CO2-Based Plastics for Downhole Water Shutoff and Alternative Sequestration Integrated Process

Abstract CO2-based plastic material uses CO2 as feedstock instead of crude oil for plastic manufacturing to reduce the CO2 footprint. This work introduces CO2-based plastics into upstream operations for both downhole water shutoff and CO2 alternative sequestration purposes in fractured reservoirs. The performance was identified and optimized by investigating the blocking and packing behaviors of CO2-based plastic particles in different fractures. A total of six CO2-based plastic samples, in which CO2 contents ranged from 15% to 40%, were evaluated and compared. All the samples were grinded into similar particle sizes 40-80 mesh. The blocking ability was tested by injecting brine into a CO2-based plastic-packed open fracture. The packing behavior was quantified by injecting a CO2-based plastic suspension into a contraction fracture. The pressure buildup during flow was monitored in both processes. The CO2-based plastics performed quite differently from the commonly used water-swelling polymer gels in fractures due to the non or slightly deformable nature of the plastics. In the blocking test, stable differential pressures linear with flow rates were observed when water flowed through the plastic pack in the open fracture, while the pressure responses to flow rates were usually non-linear for the polymer gel pack. Two CO2-based plastic samples, T2 and T9, produced much higher pressure to water flow than the other four samples at 95℃. Samples with low glass transition temperature partially melted at 95℃ and showed very weak blocking. In the packing tests, CO2-based plastic suspensions demonstrated weaker deformation and passing abilities in the contraction fracture than polymer gel, resulting in higher packing pressures. T2 and T9 suspensions showed much quicker packing and pressure buildup than other samples. The blocking capability of the in-situ formed pack to the following water flow was similar for the two samples at a fixed packing pressure. At a high temperature of 95℃, the packing was delayed with a weak blockage to the subsequent water flow. Increasing particle size was an effective way to solve this problem. This work developed a water shutoff method integrated with CO2 alternative sequestration by using CO2-based plastics. Some insights were provided on the performance of materials with different deformation abilities in fractures.