Modeling the thermal behavior of coal fly ash based polymer gel system for water reduction in oil and gas wells

Effective methods of reducing excessive water from oil and gas wells are of immense significance in mature oil fields. Thermal instability of many polymer gel systems at elevated temperatures (above 80 °C) calls for the incorporation of suitable macro/nanoparticles into the gelling solutions to achieve enhanced thermal stability. The present work develops for the first time, a support vector regression (SVR)-based model for estimating the effect of coal fly ash (CFA) as reinforcing inorganic additive in polyacrylamide (PAM) gelling solutions crosslinked by polyethyleneimine (PEI). Effect of various CFA addition on the thermal stability of PAM/PEI gels at different temperatures shows a parabolic trend. This observation indicates that various temperatures have significant impact on the PAM/PEI-CFA gel resistance to thermal degradation. Besides, weight losses experienced by these polymer gels are attributed to the escape of water molecules attached to the PAM and PEI and also due to the thermal decomposition of amide and carboxylate side groups on PEI and PAM. The results of the developed model conform to the experimental outcomes with correlation coefficient of 0.9381 and root mean square error of 14.15% measured on the testing set of data. Impregnation of CFA in the matrix of PAM/PEI gel structural network led to an improved resistance to thermal decomposition. Additionally, effects of PAM and PEI concentrations on the thermal stability of the PAM/PEI-CFA composite gels containing various CFA quantities at elevated temperatures using the developed model agree well with the experimental results.