AssayUpdate in depth

Although the AssaySynthesis and AssayUpdate modules are similar inasmuch as they produce crude descriptions from limited measurement data, the two tools are nevertheless fine-tuned to offer the most statistically reliable answers in two very different situations.

AssaySynthesis is a no prior information tool in that it generates a crude description using the data entered in the measurement grid, relying on the model to determine the nature of the crude, and to synthesise property values and profiles. On the other hand, AssayUpdate is a prior information tool in that the Base Crude is used as a basis on which to make changes to reflect the new information entered into the measurement grid. To help you choose between whether to use the AssayUpdate or AssaySynthesis modules, the following guide

should prove useful:

• If the crude name is totally unknown, there is no choice – you cannot enter a Base Crude, and so the AssaySynthesis module must be used. Do not try to guess a Base Crude for use with the AssayUpdate module (just as you would not try to guess measurement data) - the AssaySynthesis module will perform as precise a generation as it can, and adding artificial data will only reduce the reliability of the generation.

• If the number of measurements is large (say, more than a couple of measurements for each of the major properties), specifying a Base Crude may adversely bias the generation in favour of the Base Crude at the expense of the known measured values. In this case, it is often best to choose AssaySynthesis. If there are a small number of measurements and the crude name is known (crude measurement data will almost always be available with a crude name), the choice will depend upon whether a similar crude is available in the database:

• If there is a similar crude in the Database, and the new measurement values are broadly similar to the base crude values, then use the database crude as a base crude. The AssayUpdate module will holistically amend all the property information to reflect the new measurements.

• If there is a similarly named crude in the Database, yet the new measurement values are not similar to the base crude values, choose AssaySynthesis. AssayUpdate is tuned to be best for small changes and will produce poor results for measurement data widely divergent from the base crude.

• If there is no similarly named or equivalent crude in the Database, then choose AssaySynthesis, since there is no clear choice on which to base the crude generation.