Oil Recovery Performance and CO₂ Storage Potential of CO₂ Water-Alternating-Gas Injection after Continuous CO₂ Injection in a Multilayer Formation

Abstract

In this study, oil recovery performance and carbon dioxide (CO 2 ) storage potential of a CO 2 water-alternating-gas (CO 2 -WAG) injection after continuous CO 2 injection process for multilayer formation were experimentally determined under immiscible and miscible conditions. First, a slim-tube apparatus was used to measure the minimum miscibility pressure (MMP) of a CO 2 −crude oil system (MMP = 22.79 MPa), which was applied as a guide for follow-on investigations. Afterward, the CO 2 -WAG injection after the continuous CO 2 injection for a triple-layer system, horizontally placed and parallel-connected, was conducted to evaluate the capacity of enhanced oil recovery and CO 2 storage potential of the multilayer formation at different operating pressures and a reservoir temperature of 98 °C. Results revealed that the oil recovery of the entire system was determined by the recovery of a layer with the highest permeability, which was more than 90% of the entire system recovery provided by the highest permeability layer in the continuous CO 2 injection. The ensuing CO 2 -WAG injection could further enhance the oil recovery of the system after the continuous CO 2 injection. The contribution of the recovery produced by the highest permeability from 90 to 98.3% could also be reduced for the entire system recovery. The oil recovery factor of the multilayer system increased as the operating pressure increased (i.e., from 33.01% of the system at P op = 15 MPa to 39.42% of the system at P op = 25 MPa). From a view of CO 2 storage potential, the ensuing CO 2 -WAG injection at immiscible and miscible conditions could also double the amount of stored CO 2 after the continuous CO 2 injection for the multilayer system. More than 75−80% of stored CO 2 for the multilayer system was contributed by the highest permeability layer at the end of the CO 2 -WAG the CO 2 -WAG injection after the continuous CO 2 injection process under immiscible and miscible conditions. Therefore, for a multilayer formation, such as the Jilin oilfield, the layer with medium and low permeability should be further developed after CO 2 -WAG injection.

An experimental investigation to consider thermal methods efficiency on oil recovery enhancement

“…To foster a deeper understanding of potentially devastating effects of CO 2 –EOR activities on the ecological systems, regarding the possible concerns of CO 2 injection entail the formation of CO 2 which might enhance the magnitude of permeability especially along faults that allows movement of unwanted fluid and the buoyant nature of CO 2 , which has the capability to rescue from the improperly sealed wells or those wells that are susceptible to CO 2 erosion. In this comprehensive study, the emitted CO 2 could enormously influence local ecosystems based on the magnitude and continuity and it beneficially improves the oil recovery factor due to its high feasibility rather than other methodologies of injection 40‐42 …”

Experimental Investigation on the Effects of CO2 Displacement Methods on Petrophysical Property Changes of Ultra-Low Permeability Sandstone Reservoirs Near Injection Wells

“…Compared with previous experiments, the cores used in the experiments of this paper have lower initial permeability, and the decrease of permeability is more obvious after the flooding still with little change in porosity, which is consistent with the characteristics of fines migration in the core. The migration of fines detached from the core does not cause a significant reduction in the total pore volume, but the fines accumulate at the pore throat and formed blockages, which significantly reduce the fluidity of fluids in the flow channels inside the rocks [7]. Although the dissolution of minerals and fines release can lead to an increase in pore volume during the flooding process, which increases the rock permeability to a certain extent, the experimental results indicate that under the experimental conditions in this paper, especially in the ultra-low permeability cores with smaller pore throat structure, compared with the blockage caused by fines migration, the increase in permeability caused by mineral dissolution does not predominate, with the change in porosity caused by mineral dissolution is also not obvious.…”

“…Due to the significant oil displacement characteristics of CO 2 , the injection of CO 2 into oil reservoirs for storage not only significantly increases the production of oil, but is also an effective means of controlling CO 2 emissions to reduce the greenhouse effect. Among the displacement methods, CO 2 flooding and CO 2 -WAG flooding are two common displacement methods used in oilfields, CO 2 -WAG flooding is superior to CO 2 flooding in sweep efficiency and has a better effect on EOR, but the injection of fluid is more difficult [1][2][3][4][5][6][7][8][9]. However, no matter which displacement method is used, when CO 2 is injected into the formation, a series of physical and chemical reactions (CO 2 -brine-rock interactions) are triggered, changing the physical properties of the reservoirs [10][11][12][13][14][15].…”

Oil production and reservoir damage during miscible CO2 injection

“…Flooding by the injection of CO2 is being investigated for both enhanced oil recovery (EOR) and CO2 storage. It is known that both oil production performance and residual oil distribution are affected by the choice of CO2 injection method, and that this is especially the case for multi-layer reservoirs with high interlayer heterogeneity (Lei et al, 2016). Flooding with both CO2 and CO2-WAG are common EOR strategies which have been widely used in a significant number of oilfields (Han et al, 2014).…”