Mechanism Study Of Oil-well Cement Aberrant Gelation Made By Polycarboxylic Admixtures

Polycarboxylic admixtres has many advantages,such as good property, stable quality andso on, which is the hotspot in the admixtres of oil-well cement. But aberrant gelation ofcement paste was formed occasionally. It showed that the gelation of cement paste twinesaround the axis of impeller blade,and there was a obvious layering between gelation and outeroil-cement. It is extremely dangerous that using such oil-cenemt for well completion.In order to find the reason that gelation of cement paste was formed occasionally, whenadjusting cement properties with polycarboxylic admixtures. Cement sample of aberrantgelation was synthesized by oil-well cement and polycarboxylic water reducer (PCM) orpolycarboxylic retarder (DHTR), respectively. The section of gelation and no gelation werestudied by Fourier transform infrared spectrometer, X-ray Fluorescence Spectrometer,scanning electron microscopy and energy dispersive spectrometer. Based on the testing data,judge reaction process and the changed in structure or composition. Finally, the result isverified through experiments. The results show that the polycarboxylate molecule react withcalcium ion, aluminium ion and cross-linking occurs, which cause aberrant gelation ofcement paste. The mass fraction of Silicon and aluminium growth in the cement wouldincrease the degree of aberrant gelation. Research results, to prevent cement paste fromshowing a jelly, pumping was difficult, have real significance.On the basis of the reason of aberrant gelation, controlling the quality fraction ofaluminium element by using combining or precipitating. The other is combining the cation ofoil-well cement by high polymer surface active agent. The results show that aberrant gelationis solved.