Accuracy in the hydrocarbons industry is essential for financial outcomes. Whether you’re producing, transporting, or refining oil and gas, the accuracy of your measurements directly impacts your bottom line. And while error margins have long been monitored, measurement uncertainty is now taking center stage.
By definition, measurement uncertainty is a parameter associated with the result of a measurement that characterizes the dispersion of values that could reasonably be attributed to the measured quantity. In other words, it expresses the doubt about the exactness of the measurement result. This uncertainty arises because every measurement is influenced by multiple external factors, such as instrument characteristics (resolution, stability, calibration error), environmental conditions (temperature, air currents, nearby heat sources), measurement method, and operator handling, among others. Every measurement, no matter how advanced the instrument is, comes with uncertainty.
The purpose of estimating measurement uncertainty is to quantify the combined effect of these factors and provide a confidence level for the measurement result. It ensures transparency and reliability in decision-making, compliance, and operational processes
The Guide to the Expression of Uncertainty in Measurement (GUM) provides a standardized methodology to quantify these influences, helping operators understand the reliability of their data. For example, measuring ambient temperature involves not just the thermometer, but also air currents, nearby heat sources, and even the person taking the reading. Each factor contributes differently to the final uncertainty value.
Why It Matters in Hydrocarbons
The American Petroleum Institute (API) validates the GUM methodology in its MPMS 13.3 standard. In an industry where millions of barrels are moved daily, even a small uncertainty can translate into a significant financial impact. A 0.2% uncertainty in a 1-million-barrel operation could mean a $200,000 swing daily.
Measurement uncertainty affects every link in the supply chain. Producers rely on accurate volume data for royalties and financial reporting. Transporters need precision to manage custody transfers and losses. Refineries depend on reliable inputs for efficient processing.
The Problem with Static Uncertainty Values
Many companies apply a fixed uncertainty value across all systems and timeframes. But this approach can mask real losses or misattribute them. For example, assuming a station has a 0.5% uncertainty, when it’s actually 0.2%, could hide 0.3% worth of unaccounted losses.
Daily or ticket-level uncertainty calculations provide a more accurate picture. They help teams distinguish between true losses and measurement variability.
Observed Situations in Oil & Gas Operations
Based on real experiences and observations at oil and gas operators, the following situations have been identified:
- Static Tank Measurement: Crude oil tanks with capacities up to 150,000 barrels have demonstrated uncertainty levels varying from 0.14% to 0.24%. These fluctuations depend on factors such as the fill level and liquid temperature, resulting in differences that can equate to swings of 140 barrels.
- Pressurized Tanks: In gas systems, pressure is a dominant factor, contributing up to 88% of the total measurement uncertainty. Even minor changes in system pressure or small errors in pressure transmitters can cause the overall uncertainty to shift significantly, from as low as 4% to over 11%.
- Natural Gas Measurement: Daily changes in pressure and temperature have a notable effect on measurement uncertainty. For instance, a temperature variation of 35°F can lead to nearly a 1% increase in overall uncertainty.
The Financial and Operational Impact
Measurement uncertainty has a direct impact on several critical aspects of operations. First, when uncertainty is misestimated, it can distort the reporting of losses on balance sheets. Additionally, accurate volume measurements are essential to ensure fair payments for royalties and billing purposes.
Reliable data also supports better operational decisions, as improved information leads to more informed choices. Although companies often invest significant resources in calibration, advanced equipment, and regular audits, neglecting to properly account for measurement uncertainty can undermine all these efforts. Calculating uncertainty on a ticket-by-ticket basis is crucial for maintaining transparency and accuracy throughout the entire operation.
COSMOS Expanding FLOWCAL Functionality for Uncertainty Calculations
To address the evolving requirements for efficiency within oil and gas operations, COSMOS now extends the core capabilities of FLOWCAL by introducing a dedicated module for measurement uncertainty estimation on a ticket-by-ticket basis. This module is designed to provide operators with an accurate and dependable means of quantifying uncertainty for each individual measurement.
The COSMOS module integrates data sourced directly from FLOWCAL, combining it with instrumentation information consolidated from TESTit. Through this approach, users are empowered to assess the specific uncertainty associated with every measurement record, rather than relying on generalized or static values. This ensures that the estimation of measurement uncertainty is both precise and tailored to the actual operational data, supporting improved financial reporting, operational efficiency, and regulatory compliance.
Conclusion
In today’s hydrocarbons industry, measurement uncertainty is no longer optional; it’s strategic. As technology advances and regulatory expectations rise, companies must move beyond static assumptions and embrace dynamic, data-driven uncertainty analysis. This not only improves measurement but also safeguards revenue, boosts compliance, and supports operational integrity.
COSMOS, in collaboration with FLOWCAL, delivers a comprehensive platform for managing volumetric data; this platform not only validates the integrity of measurement data but also provides robust estimation of uncertainty levels for each record. By systematically evaluating and quantifying uncertainty with COSMOS, operators gain confidence in the reliability of their measurements.
Furthermore, COSMOS enables the identification of individual sources contributing to overall measurement uncertainty. By isolating and understanding these factors, operators can implement targeted improvements and maintain transparency throughout the measurement process. This structured approach ensures that data quality is upheld and that all uncertainty contributors are clearly recognized and managed.
Tory Technologies, Inc., also known as Tory-Tech, is a Houston-based corporation founded in 2012, that designs, develops, integrates, and deploys intuitive corporate software solutions for Control Room Management and Volumetric Data Management. Decades of expertise in software development and implementation have resulted in a unique suite of solutions specifically designed to solve critical challenges in control rooms and flow measurement departments.
Interested in working with a SOC 1 and SOC 2 compliant company? Contact us to learn more about our control room management software, MaCRoM®, and our volumetric data management software, COSMOS®.