Geochemical Sampling and Analysis of Geothermal Fluids in Sedimentary Basins

Summary

Techniques are described for the recovery of formation waters from deep sedimentary aquifers which enable the maximum information to be obtained from individual boreholes drilled for geothermal exploration. The scale of contamination involved in two recovery methods is illustrated and it is suggested that most reliable samples are obtained by centrifugation of interstitial water from core material. Methods used in the analysis of small volumes are listed and the need for modification of methods usually used for dilute solutions is stressed, and their limitations illustrated. A method designed to determine the ⁴He content of interstitial water from recovered cores, the problems of oxygen and hydrogen stable isotope analysis of brines, are discussed. Results from exploration boreholes in the U.K. are used as illustrations.