BETTER CHART PRACTISES

1
BETTER CHART PRACTISES

• What You Need to Know About Accurate Gas
  Measurement

Created by Andrew Rau
2
GAS MEASUREMENT

• The source of almost all of the production and
  revenue calculations.
• With accurate and reputable measurement of the
  quantity and quality of natural gas, economic
  gains can be recognized through the reduction of
  operating costs in sales of material and time.
• Accurate and reputable orifice measurement and
  volume determination is the combined
  responsibility of Field Operators, PAs and your
  chart reading service and can be achieved through
  good working practices and open communication
  between these departments.

3
(No Transcript)
4
Required Chart Information Clock Cycle

• Clock Cycle A clock cycle is the stated time
  period for a chart to make one complete
  revolution.
• Chart cycles can be 1, 7, 8, 16, 31 day duration.
  
• The recorder clock should be calibrated to
  actually perform one complete rotation in the
  specified time, if not errors may occur.

5
Required Chart Information Date/Time

• Operator must indicate the correct Date/time on
  Date/time off
• Should correspond with the time indicated by the
  differential recording.
• On Nov 23,06 0800
• Off Nov 29,06 1530
• The time off written on this chart is 241 PM
  (1441), the trace ends at 1530

6
Required Chart Information Identification

• Full LSD/UWI
• 102/02-02-002-02w2/03 Sales gas, Flare, Fuel,
  Group, etc.
• Use of chart sticker provides identification
• Misidentified charts cause reporting errors

7
Required Chart Information Orifice, etc.

• Operator must indicate the correct orifice plate
  bore size to 3 decimals
• If no temperature pen, operator must indicate
  temperature and units (C or F)
• If sales/group charts, temp must be marked daily
• If test/fuel/flare charts, temp can be marked
  once/cycle
• Operator must indicate the correct line size to 3
  decimals
• Use of chart sticker provides actual line size

8
Impact of Errors
9
Test Environment

• Treater Sales Gas - Orifice
• Orifice size was 0.875, used 0.625
• Resulted in chart volume being understated by
  49.8
• Error valued at 461/day (14,291/month)

10
Required Chart Information Ranges

• Static Differential Ranges on a chart need to
  match the meter springs to ensure correct
  calculations. Static is represented by a blue
  trace and Differential by a red trace.

11
Test Environment

• Gas Well - Static
• Static range changed from 0-500 to 0-250
• Continued to be read at 0-500
• Resulted in chart volume being understated by
  18.1
• Error valued at 285/day (8,835/month)

12
Clock Cycle
Static
Differential
Line Orifice
Complete LSD/UWI
Date/Time On/Off
61F
Temp Units
13
(No Transcript)
14
(No Transcript)
15
Proper Chart Operation Practices

• Pen Traces
• Chart pens should mark the finest trace that is
  clearly visible.
• For maximum accuracy, pens s/b in outer 1/2 of
  chart
• Eliminate differential painting
• Ensure beta ratio (plate/line) is between 0.15
  and 0.6
• Check differential pen zero position, under
  pressure, at each chart change
• Pen Offset
• Pen s/b offset by 15 minutes
• Differential is real time,
• Static lags 15 minutes,
• Temp leads by 15 minutes

16
Plunger Lift Charts

• Plunger lift charts produce highly variable
  traces
• Use of 24 or 48 hour charts will provide better
  clarity and accuracy.
• Ensure Static Differential pens are offset
  correctly.
• Indicating no flow periods assists in correct
  identification of flow

17
Handling Charts With Missing Traces

• Reasons
• Clock stopped
• Pens out of ink
• Pens frozen
• Pen over-ranged or stuck off chart
• Handling
• Mark in estimated traces with a comment or,
• Provide comments as how chart needs to be read

18
Handling Charts With Painted Traces

• Painted charts cannot be read as accurately as
  non-painted charts
• Request operations to take actions to reduce
  painting where possible
• Painted charts will be read in a wave like
  pattern from top to bottom of the painted section
  per regulatory guidelines

19
Handling Charts With DP on the Hub

• Flow/DP pen traces at the hub can cause
  significant volume error
• May be read as zero even though production
  occurred due to not being able to see daylight at
  the hub.
• By changing the range springs or orifice may
  allow pens to come off the hub for a more
  accurate volume.
• 100 of your volume could be lost by only the
  width of your pen trace

20
Orifice Plate Creating Differential

• The pressure drop or difference in pressure
  between the upstream and downstream faces of the
  Orifice Plate.
• Two key factors influence differential pressure
• Orifice plate size Gas flowrate.
• As the orifice size increases, the differential
  pressure drops (if all other factors are kept
  constant)
• As the gas flowrate increases (with the orifice
  plate and other factors kept constant), the
  differential pressure will increase

21
Static

• The constant or flowing pressure in the
  pipeline.
• This pressure is expressed in terms of gauge or
  absolute.

22
My Actuals dont match my Estimates?

• Before you call anyone, do a quick check of all
  your information.
• All required charts for the time period are
  accounted for.
• The correct charts have been applied to the
  specific meter in question.
• All core data has remained constant in the field
  (they took into consideration any static,
  differential, orifice changes).
• Chart services has caught any/all changes that
  may have occurred and are reporting all core
  information correctly (Static, Differential,
  Temperature, Line size Orifice).

23
The End Result
24
(No Transcript)
25
Tips for More Accurate Gas Volumes!

• Verify all your base meter data (line size,
  ranges, composition, static tap locations, etc.)
• Identify meters with pens riding low in the range
  for both differential and static and look at
  making orifice plate and sensor changes
• Identify charts with painted differentials and
  look at ways to eliminate painting
• Ensure all gas compositions are up to date
• Ensure that meter identification is accurate for
  all meters (LSD/UWIs, Description Meter ID)
• Ensure that audit trail and reporting
  requirements are met for all your gas measurement
  systems

26
Conclusion

• Accurate orifice measurement and volume
  determination is the combined responsibility of
  Field Operators, PAs the Chart reading
  service.
• Achieved through good working practices and open
  communication between these departments.
• By starting the chart cycle with complete and
  accurate information all parties who subsequently
  touch that chart will clearly and easily be able
  to identify and interpret the information.

27
Q A