Unit Converter
Water Viscosity (McCain, 1990)
Hydrostatic Pressure
API Gravity ↔ Specific Gravity
Gas Formation Volume Factor (Bg)
Oil Formation Volume Factor (Bo, Standing 1947)
Cement Volume (Annular)
Original Oil in Place (Volumetric)
Original Gas in Place (Volumetric)
BOE Converter
Arps Decline (Forecast & EUR)
Single-Well Economics
Uses the Arps annual production above. CAPEX hits at t=0; abandonment hits at the last positive-CF year. Revenue scales on RI (operator share of revenue). OPEX, CAPEX, and abandonment scale on WI (operator share of cost). Dollar outputs are in $M (thousands, petroleum convention).
Sensitivity to flat oil price. All other inputs held constant. Current price column is highlighted.
CO₂ Mass ↔ Volume Conversions
Enter any value; all others update. Reservoir-condition volumes use the editable density below.
CO₂ Density, Viscosity & Phase
Enter pressure and temperature at reservoir conditions. Density via Peng-Robinson EOS; viscosity is a screening approximation (see method note). Phase diagram below updates live with the inputs — the red marker is your point.
Storage Capacity (DOE/NETL Volumetric)
GCO₂ = A · h · ϕ · (1 − Swirr) · ρCO₂ · E. Per Goodman et al. (2011) / DOE-NETL Carbon Storage Atlas methodology.
CO₂ Injection Rate Conversions
Enter any rate; all others update. Surface volumes at standard conditions; reservoir volumes use ρ below.
Plume Radius (Volumetric Estimate)
Screening estimate assuming uniform radial displacement. Does NOT account for buoyancy, dissolution, residual trapping, or heterogeneity.
Quick Reference Constants
CO₂ properties & conversion constants
- CO₂ critical point: 1071 psia, 87.98°F (31.1°C, 7.38 MPa)
- CO₂ triple point: 75.13 psia, −69.83°F (−56.57°C, 0.518 MPa)
- CO₂ molecular weight: 44.01 g/mol
- Standard density (60°F, 14.696 psia): 0.1144 lb/scf ≈ 1.842 kg/sm³
- 1 tonne CO₂ ≈ 19,252 scf at standard conditions
- 1 Mt CO₂ ≈ 19.25 Bscf at standard conditions
- Typical supercritical density at CCS conditions: 0.5–0.8 g/cc
- DOE storage efficiency E: 1–4% (saline), 5–20% (depleted HC) — Goodman et al. 2011
- 1 acre = 43,560 ft²; 1 acre-ft = 7,758 bbl = 43,560 ft³ ≈ 1,233 m³
Resistivity-Porosity Salinity Calculator
Petrophysical salinity estimate from log resistivity. Estimates formation water resistivity (Rw) from Rt and ϕ via a formation factor (F = Ro/Rw) relationship, corrects Rw to a reference temperature with Arps (1953), and converts to NaCl-equivalent salinity. Used for Class VI CCS and Class II UIC USDW characterization.
Rt that would correspond to the indicated NaCl-equivalent salinity, holding ϕ, formation factor method, depth temperature, and Tref at their current values. 10,000 ppm is the USDW threshold (40 CFR §144.3); 3,000 ppm is a common Class VI confining-zone reference.
Rt, depth temperature, and Tref held constant. Active row (selected rock type) and active column (current ϕ rounded to nearest 5%) are tinted. Intersection cell is the base-case anchor. Active correlation: Gen-9.
8. Methods, references, and caveats
- Arps temperature correction: Rw(T2) = Rw(T1) · (T1 + 7) / (T2 + 7), T in °F. Arps (1953).
- Gen-9 NaCl (default): NaCl (ppm) = ROUND(5697.5 · Rw(Tref)−1.079, nearest 10). Empirical fit to the Schlumberger Gen-9 chart at Tref = 75°F.
- Schlumberger 1988 chart correlation: NaCl (ppm) = 10((3.562 − log10(Rw(Tref) − 0.0123)) / 0.955). From Schlumberger Log Interpretation Charts, 1988 edition, Gen-9.
- Archie's law: F = Ro/Rw; Rw = Rt/F under fully water-saturated, clean (shale-free) conditions. Hydrocarbon presence or shaliness will bias Rw high (and salinity low).
- Default surface T: 70°F (typical for shallow subsurface in coastal California). Adjust for site-specific MAGT (mean annual ground temperature).
- Default gradient (Mode B): 1.6°F/100 ft, representative of average California sedimentary-basin geothermal gradient. Local gradients range ~1.4–1.8°F/100 ft in non-geothermal basins, higher near the Coast Ranges and Salton Trough.
- TDS vs. NaCl-equivalent: reported salinity is NaCl-equivalent. For brines with significant Ca, Mg, sulfate, or bicarbonate, true TDS may differ materially. Apply ion-specific corrections if available.
- Shaly intervals: apply Waxman-Smits, dual-water, or Indonesia model separately. This calculator assumes clean-zone Archie analysis.
Total Compressibility (ct)
Compute total reservoir compressibility ct = crock + Sw·cw + So·co for Class II UIC water injection. Provides a defensible, citation-backed input value for ZEI / AOR calculations. Standard practice per 40 CFR §146.6.
2. Reference table — typical compressibility values
| Component | Range (× 10⁻⁶ /psi) | Notes |
|---|---|---|
| Consolidated sandstone | 3 – 5 | Most California Miocene/Pliocene reservoirs |
| Unconsolidated sand | 4 – 7 | Shallow disposal zones, friable formations |
| Limestone | 2 – 4 | Lower porosity, stiffer matrix |
| Dolomite | 3 – 6 | Variable with fabric |
| Fresh water | 3.0 – 3.3 | At reservoir T and P |
| Produced water (saline) | 2.8 – 3.2 | Lower at higher salinity |
| Dead oil (low GOR) | 5 – 10 | Above bubble point |
| Live oil (high GOR) | 10 – 25 | Above bubble point |
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4. Methods, references, and caveats
- Total compressibility equation: ct = crock + Sw·cw + So·co. Saturation-weighted additive sum of pore-volume and fluid-phase isothermal compressibilities.
- Assumptions: gas saturation = 0 (typical Class II brine disposal); single-phase oil above bubble point; isothermal; component contributions independent and additive.
- Newman (1973): "Pore-Volume Compressibility of Consolidated, Friable, and Unconsolidated Reservoir Rocks Under Hydrostatic Loading," Journal of Petroleum Technology, February 1973. Source for crock ranges.
- McCain (1990): The Properties of Petroleum Fluids, 2nd ed., PennWell Books. Source for cw and co defaults; oil compressibility above bubble point per the Vasquez-Beggs correlation.
- Regulatory basis: standard practice for Class II UIC area-of-review (AOR) and zone of endangering influence (ZEI) calculations per 40 CFR §146.6.
- Pressure / temperature dependence: component compressibilities vary with reservoir conditions. Defaults assume 100–200°F, 1000–3000 psi (typical California shallow disposal zones). For significantly different conditions, adjust component values using published correlations.
- Below bubble point: oil compressibility rises sharply as dissolved gas evolves, and this simple additive model is no longer valid. Assume single-phase oil for ct purposes.
- High-salinity brines: for >100,000 ppm TDS, cw can fall below 2.5 × 10⁻⁶ /psi; apply a salinity-corrected value if needed.
Darcy Permeability (RAT)
Effective (skin-included) permeability from a stabilized single-rate injectivity test (RAT survey) on a Class II UIC well. Computes bottomhole flowing pressure from surface injection pressure accounting for hydrostatic head and tubing friction, then applies Darcy's steady-state radial flow equation.
With assumed skin s = 0 (default), this is the effective (skin-included) permeability from the survey under steady-state radial flow. With a positive s entered above, it is the inferred intrinsic permeability corresponding to that assumption — single-rate data cannot determine skin, so any non-zero s should be reported alongside k.
Columns: Pe at ±20% in 10% steps. Rows: heff at 0.50× to 1.50× in 25% steps. All other inputs (q, μ, B, re, rw, Pwf) held constant at base values, with skin held at the entered s across the matrix. Base case (center cell) highlighted; cells within ±50% of base k tinted lighter.
8. Methods, references, and caveats
- Darcy radial flow (steady-state, field units): k (mD) = 141.2 · q (bbl/d) · μ (cP) · B (RB/STB) · (ln(re/rw) + s) / (h (ft) · ΔP (psi)), with ΔP = Pwf − Pe and s = assumed skin (dimensionless; s = 0 ⇒ bare radial form).
- Bottomhole flowing pressure: Pwf = Psurf + Phydrostatic − ΔPfriction, with Phydrostatic = L · gradient.
- Fanning friction equation (field units): ΔPf (psi) = 5.50×10⁻⁶ · f · ρ · q² · L / di⁵, with f the Fanning friction factor, ρ in lb/gal (calculator converts the lb/ft³ input ÷ 7.481), q in bbl/d, L in ft, di in inches. Derived from ΔP = 2·f·ρ·v²·L/D; equal to the v-based form f·ρ·v²·L/(25.8·di). The equivalent lb/ft³ constant is 7.36×10⁻⁷.
- Reynolds number: Re = 11.05 · ρ · q / (μ · di), ρ in lb/gal, same units as friction. Equivalent to 1.48 · ρ(lb/ft³) · q / (di · μ) and to 92.1 · SG · q / (di · μ); the specific-gravity constant 92.1 must not be applied to lb/gal.
- Swamee-Jain explicit (Fanning): f = 0.0625 / [log10((ε/di)/3.7 + 5.74/Re0.9)]², valid for Re > 4000. Laminar fallback (Re ≤ 4000): f = 16/Re.
- Water viscosity (McCain 1990, fresh water at atmospheric P): μ (cP) = 109.574 · T (°F)−1.12166.
- References: Earlougher (1977), Advances in Well Test Analysis, SPE Monograph 5; Crane Technical Paper No. 410; Swamee & Jain (1976), "Explicit equations for pipe-flow problems"; McCain (1990), The Properties of Petroleum Fluids, 2nd ed.
- Effective vs intrinsic k: with s = 0 the result is effective (skin-included) permeability. Positive skin (damage) causes the s = 0 result to underestimate intrinsic k; negative skin (stimulation) causes overestimation. To resolve true skin, run a pressure transient analysis; entering a non-zero s in §4 applies the correction explicitly under that assumption — report the assumed s alongside k in any submittal.
- Steady-state assumption: requires stabilized rate and pressure at the time of the survey. If taken during transient conditions (recent rate change, recent startup or shut-in), keff will be biased. Allow 1–2 hours of stable injection before recording.
- Observed rate vs. monthly average: use the wellhead-flowmeter rate at the stabilized portion of the survey — not the monthly injection average from regulatory reports. Monthly averages smear over downtime, rate changes, and operational variability and paired with an instantaneous pressure give a meaningless result.
- Deviated wells: friction uses measured depth (correct); hydrostatic also currently uses measured depth (approximation). For wells >30° from vertical, hydrostatic should be computed from TVD. A future revision will support separate MD/TVD entry.
- Single-phase liquid: friction model assumes single-phase water flow. Multiphase, gassy, or compressible flow requires different methodology.
- Static fluid level (Mode B): assumes the static column has equilibrated. For recently shut-in wells, fluid level may still be rising — wait for stabilization before measuring.
Single Well ZEI Calculator
Single-well, screening-level Zone of Endangering Influence for a Class II UIC permit application: Bernard / Warner-Lear ΔP, endangering pressure, and volumetric radii, sized for a one-page screenshot.
| r (ft) | ΔP | New P | ZEI? |
|---|
| r (ft) | ΔP | New P | ZEI? |
|---|
Methods, assumptions, and caveats
- Bernard / Warner-Lear log approximation (field units, t in hours): ΔP(r,t) = (162.6·Q·μ)/(k·h) · [log10(k·t/(ϕ·μ·ct·r²)) − 3.32 + 0.87·s]. Single-well, infinite-acting radial flow (Matthews & Russell 1967).
- Endangering pressure: Pc = PUSDW + (zi − zUSDW)·SGi·0.433; ΔPc = Pc − Pi. A ZEI exists only where the modeled ΔP reaches ΔPc.
- Volumetric radius: r = √(V·5.615·Bw/(π·H·ϕ)); dispersion rdisp = r + 2.3·√(D·r) (Warner & Lear 1977). Current case uses gross historical injection.
- Brine permeability (Swanson 1981): kbrine = 0.292·kair1.186 (SPE-8234-PA).
- Water viscosity (McCain, fresh water): μ = 109.574·T−1.12166, T in °F (≈0.40 cP at 150°F; editable).
- Screening scope: single well only; no superposition, faults, or transport. A rigorous transient model is built separately.