Multi-Sample Plotting

When multiple samples are input to whitson^PVT, data visulization 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 visulization 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 plotting type are the PVT experiments. This feature lets you easily visulize the PVT experiments for all samples with the chosen PVT experiment. Changing the PVT experiment is as easy as selecting the experiment type and switching it to the one you are interested in.

When looking at a PVT experiment, you can easilty change the experiment properties by going to the x-property or y-property selction and changing it. This tool lets you easily check for inconsistensies and possible data entry errors or inconsistent measured data.

Characterization

Changing the plot type to characterization lets you view two key plots that indicate if the input fluids have the same C₇₊ characterization. This can be an indication whether or not a single fluid model will be able to predict all samples in 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 avaiable, (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 curve), as this represents what the laboratories often use as a defualt, and the normal paraffin lower bound is also given (green line). The 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 indicated the proportion a fluid has of paraffinic comonents, or 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 measurment 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 different fluids in the same larger fluid system.

Compositions

The first plot of the composition plotting type is the flashed oil C₇₊ composition. This data can indicate if the distribution of the C₇₊ has the same character 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.

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. The compositions are also normalized to one to make comparison of different fluids 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 data, 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