Multi-Sample Plotting

When multiple samples are input to whitson^PVT, data visualization can be used to easily identify fluid behavior, data entry errors and data quality checks. In the following sections, several different plotting types for data visualization available in whitson^PVT are discussed briefly.

Note

All plots in whitson^PVT are interactive! Hover over the (?) symbol on the top-right of the plot to explore the hotkeys that will boost you to an expert level!

PVT Experiments

The first plot type is the PVT experiments. This feature lets you easily visualize the PVT experiments for all samples containing the chosen PVT experiment. Changing the PVT experiment is as easy as selecting the experiment type and switching to the experiment you want to see.

When looking at a PVT experiment, you can also change the experiment properties by going to the x-property or y-property selection. This tool lets you readily check for inconsistencies and possible data entry errors or incorrect data measurements.

Characterization

Changing the plot type to characterization lets you view two key plots that indicate if the inputted fluids have the same C₇₊ characterization. This can be an indication of whether or not a single fluid model will be able to predict all samples within the fluid system.

The first plot type for the characterization plots, is the specific gracity - molecular weight relationship. The data in this plot is (1) the flashed oil back-calculated C₇₊ specific gravity and molecular weights for all samples with this data available, (2) true boiling point (TBP) distillation data, and (3) BTEX SCN component data for C₇, C₈, and C₉. A reference curve using the Søreide model is also shown (grey line), as this represents what the laboratories often use as a default. The normal paraffin lower bound is also given (green line). Methods and equations related to the reason why the C₇₊ data is used, are given in the methodology section here.

The second plot type for the characterization plots, is the Watson characterization factor. The characterization factor indicates what proportion a fluid has between paraffinic and aromatic components. The Watson factor is calculated using the C₇₊ molecular weight and specific gravity as proposed by Whitson [ref]. Table 1 shows the ranges of the Watson factor and what component types it contains.

Table 1: Relationship between Watson factor and the splits of paraffin, napthane and aromatic components.

Watson Factor (K_w)	Fluid Type
>12	Paraffin
~11-12	Napthane
<11	Aromatic

This data can also indicate data entry issues or measurement errors for the density, molecular weight and compositional measurements.

Property versus Depth

If the input samples are taken at a specific depth, then it is usually of interest to plot certain fluid properties versus depth. This will show similarities and differences for various fluids in the same larger fluid system.

Compositions

The first plot of the composition graph type is the flashed oil C₇₊ composition. This data can indicate if the distribution of the C₇₊ has the same trend for all fluids in the wider fluid system. Similar to the characterization plots, the C₇₊ composition can indicate whether a single fluid model can describe multiple samples. Providing an estimation for the potential of a field-wide or multi-well fluid model.

The compositions are from the flashed oil, as this composition best represents the unknown C₇₊ components that need to be characterized in the fluid model development. These compositions are also normalized to 100% so comparison of different fluids is easier.

Property Trends

With a large amount of fluid data in the whitson^PVT database, different fluid property trends can be found. Deviations from these correlations can indicate erronious measurements, data entry errors, or different fluid behavior. Examples of data that should correlate strongly are

Saturation pressure versus C₁ content
Single-stage flash GOR versus C₇₊ content
C₁ versus C₇₊ content