Liquid Measurement — Custody Transfer

Net Standard Volume (NSV) Fundamentals

Net standard volume is the bottom line of a custody-transfer ticket — the volume of pure hydrocarbon, free of water and sediment, at 60 °F and 0 psig. Getting there is a disciplined chain of deductions and corrections defined by API MPMS Chapter 12: remove free water, correct for temperature and pressure, apply the meter factor, and deduct sediment & water.

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Result

NSV = GSV × (1 − S&W)

The settled custody quantity.

Base

60 °F & 0 psig

US petroleum standard.

Standards

API MPMS Ch. 12

Static (12.1) & dynamic (12.2).

Contents

Use this guide to:

  • Build a crude/product custody ticket.
  • Trace TOV → GOV → GSV → NSV.
  • See where CTPL and MF apply.

1. What is Net Standard Volume?

Net standard volume (NSV) is the volume of merchantable liquid hydrocarbon — with all water and sediment removed — expressed at the 60 °F / 0 psig base. It is the number on which a sale is invoiced. The chain that produces it strips away each non-hydrocarbon and non-standard component in turn, so that buyer and seller exchange a like-for-like quantity regardless of the temperature, pressure, or water content at the point of measurement.

Why each step exists: free water is not product; temperature and pressure change the volume a fixed mass occupies; a meter is imperfect (hence the meter factor); and entrained sediment & water are not oil. NSV removes all four.

2. The Gross-to-Net Volume Chain

TOV Total Observed Volume (raw gauge or meter reading) − FW Free Water (Ch. 10 — gauged at tank bottom) = GOV Gross Observed Volume (hydrocarbon + S&W, observed conditions) × CTPL Vol. Correction Factor (Ch. 11.1 — CTL × CPL, to 60 °F / 0 psig) × MF Meter Factor (Ch. 12.2 — dynamic only; static = 1) = GSV Gross Standard Volume (hydrocarbon + S&W at base conditions) × (1 − S&W/100) Sediment & Water (Ch. 10) = NSV Net Standard Volume (the custody figure)

CTPL is the combined temperature/pressure volume correction factor from the VCF calculation. The meter factor only enters for metered (dynamic) measurement; a static tank gauge has no meter factor.

3. Static vs Dynamic Measurement

Static (Tank)

No Meter Factor

Volume comes from a gauge reading and the tank strapping table (Ch. 12.1). MF = 1.0000.

Dynamic (Meter)

Meter Factor Applies

Volume comes from a meter; the meter factor from the latest proving corrects it (Ch. 12.2).

Both

Same CTPL & S&W

Temperature/pressure correction and S&W deduction apply to either path.

4. Worked Example

Static tank receipt of 35 °API crude at 80 °F. TOV = 1,010 bbl, free water = 10 bbl, S&W = 0.5%:

GOV = 1010 − 10 = 1000 bbl CTPL = 0.99051 (35 °API crude @ 80 °F, atmospheric) GSV = 1000 × 0.99051 × 1.0 = 990.51 bbl NSV = 990.51 × (1 − 0.005) = 985.56 bbl

The 1,010 bbl indicated becomes 985.56 bbl of net oil — a 24.4 bbl (2.4%) difference that, unaccounted, would be a large settlement error.

5. Standards & References

StandardScope
API MPMS Ch. 12.1Calculation of Static Petroleum Quantities (tanks)
API MPMS Ch. 12.2Calculation of Quantities — Dynamic Measurement; meter factor
API MPMS Ch. 11.1 / ASTM D1250CTL / CPL volume correction (CTPL)
API MPMS Ch. 10Sediment & Water determination
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Frequently Asked Questions

What is the difference between gross and net standard volume?

Gross standard volume (GSV) is the total liquid — hydrocarbon plus S&W — corrected to 60 °F; net standard volume (NSV) is GSV minus the sediment-and-water fraction, i.e. the saleable oil.

When is a meter factor not applied?

For static tank measurement there is no meter factor (it equals 1.0000); it applies only to dynamic, metered measurement and comes from proving.

How is free water different from BS&W?

Free water is bulk water gauged separately and removed first; BS&W is the water and sediment still entrained in the oil, applied as a percentage of the remaining volume.