Understanding the importance of obtaining the most representative PVT properties of your reservoir fluids is essential. The best way to achieve this is through a comprehensive PVT study in the laboratory, a process that cannot be overstated in its significance.
Almost all black oil properties are measured in a standard PVT experimental study. Upon receiving the study results, the crucial step is to match the measured PVT properties to specific correlations. This step is not just a formality, but a necessity. But why is it so important?
In most reservoir fluid PVT experimental studies, black oil properties are measured at a single value of reservoir temperature and a limited number of pressure points, ranging from 15 to 30. However, in petroleum engineering applications, you would need to calculate the black oil properties at almost any temperature and pressure value, and that’s why matching is required.
The purpose of the PVT matching is crucial, as it allows us to predict the black oil properties at pressures not used in the measurement. To do so, you must obtain the best-fit correlation model for the measured data. Here is how to achieve this:
It will help if you can visualize how the calculated properties are biased from the laboratory-measured data. In other words, you would need to identify the mismatch between model data and actual properties. And here is how to do so:
Bear in mind that all calculated properties must be obtained at the same reservoir temperature and the same pressure points as measured in the PVT study. Moreover, you have to input the measured field parameters (gas gravity, oil gravity, and solution gas-oil ratio at the bubble point pressure) into the correlations you would use.
So far, you have built multiple calculated models for each black oil property; it’s time to fit all calculated properties to the lab data. The best practice is to manipulate all used correlations with two modifiers, multiplier (a) and shift (b), as per the equation:
Y = AX + B, where:
And here’s how to do so:
Now it’s time to select only one PVT correlation for each black oil property. The best fit-correlation is the one with the minimum mismatch to the lab data. And here is how to select the best-fit correlation to your lab data:
This post explains how to match your experimental PVT data to several empirical correlations. The objective is to obtain the most representative model of your reservoir fluids that you can confidently use in almost any petroleum engineering applications.
PVT matching can help you predict the black oil properties at pressures not measured in the experimental study. It’s also may help in validating PVT study results as well.
