VisCalc Module 1
Friction Theory Characterization Module
This is the basic first step module for the characterization of oils, it consists of a tool that reads from a template all the relevant fluid information that can be located within a pvT report typically elaborated by commercial laboratories. The template may be an Excel® file or any other readable format our customers may require. The module processes the information and generates the appropriate EoS and Friction Theory model parameters that best characterize the fluid. The characterization module performs the following tasks:
- Mass distribution characterization.
- EoS pvT tuning and/or prediction.
- Friction Theory pηT tuning and/or prediction.
- Generation of reports and parameters text files.
This sub-module resolves the optimal distribution function for the fluid. In case chromatographic information is given, it will find the distribution function that best represents the laboratory information with a high degree of accuracy. When only limited or compromised information is available, even down to only the C7+ fraction, this sub-module will provide a predicted distribution function using other available information. This is one powerful tool in our approach, as all our internal calculations are carried out on a continuous space and are not subject to a specific discretization. That is, at the end of the characterization procedure the user will be able to choose how many pseudo-components should be generated for a specific application (from 3 to 99 pseudo-components) and produce the appropriate table of parameters or properties for exporting to other applications. Figure 1 shows a typical characterization result for a fluid’s heavy fraction.
Figure 1. Example of a fluid’s heavy fraction mass characterization.
1.2 EoS pvT tuning and/or prediction
This sub-module determines the optimal EoS parameters, the original Peng and Robinson equation of state (PR EoS) is used as the default version, other EoS can be incorporated upon request – we can even generate additional appropriate models for any other rational EoS that our customers may further require. This sub-module is capable of characterizing both live as well as stabilized fluids. In the case of live fluids it uses available phase envelope information (saturation pressure). In case of stabilized fluids it uses high-pressure density information (compressibility properties). In all cases it may use atmospheric-density information under a given range of temperatures. If no information is given, it will make a prediction with such minimum information as the API density. Some examples of results are shown in Figures 2 and 3.
Figure 2. Example of a mass characterized phase envelope.
Figure 3. Example of a pρT results for a stabilized heavy fluid, tuned and predicted.
1.3 Friction Theory pηT tuning and/or prediction
This sub-module determines the optimal parameters for the most recent version of the Friction Theory, the tuned friction model is capable of accurately describing the viscosity performance of reservoir oils over wide ranges of temperature and pressure. The mathematical parametric formulation that is currently used consists of an improved proprietary and unpublished version. Currently some viscosity information, at least one point, is required for tuning the model – other parameters may be predicted. The aim of our current research is to develop a fully predictive viscosity model based on alternative information such as characterization parameters related to the fluid’s chemical structure. The current model successfully works for a full range of temperature and high-pressure conditions that cover from typical reservoir (including deep water) to ambient conditions. Figure 4 shows some characterization results for a stabilized fluid over a representative range of temperature and pressure that results on a viscosity span over orders of magnitude.
Figure 4. Example of a phT modeling results for a stabilized fluid.
1.4 Generation of parameters text files
The final step of the Characterization Module is the generation of well-defined text files containing the specific fluid model characterization parameters. These files can be further read by other applications, such as the in-house simulators, and are also used in the blending module. The text files can also be used to generate reports at any point, including tables of properties for exporting purposes, as it may be required.
 Peng, D.-Y.; Robinson, D. B., A New Two-Constant Equation of State. Ind. Eng. Chem. Fundam. 1976, 15 (1), 59-64.
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