Using Polymer Alternating Gas to Maximize CO₂ Flooding Performance

Abstract

Carbon dioxide (CO 2 ) has been used commercially to recover oil from reservoirs by enhanced oil recovery (EOR) technologies for over 40 years. Currently, CO 2 flooding is the second most applied EOR processes in the world behind steamflooding. Water alternating gas (WAG) injection has been a popular method to control mobility and improve volumetric sweep efficiency for CO 2 flooding. The average improved recovery is about 9.7%, with a range of 6 to 20% for miscible WAG injection. Despite all the success of WAG injection, sweep efficiency during CO 2 flooding is typically a challenge to reach higher oil recovery and better apply the technology.This paper proposes a new combination method called polymer alternating gas (PAG) to improve the volumetric sweep efficiency of the WAG process. The feature of this new method is that polymers are added to water during the WAG process to improve mobility ratio. In the PAG process, polymer flooding and immiscible/miscible CO 2 injection are combined.To analyze the feasibility of PAG, models considering both miscible and polymer flooding processes are built to study the performance of PAG. In this paper, the sensitivity of polymer adsorption and concentration are studied. The feasibility of PAG in reservoirs with different permeabilities, different Dykstra-Parsons permeability variation coefficients (VDPs), and different fluids are also studied. A reservoir model from a typical section of the North Burbank Unit (NBU) is used to compare the performance between PAG, WAG, and polymer flooding. This study demonstrates that PAG can significantly improve recovery for immiscible/miscible flooding in homogeneous or heterogeneous reservoirs.

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.…”

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

“…Polymer was proposed to overcome the problems of gas breakthroughs and gravity segregation by using polymers. Polymer alternating gas (PAG), combines the elements of CO 2 flooding with polymer flooding to enhance the sweep efficiency especially in high permeable zones [12][13][14] Polymer gas alternating water (PGAW) has been experimented on Canadian heavy crude oil and the results were promising [15]. The study compared, four techniques of flooding, CO 2 immiscible flooding, WAG, polymer and PAG.…”

“…They used three different polymer concentration of 0.1 Ib/STB, 0.2 Ib/STB and 0.3 Ib/STB. The highest oil recovery factor (RF) for PAG was about 19.7%, the recovery improved up to 12% compared to WAG, however this result was obtained at polymer concentration of 0.2 Ib/STB [12]. In the second case study, they compared the effect of several flooding scenarios including CO 2 injection, WAG, polymer flooding and PAG.…”

New Method Based on CO2-Switchable Wormlike Micelles for Controlling CO2 Breakthrough in a Tight Fractured Oil Reservoir

“…Plugging gas channeling is a major preventive method to control CO 2 breakthrough. It has been widely demonstrated that methods based on gel, − foam, , and water-alternating gas , can effectively inhibit CO 2 breakthrough. However, these conventional methods are limited in tight fractured oil reservoirs because of difficult injection, poor stability, and low strength, resulting in failure to effectively improve the swept volume of CO 2 .…”