How many decimal places should we use when reporting hydrocarbon measurement results?

In inspection and custody transfer operations, it’s not only important to obtain the data correctly. It is also fundamental to process, round, and report it appropriately.

API MPMS 12.1.1 – Calculation of static petroleum quantities in vertical cylindrical tanks and vessels establishes rounding and discrimination criteria to standardize how data and results are expressed in petroleum quantity calculation computations.

According to the applicable criteria, some examples are:

• Temperature: 1 decimal
• API gravity: 1 decimal
• Density (kg/m³): 1 decimal
• Density (kg/l): 4 decimals
• Volume (m³): 3 decimals
• Volume (bbls): 2 decimals
• Metric Tons (MT): 3 decimals
• Water and Sediments (S&W) in %: 3 decimals
• CTSh – Correction for Temperature of Shell: 5 decimals

But there is especially important principle:

Important: More decimals do not mean greater accuracy.

The number of decimal places used must be consistent with the source and resolution of the original data. Adding decimal figures during processing or via a spreadsheet does not generate greater precision if the original data does not have that resolution.

API MPMS 12.1.1 also distinguishes between observed data and calculated data, establishing specific criteria for the treatment and rounding of results.

Correctly applying these principles directly contributes to improving the consistency, traceability, and comparability of information among the various parties involved in an operation.

In hydrocarbon measurement, measuring correctly also means reporting correctly.

At BZ Consulting, the correct application of technical and regulatory criteria is a fundamental part of our commitment to reliable and traceable results.

BZ Consulting, “The value of experience.”