Preparation and characterization of polymer retarder for plugging cement slurry

Abstract

The cement slurry is an important lost circulation material. However, as oil and gas exploration continues toward deeper stratum, the majority of conventional cement retarders are insufficient at these depths. This research identified a synthetic high-temperature copolymer retarder as a potential replacement product, containing sodium styrene sulfonate (SSS)/itaconic acid (IA)/N-vinylcaprolactam (NVCL). By analyzing the effects of monomer mass ratios, initiator concentration, reaction temperature, and pH value of the solution on the thickening time, the ideal reaction conditions of the copolymer retarder were confirmed to be the mass ratio of monomers SSS/IA/NVCL (SNI) = 13/4/1, initiator concentration = 1.0 wt%, reaction temperature = 55 °C, and pH value = 4. Nuclear magnetic resonance proton spectroscopy (1HNMR), thermal gravimetric analysis (TGA) and Fourier transform infrared (FTIR) were used to characterize the resulting copolymer, and its morphology was studied. The results demonstrate that SNI possesses excellent thermal resistance and that the microstructure is conducive to producing good retarding properties under high temperature (150 °C). SNI has temperature-sensitive associative characteristics, making the cement achieve good sedimentation stability due to the high-temperature retarder. SNI-based slurry has excellent overall performance, is simple to control and regulate, and can meet leakage-stopping requirements.