Investigating the role of water and nanoparticles in the performance of CO2 and ethane-based cyclic solvent injection process for heavy oil recovery

Abstract

Cyclic solvent injection (CSI) process is a promising method for enhancing heavy oil recovery in thin or deep heavy oil reservoirs. Foamy oil flow is a major phenomenon of the CSI process, but the impact of foam stabilizers like nanoparticle and water on its performance has not been well understood. Therefore, an in-depth understanding of waterflooding and nanoparticle affecting CSI performance is a crucial step toward further enhancing oil recovery. In addition, most studies only focus on one method. In fact, in order to develop an oil reservoir cost-effectively and efficiently, a variety of methods have to be applied in sequence. In this study, a well-designed experimental investigation was conducted to determine the role of water and nanoparticle in CSI process. First, several foundemental live oil depletion tests were applied to investigate the feasibility of using foamy oil additives in the CSI process, determine the optimum concentration of the additives, and evaluate the best operation conditions on the performance of the CO2 based CSI process. Second, three CO2 based CSI tests were performed using a cylindrical sandpack at different injection pressure. Test 1 conducted a normal CO2 based CSI process for comparison. Test 2 applied a waterflooding process and followed by a CO2 based CSI process. Test 3 was a hybrid process consisting of the sequence: CSI-waterflooding-CSI-Nanoparticle solution flooding- CSI. Third, two ethane based CSI tests (A blank test and a similar combination test) were applied in order to verify and compare CO2 based CSI process. Experimental parameters and results were monitored and recorded. Comprehensive data analytics were performed to examine the effect of water and nanoparticle and identify enhancing mechanisms for the CSI process. Experiment results indicate that using nanoparticles as foam stabilizers in CO2 live oil pressure depletion tests can enhance oil recovery while reducing gas recovery, with higher nanoparticle concentrations resulting in even greater oil recovery. An optimal depletion rate of 6 kPa/min was identified, and the waterflooding process had a positive impact on the performance of both CO2 and ethane based CSI methods, improving mass transfer by expanding gas/oil contact areas. The nanoparticle solution flooding applied before CSI process were able to effectively stabilize foamy oil even at high water saturation levels. The integration of CSI, water flooding, and nanoparticle solution flooding yields an overall oil recovery factor of 69.5% for the combined CO2 based hybrid EOR process and 76.1% for the ethane based hybrid EOR process. Simulation results show that the dispersed gas model exhibits strong alignment between oil and gas production data and pressure distribution in CO2 based live oil pressure depletion tests. For CO2 based CSI process, by incorporating a modified foamy oil model with separate sets of relative permeability curves for injection and production stages, and employing the dispersed gas model during production stage, a robust history-matching of oil, gas, and water production data is achieved simultaneously. In the Lloydminster area, thousands of wells have a water cut exceeding 90% after the waterflooding process and are subsequently abandoned due to the absence of an effective way to continue development. This study meticulously examines potential enhancements for the CSI process, which involve utilizing foam stabilizers in combination with synergistic water flooding methods. The findings of this study provide practical solutions to address the technical challenges encountered during the subsequent development of heavy oil wells with high initial water saturation. Additionally, the study highlights the promising prospects of combination approaches in enhancing heavy oil recovery.