The physical properties of petroleum fluids are very significant factors impacting the economic and operational success of upstream E&P projects. Many subsurface hydrocarbon systems are adequately described by assuming one (dry gas ) or two (crude oil, natural gas) hydrocarbon components, and correlating their physical fluid properties based upon the subsurface temperatures and pressures encountered. However, when abnormal compositions (e.g., when injecting CO2) or conditions (e.g., being near the "critical" pressure and temperature) are encountered, these simple correlations fail.

The EOS models used in upstream E&P describe the hydrocarbon fluid system as a series of fluid components, and the equation of state model predicts how these components interact and combine to yield vapor and liquid phases as pressure, temperature and relative component abundance change. At the heart of an EOS model is an equation that defines a set of parameters for each fluid component in the fluid system. Some of these parameters are constants while others are "adjusted" to "tune" the EOS model to produce the desired results. Many of these "tunable" parameters can be modified for each component, while standard values are published for most of the pure components of interest to upstream E&P.

The most correct strategy for using an equation of state model would be to analyze the fluid system of interest, to input all of the fluid components found and simulate the fluid properties using the standard values of those components. In reservoir simulation applications, however, the cost of each simulation run is very sensitive to the number of components in the EOS model. Therefore, the best practice is to combine several pure components into "pseudo" components so that the fluid system is simulated at a lower cost. Specialized applications are used to "match" the desired fluid behavior by "tuning" the parameters of both the pure and pseudo-components.

This XML specification is intended to describe these EOS fluid component parameters.

Possible content that is currently "out of scope" includes the (measured or generated) fluid phase properties that were "matched" by the EOS parameter set as well as metrics that describe the "goodness of fit."

One requirement that has been accepted by this project us the need to be able to fully populate a data set in memory using only commonly available XML technologies. This means that a properly constructed XML file using this specification can be parsed (into a DOM tree) so that all required information is present without having to resort to additional operations.

This effort is not intended to produce a final specification but rather a proposal for an XML specification. Once the initial effort produces its deliverables, POSC will more actively take up the standardization process in which greater industry exposure and feedback are sought.

This project is designed to deliver:

• A proposed XML specification, additional supporting technologies and supporting documentation. The supporting technologies would include the necessary components to implement the basic deliverables defined by the project participants.
• To test this proposed specification for use in middleware and end-user applications.

• a draft XML specification (DTD at this time) that can be proposed to POSC for standardization
• the documentation for the draft XML specification
• a sample XML data file covering all data items

It is our goal to determine if sufficient interest for this project exists within industry. Once interest has been verified, a project budget and schedule will be distributed to interested parties prior to an open meeting to formally establish this project.

If you are interested in participating, or would like further information, contact Gary Masters by email (masters@posc.org) or by phone (+1.713.267.5111).