Synthesis and performance evaluation of a novel biodegradable dispersant for offshore cementing

We developed a novel biodegradable oil-well dispersant, gelatin grafted acetone formaldehyde sulphonates (GAFS). This dispersant was prepared based on the chemical modification of naturally biodegradable products: gelatin. GAFS was synthesized through aldehyde ketone addition, hydroxyl condensation and Mannich amine methylation reaction. Functional groups and molecular structure of GAFS were characterized by FTIR (Fourier Transform Infrared Spectroscopy) and NMR (Nuclear Magnetic Resonance). Lab tests were conducted to determine the biodegradation rate, rheological properties, thickening time, compressive strength and dispersing property of GAFS in Class-G cement slurry. It is found that GAFS exhibits no retarding by-effect on oil well cement and can be considered biodegradable based on the biodegradation test results. The measured adsorption capacity and zeta potential of GAFS in Class-G well cement slurry show that: GAFS can be adsorbed greatly onto the surface of cement particles, resulting in strong electrostatic repulsion between cement particles and consequently generating an excellent dispersion performance.