Nomenclature
| Variable | Description |
|---|---|
| a |
Nominal (instantaneous) decline rate (Traditional Decline Analysis Theory) |
| aelf |
Decline rate at end of linear flow |
| af |
Final nominal (instantaneous) decline rate |
| ai |
Initial nominal (instantaneous) decline rate |
| alim | Limiting nominal (instantaneous) decline rate |
| A |
Area |
| AD | Areal extent of reservoir |
| Ao |
Gas-oil pore size distribution index |
| ASRV |
Area of stimulated reservoir volume |
| Aw |
Oil-water pore size distribution index |
| APE | Automatic Parameter Estimation |
| b |
Decline exponent |
| ba,pss |
Pseudo-steady state constant in the flow equation using material balance pseudo-time (gas) |
| bDpss |
Dimensionless pseudo-steady state constant |
| bpss |
Pseudo-steady state constant in the flow equation using material balance time (oil) |
| B |
Formation volume factor |
| Bg |
Formation volume factor for gas |
| Bgd | Dry gas formation volume factor, ft3/scf, m3/m3 |
| Bgi |
Formation volume factor for gas at initial reservoir pressure and temperature |
| Bginj |
Formation volume factor for injected gas |
| Bo |
Formation volume factor for oil, bbl/stb, m3/m3 |
| Bob |
Formation volume factor for oil at bubble point |
| Boi |
Formation volume factor for oil at initial reservoir pressure and temperature |
| Bw |
Formation volume factor for water |
| Bwi |
Formation volume factor for water at initial reservoir pressure and temperature |
| Bwinj |
Formation volume factor for injected water |
| c |
Compressibility |
| cd |
Relative change in pore volume due to desorption of gas |
| ce |
Effective compressibility. For oil systems,
includes oil, water, and formation compressibilities. |
| cep |
Relative change in pore volume due to formation and residual fluid expansion |
| cf |
Formation/pore compressibility |
| cf,max |
Formation compressibility at zero net overburden pressure |
| cfi |
Initial formation compressibility |
| cg |
Gas compressibility |
| c̅g |
Average gas compressibility |
| ci |
Initial compressibility |
| cma |
Matrix compressibility |
| co |
Oil compressibility |
| ct |
Total compressibility |
| c̅te |
Total compressibility at average reservoir pressure including net gas compressibility due to water influx |
| cti |
Total initial compressibility |
| cT |
Isothermal compressibility |
| cT,w |
Isothermal compressibility of water |
| cT,wf |
Isothermal compressibility of gas-free water |
| cT,wg |
Isothermal compressibility of gas-saturated water |
| cti |
Total system compressibility at original reservoir pressure |
| cw |
Water compressibility |
| cwip |
Relative change in pore volume due to water influx and production |
| C |
Transfer coefficient related to flow capacity of the formation |
| CBM | Coalbed Methane |
| CCA | Custom Calculated Attributes |
| CD |
Storage coefficient |
| CDF | Cumulative Distribution Function |
| CDI |
Formation and Connate Water Compressibility Drive Index |
| CF |
Casing Flange (reference point for depth measurements) |
| CGR |
Condensate Gas Ratio, bbl/MMscf, m3/103m3 |
| Ca |
Ash content (Langmuir Isotherm) |
| CA |
Reservoir shape factor |
| CaD |
Dimensionless apparent wellbore storage |
| CAh |
Shape factor for horizontal wells |
| CD |
Dimensionless wellbore storage |
| Cg |
Gas content |
| Cg,abdn/CO2 | Gas content at abandonment pressure or CO2 concentration |
| Cgi |
Initial gas content |
| CG |
Input gas volume fraction |
| CL |
Liquid input volume fraction |
| Cm |
Matrix swelling coefficient |
| Co |
Gas-oil entry capillary pressure |
| Cp |
Mechanical compliance coefficient |
| CpD |
Dimensionless storage pressure parameter |
| Cw |
Oil-water entry capillary pressure. Moisture content. (Langmuir Isotherm) |
| d |
Effective decline rate |
| di |
Initial effective decline rate |
| dlim |
limiting effective decline rate |
| D |
Turbulence factor |
| DDI |
Depletion Drive Index |
| DLS | Dominion Land Survey |
| DSN | Data source name |
| E | Young's modulus of elasticity |
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| EUR |
Expected Ultimate Recovery |
| Eavg |
Average error |
| Efw |
Formation expansion factor |
| Eg |
Gas expansion factor |
| Egi |
Gas expansion factor at initial conditions |
| EL |
In-situ liquid volume fraction (liquid holdup) |
| EL0 |
Horizontal liquid holdup |
| ELθ |
Inclined liquid holdup |
| Eo |
Oil expansion factor |
| Et |
Total expansion factor |
| f |
Decimal fraction |
| fc |
Compressibility modifier |
| F |
Reservoir voidage from production |
| FDBC | Fekete DataBase Connection tool |
| FCD |
Dimensionless fracture conductivity |
| gg |
Geothermal gradient |
| G |
Original gas-in-place |
| G | Separator gas specific gravity (for fluid properties) |
| GHV |
Gross Heating Value |
| GMB | Gas Material Balance |
| GOR |
Producing Gas-Oil Ratio |
| Gf |
Free gas-in-place |
| Ginj |
Cumulative gas injected |
| Gp |
Cumulative gas production |
| Gpa |
Additional gas production |
| Gp,n |
Ultimate recoverable gas |
| Gpn |
Cumulative gas production at time 'n' |
| Gr |
Remaining gas |
| GT |
Cumulative transferred gas volume in a connected reservoir |
| h |
Net pay |
| hp |
Perforated interval |
| HCPV |
Hydrocarbon Pore Volume |
| I |
Incline rate |
| IWIP |
Initial Water-In-Place |
| j |
Time interval/timestep |
| J |
Transfer coefficient |
| k |
Permeability |
| kabs |
Absolute permeability |
| kaq |
Aquifer permeability |
| ke |
Effective roughness of pipe |
| kf |
Fracture permeability |
| kg |
Effective permeability of gas |
| kh |
Horizontal permeability |
| ki |
Initial permeability |
| ko |
Effective permeability of oil |
| kr |
Pressure-dependant permeability ratio: kr = k / ki |
| kres |
Reservoir permeability |
| krg |
Gas-relative permeability |
| krgc |
Gas-relative permeability at residual oil saturation |
| krgcw |
Gas-relative permeability at connate water saturation |
| krgro |
Gas-relative permeability at residual oil saturation |
| kro |
Oil-relative permeability |
| krocw |
Oil-relative permeability at connate water saturation |
| krog |
Oil-relative permeability with respect to gas |
| krogc |
Oil-relative permeability at critical gas saturation |
| krow |
Oil-relative permeability with respect to water |
| krw |
Water-relative permeability |
| krwgc |
Water-relative permeability at critical gas saturation |
| krwro |
Water-relative permeability at residual oil saturation |
| kv |
Vertical permeability |
| kw |
Effective permeability of water |
| kx |
Permeability in the x-direction |
| ky |
Permeability in the y-direction |
| kz |
Permeability in the z-direction |
| K |
Bulk modulus (CBM Properties) Constant of proportionality (Material Balance Analysis Theory - Schilthuis Model) |
| KB |
Kelly Bushing (reference point for depth measurements) |
| L |
Horizontal wellbore length |
| LD |
Dimensionless horizontal wellbore length |
| Le |
Effective horizontal wellbore length |
| Lex |
Effective horizontal wellbore length in the x-direction |
| m |
Slope from the flow equation using material balance time (oil) |
| ma |
Slope from the flow equation using material balance pseudo-time (gas) |
| M |
Mobility Ratio (Analytical Models) (Water-drive Typecurves and Models) Constrained axial modulus (CBM Properties) |
| MD |
Measured Depth (CF or KB) |
| MPP |
Mid-Point of Perforations |
| Maq |
Aquifer mobility |
| Mo |
Molecular weight of stock tank liquid |
| Mres |
Reservoir mobility |
| n |
Moles of gas (Ideal Gas Law equation) |
| nf |
Number of fractures |
| ng |
Gas exponent |
| nog |
Oil-gas system exponent |
| now |
Oil-water system exponent |
| nw |
Water exponent |
| N |
Original oil-in-place |
| NTS | National Topographic map numbering System |
| Np |
Cumulative oil production |
| Np,n |
Ultimate recoverable oil |
| NVL |
Liquid velocity number |
| ODBC | Open Database Connectivity |
| OCIP | Original Condensate-in-Place, Mstb, 103m3 |
| OCIPSRV | Original Condensate-in-Place in Stimulated Region, Mstb, 103m3 |
| OFIP | Original Fluid-in-Place |
| OGIP |
Original Gas-in-Place, MMscf, 106m3 |
| OGIPA |
Original Adsorbed Gas-in-Place, MMscf, 106m3 |
| OGIPF |
Original Free Gas-in-Place, MMscf, 106m3 |
| OGIPSRV | Original Gas-in-Place in Stimulated Region, MMscf, 106m3 |
| OMB | Oil Material Balance |
| OOIP |
Original Oil-in-Place, Mstb, 103m3 |
| OOIPSRV | Original Oil-in-Place in Stimulated Region, Mstb, 103m3 |
| OWIP | Original Water-in-Place, Mstb, 103m3 |
| OWIPSRV | Original Water-in-Place in Stimulated Region, Mstb, 103m3 |
| p |
Pressure |
| p̅ |
Average reservoir pressure |
| pab |
Abandonment pressure |
| pair |
Air pressure |
| paq |
Aquifer pressure |
| paqi |
Initial aquifer pressure |
| pbp |
Bubble point pressure, psi(a), kPa(a) |
| pc |
Critical pressure |
| (pce)go | Gas-oil pore entry capillary pressure, psi(a), kPa(a) |
| (pce)ow | Oil-water pore entry capillary pressure, psi(a), kPa(a) |
| pcgo |
Gas-oil system capillary pressure, psi(a), kPa(a) |
| pcow |
Oil-water system capillary pressure, psi(a), kPa(a) |
| pd |
Desorption pressure |
| pdew | Dew point pressure, psi(a), kPa(a) |
| pD |
Dimensionless pressure |
| pDi |
Dimensionless pressure integral |
| pDid |
Dimensionless pressure integral derivative |
| pe |
Bulk overburden pressure |
| pflow |
Specified flowing pressure |
| pgrd |
Overburden pressure gradient |
| pi |
Initial reservoir pressure |
| pj |
Pressure at time "j" |
| pL |
Langmuir pressure |
| pmax |
Maximum pressure |
| pmin |
Minimum pressure |
| pn |
Net overburden pressure |
| pni |
Initial net overburden pressure |
| po |
Oil pressure |
| pp |
Pseudo-pressure |
| ̅pp |
Average pseudo-pressure |
| ppab |
Abandonment pseudo-pressure |
| ̅ppab |
Average abandonment pseudo-pressure |
| ppi |
Initial pseudo-pressure |
| ppwf |
Wellbore flowing pseudo-pressure |
| pr |
Reduced pressure |
| ̅pR |
Current reservoir pressure |
| psp |
Separator pressure |
| psc |
Pressure at standard conditions (14.65 psia, 101.0 kPa(a)) |
| pw | Water pressure |
| pwf | Wellbore flowing pressure |
| pwff |
Sandface forecast pressure |
| pε |
Reservoir pressure at 50% matrix strain |
| PI |
Productivity index |
| PVT |
Pressure-Volume-Temperature |
| Pc |
Capillary pressure |
| q |
Rate |
| q̅ |
Average rate |
| qab |
Abandonment rate |
| qD |
Dimensionless rate |
| qDd |
Dimensionless decline rate |
| qDde |
Dimensionless decline rate accounting for total pool production |
| qDd, integral |
Dimensionless rate integral |
| qelf |
Rate at end of linear flow |
| qf |
Final rate (abandonment rate) |
| qg |
Instantaneous gas rate |
| qginj |
Injected gas rate |
| qi |
Initial rate |
| qintegral |
Rate integral |
| qj |
Rate at time "j" |
| qo |
Instantaneous oil rate |
| qs |
Gas flow rate from separator |
| qtot |
Pool total production rate |
| qw |
Instantaneous water rate |
| qwe |
Rate of water influx |
| qwinj |
Rate of water injection |
| Q |
Cumulative production |
| QD |
Dimensionless cumulative production |
| QDA |
Area-based dimensionless cumulative production |
| QDd |
Dimensionless cumulative decline production |
| Qf |
Final cumulative production |
| Qg,dry |
Cumulative surface gas production |
| Qg,wet |
Cumulative well stream gas produced at the sandface |
| Qi |
Initial cumulative production |
| Qm |
Modified cumulative production |
| Qn |
Normalized cumulative production |
| Qtot |
Pool cumulative production |
| r |
Radius |
| raq |
Aquifer exterior radius |
| re |
Reservoir effective radius |
| reD |
Dimensionless effective radius |
| ro |
Reservoir outer boundary radius (Water-drive Typecurves and Models) Distance to observation well from active well, for cylindrical reservoirs (Well Locations and Boundaries) |
| rw |
Wellbore radius |
| rwa |
Apparent wellbore radius |
| rwD |
Dimensionless wellbore radius |
| rwe |
Effective wellbore radius |
| R |
Ideal gas law constant |
| RC | Rate vs Cumulative production |
| RF |
Recovery factor |
| RR |
Remaining Recoverable |
| RT | Rate vs Time |
| Rp |
Solution gas-oil ratio based on cumulative oil and gas production |
| Rs |
Solution gas-oil ratio, scf/bbl, m3/m3 |
| Rsb | Solution gas-oil ratio at bubble point |
| Rsi |
Initial solution gas-oil ratio |
| Rsr |
Reduced solution gas-oil ratio |
| Rsw |
Gas solubility in water |
| Rv | Vaporized oil ratio, bbl/MMscf, m3/103m3 |
| s |
Skin |
| sd |
Near-wellbore skin damage |
| sdφ |
Interporosity skin |
| sf |
Fracture face skin |
| S |
Salinity of water |
| SDI |
Segregation (gas cap) Drive Index |
| SI | International system of units. For more information, see http://dictionary.reference.com/browse/si+units?s=t |
| SL |
Surface losses |
| SPE | Society of Petroleum Engineers |
| SRV |
Stimulated Reservoir Volume |
| Sg |
Gas saturation |
| Sgc |
Critical gas saturation |
| Sgi |
Initial gas saturation |
| Sgn |
Normalized gas saturation |
| Siw |
Irreducible water saturation (Relative Permeability Correlations) |
| So |
Oil saturation |
| Soi |
Initial oil saturation |
| Son |
Normalized oil saturation |
| Sor |
Residual oil saturation |
| Sorg |
Residual oil saturation to gas |
| Sorw |
Residual oil saturation to water |
| Sw |
Water saturation |
| Swc |
Critical water saturation (Capillary Pressure) |
| Swc |
Connate water saturation (Relative Permeability) |
| Swi |
Initial water saturation |
| Swirr |
Irreducible water saturation (Capillary Correlations) |
| Swn |
Normalized water saturation |
| ̅Sw |
Average water saturation |
| t |
Time |
| ta |
Pseudo-time |
| tc |
Material balance time |
| tca |
Material balance pseudo-time |
| tcae |
Total material balance pseudo-time for gas |
| tce |
Total material balance pseudo-time for oil |
| tco |
Length of the first time period in material balance time |
| tD |
Dimensionless time |
| tDA |
Area-based dimensionless time |
| tDd |
Dimensionless decline time |
| tDde |
Dimensionless decline time accounting for total pool production |
| tDxf |
Dimensionless time based on fracture half-length (xf) |
| tDye |
Dimensionless time based on reservoir width (Ye) |
| telf |
Time at end of linear flow |
| tf |
Time at start of forecast date |
| tflow |
Specified flow time |
| tj |
Time at the "jth" time period/timestep |
| tlim |
Limiting time |
| tshut-in |
Specified shut-in time |
| tstab |
Time to stabilization |
| T |
Temperature |
| TVD |
True Vertical Depth (CF or KB) |
| TPC | Tubing Performance Curve |
| Tc |
Critical temperature |
| Tf |
Formation temperature |
| Ti |
Initial temperature |
| Tpp |
Pour point temperature |
| Tr |
Reduced temperature |
| Tsp |
Separator temperature |
| Tsc |
Temperature at standard conditions (60oF/15oC) |
| Tsp |
Separator temperature |
| vg |
Gas velocity |
| vL |
In-situ liquid velocity |
| vm |
Mixture velocity |
| vsg |
Superficial gas velocity |
| vsl |
Superficial liquid velocity |
| V |
Volume |
| VR |
Voidage replacement |
| VRR |
Voidage Replacement Ratio |
| Vaq |
Aquifer volume |
| VHCP |
Hydrocarbon pore volume |
| Vi |
Initial volume |
| VL |
Langmuir volume |
| VLi |
Initial Langmuir volume |
| Vp |
Pore volume |
| VR |
Volatile oil ratio Rock volume |
| Vsc |
Volume at standard conditions |
| VT |
Total volume |
| Vw |
Wellbore volume |
| wf |
Fracture width |
| WDI |
Water Drive Index |
| WOR |
Water-Oil Ratio |
| We |
Water encroachment from aquifer |
| Wei |
Initial water encroachment from aquifer |
| Winj |
Cumulative water injection |
| Wp |
Cumulative water production |
| xf |
Fracture half-length |
| xfx |
Fracture-half length in the x-direction |
| xfy |
Fracture-half length in the y-direction |
| Xe |
Reservoir length |
| XeD |
Dimensionless reservoir length |
| Xw |
Active well location in the x-direction |
| Y |
Distance of investigation at time t |
| Ye |
Reservoir width |
| Yw |
Active well location in the y-direction |
| Ye/Yw |
Ratio of reservoir width to well location in the y-direction |
| Z |
Gas compressibility factor |
| Z** |
Modified gas compressibility factor |
| Z̅ |
Average gas compressibility factor |
| Zab |
Compressibility factor at reservoir abandonment pressure |
| Zi |
Compressibility factor at initial pressure and temperature |
| Zi** |
Modified compressibility factor at initial pressure and temperature |
| Zo |
Location of observation well from top of zone (z-direction) for rectangular reservoirs |
| Zsc |
Compressibility factor at standard conditions |
| Zw |
Well location in the z-direction (only applicable to horizontal wells) |
| α |
Biot's coefficient (Geomechanical Reservoir Models - Dobrynin Correlation) Separation factor/selectivity ratio (Langmuir Isotherm) |
| β |
Square root of the anisotropic ratio kh/kv |
| βD |
Ratio of total pool production to individual well production |
| γ |
Permeability modulus (Geomechanical Reservoir Models - Yilmaz & Nur Pressure-Dependant Permeability Correlation) Dimensionless correlation factor (Geomechanical Reservoir Models - Dobrynin Pressure-Dependant Permeability Correlation) Grain compressibility (CBM Properties) Euler's constant = 0.57721 (Material Balance Pseudo-Time for Gas), (Abandonment Pressure Calculations), (Blasingame Typecurve Analysis Theory - Horizontal Well) |
| γAPI |
Specific gravity of liquid hydrocarbons/condensate in oAPI |
| γg |
Specific gravity of gas |
| γg(psp) |
Specific gravity of gas at separator pressure conditions |
| γo |
Specific gravity of liquid hydrocarbons/condensate |
| γt |
Recombined gas gravity |
| γw |
Specific gravity of water |
| ∆k |
Change in permeability |
| ∆pf |
Change in pressure due to friction |
| ∆pHH |
Change in pressure due to hydrostatic head |
| ∆Q |
Forecast cumulative production |
| ∆t |
Forecast duration |
| ∆Vd |
Change in reservoir volume due to desorption of gas |
| ∆Vep |
Change in reservoir volume due to formation and residual fluid expansion |
| ∆Vp |
Reduction in hydrocarbon pore volume |
| ∆Vw |
Expansion of initial water volume |
| ∆Vwip |
Change in reservoir volume due to water influx and production |
| ∆Xo |
Location of observation well from active well in the x-direction, for rectangular reservoirs |
| ∆Yo | Location of observation well from active well in the y-direction, for rectangular reservoirs |
| ∆Z |
Change in elevation |
| ε |
Tensile strain |
| εexp |
Net strain between overburden stress effect and matrix shrinkage as measured experimentally |
| εL |
Langmuir strain |
| θ |
Angle of inclination |
| θr |
[(T + 459.67) / 459.67] = relative temperature |
| λ |
Interporosity flow coefficient (Dual Porosity) Pore size distribution index (Capillary Correlations - Brooks/Corey) |
| λgo | Gas-oil pore size distribution index |
| λow | Oil-water pore size distribution index |
| μ |
Viscosity of primary fluid (gas/oil/water) |
| µ̅ |
Average viscosity |
| μaq |
Aquifer viscosity |
| μg |
Gas viscosity, cP, mPa.s |
| ̅μg |
Viscosity of gas at average pressure |
| μi |
Viscosity at initial reservoir pressure |
| μL |
Liquid viscosity |
| μm |
Mixture viscosity |
| μNS |
No-slip viscosity |
| μo |
Oil viscosity, cP, mPa.s |
| μob |
Oil viscosity at bubble point |
| μod |
Viscosity of dead oil |
| μos |
Viscosity of saturated oil |
| μres |
Reservoir viscosity |
| μw |
Water viscosity, cP, mPa.s |
| ν |
Poisson's ratio |
| ξ |
Reduced inverse viscosity |
| ρ |
Density |
| ρa |
Apparent density of surface gas |
| ρair |
Air density |
| ρbs |
Pseudo-liquid density at reservoir pressure and standard temperature |
| ρB |
Bulk density |
| ρG |
Gas density |
| ρL |
Liquid density |
| ρm |
Mixture density |
| ρmol |
Molar density |
| ρNS |
No-slip density |
| ρo |
Oil density |
| ρob |
Oil density at bubble point |
| ρoR |
Oil density at reservoir conditions |
| ρpo |
Pseudo-liquid density at standard conditions |
| ρst |
Stock tank oil density |
| ρw |
Water density |
| σ |
Interfacial tension (Capillary Pressure) Effective horizontal stress (CBM Properties) |
| σi |
Effective horizontal stress at initial reservoir pressure |
| φ |
Porosity |
| φi |
Initial porosity |
| φt |
Total porosity |
| Ψ |
Pseudo-pressure |
| Ψ̅ |
Pseudo-pressure at average pressure |
| Ψi |
Pseudo-pressure at initial reservoir pressure |
| Ψwf |
Pseudo-pressure at sandface flowing pressure |
| ω |
Storativity ratio |