CO2-triggered gelation for mobility control and channeling blocking during CO2 flooding processes

Petroleum Science, Apr 2016

CO2 flooding is regarded as an important method for enhanced oil recovery (EOR) and greenhouse gas control. However, the heterogeneity prevalently distributed in reservoirs inhibits the performance of this technology. The sweep efficiency can be significantly reduced especially in the presence of “thief zones”. Hence, gas channeling blocking and mobility control are important technical issues for the success of CO2 injection. Normally, crosslinked gels have the potential to block gas channels, but the gelation time control poses challenges to this method. In this study, a new method for selectively blocking CO2 channeling is proposed, which is based on a type of CO2-sensitive gel system (modified polyacrylamide-methenamine-resorcinol gel system) to form gel in situ. A CO2-sensitive gel system is when gelation or solidification will be triggered by CO2 in the reservoir to block gas channels. The CO2-sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N2 and CO2 atmospheres. Sand pack flow experiments were conducted to investigate the shutoff capacity of the gel system under different conditions. The injectivity of the gel system was studied via viscosity measurements. The results indicate that this gel system was sensitive to CO2 and had good performance of channeling blocking in porous media. Advantageous viscosity-temperature characteristics were achieved in this work. The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs. The experimental results can provide guidelines for the deployment of the CO2-sensitive gel system for field applications.

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CO2-triggered gelation for mobility control and channeling blocking during CO2 flooding processes

CO2-triggered gelation for mobility control and channeling blocking during CO2 flooding processes De-Xiang Li 0 1 Liang Zhang 0 1 Yan-Min Liu 0 1 Wan-Li Kang 0 1 Shao-Ran Ren 0 1 0 Edited by Yan-Hua Sun 1 School of Petroleum Engineering, China University of Petroleum , Qingdao 266580, Shandong , China CO2 flooding is regarded as an important method for enhanced oil recovery (EOR) and greenhouse gas control. However, the heterogeneity prevalently distributed in reservoirs inhibits the performance of this technology. The sweep efficiency can be significantly reduced especially in the presence of ''thief zones''. Hence, gas channeling blocking and mobility control are important technical issues for the success of CO2 injection. Normally, crosslinked gels have the potential to block gas channels, but the gelation time control poses challenges to this method. In this study, a new method for selectively blocking CO2 channeling is proposed, which is based on a type of CO2-sensitive gel system (modified polyacrylamide-methenamine-resorcinol gel system) to form gel in situ. A CO2-sensitive gel system is when gelation or solidification will be triggered by CO2 in the reservoir to block gas channels. The CO2-sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N2 and CO2 atmospheres. Sand pack flow experiments were conducted to investigate the shutoff capacity of the gel system under different conditions. The injectivity of the gel system was studied via viscosity measurements. The results indicate that this gel system was sensitive to CO2 and had good performance of channeling blocking in porous media. Advantageous viscosity-temperature characteristics were achieved in this work. The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs. The experimental results can provide guidelines for the deployment of the CO2-sensitive gel system for field applications. CO2 flooding sensitivity; Sweep efficiency; Mobility control; Gas channeling; CO2; Enhanced oil recovery 1 Introduction In recent years, sequestration and utilization of CO2 is becoming an important research topic (Ren et al. 2010; Zhang et al. 2010) . With the promotion of CO2 capture and storage technology, the problem of CO2 gas source can be solved and an increasing number of oil reservoirs will be candidates for CO2 EOR projects (Ren et al. 2014) . Injection of CO2 into oil and gas reservoirs may have both economic and environmental benefits (Elsharkawy et al. 1996; Sweatman et al. 2009; Talebian et al. 2014) . Targets for reducing greenhouse gas emission were also emphasized during the 21st session of the conference of the parties (COP21) which was held in 2015. Carbon dioxide capture and storage (CCS) is a promising way of making low-carbon energy solutions sustainable. However, CCS has made limited progress. An important route to making CCS a more sustainable option is via CO2 EOR as part of carbon capture, utilization and storage (CCUS) systems (http://www.bbc.co.uk/news/science-environment35086346). In the southern states of the United States, CO2 flooding has been one of the main techniques for EOR due to their abundant natural CO2 sources (Zhu et al. 2011). It has been demonstrated that CO2 flooding can be one of the most effective EOR technologies proven in field tests and indoor experiments. There is a large-scale CO2 EOR project in the Weyburn Oilfield of Canada to deal with the industrial carbon emissions. Since 2000, about 1.8 million tons of CO2 per year captured from a coal gasification plant in the North Dakota have been transported to the Weyburn Oilfield through pipelines for injection to meet the requirements of storage and enhancing oil recovery. The potential of CO2 storage in the field is over 50 million tons and the incremental oil recovery can be achieved is approximately 9.8 % OOIP (Preston et al. 2005) . Also a large-scale CO2 EOR project has been under way in China since 2006 in the Jinlin Oilfield (Northeast China) (Li and Fang 2007) , in which CO2 produced and separated from natural gas reservoirs nearby is utilized, and about 0.3–0.5 million tons of CO2 per year have been injected into oil reservoirs since then. Meanwhile, in the Shengli Oilfield CO2 is captured from a coal-fired electricity plant for EOR and the capacity of CO2 injection will be over 0.5 million tons per year. For the oil and gas industry, CO2 EOR has been demonstrated as a feasible technology to improve oil recovery. The EOR mechanisms include interfacial tension (IFT) reduction, CO2 dissolution into oil to reduce its viscosity and swell oil, permeability improvements as the reaction of carbonic acid (due to CO2 dissolution in water) with the limestone/dolomite, and wettability alteration due to asphaltene precipitation. It is notable that CO2 and oil may become miscible when the reservoir pressure exceeds the minimum misci (...truncated)


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De-Xiang Li, Liang Zhang, Yan-Min Liu, Wan-Li Kang, Shao-Ran Ren. CO2-triggered gelation for mobility control and channeling blocking during CO2 flooding processes, Petroleum Science, 2016, pp. 247-258, Volume 13, Issue 2, DOI: 10.1007/s12182-016-0090-9