DownHole SAT: Old Standards and Sophisticated Indices

We all have favorite, or at least familiar indices which assist in the assessment of the scale potential of a water, and which provide some insight into the impact of concentrating or heating a water, or of mixing waters in various ratios. The common indices provide an excellent starting point for evaluating a water chemistry and scale potential.

Prior to the advent of cost effective personal computers, sophisticated indices were beyond the reach of most water chemists. The indices and calculation methods practical for manual use are simplifications which include assumptions that can cause misleading interpretations, and limit the applicability of the indices to a single water, or similar waters.

Though helpful, the indices and calculation methods practical for manual use are simplifications which include assumptions that can cause misleading interpretations, and limit the applicability of the indices to a single water, or similar waters.

The old standards provide insight into scale potential for single scales. They are limited to simple estimation methods, and do not take into account phenomena such as "Common Ion Effects." Sophisticated indices such as ion association model saturation levels account for these effects and can be calculated for most foulants.

Ion association model indices also provide a more realistic view of scale potential than the old standbys. They base their calculations upon free ion concentrations rather than the total analytical values used for most indices.

In natural waters, calcium (for example) is not typically found as 100% free calcium. A portion of the calcium may be bound to sulfate, another portion of the total may be tied up by bicarbonate, hydroxide or other species with which it associates. Ions in water are typically associated with other ions. Indices calculated based upon total ion present (e.g. total analytical calcium) can be misleading.

In high TDS waters, they can grossly over estimate the driving force for scale formation and growth. The ion association model indices overcome this shortcoming by estimating the concentration of free ions, and calculating indices using the free concentration rather than the total. Ion association model indices improve the realism, and the accuracy, of scale prediction in this manner.

The DownHole Series uses an ion association model to extend the applicable ionic strength for calculations, and to provide consistent, reproducible indices for common, and not so common, scale forming species.

Ion Association Model Saturation Levels and Momentary Excess Values Calculated by DownHole SAT

Acknowledgments
Acumer is a trademark of the Rohm & Haas Company
Aquatreat is a trademark of the ALCO Chemical Division of National Starch
Bayhibit is a trademark of Bayer
Belclene, Belcor, Belsol, and Belsperse are trademarks of FMC
Dequest is a trademark of Monsanto Chemical Company
Goodrite is a trademark of the BFGoodrich Company
Versa is a trademark of the National Starch and Chemical Company
DownHole SAT and DownHole R_x are trademarks of French Creek Software

Tables Include

Graphs Include

DownHole SAT (Version 6) Pricing

Premium Editions 

DownHole R_x Engineer's Edition

The Engineer's Edition performs all of the functions and has all of the features of the basic DownHole SAT program. It adds the ability to select a water treatment product and obtain dosage recommendations. Each table has an additional line for Dosage or Predicted Corrosion Rate in the R_x series, of which the Salesman Edition is the first. An additional graph selection appears for all two (2D) and three (3D) dimensional graphs - the Dosage Profile.

The Engineer's edition can load a Product File (.PRD) for use in determining treatment rates and developing dosage profiles. But, alas, the Engineer's Edition lacks the ability to edit or create Product Files, or even look at the ingredients. They must be created (and edited) using a higher member of the DownHole R_x Series. Both the Formulator and Laboratory Editions can create and edit Product Files.

DownHole R_x Formulator Edition

The Formulator Edition adds the ability to create and edit product files. Creating a Product File is as simple as filling in a computerized formula (batch) sheet. Product Files can be password protected to maintain confidentiality. Files so created can be used by the Formulator Edition or copied to the \DHSAT\INHIB sub-directory on other computers with DownHole R_x programs.

Formulator Editions are used extensively by water treatment companies who wish to use the inhibitor models supplied by French Creek, by Corporate Chemists who wish to evaluate and compare the treatment programs proposed for wells, and by consultants for performing in-depth technical and economic analyses of aqueous systems.

DownHole R_x Laboratory Edition

The Laboratory Edition adds the ability to develop scale inhibitor, corrosion inhibitor, and corrosion rate predictive models from laboratory data, field data, or a combination of both. Dosages (or Rates) can be modeled as a function of any parameters input into the program in their raw form, calculated indices, and other parameters calculated by the program.

Transforms are available and can be applied independently to each variable. For example, a CaCO₃ inhibitor might be modeled:

• log(DOSAGE) = f( log(Calcite Saturation - 1), 1./RT, log(time))

This is, in fact, a common model for phosphonate inhibitors.

A simple corrosion rate model might be correlated as follows:

• log(Rate) = f( log(Ca), 1./RT, log(Cl), log(SO₄ ), pH)

Inhibitor models developed by the Laboratory Edition are output to the .INH files used to develop Product Files. Raw data is stored in .COR files. Statistics are, of course, provided on each variable as you develop a model.

Laboratory Editions are used extensively by scale inhibitor synthesizers, and by major water treatment companies and industrial laboratories doing inhibitor and/or corrosion research.

The Laboratory Edition is used by major inhibitor suppliers, and by top industry consultants.