Pipeline flow computers are designed for single-phase liquids and gases, requiring high accuracy measurement. Upstream flow computers must handle multiphase liquids and gases with impurities, prioritizing lower cost, tolerance of errors, and ease of use over high accuracy, as they are used to estimate well production for allocation rather than custody transfer. While upstream systems still need to conform to regulatory record keeping, API standards like 21.2 are designed for pipeline applications and do not directly apply to the measurement challenges in upstream production.

1. Pipeline Vs. Upstream
Flow Computers
Understanding the Differences
Grant Van Hemert, P.E.

2. Flow Computation
• Very Important Process Criteria
• Used In A Variety Of Industries
• Flow Is Determined By Two Means
– Flow Meter
– Flow Computers

3. Flow Computers vs. Flow Meters
Flow Computer Flow Meter
Flow Direction
Leak Detection
Flow Total
Flow Composition
Determination
Revenue Billing Oil & Gas Drinking Water, Steam, etc.
Revenue Billing Based
on Flow Composition
Needs Flow Meter to
Function
Not Applicable

4. Flow Computer Uses
• Oil or Gas Well Measurement
• Pipeline Applications
• STAR (Ship, Truck, Airplane, Rail) loading
• WAGES (Water, Air, Gas, Electric, Steam) billing
• Others
We Will Focus On Well and Pipeline Applications

5. O&G Flow Computer Differences
• Gas
– Measures 1 or more
types of gasses
– Must preserve records
– Interfaces with Gas
Chromatograph
– Typically compliant with
API-21.1
• Liquid
– Measures 1 or more
types of liquids
– Must preserve records
– Interface with Density
Meters
– Typically compliant with
API-21.2

6. Gas Measurement
• Easily Separates From Oil And Water
• Natural Gas Has Multiple Components
– Natural Gas Found At Production Well
• Transmission Can Be Pure, Or Natural
Gas
• Gas Chromatograph Can Determine
Composition
• Governed By API-21.1
Transportation
and Production
Product Is
Similar

7. Liquids Measurement
• Does Not Separates Easily From Water
• Refined Liquids ≠ Unrefined Liquids
• Volume Varies By Temp Not Pressure
• Different Liquids Applications
• Governed by API-21.2

8. Liquid Pipeline Application
Transportation
Heating Oil
Gasoline
Diesel
Heating Oil
Gasoline
Diesel
Pipeline
Same Pipeline could be used to
Transport Different Liquids

9. Liquid Pipeline Application
Transportation
Heating Oil
Gasoline
Diesel
Heating Oil
Gasoline
Diesel
Pipeline
Same Pipeline could be used to
Transport Different Liquids

10. Liquid Pipeline Application
Transportation
Heating Oil
Gasoline
Diesel
Heating Oil
Gasoline
Diesel
Pipeline
Same Pipeline could be used to
Transport Different Liquids

11. Production Pipeline Application
• Same Liquid
• Multiple Destinations (Refinery)
• Multiple Sources (Batteries & Fields)
• Custody Transfer At Input and Output

12. Upstream Application
• Only Three Products
– Liquid (Sellable)
– Gas (Sellable
– Water (Non-Sellable)
• No Change To
– Source (Always the Same Wells)
– Destination (Same Tank or Pipeline)
– Pipeline Contents
Water Must Be
Accounted For
and Managed

13. Upstream Application
• Separation Measurement
– Test Separators
– Portable Separators
– Continuous Net Oil Measurement
• Calculations
– Allocation
• Estimate of Actual Production
Assigned to Each Well
– Proration
• Estimate of Forecast Production
From Each Well
Allocation and
Proration
Balanced at end
of Month
Sporadic Well
Testing
Result is
Rounding and
Estimating

14. Pipeline Versus Upstream
Pipeline
Upstream
• Permanent Provers
• Pure Liquid
• High Accuracy Measurement
• Not Tolerant of Instrument
Errors
• Small Volume Temporary
Provers
• Mix of Water and Oil
• Harder To Measure
• Tolerant of Instrument
Errors

15. About API-21.2
“…apply to new metering systems that
performs continuous on-line gross
standard volume (GSV) calculations.”

16. About API-21.2
“…apply to new metering systems that
performs continuous on-line gross
standard volume (GSV) calculations.”
Upstream Allocation ≠ Continuous Measurement
•Test Separator
•Portable Separators

17. About API-21.2
“Single-phase liquid hydrocarbon streams
may include permissible amounts of water
or other nonsalable components.
Measurement of gas/liquid two-phase
mixtures is not covered

18. About API-21.2
“Single-phase liquid hydrocarbon streams
may include permissible amounts of water
or other nonsalable components.
Measurement of gas/liquid two-phase
mixtures is not covered
Upstream:
•Too Much Water For “Permissible” Clause
•Water & Oil = Two Phase mixture

19. What about API21.2
in Upstream
• Theory:
– Does Not Apply
• Reality:
– Must Conform to Record
Keeping and QTR
– Required by BLM, and
others.
Upstream = Accurate Low
Cost Measurement of 3
Phase Liquids

20. Other Upstream
Considerations?
• More tolerant
– Meter failure
– Impurities
• Simpler to use and
configure
• Less Expensive Then
Pipeline
Upstream = Accurate Low
Cost Measurement of 3
Phase Liquids

21. Conclusion
• Flow Meters ≠ Flow
Computers
• Many Flow Computers
Designed for Pipelines
• Not Suited for Upstream
Applications
– Allocation Determination
– Tolerant of Impurities
– Ease of Use
– Lower Cost