Development of Greener D-Metal Inorganic Crosslinkers for Polymeric Gels Used in Water Control in Oil and Gas Applications

Crosslinkable polymers, such as polyacrylamide (PAM), are widely applied for water control in oil and gas reservoirs. Organic and inorganic crosslinkers are used to formulate a gel with PAM. Although chromium has a high level of toxicity, it has been implemented as an effective crosslinker combined with carboxylates because of the controllability of crosslinking time at low temperatures. The objective of this work was to develop greener d-metal inorganic crosslinkers based on cobalt, copper, and nickel to replace chromium for application at reservoir conditions. The obtained results showed that the gelation chemistry of the developed systems depends on the metal charge density. The gelation of PAM with d-metals depends on pH and temperature for low- and high-charge density, respectively. Cobalt (II) acetate (CoAc) was effective at high temperatures (130–150 °C) and forms (4% CoAc + 9%PAM) stable, and strong gels at a pH > 7 with a storage modulus exceeding 4300 Pa. However, Nickel Acetate and Cupper Acetate formed stable weak gels at low temperatures (50–70 °C) and a pH > 6 and gel decomposition was observed upon increasing the temperature. The developed formulations were compatible with low-salinity water (1000 ppm NaCl).