Key Problems and Countermeasures in CO₂ Flooding and Storage

Abstract

Based on literature research in combination with the practice of CO2 flooding and storage in Jilin Oilfield, this study assesses the key problems in CO2 flooding and storage, proposing the corresponding countermeasures from five aspects of CO2 gas source condition, namely geological condition evaluation, scheme design incoordination with other production methods, economic and effectiveness evaluation, together with dynamic monitoring and safety evaluation. The results show that CO2 flooding is the most economic and effective CO2 storage method. In eastern China, inorganic origin CO2 gas reservoirs are widely developed and are especially the most enriched in the Paleozoic carbonate rock strata and the Cenozoic Paleogene–Neogene system, which provide a rich resource base for CO2 flooding and storage. In the future, CO2 generated in the industrial field will become the main gas source of CO2 flooding and storage. The evaluation of geological conditions of oil and gas reservoirs is the basis for the potential evaluation, planning scheme design and implementation of CO2 flooding and storage. CO2 storage should be below the depth of 800 m, the CO2 flooding and storage effects in low‐permeability oil reservoirs being the best. CO2 geological storage mechanisms primarily consist of tectonic geological storage, bound gas storage, dissolution storage, mineralization storage, hydrodynamic storage and coalbed adsorption storage. The practice of CO2 flooding and storage in Jilin Oilfield demonstratesthat the oil increment by CO2 flooding is at least 24% higher than by conventional water flooding. The most critical factor determining the success or failure of CO2 flooding and storage is economic effectiveness, which needs to be explored from two aspects: the method and technology innovation along with the carbon peaking and carbon neutrality policy support. After CO2 is injected into the reservoir, it will react with the reservoir and fluid, the problem of CO2 recovery or overflow will occur, so the dynamic monitoring and safety evaluation of CO2 flooding and storage are very important. This study is of great significance to the expansion of the application scope of CO2 flooding and storage and future scientific planning and deployment.

Characteristics and Mechanisms of CO2 Flooding with Varying Degrees of Miscibility in Reservoirs Composed of Low-Permeability Conglomerate Formations

“…The recovery rate is only 15% different from the latter pressure point of 24 MPa, where complete miscibility can be achieved, proving that near-miscible flooding can be achieved in a small pressure range before the miscible pressure, and near-miscible flooding can also achieve a higher level of recovery. This discovery is consistent with the findings of Hao Chen, Narendra Kumar, et al [11,43].…”

“…The recovery rate is only 15% different from the latter pressure point of 24 MPa, where complete miscibility can be achieved, proving that near-miscible flooding can be achieved in a small pressure range before the miscible pressure, and near-miscible flooding can also achieve a higher level of recovery. This discovery is consistent with the findings of Hao Chen, Narendra Kumar, et al [11,43]. The image shows that before the CO2 breakthrough, the recovery factor increases approximately linearly with the increase in the injection volume multiple, and the majority of the oil is produced at this stage; after the CO2 breakthrough, oil production drops rapidly, and the recovery factor gradually stabilizes.…”

“…Nuclear magnetic resonance T2 testing (NMR) and nuclear magnetic resonance imaging (MRI) scanning can figure out the relationship between the peak value and relaxation time of the "H" fluid signal contained in the core at various intervals and provide visual imaging of the fluid-swept area [43]. The nuclear magnetic resonance high- The long core CO 2 -flooding experimental procedure is described below: (1) Use N 2 calibration and harmonic average sorting to splice long core porosity and permeability data.…”

The Thermodynamic Change Laws of CO2-Coupled Fractured Rock

“…The mechanical mechanism of hydraulic fracturing for coal structure destruction is investigated, revealing that hydraulic fracturing can enhance the effectiveness of top coal pre-cracking [18]. Li et al [19][20][21] investigated the mechanism of fracture morphology evolution in fractured coal under water and supercritical CO 2 fracturing conditions. CO 2 significantly affects coal rock wettability and fracture expansion.…”