Experimental identification of CO2–oil–brine–rock interactions: Implications for CO2 sequestration after termination of a CO2-EOR project

Abstract

Carbon dioxide enhanced oil recovery (CO 2-EOR) has been widely applied to the process of carbon capture, utilization, and storage (CCUS). Here, we investigate CO 2-oil-water-rock interactions under reservoir conditions (100°C and 24 MPa) in order to understand the fluid-rock interactions following termination of a CO 2-EOR project. Our experimental results show that CO 2-rich fluid remained the active fluid controlling the dissolution-precipitation processes in an oil-undersaturated sandstone reservoir; e.g., the dissolution of feldspar and calcite, and the precipitation of kaolinite as well as solid phases comprising O, Si, Al, Na, C, and Ti. Mineral dissolution rates were reduced in the case that mineral surfaces were coated by oil. Mineral wettability and composition, and oil saturation were the main controls on the exposed surface area of grains, and mineral wettability in particular led to selective dissolution. In addition, the permeability of the reservoir decreased substantially due to the precipitation of kaolinite and solid-phase particles, and due to the clogging of less soluble mineral particles released by the dissolution of K-feldspar and carbonate cement, whereas porosity increased. The results provide insight into potential formation damage resulting from CO 2-EOR projects.

Formation damage due to asphaltene precipitation during CO2 flooding processes with NMR technique

“…The k: gas porosity of the core plugs; u: absolutely gas permeability of the core plugs; S oi : initial oil saturation; S wc : initial connate water saturation. experimental result is different from similar experimental results in other literature that the CO 2 /bine/rock reactions occur and change the pore structure in the cores during CO 2 coreflood tests [31,32]. That is because that the reaction time of these coreflood tests is too short in comparison with experiments in other literature.…”

Experimental Investigation of Oil Recovery Performance and Permeability Damage in Multilayer Reservoirs after CO2 and Water–Alternating-CO2 (CO2–WAG) Flooding at Miscible Pressures

“…In addition, when CO2 is in contact with fluids and rocks in reservoirs during the injection process, the processes of organic (i.e., asphaltene) and inorganic (i.e., metal carbonate) precipitation are triggered [23][24] . When the pressure reaches a certain value in the CO2 injection process, changes in composition of the crude oil due to the dissolved CO2 lead to asphaltene precipitation.…”

“…Both of these inorganic processes can also cause pore throats to be blocked [29][30][31] . The above mentioned precipitation and blockage, especially for rocks with low permeability, which have smaller pore-throat structure, cause greater damage to the reservoirs, usually resulting in a decrease of permeability, affecting the flow of fluid in the reservoir, and reducing the effect of CO2-EOR [23] .…”

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

“…The comparison between the two categories of pore microstructure indicates that during the long-term injection of CO 2 in two ways of displacement, the original compact structure of the authigenic clay mineral in the core is destroyed, and the exfoliated or newly generated clay mineral fragments loosely adhere to pore walls and accumulate in the pores [12,18]. At the same time, debris are released and migrate with the fluid, finally depositing in the fluid flow path.…”

“…Physical property changes in rocks caused by above factors damage the injection capacity of CO 2 and brine, changing the concentrations and types of ions contained in fluids. Due to these interactions, the released fines migrate to the distant reservoir with the flow of fluid, which will cause serious damage to the reservoir and ultimately affect the efficiency of EOR and CO 2 storage [16][17][18][19][20]. On the other hand, the in-situ multiphase flow characteristics in rocks under different CO 2 displacement methods are different, and these also have different effects on physical properties changes.…”