Troubleshooting Common Errors in Petroleum Office

When a Petroleum Office function encounters a problem, it returns a standard Excel error. This guide explains what each error means and how to fix it.

#NAME? — Function Not Recognized

What it means: Excel does not recognize the function name.

Common causes:

  • Add-in not loaded — Petroleum Office is not active in this Excel session
  • Typo in function name — the function name is misspelled
  • No active license — functions require a valid subscription

How to fix:

  1. Check that the Petroleum Office tab is visible in the ribbon. If not, the add-in is not loaded — see The Petroleum Office tab is missing below
  2. Verify the function name is correct — use IntelliSense by typing =PO. to browse available functions
  3. Check your licence status — Settings → Licensing. Licensing and Your Account explains what each status means

#VALUE! — Invalid Input

What it means: One or more input parameters have an invalid type or format.

Common causes:

  • Passing text where a number is expected
  • Passing an empty cell for a required parameter
  • Using an unrecognized unit abbreviation in unit conversion functions

How to fix:

  1. Check that all parameters are the correct type (numbers for numeric inputs, text for string inputs)
  2. Make sure required cells are not empty
  3. For PO.UnitConverter(), verify that the unit abbreviations are valid — open the Unit Converter in the Tools group to browse the available units by category

#NUM! — Value Out of Range

What it means: A parameter is outside the valid range for the correlation, or the calculation produced an invalid result (e.g., negative pressure).

Common causes:

  • Temperature or pressure outside the correlation's applicable range
  • Negative values where only positive values are valid
  • Hyperbolic exponent b outside 0–1 range for Arps decline

How to fix:

  1. Check the function's IntelliSense tooltip for parameter constraints
  2. Verify your input values are physically reasonable
  3. Try a different correlation that covers a wider range

#N/A — No Result Available

What it means: The function could not produce a result for the given inputs, or an output validation check failed.

Common causes:

  • Convergence failure in iterative calculations (e.g., flash calculations)
  • Requesting a property that doesn't exist for the given conditions
  • Unit mismatch in input parameters

How to fix:

  1. Check that input values are consistent (e.g., pressure in psi, temperature in degF)
  2. For EoS functions, verify that the composition sums to 1.0
  3. Try slightly different input values to check if the problem is near a boundary condition

#SPILL! — Blocked Spill Range

What it means: An array function is trying to return multiple values, but one or more cells in the output range are not empty.

How to fix:

  1. Clear the cells adjacent to the formula cell (below for vertical spill, to the right for horizontal spill)
  2. Move the formula to a location with enough empty space
  3. See the Using Array Functions guide for details on spill ranges

#DIV/0! — Division by Zero

What it means: The calculation encountered a division by zero.

Common causes:

  • A required input is zero when it shouldn't be (e.g., zero flow rate, zero thickness)
  • Intermediate calculation produced a zero denominator

How to fix:

  1. Check that none of your inputs are zero unless the function explicitly accepts it
  2. Verify that input values are physically meaningful

General Troubleshooting Tips

The Petroleum Office tab is missing

Petroleum Office is an Excel add-in (an .xll), so it is managed under Excel Add-ins — not under COM Add-ins, where it will never appear.

  1. Go to File > Options > Add-ins
  2. At the bottom, set Manage to Excel Add-ins and click Go
  3. Tick the box next to Petroleum Office and click OK

If Petroleum Office is not in that list, Excel may have disabled it after a crash or a slow load:

  1. Go to File > Options > Add-ins
  2. Set Manage to Disabled Items and click Go
  3. If Petroleum Office is listed, select it, click Enable, then restart Excel

Excel keeps an add-in in the disabled list until you re-enable it, so reinstalling on its own will not bring the tab back.

If it is in neither list, the add-in is not registered — re-run the installer, and check the System Requirements guide for the .NET runtime the add-in needs.

Check your version

If functions behave unexpectedly, make sure you're running the latest version:

  1. Go to the Petroleum Office tab
  2. In the Settings group, click Settings
  3. Open the Add-in panel — it compares your installed version against the latest release, and Download opens the download page if you are behind

Verify Units

Most Petroleum Office functions expect inputs in field units (psi, degF, scf/STB, cp, etc.). If your data is in SI units, convert first using PO.UnitConverter() or the Unit Converter in the Tools group.

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