Compositional Simulation on the Flow of Polymeric Solution Alternating CO₂ through Heavy Oil Reservoir

Abstract

Water-alternating-gas (WAG) method provides superior mobility control of CO2 and improves sweep efficiency. However, WAG process has some problems in highly viscous oil reservoir such as gravity overriding and poor mobility ratio. To examine the applicability of carbon dioxide to recover viscous oil from highly heterogeneous reservoirs, this study suggests polymer-alternating-gas (PAG) process. The process involves a combination of polymer flooding and CO2 injection. In this numerical model, high viscosity of oil and high heterogeneity of reservoir are the main challenges. To confirm the effectiveness of PAG process in the model, four processes (waterflooding, continuous CO2 injection, WAG process, and PAG process) are implemented and recovery factor, WOR, and GOR are compared. Simulation results show that PAG method would increase oil recovery over 45% compared with WAG process. The WAG ratio of 2 is found to be the optimum value for maximum oil recovery. The additional oil recovery of 3% through the 2 WAG ratio is achieved over the base case of 1: 1 PAG ratio and 180 days cycle period.

Comparative numerical study for polymer alternating gas (PAG) flooding in high permeability condition

“…The results showed good mobility ratio and the PAG process represented the highest oil recovery factor of 37%. However, the result showed high improvement compare to the previous work in North Burbank Unit, which might be due to the porosity and permeability characteristic of the synthetic model [17].…”

“…However, the study was limited in demonstrating the influence of each scenario on gas production, water production and residual oil saturation. Another simulation study done by Jeong et al (2014) in heterogeneous model considered four scenario, water flooding, CO 2 flooding, WAG and PAG. The results showed good mobility ratio and the PAG process represented the highest oil recovery factor of 37%.…”

Chemical enhanced oil recovery and the role of chemical product design

“…Therefore, Surfactant (SAG) and Polymer Alternating Gas (PAG) combine the characteristics recently mentioned with the properties of surfactants and polymers, respectively [437]. This is the reason why these processes are also called chemically enhanced Water Alternating Gas methods [363,[438][439][440][441][442][443][444][445][446][447][448][449]. However, these are just recent developments, so it is considered that further research must be carried out in the laboratory as well as in field pilot tests to validate the results obtained so far.…”

Direct Investigation of Oil Recovery Mechanism by Polymer-Alternating-Gas CO2 through Micromodel Experiments

“…The results suggested the oil recovery from PAG is 7 to 15% higher than that from WAG when the permeability is higher than 500 mD in a homogeneous reservoir, and the PAG could increase oil recovery from WAG in both miscible and immiscible flooding in heterogeneous reservoirs. The PAG study was examined in a highly heterogeneous reservoir with heavy oil (viscosity = 94 cP), and PAG gave an incremental RF of 11% from WAG because the improved mobility control by polymer can reduce viscous fingering effects and form a stable flood front . The sensitivity analysis of PAG was performed by varying well locations, a number of injection cycles, CO 2 /polymer injection rate and time, and polymer concentration …”

“…The PAG study was examined in a highly heterogeneous reservoir with heavy oil (viscosity = 94 cP), and PAG gave an incremental RF of 11% from WAG because the improved mobility control by polymer can reduce viscous fingering effects and form a stable flood front. 15 The sensitivity analysis of PAG was performed by varying well locations, a number of injection cycles, CO 2 / polymer injection rate and time, and polymer concentration. 16 For the pore-scale investigation, oil recovery mechanisms and displacement processes by miscible and immiscible CO 2 flooding were studied in homogeneous and heterogeneous systems by using a 2D micromodel and the profound displacement mechanism was viscous fingering up to gas breakthrough.…”