Polyelectrolyte-Complex Nanoparticles for Fluid-Loss Control in Oilwell Cementing

This paper focuses on the application of polyelectrolyte-complex (PEC) nanoparticles to fluid-loss control of oilwell cements. Cement-slurry design involves considerable complexities, including the interplay of viscosity, yield point (YP), fluid-loss control, setting time, sedimentation, gel-strength development, and density. Polymers such as hydroxyethyl cellulose (HEC), carboxymethyl HEC (CMHEC), and polyvinyl alcohol have been used extensively for fluid-loss control in oilwell cementing. However, the resulting increase in slurry viscosity often led to unwanted side effects, such as increased pumping requirements. PECs were originally developed as drug carriers for pharmaceutical applications. Our previous work (Cordova et al. 2008; Lin et al. 2014; Johnson et al. 2016) showed that they can also be effective in improved-oil-recovery applications. In this study, we explore the potential of using PEC nanoparticles to achieve effective fluid-loss control while maintaining good fluid properties of the cement slurry. Results from this proof-of-concept study demonstrated that a PEC system comprising common oilfield polymers can be used to achieve effective fluid-loss control. Simultaneously, the system shows improved rheological properties over control samples while maintaining other desirable slurry characteristics.