Enhancing Performance of Co2-Based CSI Process by Water Flooding and/or Nanoparticle Solution Flooding

Foamy oil flow is a pivotal aspect of the cyclic solvent injection (CSI) process, yet the influence of water and foam stabilizers, such as nanoparticles, on its efficacy remains insufficiently elucidated. Consequently, a profound comprehension of how waterflooding and nanoparticles impact CSI performance is imperative for advancing oil recovery strategies. This study conducted a meticulously designed experimental investigation to investigate the roles of water and nanoparticles in a CO2-based CSI process. Three distinct tests were executed utilizing a cylindrical sandpack at varying injection pressures. Test 1 entailed a standard CO2-based CSI process for baseline comparison. Test 2 involved a waterflooding process with an injection volume of 1.5 PV, succeeded by a CO2-based CSI process. Test 3 featured a hybrid process comprising the sequence: CSI-waterflooding-CSI-Nanoparticle solution flooding-CSI. Key parameters including injection rate, injection volume, sandpack pressure, production rate, cumulative production, and water cut were meticulously monitored and recorded. Thorough data analytics were then employed to scrutinize the impact of water and nanoparticles, identifying mechanisms for enhancing the CSI process. Laboratory results revealed that the total oil recovery in Test 2 CSI process exceeded that of Test 1 by 7.9%, underscoring the increased efficiency of Test 2. This efficiency was attributed to a 33.2% lower oil saturation after the waterflooding process in Test 2 compared to Test 1. The positive impact of waterflooding on CO2-based CSI processes extended to Test 3, where the oil recovery factor of the CSI phase following waterflooding increased by 7.1% compared to the pre-waterflooding CSI phase. After nanoparticle solution flooding, the subsequent CSI phase yielded an additional 5.9% original oil in place (OOIP), demonstrating the nanoparticles' capacity to enhance foam stability even after multiple second oil recovery (SOR)/ enhanced oil recovery (EOR) processes. As the combined process progressed, the instantaneous gas-oil-ratio increased, facilitated by expanded space for CO2 injection amid heavy oil production. The amalgamated process achieved an impressive total oil recovery factor of 69.5%, more than doubling that of the CSI process in isolation.