Abnormal gelation phenomenon of Class G oil well cement incorporating polycarboxylic additives and its countermeasures

摘要

Cementing security is endangered by the abnormal gelation phenomenon of cement slurry incorporating polycarboxylic additives occurred around 120 degrees C. The differences between gelatinous and non-gelatinous sections were investigated through various techniques. The polymer structural change around 120 degrees C could explain the abnormal gelation phenomenon by viscosity-temperature characterization. The other reasons are the polycarboxylic additives combine with Ca2+, SiO42- and aluminate hydrate by cross linking reaction. The cross-linking structure developed flocs which was embedded in calcium silicate hydrate (C-S-H) gel and intertwined around stirring shaft. The practicable methods were proposed to relieve or solve the abnormal phenomenon of cement slurry. (C) 2017 Elsevier Ltd. All rights reserved.