Multiphase Flow Meter (MPFM) Calculators
Two MPFM calculators: convert standard phase rates to phase fractions at line conditions, and compare the MPFM reading with the test separator phase by phase.
Educational quick-check calculators: not an approved procedure and not a substitute for your company software or a qualified engineer’s review.
GVF, WLR, water cut and GOR
GVF and WLR are volume fractions at line (actual) conditions; water cut and GOR are at standard conditions.
How it is calculated
Qg,line = (Qg − Rs · Qo) · Bg / 5.6146 [bbl/d]
Ql,line = Qo · Bo + Qw · Bw
GVF = Qg,line / (Qg,line + Ql,line)
WLR = Qw · Bw / Ql,line ; WC = Qw / (Qo + Qw)
GOR = Qg / Qo ; GLR = Qg / (Qo + Qw)
Assumptions
- Bo, Rs and Z at line pressure and temperature from a PVT report; dissolved gas is not counted as free gas.
- Absolute pressure = line pressure + 14.696 psi. No phase slip in this volumetric calculation.
Worked example
Qo = 1000 STB/d, Qw = 250 bbl/d, Qg = 0.8 MMscf/d, 300 psig, 120°F, Z = 0.95, Bo = 1.25, Rs = 150 scf/STB, Bw = 1.0 → Bg = 0.049486 ft³/scf, free gas = 650,000 scf/d = 5,729 bbl/d at line, liquid = 1,500 bbl/d, so GVF = 79.25%, WLR = 16.67%, water cut = 20.00%, GOR = 800 scf/STB.
Sources: API MPMS Chapter 20.3 (measurement of multiphase flow; GVF and WLR definitions) · NFOGM / Tekna — Handbook of Multiphase Flow Metering, Rev. 2 (2005) · McCain, W.D. — The Properties of Petroleum Fluids (Bg, Bo, Rs)
Educational quick-check tool, not an approved procedure. Follow your company procedures and the manufacturer’s data.
MPFM vs test separator comparison
Deviation of the MPFM reading from the separator for each phase, with pass/fail against your tolerances.
How it is calculated
Pass if |deviation| ≤ tolerance (oil and liquid: liquid tolerance; gas: gas tolerance)
WLR difference (points) = WLR_MPFM − WLR_sep ; WLR = Qw / (Qo + Qw)
Water rate and GOR: shown for information
Assumptions
- Default tolerances (±5% liquid, ±10% gas, ±3 points WLR) are examples only; real acceptance limits come from the contract, the regulator or company procedure.
- Rates at the same (standard) conditions over the same period; the separator is the reference even though it has its own uncertainty.
- A small water rate gives a large relative deviation, so water is judged by the absolute WLR difference.
Worked example
MPFM: 980 / 262 / 0.89 MMscf/d, separator: 1000 / 250 / 0.80 → oil −2.00% (pass), liquid 1242 vs 1250 = −0.64% (pass), gas +11.25% (fail at ±10%), WLR 21.10% vs 20.00% = +1.10 points (pass).
Sources: API MPMS Chapter 20.3 (measurement of multiphase flow; in-situ verification against a test separator) · NFOGM / Tekna — Handbook of Multiphase Flow Metering, Rev. 2 (2005)
Educational quick-check tool, not an approved procedure. Follow your company procedures and the manufacturer’s data.