V 4 Assay Migration Details

Due to significant differences in how naphtha components are handled in V4 assays, all assays containing PONA data must be migrated and re-synthesized when loading cases from V3. Matters are further complicated as V3 distinguished between assayed and non-assayed streams. In order to model pure component streams (for example, light ends, steam), users were able to attach assays to streams but override composition. In V4, all streams are assayed and such hybrid configurations are disallowed to ensure data consistency. Therefore, several scenarios are accounted for when migrating V3 cases into V4.

Migration Technique

Each V3 assay requiring migration is divided into 12 contiguous cuts, with cut points determined by the fluid package's hypothetical components. Values for all properties defined in the assay are calculated for each cut, and a contiguous cut is generated for light ends composition. Finally, the bulk PONA values are calculated from the original assay and added as specifications in a naphtha components cut. This data is then synthesized to generate an assay using the V4 architecture. Since this is a discrete and imperfect technique, V4 assays are not expected to be identical to their V3 counterparts, but there should be a reasonable resemblance.

The synthesis data for each assay that is migrated using this procedure is saved in the oil manager for user inspection. They are named using the original assay's name with the suffix “ Migrated”.

Synthesis Assays

All refinery assays in the oil environment defined using cut definitions from lab data or other are simply re-synthesized on load. All streams defined from these assays and with a composition vector that has not been modified will use the re-synthesized version of the assay.

Stream Source Assays With No PONA Data

All refinery assays in the oil environment originally defined by clicking the “Save Assay” button on a stream's Composition page and which do not have PONA data are left as-is on load. All streams defined from these assays and with a composition vector that has not been modified will continue to use the assay's property matrix.

Stream Source Assays With PONA Data

All refinery assays in the oil environment originally defined by clicking the “Save Assay” button on a stream’s Composition page and which contain PONA data are migrated using the outlined technique on load. All streams defined from these assays and with a composition vector that has not been modified will now be defined using the migrated synthesis assay.

Pure Component or Water Streams

Streams that have a specified composition consisting only of pure components, or with enough water that its type would be classified as Sour Water (see Stream Type page of Simulation tab in Preferences), have their assays removed and are self-synthesized from this composition.

Streams With Composition Differing From Attached Assay

All streams with composition vectors differing from their assays' are migrated on load, regardless of whether attached to a synthesis or stream source assay. Recycle streams usually fall into this category. The cut data and PONA values are based on the assay's data, but using the stream's composition, in order that the stream will resemble as closely as possible its V3 counterpart after migration. The migrated assay is exported to the oil environment using the stream's name and suffix “ Migrated”, and the stream uses this assay.

If the stream contains any water, the assay is migrated as above, but is named with the suffix “ Migrated (Dry)”. This migrated assay is not directly attached to the stream. Rather the stream uses the assay matrix but scales the composition so that the same amount of water will be present in V4 as in V3.