Study on Gas Channeling Characteristics and Suppression Methods in CO2 Flooding for Low Permeability Reservoirs

Abstract

This paper shows the close relation between the displacement effects and reservoir properties in CO2 flooding for low permeability reservoirs. Low permeability reservoirs are characterized by tight matrix, strong heterogeneity and developed fractures. With the increase of CO2 injection rate, the CO2 viscous fingering gets worse in low permeability homogeneous reservoirs. While for low permeability heterogeneous reservoirs, the increase in displacement differential pressure contributes to the enhanced oil recovery in less permeable layers. The moderate increase in effective pressure is conductive to improveing the oil recovery in matrix. The displacement effect and CO2 channeling can be improved through the adjustment of injection-production parameters in CO2 flooding. Additionally, the interaction among CO2, oil and brine can improve the water-oil viscosity ratio. The gas viscous fingering can be weakened. The temporary performance of oil-water emulsion band formed in carbonate water can plug high permeability layers, and the production capacity of low permeability layers can be enhanced. The compound gel system in the sour environment of CO2 can plug large gas-channeling paths, restrict gas channeling and enlarge the sweep efficiency.

Innovative Zoning Control Techniques for Optimizing a Megaton-Scale CCUS-EOR Project with Large-Pore-Volume CO2 Flooding

“…Previous studies have shown that miscibility has advantages in enhancing oil recovery and controlling CO 2 breakthrough. 62 To investigate the influence of miscibility on large PV CO 2 flooding and storage, we characterized the life cycle miscibility range. In Figure 15, we can observe the changes in miscibility degree, miscibility range, residual oil distribution, and CO 2 storage efficiency throughout the entire development life cycle.…”

“…24,25 Nevertheless, there were also problems or challenges in its application. 26 Due to gravity overlap and viscous fingering, CO 2 is highly prone to breakthrough. For example, after a large amount of CO 2 is injected into fractured reservoirs or naturally fractured reservoirs, CO 2 will first flow through high permeability layers or fractures, causing premature gas breakthrough.…”

Foam Formation and Interaction with Porous Media

“…An important industrial application of foams is enhanced oil recovery [4,[9][10][11] where foams can be used to increase the amount of crude oil that can be extracted from an oil field. In this process usually, gas flooding is used where CO 2 and/or N 2 are injected into the reservoir [10,11]. The issue that arises is that these gases are normally less viscous, less dense and highly mobile than both crude and water resulting in gas channeling [10,11].…”

“…In this process usually, gas flooding is used where CO 2 and/or N 2 are injected into the reservoir [10,11]. The issue that arises is that these gases are normally less viscous, less dense and highly mobile than both crude and water resulting in gas channeling [10,11]. This is when the injected gas goes through high permeability layers and fractures in the porous structure inducing poor displacement of the crude oil.…”

“…Another issue is gravity override, this is a phenomenon of multiphase flow within a reservoir where less dense fluid flows on top of the denser crude further reducing displacement [12]. This means to increase the displacement the gas channeling and gravity override has to be reduced; this is done by creating a foam to work as a mobility control [10][11][12]. The foam has an apparent viscosity greater than the The investigated below method of foam formation using compression of soft porous materials is classified as mechanical action, as the foam is formed by the pressure reduction when compressing the soft porous material (sponge).…”