salinity to conductivity
by cpetrone on 08/04/05 at 11:53:44

Does anyone know the conversion from salinity (ppt or PSU) to Conductivity?

Re: salinity to conductivity
by Robert Fogt on 08/05/05 at 03:44:21

I found this site here: http://www.es.flinders.edu.au/~mattom/Utilities/salinity.html

Re: salinity to conductivity
by Chris Petrone on 08/05/05 at 11:11:04

Thanks! But it does not do salinity TO conductivity.

Re: salinity to conductivity
by Robert Fogt on 08/05/05 at 14:43:43

I sent a message to the webmaster of that site asking the question. Hopefully I will have your answer soon.

I found another calculator here: http://www.es.flinders.edu.au/~mattom/Utilities/salcon.html

But it also converts only conductivity to salinity. Not the direction you were looking for.

I viewed the source of the page, and could use algebra to work out the conversion for the other way, but the formula is fairly complex so I would rather email them first and see if its already worked out.

Re: salinity to conductivity
by Chris Petrone on 08/05/05 at 15:06:54

I also emailed them (earlier) asking them for the equation, but didn't think to check the page source. Perhaps two emails in one day will lead to them posting it on the page itself!

Thanks for all your help!

Re: salinity to conductivity
by Dean Feller on 08/24/05 at 22:11:37

Chris,

First of all, are you converting a value for use with or from a wire-line well log? It sounds like you may be.

I cannot give you a specific number to use to convert, but I can guide you where to look. Service companies in the oil industry, such as Schlumberger, BakerHughes/Baker Atlas, or Halliburton, provide wire-line logging services. If you find a Well Log Interpretation Manual from one of these companies or a book on Formation Evaluation, you can find a nomograph that has a title of, "Resistivity of Sodium Chloride (NaCl) solutions as a function of temperature and salinity," or something similar to that. This plot is used to convert between salinity and resistivity (resistivity is the inverse of conductivity, or 1 divided by conductivity) for a sodium chloride (table salt or halite) solution. The conversion is also dependent upon the temperature of the solution. The conversion is different for solutions that contain other solutes.

I am looking at one such graph, now. Besides converting between resistivity and conductivity, you will also need to convert between ppt and ppm (1 ppt = 1000 ppm).

Let me give you an example of a conversion and how the nomograph is used. Let's say that you have the following:

NaCl (sodium chloride or common table salt) solution in water Temperature = 75 degrees Fahrenheit Salinity = 1 ppt (part per thousand)

First, convert the salinity from ppt to ppm: Multiply by the conversion factor: 1 ppt x 1000 ppm/1 ppt = 1000 ppm (the ppt units cancel out)

Now on to the nomograph.

Find 1000 ppm on the scale at the top and follow the diagonal line down to the left until it meets the horizontal line with the temperature of your solution, in this case, 75 degrees F. At that intersection point, follow a vertical line (or an imaginary line parallel to one of the plotted vertical lines) down to the bottom of the nomograph. The value from the scale here, at the bottom of the nomograph is the resistivity of the solution in ohm-m. For this example, the value is 5 ohm-m. Finally, take the inverse of this resistivity value by taking, 1 divided by the resistivity value, which is 5 ohm-m. This gives you a conductivity of: 1 / 5 = 0.2 mhos or 1/ohm-m [mhos or 1/ohm-m are two ways to write the unit for conductivity]

The salinity-conductivity conversion is more involved than many others, but you should be able to work your way through it with a nomograph by referring back to the example I gave above. If you do some searching, you may find an online conversion between salinity and resistivity or conductivity on the website of one of the service companies I listed above. By the way, the nomograph that I used was published by Schlumberger.

One final note: If you or your company needs help in the petroleum or mining industry realm, we at Gustavson Associates may be able to be of service.