Identification of the Critical Coagulation Concentration of Sodium Bentonite Mixes Used in the Oil and Gas Industry

Sodium bentonite mixes commercially used in oil and gas well operations and plugging were evaluated to identify the critical coagulation concentration (CCC) of electrolyte salts that may be present in the wellbore environment or the well cement. Concentrations of the sodium bentonite mixes from 4% to 10% were prepared, mixed with small amounts of CaCl2 (from 2 g to 18 g) and NaCl (in amounts from 8 g to 90 g) and the degree of dispersion was recorded over time as agglomeration and eventually sedimentation occurred in the samples. The CCC of the electrolyte salts of each sodium bentonite mix concentration was identified. Relatively low levels of CaCl2, at levels commonly found in public water sources, were identified as the CCC where significant flocculation occurs, highlighting the importance to provide guidance on mix water testing.