Abstract
Polymer gels are potential plug agents to solve near wellbore issues. To meet the requirements of harsh reservoir conditions, enhancing the thermal stability and strength of polymer gels is still a challenging problem. In this study, we discuss the properties of phenolic/aldehyde-based polymer gels, aiming to provide suggestions of gel formulations for temporary blocking in SAGD wells. A power law relation, with an exponent of 1.2, was found between the modulus of HP AM gels and the polymer concentrations. It is also found that the strength of gels was increased with the hydrolysis degree and molecular weight of HP AM. Acetic acid and silica nanoparticles were proved to be effective additives to enhance the thermal stability of gels. It is demonstrated that acetic acid catalyzes the decomposing of hexamethylenetetramine (HMT) at low temperatures, while protects the dihy-droxybenzene (DBH) from oxidation at higher temperatures. Experiments results showed that the HPAM gels could be stable for more than 7 days at 175 °C, while the co-polymer with heat resistance groups improved the applied temperature to 200 °C. Rupture pressure measurements showed that the polymer gels exhibit great blocking efficiency in sandpacks. However, the rupture pressure in wellbore is relatively lower as a result of squeeze out, rather than the destruction of gel structure. Finally, filed applications in 4 vertical wells and 1 horizontal well were introduced in detail. It is demonstrated that the gel plugs are applicable in a wide range of wellbore temperatures, from 60 °C to 191 °C.
NSTL