Experimental Study on Anti-Scaling Effect of Anti-Scaling Agent in Near-Well Zone of Deep-Water Gas Wells

Abstract During the production process of gas wells, a sudden pressure drop occurs in the near-well zone of the formation near the wellbore, resulting in the CO2 originally dissolved in the formation water precipitating out, destroying the original precipitation dissolution equilibrium in the formation water, and generating calcium carbonate scale precipitates, leading to a significant decline in gas well production. Therefore, the field usually take the anti-scaling agent squeeze injection method to inhibit the generation and deposition of calcium carbonate scale in the porous medium. This paper evaluates the anti-scaling effect of commonly used anti-scaling agents (Polyepoxysuccinic acid, Copolymer of maleic and acylic acid, Etidronic acid, Hydrolysed polymaleic anhydride) in oil and gas field production with the measured data of a deep-water gas well in the South China Sea. According to the experimental results, the static anti-scaling rate of PESA was 94.29% at 100 mg·L−1 under case well conditions. When the concentration of PESA was lower than 80 mg·L−1, the anti-scaling effect increased significantly with the increase of concentration, and when the concentration was higher than 80 mg·L−1, the change of PESA concentration did not have a significant effect on the anti-scaling effect of the anti-scaling agent. According to the experimental results of dynamic anti-scaling effect evaluation, it can be realized that the dynamic anti-scaling effect of PESA is the best, and the gas-water mixture still has a certain flow ability in the core after injecting the formation water solution containing 80 mg·L−1 PESA into the core for 6 h. The gas-water mixture has a certain flow ability in the core after injecting 80 mg·L−1 PESA into the core. Therefore, under the case well conditions, the anti-scaling effect of PESA is better than the other three selected anti-scaling agents, and it is the optimal choice for anti-scaling operation in the near-well zone.