Storage Of CO2 In Oil Reservoirs Research Articles

A Review of Phase Behavior Mechanisms of CO2 EOR and Storage in Subsurface Formations

The emissions of CO2 have been recognized as the main cause of climate change. As an important strategy being used to reduce the CO2 concentration in the atmosphere, carbon capture, utilization and storage (CCUS) has attracted significant attention in recent years. Geological formations, including depleted oil and gas reservoirs and saline aquifers, are popular CO2 storage options. During the process of CO2 storage in subsurface formations, the interactions between CO2 and formation fluids must be considered as they could greatly affect the CO2 trapping mechanisms and CO2 storage capacity. In this paper, we give a brief review of the phase behavior mechanisms associated with CO2 storage in subsurface formations. Two different CO2-storage strategies are considered in this paper: CO2 storage in saline aquifers and CO2 storage in oil reservoirs. Multiphase equilibria, including two-phase, three-phase, and four-phase equilibria, can be observed during CO2 injection into underground formations. Both the experimental and modeling studies on the related phase behavior mechanisms are included in this Review. We also introduce some recently developed robust algorithms for the multiphase equilibria calculations, which could be essential for the design of the CO2 storage process and prediction of CO2 storage capacity.

Using propanol as an additive to CO2 for improving CO2 utilization and storage in oil reservoirs

CO2 flooding has been recognized as one of the major alternatives for CO2 emission reduction and as well as increasing in the recovery from the oil reservoirs. However, CO2 is scrutinized for its potential low efficiency for oil recovery coupled with CO2 storage for various reasons, mainly miscibility requirements, character of the oil and as well as the reservoir heterogeneity related complications. Furthermore, heavier (viscous) oils will lead to additional complications in terms of efficiency. In this study, propanol is proposed as a novel cosolvent to improve CO2 for heavy oil recovery, while assisting CO2 storage in oil reservoirs. Influence of propanol on the solubility of CO2 in heavy oil is first investigated to reveal the mechanism of propanol in assisting CO2 for oil viscosity reduction. Performance of propanol assisted CO2 flooding is then compared with that of propane assisted CO2 flooding to validate the potential of propanol as an additive to CO2 for heavy oil recovery while assisting CO2 storage in oil reservoirs. Results show that propanol results in the largest decrease in the viscosity of oil-phase by more than 50% compared to pure CO2 and propane by improving CO2 solubility in the oil-phase. Propanol assisted CO2 flooding has better performance in recovering heavy oil from the medium-permeability cores by more than 19% than propane assisted CO2 flooding, especially from the smaller pores. In addition, the flowback ratio is as high as 95% for propanol, suggesting that propanol can be used as a clean additive to CO2 for reservoir development. More importantly, compared to propane, propanol favors up to 13 % more CO2 storage in oil reservoirs, suggesting that propanol is also a suitable agent for assisting CO2 sequestration.

Potential evaluation of CO2 EOR and sequestration in Yanchang oilfield

CO2 storage in oil reservoirs is not only an effective method for reducing CO2 emissions and greenhouse effect, but also a superior choice by enhancing oil recovery economically. This option, which lowers CO2 sequestration cost by recovering incremental oil, is particularly attractive in mature oil fields, such as Yanchang oilfield in China where many oil pools are near depletion and where most of the needed infrastructure is already in place. Using screening criterion, MMP determination and capacity evaluation methods, the feasibility of CO2 flooding, potential CO2 EOR and CO2 storage capacity of twenty-seven reservoirs in Yanchang Oilfield were evaluated. Results show that of all the 27 reservoirs only 8 are suitable for implementing CO2 EOR and sequestration project with average CO2 storage coefficient of 0.185, demonstrated the CO2.sequestration potential in Yanchang oilfield is very limited.

Estimation of CO<sub>2</sub> Storage Capacity in Oil Reservoir after Waterflooding：Case Studies in Xinjiang Oilfield from West China

CO2 storage in oil reservoirs is an important method to reduce Greenhouse Gas Emission. It was proven to have a great CO2storage capacity and economic potentials via EOR by injecting CO2into oil reservoirs. In China, most oil reservoirs went through waterflooding, and have high water saturation at present. The storage capacity in these oil reservoirs can be estimated on base of material balance method which considers the volume of displaced water and oil, CO2 sweep efficiency, and CO2 solution in oil and water. Case studies of four reservoirs selected from Xinjiang oilfield in China are conducted, the theoretical storage capacity and effective storage capacity is estimated. The results show that oil reservoir can provide much larger storage capacity, and oil and water displacement and CO2dissolution in remaining oil and water are the main forms of CO2storage in oil reservoirs after waterflooding. It’s a great option to inject CO2 into these reservoirs to reduce Greenhouse Gas emission, and the detailed storage capacity is worth further studies.

Methanogenesis from Anaerobic Crude Oil Degradation Amended with CO_2

Carbon capture and sequestration(CCS) is nowadays regarded as a strategic approach to reduce atmospheric CO2,among which CO2storage in oil reservoir is one of the reliable technologies.However,it is yet not clear whether the stored CO2 can be reduced to CH4 via methanogenesis in oil reservoir.An investigation was thus conducted with a oil production mixture sampled from Qinghai Oilfield in which HCO3-was added to mimic CO2storage in oil reservoir.The result revealed that HCO3addition led to the detection of more relative contents of methanogenic archaea and CH4,along with degradation of aromatic hydrocarbons and asphaltenes,suggesting sequestrated CO2 in Qinghai Oilfield could be transformed to CH4,and resulting in enhanced oil recovery.