Volume 30,Issue 2,2023 Table of Contents
2023, 30(2):1-17.
DOI: 10.13673/j.cnki.cn37-1359/te.202112048
Abstract:
The carbon capture，utilization and storage（CCUS）technology is an effective means of reducing carbon emissions and an important supporting technology for achieving China’s carbon peaking and carbon neutrality goals. The carbon dioxide（CO2）flooding，namely the application of CCUS for enhanced oil recovery（CCUS-EOR），is one of the main CO2 utilization methods in this regard. This paper summarizes the whole process of CCUS-EOR and systematically describes the development status and prospects of capture technologies，transport methods，and flooding and storage processes. For the capture process，emphasis is laid on analyzing the advantages and disadvantages，costs，and development trends of different CO2 capture technologies，and China’s problems in large-scale carbon capture costs and capture processes are exposed. In terms of the transport process，the challenges，such as pipeline construction，pipeline transport processes，and pipeline transport equipment，faced by supercritical pipeline transport are highlighted. As for the CO2 flooding process，the deficiencies in the technical level，application scale，and production effect of the CCUS-EOR technologies in China are examined.As far as the CO2 storage process is concerned，storage safety is analyzed，and the methods of monitoring possible CO2 leakage are listed. The guidance of the carbon peaking and carbon neutrality policy，the source-sink matching around major oil·producing basins，and the low-permeability reservoirs with abundant reserves have laid a solid foundation for the development of CCUS-EOR technologies in China. Nevertheless，China’s large-scale low-concentration capture technology，longdistance supercritical pipeline transport technology，large-scale flooding and storage technology，and intelligent monitoring technology still lag behind the more well-established industrial CCUS technologies abroad. In response，this paper puts forward suggestions from the perspectives of policy guidance，technological breakthrough，and supporting infrastructure construction，and they can provide a reference for the development of large-scale CCUS technologies in China.
The carbon capture，utilization and storage（CCUS）technology is an effective means of reducing carbon emissions and an important supporting technology for achieving China’s carbon peaking and carbon neutrality goals. The carbon dioxide（CO2）flooding，namely the application of CCUS for enhanced oil recovery（CCUS-EOR），is one of the main CO2 utilization methods in this regard. This paper summarizes the whole process of CCUS-EOR and systematically describes the development status and prospects of capture technologies，transport methods，and flooding and storage processes. For the capture process，emphasis is laid on analyzing the advantages and disadvantages，costs，and development trends of different CO2 capture technologies，and China’s problems in large-scale carbon capture costs and capture processes are exposed. In terms of the transport process，the challenges，such as pipeline construction，pipeline transport processes，and pipeline transport equipment，faced by supercritical pipeline transport are highlighted. As for the CO2 flooding process，the deficiencies in the technical level，application scale，and production effect of the CCUS-EOR technologies in China are examined.As far as the CO2 storage process is concerned，storage safety is analyzed，and the methods of monitoring possible CO2 leakage are listed. The guidance of the carbon peaking and carbon neutrality policy，the source-sink matching around major oil·producing basins，and the low-permeability reservoirs with abundant reserves have laid a solid foundation for the development of CCUS-EOR technologies in China. Nevertheless，China’s large-scale low-concentration capture technology，longdistance supercritical pipeline transport technology，large-scale flooding and storage technology，and intelligent monitoring technology still lag behind the more well-established industrial CCUS technologies abroad. In response，this paper puts forward suggestions from the perspectives of policy guidance，technological breakthrough，and supporting infrastructure construction，and they can provide a reference for the development of large-scale CCUS technologies in China.
2023, 30(2):18-26.
DOI: 10.13673/j.cnki.cn37-1359/te.202208048
Abstract:
As carbon peak and carbon neutrality development strategy and the social and economic development continuously require petroleum and other energy，CO2 flooding and storage technology has met great development opportunities，as well as unprecedented challenges. According to the research status of CO2 flooding and storage both in China and abroad，the problems and the future trend of CO2 flooding and storage are introduced by analyzing the mechanism and influencing factors of CO2 flooding and storage. Based on practice，the research contents of CO2 flooding and storage are summarized as six aspects，namely，target optimization，experimental study of relevant mechanisms，technical breakthrough，economic evaluation，safety evaluation，and field practice. The problems of CO2 flooding and storage include①CO2 flooding and storage technology is applied to very limited types of reservoirs. ②The distribution characteristics of the CO2 gas field and its temporal and spatial matching relationship with target reservoirs of CO2 flooding and storage have not been paid enough attention. ③There are still many problems in the study of CO2 flooding and storage mechanism. ④CO2 flooding and storage scheme design needs to be optimized. ⑤The economic effectiveness evaluation system of CO2 flooding and storage has not been established. ⑥The tracking assessment of CO2 storage safety still faces a series of problems. The future trend of CO2 flooding and storage technology research includes①Exploring the applicable reservoir types and development stages of CO2 flooding and storage. ②Studying the distribution law of the CO2 gas field and its temporal and spatial matching relationship with suitable reservoirs of CO2 flooding and storage. ③Deepening studies on the CO2 flooding and storage mechanism. ④Optimizing CO2 flooding and storage scheme design. ⑤Evaluating the economic effectiveness of CO2 flooding and storage. ⑥Conducting CO2 storage safety tracking monitoring and evaluation.
As carbon peak and carbon neutrality development strategy and the social and economic development continuously require petroleum and other energy，CO2 flooding and storage technology has met great development opportunities，as well as unprecedented challenges. According to the research status of CO2 flooding and storage both in China and abroad，the problems and the future trend of CO2 flooding and storage are introduced by analyzing the mechanism and influencing factors of CO2 flooding and storage. Based on practice，the research contents of CO2 flooding and storage are summarized as six aspects，namely，target optimization，experimental study of relevant mechanisms，technical breakthrough，economic evaluation，safety evaluation，and field practice. The problems of CO2 flooding and storage include①CO2 flooding and storage technology is applied to very limited types of reservoirs. ②The distribution characteristics of the CO2 gas field and its temporal and spatial matching relationship with target reservoirs of CO2 flooding and storage have not been paid enough attention. ③There are still many problems in the study of CO2 flooding and storage mechanism. ④CO2 flooding and storage scheme design needs to be optimized. ⑤The economic effectiveness evaluation system of CO2 flooding and storage has not been established. ⑥The tracking assessment of CO2 storage safety still faces a series of problems. The future trend of CO2 flooding and storage technology research includes①Exploring the applicable reservoir types and development stages of CO2 flooding and storage. ②Studying the distribution law of the CO2 gas field and its temporal and spatial matching relationship with suitable reservoirs of CO2 flooding and storage. ③Deepening studies on the CO2 flooding and storage mechanism. ④Optimizing CO2 flooding and storage scheme design. ⑤Evaluating the economic effectiveness of CO2 flooding and storage. ⑥Conducting CO2 storage safety tracking monitoring and evaluation.
2023, 30(2):27-35.
DOI: 10.13673/j.cnki.cn37-1359/te.202201034
Abstract:
By combining CO2 emission reduction in the coal chemical industry with CO2 resources utilization，Yanchang Oilfield created a linkage development model of the low-carbon development of the coal chemical industry and the green and efficient development in low-permeability tight reservoirs in the northern Shaanxi Province. This study systematically presented the whole-process integration technology of carbon capture，utilization，and storage（CCUS）and field tests. For CO2 capture，the low-temperature methanol washing technology in the coal chemical industry was formed，which had low costs.For CO2 flooding，a new theory of“corrosion increasing permeability，wetting promoting permeability”was proposed for CO2 immiscible flooding in low-permeability tight reservoirs. In addition，the efficient CO2 flooding technology was developed to improve CO2 miscibility and recovery the reservoirs by CO2 flooding in a three-dimensional and balanced manner. For CO2 storage，the sealing mechanism of overlying layers was clarified，and the evaluation methods for the capping capacity of cap layers and CO2 storage potential and the CO2 safety monitoring system of reservoirs were improved. Field practice shows that the application prospects of CO2 flooding and storage technologies are broad in low-permeability tight reservoirs.
By combining CO2 emission reduction in the coal chemical industry with CO2 resources utilization，Yanchang Oilfield created a linkage development model of the low-carbon development of the coal chemical industry and the green and efficient development in low-permeability tight reservoirs in the northern Shaanxi Province. This study systematically presented the whole-process integration technology of carbon capture，utilization，and storage（CCUS）and field tests. For CO2 capture，the low-temperature methanol washing technology in the coal chemical industry was formed，which had low costs.For CO2 flooding，a new theory of“corrosion increasing permeability，wetting promoting permeability”was proposed for CO2 immiscible flooding in low-permeability tight reservoirs. In addition，the efficient CO2 flooding technology was developed to improve CO2 miscibility and recovery the reservoirs by CO2 flooding in a three-dimensional and balanced manner. For CO2 storage，the sealing mechanism of overlying layers was clarified，and the evaluation methods for the capping capacity of cap layers and CO2 storage potential and the CO2 safety monitoring system of reservoirs were improved. Field practice shows that the application prospects of CO2 flooding and storage technologies are broad in low-permeability tight reservoirs.
2023, 30(2):36-43.
DOI: 10.13673/j.cnki.cn37-1359/te.202209043
Abstract:
The ultra-low permeability reservoirs have poor physical properties，which leads to difficult fluid flow，often showing the characteristics of non-linear flow. In the past，the study on non-linear flow laws focused more on water flooding but less on CO2 flooding. Considering the insufficient understanding of the non-linear flow laws of CO2 flooding in ultra-low permeability reservoirs in Gao89 area of Shengli Oilfield，an experimental study in this regard was carried out to reveal the influence of the interaction between CO2 and crude oil on the flow characteristics of crude oil. The calculation formula of the minimum threshold pressure gradient and the non-linear flow characteristic representation model of CO2 flooding under different permeability were constructed. The results show that there is threshold pressure in CO2 flooding in the ultra-low permeability reservoirs，and the minimum threshold pressure gradient of crude oil has a good power function relationship with fluidity. With the increase in fluidity，the threshold pressure gradient decreases significantly.In addition，the flow curve of CO2 flooding shows the characteristics of two stages，i.e.，non-linear stage+linear stage. The flow velocity at the linear stage has a good linear relationship with the pressure gradient，and that at the non-linear stage has a good quadratic function relationship with the pressure gradient. CO2 dissolved in crude oil has a significant swelling and viscosity reduction effect，which drastically lowers the minimum threshold pressure gradient of crude oil and enhances the flow capability of crude oil，and the non-linear stage in the flow curve is shortened.
The ultra-low permeability reservoirs have poor physical properties，which leads to difficult fluid flow，often showing the characteristics of non-linear flow. In the past，the study on non-linear flow laws focused more on water flooding but less on CO2 flooding. Considering the insufficient understanding of the non-linear flow laws of CO2 flooding in ultra-low permeability reservoirs in Gao89 area of Shengli Oilfield，an experimental study in this regard was carried out to reveal the influence of the interaction between CO2 and crude oil on the flow characteristics of crude oil. The calculation formula of the minimum threshold pressure gradient and the non-linear flow characteristic representation model of CO2 flooding under different permeability were constructed. The results show that there is threshold pressure in CO2 flooding in the ultra-low permeability reservoirs，and the minimum threshold pressure gradient of crude oil has a good power function relationship with fluidity. With the increase in fluidity，the threshold pressure gradient decreases significantly.In addition，the flow curve of CO2 flooding shows the characteristics of two stages，i.e.，non-linear stage+linear stage. The flow velocity at the linear stage has a good linear relationship with the pressure gradient，and that at the non-linear stage has a good quadratic function relationship with the pressure gradient. CO2 dissolved in crude oil has a significant swelling and viscosity reduction effect，which drastically lowers the minimum threshold pressure gradient of crude oil and enhances the flow capability of crude oil，and the non-linear stage in the flow curve is shortened.
5 Collaborative evaluation method of CO2 flooding and storage in low-permeability and tight reservoirs
CAO Xiaopeng
,
XIONG Ying
,
FENG Qihong
,
ZHAO Lekun
,
ZHANG Shiming
,
LIU Tongjing
,
WANG Sen
,
YANG Yuxuan
2023, 30(2):44-52.
DOI: 10.13673/j.cnki.cn37-1359/te.202212015
Abstract:
Research on collaborative evaluation indexes and methods of CO2 flooding and storage technology（CCUS-EOR）in reservoir engineering theory of CO2 flooding and storage is few. Therefore，from the perspective of collaborative design of CO2 flooding and storage，the design principles of CO2 flooding and storage reservoir engineering scheme were defined，and the evaluation index system of CO2 flooding and storage reservoir engineering was constructed. The internal relationships between the evaluation indexes of CO2 flooding and storage were analyzed，and two new indexes were constructed：CO2 flooding index and CO2 storage index. On this basis，the collaborative evaluation index of CO2 flooding and storage reservoir engineering was constructed，namely the synergy index of CO2 flooding and storage，the collaborative evaluation model of CO2 flooding and storage was established，and the collaborative evaluation method of CO2 flooding and storage was formed.The practical application in low-permeability and tight reservoir test wells shows that the collaborative evaluation method is helpful to clarify the technical policy limits of the key injection and production parameters in the CO2 flooding and storage reservoir engineering scheme，and the recommended scheme can simultaneously achieve positive oil flooding effect and large storage volume.
Research on collaborative evaluation indexes and methods of CO2 flooding and storage technology（CCUS-EOR）in reservoir engineering theory of CO2 flooding and storage is few. Therefore，from the perspective of collaborative design of CO2 flooding and storage，the design principles of CO2 flooding and storage reservoir engineering scheme were defined，and the evaluation index system of CO2 flooding and storage reservoir engineering was constructed. The internal relationships between the evaluation indexes of CO2 flooding and storage were analyzed，and two new indexes were constructed：CO2 flooding index and CO2 storage index. On this basis，the collaborative evaluation index of CO2 flooding and storage reservoir engineering was constructed，namely the synergy index of CO2 flooding and storage，the collaborative evaluation model of CO2 flooding and storage was established，and the collaborative evaluation method of CO2 flooding and storage was formed.The practical application in low-permeability and tight reservoir test wells shows that the collaborative evaluation method is helpful to clarify the technical policy limits of the key injection and production parameters in the CO2 flooding and storage reservoir engineering scheme，and the recommended scheme can simultaneously achieve positive oil flooding effect and large storage volume.
2023, 30(2):53-67.
DOI: 10.13673/j.cnki.cn37-1359/te.202208001
Abstract:
To realize long-term objectives of carbon peaking and neutrality in China，injecting captured CO2 generated by fossil fuel combustion into high-water-cut reservoirs may not only enhance oil recovery，but realize CO2 geological storage in oil layers. This is conducive to achieving the dual goals of increasing oil and gas production and reducing carbon emissions. In view of the characteristics of high-water-cut reservoirs，a comprehensive review is carried out from the aspects of CO2 flooding and geological storage mechanisms，storage modes，storage-capacity calculation methods，CO2 migration，and leakage-risk prediction and evaluation. Based on the research status of CO2 flooding and geological storage in high-watercut reservoirs in China and abroad，as well as the closely related scientific fields and the problems faced by mines，this paper puts forward ten key issues needing further research，such as reaction of CO2 with reservoir rocks and fluids，CO2 flooding mechanism and storage mode，storage capacity，storage efficiency，and leakage-risk prevention and control. This provides a reference for research directions of CO2 flooding and geological storage，as well as industrial technology reserves.The solution to the key issues of CO2 flooding and geological storage is of great significance for serving“carbon emission reduction”and“carbon sink increase”to achieve the strategic goals of carbon peaking and neutrality in China.
To realize long-term objectives of carbon peaking and neutrality in China，injecting captured CO2 generated by fossil fuel combustion into high-water-cut reservoirs may not only enhance oil recovery，but realize CO2 geological storage in oil layers. This is conducive to achieving the dual goals of increasing oil and gas production and reducing carbon emissions. In view of the characteristics of high-water-cut reservoirs，a comprehensive review is carried out from the aspects of CO2 flooding and geological storage mechanisms，storage modes，storage-capacity calculation methods，CO2 migration，and leakage-risk prediction and evaluation. Based on the research status of CO2 flooding and geological storage in high-watercut reservoirs in China and abroad，as well as the closely related scientific fields and the problems faced by mines，this paper puts forward ten key issues needing further research，such as reaction of CO2 with reservoir rocks and fluids，CO2 flooding mechanism and storage mode，storage capacity，storage efficiency，and leakage-risk prevention and control. This provides a reference for research directions of CO2 flooding and geological storage，as well as industrial technology reserves.The solution to the key issues of CO2 flooding and geological storage is of great significance for serving“carbon emission reduction”and“carbon sink increase”to achieve the strategic goals of carbon peaking and neutrality in China.
2023, 30(2):68-76.
DOI: 10.13673/j.cnki.cn37-1359/te.202211045
Abstract:
The oil in place from Qiuling Oilfield in Tuha Basin is light. The heterogeneity of the reservoirs leads to low water flooding recovery，and the reservoir has entered the high water-cut stage. In view of the feasibility of gas miscible flooding after water flooding of the reservoir，the miscible pressure of the first-stage separator gas（PSN gas）and oil in place was tested by a slim tube experiment，and the type of miscible additives（liquefied petroleum gas（LPG），toluene，2-Butoxy ethanol，CO2，and enriched natural gas）and the amount of slug injection were optimized. Then，the oil displacement effect of miscible additive slug flooding+PSN gas flooding+subsequent water flooding at the high water-cut stage was studied by using a long core model composed of formation core in the oilfield. The results of the slim tube experiment show that miscible flooding cannot be achieved through the displacement of oil in place by PSN gas under current formation conditions，and it is necessary to add a miscible additive slug in front of injected gas. Long core experiments show that gas flooding after water flooding can greatly enhance the recovery of oil in place. The oil displacement effect is greatly improved by adding a miscible additive slug in front of the injected gas，and the recovery increases with the increment of the injection amount in the miscible additive slug. However，the effect of miscible additives（CO2 and enriched natural gas）with weak solubility in oil in place is different from that of miscible additives（LPG）with strong solubility，and higher injection volume may yield a worse effect.
The oil in place from Qiuling Oilfield in Tuha Basin is light. The heterogeneity of the reservoirs leads to low water flooding recovery，and the reservoir has entered the high water-cut stage. In view of the feasibility of gas miscible flooding after water flooding of the reservoir，the miscible pressure of the first-stage separator gas（PSN gas）and oil in place was tested by a slim tube experiment，and the type of miscible additives（liquefied petroleum gas（LPG），toluene，2-Butoxy ethanol，CO2，and enriched natural gas）and the amount of slug injection were optimized. Then，the oil displacement effect of miscible additive slug flooding+PSN gas flooding+subsequent water flooding at the high water-cut stage was studied by using a long core model composed of formation core in the oilfield. The results of the slim tube experiment show that miscible flooding cannot be achieved through the displacement of oil in place by PSN gas under current formation conditions，and it is necessary to add a miscible additive slug in front of injected gas. Long core experiments show that gas flooding after water flooding can greatly enhance the recovery of oil in place. The oil displacement effect is greatly improved by adding a miscible additive slug in front of the injected gas，and the recovery increases with the increment of the injection amount in the miscible additive slug. However，the effect of miscible additives（CO2 and enriched natural gas）with weak solubility in oil in place is different from that of miscible additives（LPG）with strong solubility，and higher injection volume may yield a worse effect.
2023, 30(2):77-85.
DOI: 10.13673/j.cnki.cn37-1359/te.202108008
Abstract:
Aiming at the problem of low oil recovery in shale reservoir with primary depletion development after fracturing，an experimental method of supercritical CO2/H2O mixture huff and huff to enhance shale oil recovery was proposed based on the low porosity and ultra-low permeability of shale reservoir. In this paper，the effect of supercritical CO2/H2O mixture on huffing and puffing shale oil was evaluated by indoor self-designed core experiment，during which the influence of injection medium，soaking time，injection pressure and huff and puff cycles on enhanced oil recovery（EOR）was studied. At the same time，the producing ratio of oil in different pores by supercritical CO2/H2O mixture was determined by nuclear magnetic resonance technology. The results show that the supercritical CO2 /H2O mixture huff and huff can effectively enhance shale oil recovery. The soaking time has a great influence on EOR in shale cores with poor porosity and permeability. The injection pressure is closely related to the diffusion rates and flow capacity of the supercritical CO2/H2O mixture，and the increment of enhancing oil recovery under miscible conditions is significant. The producing ratio of oil in large pores enhances as the the huff and huff cycle increases，but it is not possible to produce more oil in small pores by increasing huff and puff cycles.
Aiming at the problem of low oil recovery in shale reservoir with primary depletion development after fracturing，an experimental method of supercritical CO2/H2O mixture huff and huff to enhance shale oil recovery was proposed based on the low porosity and ultra-low permeability of shale reservoir. In this paper，the effect of supercritical CO2/H2O mixture on huffing and puffing shale oil was evaluated by indoor self-designed core experiment，during which the influence of injection medium，soaking time，injection pressure and huff and puff cycles on enhanced oil recovery（EOR）was studied. At the same time，the producing ratio of oil in different pores by supercritical CO2/H2O mixture was determined by nuclear magnetic resonance technology. The results show that the supercritical CO2 /H2O mixture huff and huff can effectively enhance shale oil recovery. The soaking time has a great influence on EOR in shale cores with poor porosity and permeability. The injection pressure is closely related to the diffusion rates and flow capacity of the supercritical CO2/H2O mixture，and the increment of enhancing oil recovery under miscible conditions is significant. The producing ratio of oil in large pores enhances as the the huff and huff cycle increases，but it is not possible to produce more oil in small pores by increasing huff and puff cycles.
9 Experimental study on enhanced oil recovery by different injection-production modes of CO2 flooding
2023, 30(2):86-93.
DOI: 10.13673/j.cnki.cn37-1359/te.202209037
Abstract:
The heterogeneity and viscous fingering are the key factors to determine the development effect of CO2 flooding.The adjustment of injection-production modes is an effective means to control gas channeling and expand the swept area.At present，research on the above directions mainly focuses on the numerical simulation. Therefore，it is urgent to carry out physical simulation research on different injection-production modes of CO2 flooding，so as to further clarify the production mechanism，development characteristics，and reservoir adaptability of modes of CO2 flooding such as continuous gas injection，rotation production，and injection-production coupling. In this paper，the development characteristics of these modes were compared through similar physical simulation experiments of CO2 flooding，and the applicability of different injectionproduction modes of CO2 flooding was analyzed. The results show that the development effect in areas with different permeability is different under the continuous gas injection，and the potential for enhanced oil recovery after gas breakthrough is very low in low-permeability areas，so CO2 continuous gas flooding is suitable for developing relatively homogeneous reservoirs. For the rotation production mode，the directions of the mainstream line between injection-production wells can be changed by opening production wells alternately，so as to effectively improve the development effect of low-permeability areas in heterogeneous reservoirs. Therefore，this mode is suitable for strongly heterogeneous reservoirs or the development adjustment stage after gas channeling. The injection-production coupling mode can expand the swept area of the whole reservoir in a more balanced way by alternating injection-production to cause alternating changes in the pressure field，so as to improve the reserves producing ratio in the corner area of the reservoir. Therefore，it is suitable for weak heterogeneous reservoirs or the initial development stage.
The heterogeneity and viscous fingering are the key factors to determine the development effect of CO2 flooding.The adjustment of injection-production modes is an effective means to control gas channeling and expand the swept area.At present，research on the above directions mainly focuses on the numerical simulation. Therefore，it is urgent to carry out physical simulation research on different injection-production modes of CO2 flooding，so as to further clarify the production mechanism，development characteristics，and reservoir adaptability of modes of CO2 flooding such as continuous gas injection，rotation production，and injection-production coupling. In this paper，the development characteristics of these modes were compared through similar physical simulation experiments of CO2 flooding，and the applicability of different injectionproduction modes of CO2 flooding was analyzed. The results show that the development effect in areas with different permeability is different under the continuous gas injection，and the potential for enhanced oil recovery after gas breakthrough is very low in low-permeability areas，so CO2 continuous gas flooding is suitable for developing relatively homogeneous reservoirs. For the rotation production mode，the directions of the mainstream line between injection-production wells can be changed by opening production wells alternately，so as to effectively improve the development effect of low-permeability areas in heterogeneous reservoirs. Therefore，this mode is suitable for strongly heterogeneous reservoirs or the development adjustment stage after gas channeling. The injection-production coupling mode can expand the swept area of the whole reservoir in a more balanced way by alternating injection-production to cause alternating changes in the pressure field，so as to improve the reserves producing ratio in the corner area of the reservoir. Therefore，it is suitable for weak heterogeneous reservoirs or the initial development stage.
2023, 30(2):94-103.
DOI: 10.13673/j.cnki.cn37-1359/te.202106020
Abstract:
As the conglomerate reservoir of Lower Karamay Formation in Well530 Area of Xinjiang Oilfield has a complex multi-modal pore structure，rich volcanic tuff，and high iron content，it is difficult to predict the effect of CO2 flooding field test. With the Lower Karamay Formation reservoir as the research object，the changes in mineral composition，pore structure，fluid ion concentration，and other parameters before and after the reaction of rock fragments，rock powder，core slugs with CO2 were compared through cast thin section，XRD，XRF，ICP ion concentration analysis，NMR，etc. The controlling factors of the reaction were discussed from the aspects of mineral composition，grain size，physical properties，pore structure，and reaction time. The results show that the impact of CO2 injection on the reservoir is small. The change in mineral composition shows that the relative content of quartz and clay increases while feldspar and carbonate minerals decrease，and iron minerals precipitate again after dissolution. Elements and pore structure change little，and the average change of porosity is less than 0.5%. The concentration of Ca2+and Mg2+in the liquid phase changes relatively greatly，and the newly added Al3+，Fe3+，Si4+changes slightly. The interaction mechanism between CO2 and reservoir rocks is the dissolution of feldspar and calcite as well as the first dissolution and then precipitation of iron minerals. As the calcite content of reservoir rock is higher，the variation of pore structure after the reaction is greater. After the reaction，the change in the pore structure of classⅡreservoir is greater than that of classⅢreservoir. The reaction rate of rock powder is stronger than that of rock fragments. The reaction reaches equilibrium within 0-7 days，during which the main action is dissolution. The components of the reaction change little within 7-30 days，and there is the precipitation of Al（OH）3 and Fe（OH）3.
As the conglomerate reservoir of Lower Karamay Formation in Well530 Area of Xinjiang Oilfield has a complex multi-modal pore structure，rich volcanic tuff，and high iron content，it is difficult to predict the effect of CO2 flooding field test. With the Lower Karamay Formation reservoir as the research object，the changes in mineral composition，pore structure，fluid ion concentration，and other parameters before and after the reaction of rock fragments，rock powder，core slugs with CO2 were compared through cast thin section，XRD，XRF，ICP ion concentration analysis，NMR，etc. The controlling factors of the reaction were discussed from the aspects of mineral composition，grain size，physical properties，pore structure，and reaction time. The results show that the impact of CO2 injection on the reservoir is small. The change in mineral composition shows that the relative content of quartz and clay increases while feldspar and carbonate minerals decrease，and iron minerals precipitate again after dissolution. Elements and pore structure change little，and the average change of porosity is less than 0.5%. The concentration of Ca2+and Mg2+in the liquid phase changes relatively greatly，and the newly added Al3+，Fe3+，Si4+changes slightly. The interaction mechanism between CO2 and reservoir rocks is the dissolution of feldspar and calcite as well as the first dissolution and then precipitation of iron minerals. As the calcite content of reservoir rock is higher，the variation of pore structure after the reaction is greater. After the reaction，the change in the pore structure of classⅡreservoir is greater than that of classⅢreservoir. The reaction rate of rock powder is stronger than that of rock fragments. The reaction reaches equilibrium within 0-7 days，during which the main action is dissolution. The components of the reaction change little within 7-30 days，and there is the precipitation of Al（OH）3 and Fe（OH）3.
2023, 30(2):104-111.
DOI: 10.13673/j.cnki.cn37-1359/te.202106030
Abstract:
The development of low permeability reservoirs has become an important field of oil and gas development in China. CO2 flooding in such reservoirs can achieve the dual purposes of enhanced oil recovery and CO2 geological storage，but the adaptability varies with injection methods. On the basis of typical physical properties and fluid parameters of a low permeability reservoir，the numerical simulation is conducted for the adaptability of continuous gas injection（CGI），constant water alternating gas（CWAG），and tapered water alternating gas（TWAG）for enhanced oil recovery and geological storage.The results show that three injection methods can obtain the highest cumulative oil production and CO2 storage capacity for the reservoir with the permeability of 1 mD. The working system constrained by the production gas-oil ratio（GOR）is more conducive to enhanced oil recovery or geological storage by CO2 flooding. CGI is more suitable for CO2 storage projects under 0.4 times the maximum GOR. CWAG is of more advantage in the project combining CO2 enhanced oil recovery with geological storage under 0.2 times the maximum GOR. TWAG is more suitable for CO2 enhanced oil recovery under 0.6 times the maximum GOR.
The development of low permeability reservoirs has become an important field of oil and gas development in China. CO2 flooding in such reservoirs can achieve the dual purposes of enhanced oil recovery and CO2 geological storage，but the adaptability varies with injection methods. On the basis of typical physical properties and fluid parameters of a low permeability reservoir，the numerical simulation is conducted for the adaptability of continuous gas injection（CGI），constant water alternating gas（CWAG），and tapered water alternating gas（TWAG）for enhanced oil recovery and geological storage.The results show that three injection methods can obtain the highest cumulative oil production and CO2 storage capacity for the reservoir with the permeability of 1 mD. The working system constrained by the production gas-oil ratio（GOR）is more conducive to enhanced oil recovery or geological storage by CO2 flooding. CGI is more suitable for CO2 storage projects under 0.4 times the maximum GOR. CWAG is of more advantage in the project combining CO2 enhanced oil recovery with geological storage under 0.2 times the maximum GOR. TWAG is more suitable for CO2 enhanced oil recovery under 0.6 times the maximum GOR.
2023, 30(2):112-121.
DOI: 10.13673/j.cnki.cn37-1359/te.202207019
Abstract:
CO2 flooding has broad application prospects in the long term owing to the booming of industries involving carbon capture，utilization，and storage amid the vigorous implementation of the“carbon peaking and carbon neutrality”policy.As low- and ultralow-permeability reservoirs have complex pore spaces and structures，the conventional water flooding development is invariably faced with difficult water injection and low oil recovery. In contrast，CO2 flooding offers a variety of oil displacement mechanisms and can well solve the problem of difficult water flooding development.In this paper，PVT fitting was carried out based on information on crude oil composition and experimental data on constant composition expansion and a component model with seven pseudo-components was constructed according to the conditions of the low-porosity and low-permeability reservoirs in Block A，Shengli Oilfield. The initial miscibility pressure obtained was 30.1 MPa，and the multi-contact miscibility pressure was 26.6 MPa. This paper proposed an empirical formula for calculating the gas injection rate of CO2 flooding with gas channeling as the constraint for the first time. The engineering parameters of CO2 flooding reservoirs in Block A were optimized with the homogeneous component model. The optimal injection-production parameters were thereby determined as a five-spot well pattern，a well spacing of 250 m，a gas injection rate of 20 t/d，and a production pressure of 26.0 MPa. Furthermore，the injection-production parameters of different development modes were optimized，and the development modes were respectively depletion development，water flooding，CO2 huff and puff，continuous CO2 injection，and water-alternating-gas（WAG）. The optimization results of different development modes were comparatively analyzed. The results showed that continuous gas injection had certain advantages. Finally，the dominant physical property area in the southwest of Block A was selected as a pilot development area to predict the effect of a continuous gas injection development scheme for a well group according to the optimization results. The results revealed that the recovery of the well group was 15.1% in 10 a and 22.4% in 20 a.
CO2 flooding has broad application prospects in the long term owing to the booming of industries involving carbon capture，utilization，and storage amid the vigorous implementation of the“carbon peaking and carbon neutrality”policy.As low- and ultralow-permeability reservoirs have complex pore spaces and structures，the conventional water flooding development is invariably faced with difficult water injection and low oil recovery. In contrast，CO2 flooding offers a variety of oil displacement mechanisms and can well solve the problem of difficult water flooding development.In this paper，PVT fitting was carried out based on information on crude oil composition and experimental data on constant composition expansion and a component model with seven pseudo-components was constructed according to the conditions of the low-porosity and low-permeability reservoirs in Block A，Shengli Oilfield. The initial miscibility pressure obtained was 30.1 MPa，and the multi-contact miscibility pressure was 26.6 MPa. This paper proposed an empirical formula for calculating the gas injection rate of CO2 flooding with gas channeling as the constraint for the first time. The engineering parameters of CO2 flooding reservoirs in Block A were optimized with the homogeneous component model. The optimal injection-production parameters were thereby determined as a five-spot well pattern，a well spacing of 250 m，a gas injection rate of 20 t/d，and a production pressure of 26.0 MPa. Furthermore，the injection-production parameters of different development modes were optimized，and the development modes were respectively depletion development，water flooding，CO2 huff and puff，continuous CO2 injection，and water-alternating-gas（WAG）. The optimization results of different development modes were comparatively analyzed. The results showed that continuous gas injection had certain advantages. Finally，the dominant physical property area in the southwest of Block A was selected as a pilot development area to predict the effect of a continuous gas injection development scheme for a well group according to the optimization results. The results revealed that the recovery of the well group was 15.1% in 10 a and 22.4% in 20 a.
2023, 30(2):122-134.
DOI: 10.13673/j.cnki.cn37-1359/te.202106026
Abstract:
Abstract：Due to the large viscosity difference between oil and gas and the heterogeneity of oil reservoirs，gas channeling occurs during CO2 flooding，reducing the sweep efficiency of CO2. Gel system is an effective channeling blocking agent for the process of CO2 flooding and is widely used in China and abroad. This paper outlines the channeling blocking mechanisms and research progress of four kinds of gel systems：retardant cross-linked polyacrylamide gels，pre-crosslinked gel particles，two-stage channeling blocking gel systems，and foam gels. Retardant cross-linked acrylamide gels have good mobility and low price，although the gel strength and gelling time are uncontrollable. More importantly，they are not resistant to acid corrosion. Pre-crosslinked gel particles enjoy controllable gelling time and gel strength and are resistant to high temperature and high salinity. Nevertheless，their large particle size prevents them from entering formations with low permeability. The two-stage channeling blocking gel systems，combining the advantages of rigid gels with those of small molecules，can simultaneously block fractures of different sizes. However，their blocking effect decreases when fractures exceed a certain size. Foam gels cause little damage to the formation，although they are not resistant to high temperatures. At present，the gel systems used for gas channeling treatment during CO2 flooding have the problem of irresistibility to acid corrosion.Keeping gel systems in CO2 acid environments for a long time stable is the future research direction.
Abstract：Due to the large viscosity difference between oil and gas and the heterogeneity of oil reservoirs，gas channeling occurs during CO2 flooding，reducing the sweep efficiency of CO2. Gel system is an effective channeling blocking agent for the process of CO2 flooding and is widely used in China and abroad. This paper outlines the channeling blocking mechanisms and research progress of four kinds of gel systems：retardant cross-linked polyacrylamide gels，pre-crosslinked gel particles，two-stage channeling blocking gel systems，and foam gels. Retardant cross-linked acrylamide gels have good mobility and low price，although the gel strength and gelling time are uncontrollable. More importantly，they are not resistant to acid corrosion. Pre-crosslinked gel particles enjoy controllable gelling time and gel strength and are resistant to high temperature and high salinity. Nevertheless，their large particle size prevents them from entering formations with low permeability. The two-stage channeling blocking gel systems，combining the advantages of rigid gels with those of small molecules，can simultaneously block fractures of different sizes. However，their blocking effect decreases when fractures exceed a certain size. Foam gels cause little damage to the formation，although they are not resistant to high temperatures. At present，the gel systems used for gas channeling treatment during CO2 flooding have the problem of irresistibility to acid corrosion.Keeping gel systems in CO2 acid environments for a long time stable is the future research direction.
2023, 30(2):135-143.
DOI: 10.13673/j.cnki.cn37-1359/te.202207029
Abstract:
Geological CO2 storage has been thought of as an important technical means for alleviating the greenhouse effect，and the leakage risk assessment of the storage system is the basis of safe storage. In this study，the influencing factors in the leakage of the geological CO2 storage system were comprehensively analyzed. It is believed that the leakage risk is mainly induced by the alternating stress on the wellbore and caprock produced by cryogenic fluids of CO2 and the integrity failure of the wellbore and caprock caused by the comprehensive action of CO2-water and rock corrosion reactions. Hence，the multi-factor influence on the leakage of the geological CO2 storage system was taken into account. Then，the fuzzy comprehensive evaluation（FCE）theory was used to construct a model for the hierarchical relationships between factors leading to CO2 leakage risks，and the model was employed to assess the leakage risks of the geological CO2 storage system. Specifically，the nonlinear normal membership function was applied to construct the membership matrix of the influencing factors with regard to comments. The analytic hierarchy process（AHP）was used to construct the comparison matrices between the influencing factors to obtain the weight subset of these influencing factors. In addition，a geological CO2 storage system was taken as an example for leakage risk assessment. It is concluded that the wellbore for geological CO2 storage faces a low risk of leakage while the cap rock and the storage system have a moderate leakage risk. Moreover，the leakage risk of the geological CO2 storage system can be dynamically tracked upon the collection of the changes of influencing factors in the process of CO2 storage for the update of the fuzzy calculation model.
Geological CO2 storage has been thought of as an important technical means for alleviating the greenhouse effect，and the leakage risk assessment of the storage system is the basis of safe storage. In this study，the influencing factors in the leakage of the geological CO2 storage system were comprehensively analyzed. It is believed that the leakage risk is mainly induced by the alternating stress on the wellbore and caprock produced by cryogenic fluids of CO2 and the integrity failure of the wellbore and caprock caused by the comprehensive action of CO2-water and rock corrosion reactions. Hence，the multi-factor influence on the leakage of the geological CO2 storage system was taken into account. Then，the fuzzy comprehensive evaluation（FCE）theory was used to construct a model for the hierarchical relationships between factors leading to CO2 leakage risks，and the model was employed to assess the leakage risks of the geological CO2 storage system. Specifically，the nonlinear normal membership function was applied to construct the membership matrix of the influencing factors with regard to comments. The analytic hierarchy process（AHP）was used to construct the comparison matrices between the influencing factors to obtain the weight subset of these influencing factors. In addition，a geological CO2 storage system was taken as an example for leakage risk assessment. It is concluded that the wellbore for geological CO2 storage faces a low risk of leakage while the cap rock and the storage system have a moderate leakage risk. Moreover，the leakage risk of the geological CO2 storage system can be dynamically tracked upon the collection of the changes of influencing factors in the process of CO2 storage for the update of the fuzzy calculation model.
LIU Ying
,
WANG Xiangzeng
,
YANG Hong
,
LIANG Quansheng
,
SHEN Zhenzhen
,
WANG Wei
,
WANG Weibo
,
ZHENG Jing
,
KANG Yuanyong
2023, 30(2):144-152.
DOI: 10.13673/j.cnki.cn37-1359/te.202211026
Abstract:
The loess tableland has complex surface conditions，and CO2 flooding in ultra-low permeability reservoirs faces the high density of well patterns，the high injection pressure，and the easy gas channeling. Moreover，the development is characterized by water-alternating-gas injection to mitigate gas-channeling.As a result，there are multiple CO2 leakage points and high intensity in this area，so the layout and monitoring accuracy of CO2 monitoring points are demanding，and the existing safety monitoring systems are hardly applicable. In view of these problems，according to the identification of CO2 leakage risks in ultra-low permeability reservoirs in the loess tableland and the analysis of CO2 spatial migration in geological bodies，a three-dimensional multi-index CO2 safety monitoring system was established，covering cap rock，wellbores，deep and shallow groundwater，soil，surface water，and atmosphere. Besides，CO2 safety monitoring was practically carried out to further build a safety evaluation system of CO2 storage. From the results of safety monitoring and evaluation，there was no abnormality for all indexes after CO2 injection and no CO2 geological leakage occured in the test area. The safety of CO2 storage was at the levelⅠ.
The loess tableland has complex surface conditions，and CO2 flooding in ultra-low permeability reservoirs faces the high density of well patterns，the high injection pressure，and the easy gas channeling. Moreover，the development is characterized by water-alternating-gas injection to mitigate gas-channeling.As a result，there are multiple CO2 leakage points and high intensity in this area，so the layout and monitoring accuracy of CO2 monitoring points are demanding，and the existing safety monitoring systems are hardly applicable. In view of these problems，according to the identification of CO2 leakage risks in ultra-low permeability reservoirs in the loess tableland and the analysis of CO2 spatial migration in geological bodies，a three-dimensional multi-index CO2 safety monitoring system was established，covering cap rock，wellbores，deep and shallow groundwater，soil，surface water，and atmosphere. Besides，CO2 safety monitoring was practically carried out to further build a safety evaluation system of CO2 storage. From the results of safety monitoring and evaluation，there was no abnormality for all indexes after CO2 injection and no CO2 geological leakage occured in the test area. The safety of CO2 storage was at the levelⅠ.
2023, 30(2):153-161.
DOI: 10.13673/j.cnki.cn37-1359/te.202203023
Abstract:
Abandoned gas reservoirs are ideal sites for carrying out carbon dioxide（CO2）storage projects. However，impurities in gas reservoirs can affect the CO2 dissolution in saline aquifers. To this end，a fugacity-activity thermodynamic model is constructed to capture the features of impurities，CO2，and saline aquifers. On this basis，the operator-based linearization approach is implemented to solve the mass conservation equations accurately and efficiently. Then the effects of gas mixtures on CO2 diffusion-convection are studied. With the Pernis gas reservoir in the Netherlands as an example，the storage potential of abandoned gas reservoirs is evaluated. The results show that the CO2 solubility in saline aquifers increases with the rising pressure while decreases with higher temperature and salinity. At the same pressure，the CO2 solubility at 25 ℃ is about twice that at 90 ℃. In addition，different impurities have different effects on CO2 dissolution，and CH4 reduces the CO2 solubility by around 12%. 2D simulation results show that the fingering rate of CO2 plume in saline aquifers is limited by the impurities. Meanwhile，the onset time of convection is extended due to the impurities. The onset time of CO2 mixture with 5% methane is around 2.5 times that of pure CO2. Considering the long timescale，the final dissolution is not affected by the impurities significantly. Through the studies of the Pernis gas reservoir，abandoned gas reservoirs have a large potential for CO2 storage. In the short run，CO2 exists in porous media as free gas and residual gas，while the amount of dissolved gas is relatively small. In 30 years after shutting the wells，the free gas accounts for 74.2%，and residual gas is 19.1%，while only 6.7% gas is dissolved into the aquifer.
Abandoned gas reservoirs are ideal sites for carrying out carbon dioxide（CO2）storage projects. However，impurities in gas reservoirs can affect the CO2 dissolution in saline aquifers. To this end，a fugacity-activity thermodynamic model is constructed to capture the features of impurities，CO2，and saline aquifers. On this basis，the operator-based linearization approach is implemented to solve the mass conservation equations accurately and efficiently. Then the effects of gas mixtures on CO2 diffusion-convection are studied. With the Pernis gas reservoir in the Netherlands as an example，the storage potential of abandoned gas reservoirs is evaluated. The results show that the CO2 solubility in saline aquifers increases with the rising pressure while decreases with higher temperature and salinity. At the same pressure，the CO2 solubility at 25 ℃ is about twice that at 90 ℃. In addition，different impurities have different effects on CO2 dissolution，and CH4 reduces the CO2 solubility by around 12%. 2D simulation results show that the fingering rate of CO2 plume in saline aquifers is limited by the impurities. Meanwhile，the onset time of convection is extended due to the impurities. The onset time of CO2 mixture with 5% methane is around 2.5 times that of pure CO2. Considering the long timescale，the final dissolution is not affected by the impurities significantly. Through the studies of the Pernis gas reservoir，abandoned gas reservoirs have a large potential for CO2 storage. In the short run，CO2 exists in porous media as free gas and residual gas，while the amount of dissolved gas is relatively small. In 30 years after shutting the wells，the free gas accounts for 74.2%，and residual gas is 19.1%，while only 6.7% gas is dissolved into the aquifer.
2023, 30(2):162-167.
DOI: 10.13673/j.cnki.cn37-1359/te.202201028
Abstract:
The storage of saline aquifers has the greatest potential in the CO2 geological storage. At present，the successful demonstration projects of typical CO2 geological storage in the saline aquifer in the world include Sleipner and Sn?hvit in Norway，In Salah in Algeria，and Shenhua in Ordos Basin，China. These projects provide long-term Carbon Capture and Storage（CCS）experience and are of reference significance for the implementation of future CO2 geological storage projects.Given the geological characteristics of the structure，reservoir，and caprock，this paper analyzed each case in combination with the injection and monitoring plans of each demonstration project and extracted geological and engineering parameters.Then，the influence of geological characteristics on CO2 geological storage was analyzed to clarify the feasibility of CO2 geological storage with structural features such as anticlines，fault blocks，and fractures. The injection and monitoring plans for CO2 geological storage in the saline aquifers were also compared. The following conclusions are drawn：①The success of the Sleipner CO2 geological storage project is attributed to the simple structure，large area，good physical properties of the reservoir as well as the large and stable caprock thickness. The faults developed in Sn?hvit and fractures in In Salah also verify the possibility of CO2 geological storage with different structural characteristics，and the distribution of CO2 plume is controlled by geological characteristics. ②There are relatively few injection wells for CO2 geological storage in saline aquifers，but the injection volume is relatively large，and horizontal wells dominate. ③High-quality monitoring data can effectively reduce potential leakage risk，and a variety of monitoring combinations can contribute to the long-term safe CO2 geological storage.
The storage of saline aquifers has the greatest potential in the CO2 geological storage. At present，the successful demonstration projects of typical CO2 geological storage in the saline aquifer in the world include Sleipner and Sn?hvit in Norway，In Salah in Algeria，and Shenhua in Ordos Basin，China. These projects provide long-term Carbon Capture and Storage（CCS）experience and are of reference significance for the implementation of future CO2 geological storage projects.Given the geological characteristics of the structure，reservoir，and caprock，this paper analyzed each case in combination with the injection and monitoring plans of each demonstration project and extracted geological and engineering parameters.Then，the influence of geological characteristics on CO2 geological storage was analyzed to clarify the feasibility of CO2 geological storage with structural features such as anticlines，fault blocks，and fractures. The injection and monitoring plans for CO2 geological storage in the saline aquifers were also compared. The following conclusions are drawn：①The success of the Sleipner CO2 geological storage project is attributed to the simple structure，large area，good physical properties of the reservoir as well as the large and stable caprock thickness. The faults developed in Sn?hvit and fractures in In Salah also verify the possibility of CO2 geological storage with different structural characteristics，and the distribution of CO2 plume is controlled by geological characteristics. ②There are relatively few injection wells for CO2 geological storage in saline aquifers，but the injection volume is relatively large，and horizontal wells dominate. ③High-quality monitoring data can effectively reduce potential leakage risk，and a variety of monitoring combinations can contribute to the long-term safe CO2 geological storage.
2023, 30(2):168-173.
DOI: 10.13673/j.cnki.cn37-1359/te.202211013
Abstract:
The life cycle of CCUS-EOR development can be divided into two parts. One is the simultaneous sequestration phase（SSP），and the other is the deep burial phase（DBP）of CCS. Determining the time length of SSP is an important part of CCUS-EOR development scheme design. According to the change trend of oil production under CO2 flooding，SSP can be further divided into an oil production rising period，a stable oil production period，and an oil production declining period.The time length of the oil production rising period is calculated from the annual gas injection rate and the cumulative injection amount at the gas emergence time. The time length of the stable oil production period under gas flooding is calculated by means of“centralized recovery time of oil bank”. The change of stage recovery during the oil production declining period is studied by using the representative decline curves. The oil recovery rate during the stable oil production period and oil production decline rate under gas flooding are measured based on the concept of“oil production multiplier due to gas flooding”. Thus，a mathematical model for evaluating stage recovery in the case of CO2 flooding is established. The moment when the stage recovery under CO2 flooding approaches the estimated ultimate recovery is proposed as the transition point between SSP and DBP. On this basis，a phase transition criterion is introduced. The time length of SSP minus those of the oil production rising period and the stable oil production period is the time length of the oil production declining period.
The life cycle of CCUS-EOR development can be divided into two parts. One is the simultaneous sequestration phase（SSP），and the other is the deep burial phase（DBP）of CCS. Determining the time length of SSP is an important part of CCUS-EOR development scheme design. According to the change trend of oil production under CO2 flooding，SSP can be further divided into an oil production rising period，a stable oil production period，and an oil production declining period.The time length of the oil production rising period is calculated from the annual gas injection rate and the cumulative injection amount at the gas emergence time. The time length of the stable oil production period under gas flooding is calculated by means of“centralized recovery time of oil bank”. The change of stage recovery during the oil production declining period is studied by using the representative decline curves. The oil recovery rate during the stable oil production period and oil production decline rate under gas flooding are measured based on the concept of“oil production multiplier due to gas flooding”. Thus，a mathematical model for evaluating stage recovery in the case of CO2 flooding is established. The moment when the stage recovery under CO2 flooding approaches the estimated ultimate recovery is proposed as the transition point between SSP and DBP. On this basis，a phase transition criterion is introduced. The time length of SSP minus those of the oil production rising period and the stable oil production period is the time length of the oil production declining period.
2023, 30(2):174-180.
DOI: 10.13673/j.cnki.cn37-1359/te.202301025
Abstract:
CO2 storage in the brine layers is one of the common countermeasures to alleviate the greenhouse effect，and dissolved CO2 storage is a relatively stable storage mode in the process of storage，so it is urgent to find a method to accurately calculate the potential of dissolved CO2 storage. In this paper，the CO2 dissolution coefficient in water is calculated by using the prediction model proposed by Duan et al.，and then the theoretical dissolved CO2 storage is obtained. Then，the index of the effective CO2 storage coefficient is established，and the main controlling factors of dissolved CO2 storage are considered.According to the numerical simulation and regression analysis，the prediction model of the effective storage coefficient of dissolved CO2 storage is established. The results show that when the horizontal permeability and the formation dip angle are constant，the effective storage coefficient of dissolved CO2 storage increases with the increase in initial pressure. When the initial pressure is constant，the effective storage coefficient of dissolved CO2 storage increases with the increase in horizontal permeability and decreases with the increase in formation dip angle. The predicted results of the prediction model are in good agreement with the results of the numerical simulation. According to the actual parameters of Block7 in Gudong Oilfield，the theoretical storage is 65.382 Mt，the effective storage coefficient of dissolved CO2 storage is 0.079，and the effective storage of dissolved CO2 storage is 5.178 Mt.
CO2 storage in the brine layers is one of the common countermeasures to alleviate the greenhouse effect，and dissolved CO2 storage is a relatively stable storage mode in the process of storage，so it is urgent to find a method to accurately calculate the potential of dissolved CO2 storage. In this paper，the CO2 dissolution coefficient in water is calculated by using the prediction model proposed by Duan et al.，and then the theoretical dissolved CO2 storage is obtained. Then，the index of the effective CO2 storage coefficient is established，and the main controlling factors of dissolved CO2 storage are considered.According to the numerical simulation and regression analysis，the prediction model of the effective storage coefficient of dissolved CO2 storage is established. The results show that when the horizontal permeability and the formation dip angle are constant，the effective storage coefficient of dissolved CO2 storage increases with the increase in initial pressure. When the initial pressure is constant，the effective storage coefficient of dissolved CO2 storage increases with the increase in horizontal permeability and decreases with the increase in formation dip angle. The predicted results of the prediction model are in good agreement with the results of the numerical simulation. According to the actual parameters of Block7 in Gudong Oilfield，the theoretical storage is 65.382 Mt，the effective storage coefficient of dissolved CO2 storage is 0.079，and the effective storage of dissolved CO2 storage is 5.178 Mt.
2023, 30(2):181-186.
DOI: 10.13673/j.cnki.cn37-1359/te.202204009
Abstract:
As the most effective and potential carbon capture，utilization，and storage（CCUS）technology，Carbon dioxide capture，EOR-utilization and storage（CCUS-EOR）is one of the important means to realize carbon peaking and carbon neutrality goals. However，its development and application are restricted by economical efficiency at present. To explore the actual economic effect of CCUS-EOR projects and its improvement methods，this paper conducted the economic evaluation of four typical projects in China and probed into the key economic factors influencing its economical efficiency via the comparative analysis of key parameters and sensitivity analysis. Then，the benchmark balance boundary of key economic parameters was calculated by the benchmark balance analysis technology. The results show that the international oil price of about 70 US dollars/barrel is needed for the internal rate of return of most projects to reach the standard when the CO2 price is 300 yuan/ton. The economic effect of CCUS-EOR projects is mainly influenced by the oil price，oil production increment，CO2 price，oil draining ratio，and construction investment. In a bid to ensure that the projects’rate of return can reach the standard，the CO2 price should be less than 300 yuan/ton，the oil draining ratio smaller than 4.5 tCO2/toil，and the construction investment less than 700 yuan/ton. The lower these are，the projects’internal rate of return is higher. The paper also discussed three ways of carbon trading benefits，financial support and tax incentives，and simultaneous storage of multiple reservoirs to improve the economic effect of the projects from the outside in hope of providing reference for CCUS-EOR technology development planning and project implementation.
As the most effective and potential carbon capture，utilization，and storage（CCUS）technology，Carbon dioxide capture，EOR-utilization and storage（CCUS-EOR）is one of the important means to realize carbon peaking and carbon neutrality goals. However，its development and application are restricted by economical efficiency at present. To explore the actual economic effect of CCUS-EOR projects and its improvement methods，this paper conducted the economic evaluation of four typical projects in China and probed into the key economic factors influencing its economical efficiency via the comparative analysis of key parameters and sensitivity analysis. Then，the benchmark balance boundary of key economic parameters was calculated by the benchmark balance analysis technology. The results show that the international oil price of about 70 US dollars/barrel is needed for the internal rate of return of most projects to reach the standard when the CO2 price is 300 yuan/ton. The economic effect of CCUS-EOR projects is mainly influenced by the oil price，oil production increment，CO2 price，oil draining ratio，and construction investment. In a bid to ensure that the projects’rate of return can reach the standard，the CO2 price should be less than 300 yuan/ton，the oil draining ratio smaller than 4.5 tCO2/toil，and the construction investment less than 700 yuan/ton. The lower these are，the projects’internal rate of return is higher. The paper also discussed three ways of carbon trading benefits，financial support and tax incentives，and simultaneous storage of multiple reservoirs to improve the economic effect of the projects from the outside in hope of providing reference for CCUS-EOR technology development planning and project implementation.
Online Submit
Reviewer
Editor
Reader
Quick Search
External Links
