Sorption capacity and swelling behavior
The Cation Exchange Capacity (CEC) is an accurate indicator of the sorption capacity and swelling behavior of a rock sample. It has been shown to relate to several mechanical properties and is a good index property to assess formation damage potential. In addition, CEC is an essential parameter in the evaluation of log data, because cation exchange sites contribute substantially to the electrical properties of a formation.
Our analysis protocol is based on the exchange of the sample with a complex of Cu-triethylenetetramine (“Cu-trien”) or with Co-hexamine trichloride ("Co-Hex") and the subsequent spectrophotometric analysis of the exchanged liquid (see Meier & Kahr, 1999 and Stanjek & Künkel, 2016). To avoid influences of changing pH due to sample specific properties, all measurements are pH-corrected.
Figure. Relation between CEC and the total Smectite content in a series of 20 clay samples.