Understanding Uncertainty in Petrophysical Interpretation

All petrophysical interpretations carry a degree of uncertainty - this is not a flaw, but a fundamental reality of the process. From the moment data is acquired, uncertainty begins to accumulate. Even the most carefully calibrated, environmentally corrected, and properly functioning logging tools do not produce absolute values. Instead, they operate within a defined precision. 

Take, for example, two runs of a density log. Each will yield slightly different results, leading to different porosity estimates. Which one is correct? The answer is: neither is absolutely correct, but both fall within a distribution of possible outcomes. 

This uncertainty compounds as we move through the interpretation workflow. Parameters such as grain density, water salinity, and clay volume all introduce their own variability. The result? A potentially wide range in key outputs like hydrocarbon pore feet. 

So how uncertain is your interpretation? What are the P10, P50, and P90 values and which inputs are driving the most uncertainty? 

Quantifying Uncertainty with Monte Carlo Simulation 

IP’s Monte Carlo module is designed to answer these questions. By running thousands of interpretations using user-defined ranges for each input log and parameter, the module provides a robust statistical view of your results across the entire workflow, including complex workflows like Facies Prediction, Saturation Height Modelling, Pore Pressure and Wellbore Stability. 

This approach doesn’t just quantify uncertainty; it helps you understand it. You’ll gain insights into which parameters have the greatest impact on your interpretation, enabling better decision-making and risk assessment. 

Interested to find out more? Get in touch to arrange an overview with one of our experts.