Fingerprinting formation-waters using standard hydrochemistry and "water catalogs" has been in use for years. However these "conventional techniques" have 3 inherent shortfalls:

1. What if there is no "catalog" formation water analysis available?
2. What if the drilling fluid is relatively "fresh water" and the true formation-water is similarly "fresh"?
3. What if the drilling fluid is artificially "saline" and the true formation-water is a saturated brine?

Major ion chemistries are also non-diagnostic due to the following reasons:

1. Major ions comprise salts dissolved in water. In contrast, stable isotope analysis provides information on the composition of the water molecules rendering stable isotope analysis much more informative as of the ultimate origin and/or history of formation waters.
2. Most major ions exhibit non-conservative behavior, i.e., the amount and distribution of these is governed by common dissolution/re-precipitation reactions and water-rock interaction. As a result, major ion compositions of formation waters are often non-unique and thus non diagnostic as of water?fs ultimate origin or formation of residence.
3. The current analytical techniques available to the resource companies provide unacceptably large analytical errors (?}5 to 20%). In contrast, the analytical errors of stable isotope analysis are about one order of magnitude smaller (e.g., 1ƒÐ ?} 0.1 to 2 parts per billion). The development and use of the NAA technique for analysis of dissolved ions by Isobrine and the University of Alberta has also resulted in significantly smaller analytical errors for both major ions (e.g., Cl) and minor conservative tracers (e.g., Br, I) than those provided by mainstream laboratories.

Isotopic fingerprinting (and other trace-element techniques) can work in these situations to identify true formation-waters when other techniques can not.

 


Fingerprinting Formation-Waters using Stable Isotopes

Regional Variations in Oxygen Isotopic Compositions in the Yeoman
and Duperow Aquifers