinite dimensions | |
| English | ||
| a | A | abandonment |
| a | A,α | acoustic |
| a | active, activity, or acting | |
| a | altered | |
| a | Ap | apparent (general) |
| a | A | atmosphere, atmospheric |
| aF | air/fuel | |
| an | AN | annulus apparent (from log readings: use tool description subscripts) |
| anh | anhydrite | |
| ani | anisotropic | |
| ar | after royalty | |
| at | after taxes | |
| A | a | amplitude log |
| A | areal | |
| b | B | band or oil band |
| b | bank or bank region | |
| b | r,β | base |
| b | bubble | |
| b | s,bp | bubblepoint (saturation) |
| b | B,t | bulk (usually with volume, Vb) |
| b | B | burned or burning |
| bE | burned in experimental tube run (usually with volume, VbE) | |
| bh | w, BH | bottomhole |
| bp | bubblepoint or saturation (usually with volume, Vbp) | |
| Br | before royalty | |
| Bt | B | before taxes |
| B | turbulence (used with F only, FB) | |
| BT | bt | breakthrough |
| c | C | capillary (usually with capillary pressure, Pc) |
| c | cg | casing or casinghead |
| c | chemical | |
| c | C | compressional wave |
| c | C | constant |
| c | C | contact (usually with contact angle, θc) |
| c | conversion (usually with conversion factor in Newton’s laws of motion, gc) | |
| c | C | core |
| c | cr | critical |
| c | ec | electrochemical |
| cap | capture | |
| cb | CB | cement bond log |
| cf | casing, flowing (usually with pressure) | |
| cl | cla | clay |
| cn | cln | clean |
| cor | corrected | |
| cp | compaction | |
| cs | casing, static (usually with pressure) | |
| C | calc | calculated |
| C | c | caliper log |
| C | c | coil |
| C | components(s) | |
| C | convective | |
| CB | cb | bond log, cement |
| CD | cd | compensated density log |
| CL | cl | chlorine log |
| CN | cn | compensated neutron log |
| CO | carbon monoxide | |
| CO2 | carbon dioxide | |
| C1 | methane | |
| C2 | ethane | |
| d | decay | |
| d | δ | delay |
| d | δ | depleted region, depletion |
| d | dewpoint | |
| d | differential separation | |
| d | dip (usually with angle, αd) | |
| d | D | dispersed |
| d | s,D | displaced |
| d | drainage (usually with drainage radius, rd) | |
| dh | DH | downhole |
| dol | dolomite | |
| dy | dty | dirty (clayey, shaly) |
| D | d | density log |
| D | dimensionless quantity | |
| D | s,σ | displacing or displacement (efficiency) |
| DI | di | dual induction log |
| DLL | dll (script ll) | dual laterolog |
| DM | dm | diplog, dipmeter |
| DR | dr | directional survey |
| DT | dt | differential temperature log |
| Db | displacement from burned portion of in-situ combustion pattern (usually with efficiency, EDb) | |
| Dm | dimensionless quantity at condition m | |
| Du | displacement from unburned portion of in-situ combustion pattern (usually with efficiency, EDu) | |
| e | o | boundary conditions, external |
| e | i | cumulative influx (encroachment) |
| e | E | earth |
| e | effective (or equivalent) | |
| e | E | electric, electrical |
| e | E | entry |
| e | o | external or outer boundary conditions |
| el | eℓ (script el) | electron |
| eq | EV | equivalent |
| ext | extrapolated | |
| E | e | electrode |
| E | EM | empirical |
| E | est | estimated |
| E | EX | experimental |
| Eg | experimental value per mole of produced gas (usually with fuel consumption, mEg) | |
| EL | el,ES | electrolog, electrical log, electrical survey |
| EP | ep | electromagnetic pipe inspection log |
| f | F | finger or fingering |
| f | F | flash separation |
| f | fl | fluid |
| f | fm | formation (rock) |
| f | R | fraction or fractional |
| f | F | fracture, fractured, or fracturing |
| f | F | front, front region, or interface |
| d | future | |
| f | fm | rock (formation) |
| F | F | fill-up |
| F | f | free (usually with gas or gas/oil ration quantities) |
| F | fuel (usually with fuel properties, such as ρF) | |
| Ff | free fluid | |
| Fi | free value, initial (usually with gas, GFi) | |
| FP | cumulative produced free value (usually with gas GFp) | |
| G | G | gas |
| ga | gas at atmospheric conditions | |
| gb | gas at bubblepoint conditions | |
| gD | gas, dimensionless | |
| gr | grain | |
| gyp | gypsum | |
| G | geometrical | |
| ls | lst | limestone |
| L | ℓ (script l) | lateral, lineal |
| L | ℓ (script l) | lateral (resistivity log) |
| L | ℓ (script l) | liquid or liquid phase |
| Lp | cumulative produced liquid (usually with condensate, GLp) | |
| LL | ℓℓ (script ll) | laterolog (add further tool configuration subscripts as needed) |
| LLD | ℓℓ (script ll) | deep laterolog |
| LLS | ℓℓs (script ll) | shallow laterolog |
| LOG | log | log |
| Lp | liquid produced, cumulative (usually with condensate, GLp) | |
| LP | ℓp (script l) | light phase |
| M | mass of fuel (usually with fuel concentration, Cm) | |
| M | mud | |
| ma | grain (matrix, solids) | |
| ma | matrix [solids except (nonstructural) clay or shale] | |
| max | maximum | |
| mc | mudcake | |
| Mf | mud filtrate | |
| min | minimum | |
| M | z,m | mixture |
| M | molal (usually with volume, VM) | |
| M | m | Mth period or interval |
| M | z,m | slurry ("mixture") |
| ML | mℓ (script l) | contact log, microlog, minilog |
| MLL | mℓℓ (script ll) | microlaterolog |
| n | net | |
| n | normal | |
| n | r,R | normalized (fractional or relative) |
| ne | noneffective | |
| nw | NW | nonwetting |
| N | n | neutron |
| N | n | neutron log |
| N | n | normal (resistivity) log (add numerical spacing to subscript N; e.g., N16) |
| N2 | nitrogen | |
| NA | na | neutron activation log |
| NE | ne | neutron log, epithermal |
| NF | nf | neutron log, fast |
| NL | nℓ (script l) | neutron lifetime log, TDT |
| NM | nm | nuclear magnetism log |
| NT | nt | neutron log, thermal |
| o | N | oil (except when used with resistivity) |
| ob | oil at bubblepoint conditions (usually with formation volume factor, Bob) | |
| ob | oil from burned volume (usually with displacement ratio, δob) | |
| oD | oil, dimensionless | |
| og | oil in gas cap (usually with saturation, Sog) | |
| ou | oil from unburned volume (usually with displacement ratio, δou) | |
| O2 | oxygen | |
| p | particle (usually with diameter, dp) | |
| p | P | pore (usually with volume, Vp) |
| P | present | |
| p | P | produced |
| p | produced, cumulative | |
| p | P | production period (usually with time, tp) |
| p | pseudo | |
| pressure, mean or average | ||
| pc | pseudocritical | |
| pD | pore value, dimensionless (usually with volume, VpD) | |
| pD | pseudodimensionless | |
| pE | produced in experiment | |
| pj | produced component j (usually with moles, npj) | |
| po | payout | |
| pr | pseudoreduced | |
| pSP | pseudo-SP | |
| pv | present value | |
| P | pattern (usually with pattern efficiency, Ep) | |
| P | phase or phases | |
| P | p | proximity log |
| r | R | radius, radial, or radial distance |
| r | reduced | |
| r | b,ρ | reference |
| r | R | relative |
| r | R | residual |
| R | rate | |
| R | ratio | |
| R | recovery (usually with recovery efficiency, ER) | |
| R | r | reservoir |
| R | resistivity | |
| R | r,ρ | resistivity log |
| Rb | reservoir rock, burned | |
| Ru | reservoir rock, unburned | |
| Re | Reynolds (used with Reynolds number only, NRe) | |
| s | d | damage or damaged (includes "skin" conditions) |
| s | formation, surrounding | |
| s | gas/oil ratio, solution | |
| s | S,σ | segregation (usually with segregation rate, qs) |
| s | τ | shear |
| s | τ | shear wave |
| s | S | skin (stimulation or damage) |
| s | σ | slip or slippage |
| s | σ | solid (usually with volume or density) |
| s | solution (usually with gas/oil ratios) | |
| s | spacing | |
| s | specific (usually with J and I) | |
| s | S | stabilization (usually with time) |
| s | S | steam or steam zone |
| s | S | stimulation (includes "skin" conditions) |
| s | σ | surface |
| s | surrounding formation | |
| s | S,σ | swept or swept region |
| s | σ | system |
| sb | solution at bubblepoint conditions (usually with gas/oil ratio, Rsb) | |
| sc | scattered, scattering | |
| sc | σ | standard conditions |
| sd | sa | sand |
| sE | solids in experiment | |
| sh | sha | shale |
| si | solution, initial (usually with gas/oil ratio, Rsi) | |
| sl | slt | silt |
| sp | separator conditions | |
| sp | single payment | |
| ss | sst | sandstone |
| st | stock-tank conditions | |
| st | s | structural |
| sw | solution in water (usually with gas solubility in water, Rsw) | |
| S | SW | sidewall |
| S | s,σ | storage or storage capacity |
| saturation, mean or average | ||
| SN | sn | neutron log, sidewall |
| SP | sp | self potential |
| SSP | spontaneous self potential | |
| SV | sv | sonic, velocity, or acoustic log |
| SWN | swn | sidewall neutron log |
| t | T | gross (total) |
| t | T | total |
| t | Τ | treatment or treating |
| t | tr | true (electrical logging) (opposed to apparent) |
| t | tg | tubing or tubinghead |
| tD | time, dimensionless | |
| tf | tubing flowing (usually with pressure) | |
| ti | total initial in place in reservoir | |
| ts | tubing, static (usually with pressure) | |
| T | h,θ | temperature |
| T | t,h | temperature log |
| T | t | tool, sonde |
| T | t | transmissibility |
| TV | tv | televiewer log, borehole |
| u | unburned | |
| u | U | unit |
| u | U | unswept or unswept region |
| u | U | upper |
| ul | a | ultimate |
| v | V | vaporization, vapor, or vapor phase |
| v | V | velocity |
| V | v | vertical |
| V | v | volume or volumetric |
| Vb | volumetric or burned portion of in-situ combustion pattern (usually with efficiency, EVb) | |
| VD | vd | microseismogram log, signature log, variable density log |
| w | W | water |
| w | well conditions | |
| w | W | wetting |
| wa | wellbore, apparent (usually with wellbore radius, rwa) | |
| wb | water from burned volume (usually with displacement ratio, δwb) | |
| wD | water, dimensionless | |
| wf | bottomhole, flowing (usually with pressure or time) | |
| wf | f | well, flowing conditions (usually with time) |
| wF | water/fuel | |
| wg | water in gas cap (usually with saturation, Swg) | |
| wg | wet gas (usually with composition or content,Cwg) | |
| wgp | wet gas produced | |
| wh | th | wellhead |
| wo | water/oil (usually with instantaneous producing water/oil ratio, Fwo) | |
| wop | water/oil, produced (cumulative) (usually with cumulative water/oil ratio, Fwop) | |
| ws | static bottomhole (usually with pressure or time) | |
| ws | s | well, static, or shut-in conditions (usually with time) |
| W | w | weight |
| xo | flushed zone | |
| Y | Young’s modulus, refers to | |
| z | conductive liquids in invaded zone | |
| z | zone, conductive invaded |