Geofluids
Volume 2017 (2017), Article ID 6126505, 25 pages
https://doi.org/10.1155/2017/6126505

Review Article

Worldwide Status of CCUS Technologies and Their Development and Challenges in China

H. J. Liu,¹ P. Were,² Q. Li,³ Y. Gou,2,4 and Z. Hou2,4,5

¹INRS-ETE, Universite du Québec, Québec, QC, Canada
²Energie-Forschungszentrum Niedersachsen, Clausthal University of Technology, Goslar, Germany
³State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, China
⁴Sino-German Energy Research Center, Sichuan University, Chengdu, China
⁵Institute of Petroleum Engineering, Clausthal University of Technology, Clausthal-Zellerfeld, Germany

Correspondence should be addressed to Y. Gou; yang.gou@efzn.de and Z. Hou; hou@tu-clausthal.de

Received 19 February 2017; Revised 12 May 2017; Accepted 20 June 2017; Published 28 August 2017

Academic Editor: Weon Shik Han

Copyright © 2017 H. J. Liu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Carbon capture, utilization, and storage (CCUS) is a gas injection technology that enables the storage of CO₂ underground. The aims are twofold, on one hand to reduce the emissions of CO₂ into the atmosphere and on the other hand to increase oil/gas/heat recovery. Different types of CCUS technologies and related engineering projects have a long history of research and operation in the USA. However, in China they have a short development period ca. 10 years. Unlike CO₂ capture and CO₂-EOR technologies that are already operating on a commercial scale in China, research into other CCUS technologies is still in its infancy or at the pilot-scale. This paper first reviews the status and development of the different types of CCUS technologies and related engineering projects worldwide. Then it focuses on their developments in China in the last decade. The main research projects, international cooperation, and pilot-scale engineering projects in China are summarized and compared. Finally, the paper examines the challenges and prospects to be experienced through the industrialization of CCUS engineering projects in China. It can be concluded that the CCUS technologies have still large potential in China. It can only be unlocked by overcoming the technical and social challenges.

1. Introduction

Fossil fuels, especially coal that is rich in carbon, constitute the highest proportion of primary energy in China [1]. In recent years, the rapid urbanization and development of industries including power plants, cement factories, steel plants, biotransformation, and fossil fuel transformation plants, which are highly dependent on large consumption of fossil fuels, have been a great challenge to the Chinese environment [2, 3]. Since the winter of 2012/2013, most cities in China have been faced with serious atmospheric pollution from a haze formed from a combination of SO₂, NOx, and inhalable particles within the mist, containing fine particle concentrations of up to ca. 900 μg/m³ [4]. Automobile exhausts, industrial emissions, waste incineration, and fugitive dust from construction sites are the main sources of the haze. Based on statistical data from Beijing, reported by China Central Television (CCTV) in 2014, haze particles from automobile exhausts contributed 22.2%, while the burning of coal, dust, and industrial emissions accounted for proportions of 16.7%, 16.3%, and 15.7%, respectively. Therefore, a reduction in the emissions from coal and industry has become the key to improving the quality of the environment.

The increase in the concentration of greenhouse gases has had a large impact on global climate change, since industrialization. Many countries have set targets for reducing the emissions of greenhouse gases in order to mitigate global warming. Among them, top on the list of CO₂ emissions in the world, China aims at reducing 40%–45% of its CO₂ emissions per unit GDP by 2020, based on the 2005 level [5–7]. This requires considerable changes not only in the framework of fossil fuel consumption, but also in the development of renewable energy from wind, solar, geothermal, and so on, together with an enlargement in the area covered by forests and innovations in technologies that can enable permanent storage of the CO₂ underground.

CO₂ emissions in China come mainly from the combustion of fossil fuels (90%) and during the process of cement manufacturing (10%). For example, in 2012, 68% of the emitted CO₂ was sourced mainly from the combustion of coal, while 13% came from oil and 7% from natural gas [8]. According to the statistics, annual emissions of CO₂ from large stationary point sources, that is, >0.1 Mt/year, amount to 3.89 GtCO₂, which accounts for 67% of the total emissions. Among which, 72% is from power stations [9]. This demonstrates that a reduction of the CO₂ emissions from the large stationary point sources is the key to realizing China’s target [10, 11].

China’s main target for the transformation in its energy framework is to reduce the combustion of coal, while increasing the supply of natural gas and other clean energy, and controlling the emissions of CO₂, SO₂, NOx, and so on. CO₂ capture and sequestration (CCS) and utilization (CCUS) technologies can be applied to store CO₂ underground effectively, thus reducing its emission into the atmosphere. This technology is now highly developed and is likely to play a significant role in China, especially when the operation costs are reduced. This paper reviews the state of the art of CCS and CCUS technologies worldwide while paying more attention on its status and development in China. The mature technology will be examined in various engineering projects. Therefore, this paper considers the state of operation of CCS and CCUS projects in detail and concludes by presenting the likely challenges to be experienced through the industrialization of these projects in China. Due to space limitation, it has not been possible to include a review of the current research status on the conversion of CO₂ to produce some commercial products or its use in the food industry, for example, as an additive in beverages or as a preservative for fruits and vegetables. Henceforth, only its utilization for geologic and geoengineering purposes such as EOR, ECBM, ESG, and EGR has been considered in this paper.

2. Worldwide Development of CCS and CCUS

The CCS technology is a means to control emissions of CO₂ that are captured from different processes including precombustion, postcombustion, and oxy-fuel combustion. The stages of a CCS project can be divided into () CO₂ capture, () CO₂ transportation, () CO₂ injection, and () postinjection of CO₂ [12–19].

In the short term, depending on the purpose of the CCS project, CO₂ can be stored in different geological sites, including deep saline formations, depleted oil or gas reservoirs, deep unmineable coal seams, and shale formations, to reduce the CO₂ emissions [20, 21], Figure 1. In comparison with the pure CCS technology, CCUS technology pays more attention to utilization (U) of the captured CO₂ while sequestration (S) plays a secondary role. CCUS can reduce the cost of sequestration and bring benefits by enhancing the production of hydrocarbons or heat energy, thus becoming very popular in recent years. Based on the purpose of the CO₂ injection, a number of related technologies have been developed including () Enhanced Oil Recovery (EOR), () Enhanced Coalbed Methane Recovery (ECBM), () Enhanced Gas Recovery (EGR), () Enhanced Shale Gas Recovery (ESG), and () Enhanced Geothermal System (EGS).

Figure 1: Schematic diagram of the CCUS technology in different geological reservoirs for both long and short-term sequestration of CO₂.

The engineering projects for both CCS and CCUS technologies are systematically complicated, with their success depending on rigorous research in engineering and science disciplines including geology, geoengineering, geophysics, environmental engineering, mathematics, and computer sciences. In addition, key to success in site selection for any such a project demands strict considerations of safety, economy, environment, and public acceptance at all levels of operation, that is, countrywide, basin-wide, regional, or subbasin levels [22–26], Figure 2. Although CCS and CCUS technologies share similarities in site selection, each will induce a series of different physical and chemical responses in the underground porous or fractured rock formations, in terms of the existing local hydrological (H), thermal (T), mechanical (M), and chemical (C) fields [27–29], Figure 2. Coupling of the THMC processes during and after CO₂ injection related to CCS and CCUS technologies has become a research hotspot in recent years [26, 30–33]. The two technologies, however, have minor differences, in terms of purpose, storage duration, injection depth and rate, fluid and reservoir types, scheme of drilling, completion and monitoring, and so on.

Figure 2: Schematics of the two main topics, that is, the site selection system () and the THMC responses () associated with CCS and CCUS technologies.

2.1. CCS

CCS is a viable option for significantly reducing CO₂ emissions from large-scale emission sources. When its only purpose is for CO₂ sequestration, the storage sites may include deep saline formations, deep unmineable coal seam, depleted oil or gas reservoir, and rock salt caverns [35–38]. This technology is mature but still very expensive for widespread commercial application.

2.2. CCUS: CO₂-EOR

The first CO₂-EOR field test was held in 1964 in Mead Strawn Texas, in the USA. Since the 1970s, CO₂ has been used on a commercial scale for oil production projects [20, 21]. Up to the present time, there have been more than 100 CO₂-EOR projects in operation. Among them, the CO₂-EOR project in Weyburn, Canada, is the most successful example. It uses mixed gases separated from natural gas production, coal gasification, and coal power from the Great Plains Synfuels Plant near Beulah, North Dakota, USA [39]. The injection gas is mainly composed of CO₂ (96.8%), plus H₂S (1.1%) and a minor amount of hydrocarbons that are piped to the Weyburn Basin through a pipeline 339 km in length [7]. The purpose of the project is to inject 2 million tons of CO₂ into the depleting oil reservoir over a 20-year period, in order to increase oil recovery to 130 million barrels and to extend the production of oil in this oilfield to 25 years [40].

2.3. CCUS: CO₂-ECBM

The conventional method to produce coalbed methane is to decrease the pressure in the coalbed reservoir, making the methane desorb from the matrix. However, the recovery of coalbed methane production using this method is less than 50%. The alternative is to desorb more CH₄ from the coalbed matrix by injecting gases including CO₂ or N₂ [41–44]. Studies on enhancing coalbed methane by CO₂ injection started in the 1990s [7, 45]. When CO₂ is injected in the coalbed layer, both the gaseous and adsorbed-state of CH₄ and CO₂ will exist in equilibrium [46]. Because the coalbed has a much stronger adsorption capacity for CO₂ than CH₄, the injection of CO₂ will make the adsorbed CH₄ desorb, thus enhancing the CH₄ recovery. A proportion of the injected CO₂ will be stored in the coalbed formation, making it difficult for it to leak to the surface. Therefore, this technology can bring both economic benefits and also guarantee the safe storage of CO₂ [47, 48].

The successful injection of CO₂ to enhance coalbed methane recovery has been proved by many experimental and numerical studies. However, the production efficiency is strongly site-dependent, in relation to the permeability of the coalbed matrix, production history, gas transportation process, maturation of coal, geological configuration, completion scheme, hydraulic pressure, and so on [42–44, 49–52]. Nevertheless, the maturity of its commercial application is still very low. Pilot-scale CO₂-ECBM projects so far include those in Alberta, Canada, which started in 1997, the Burlington project in the San Juan Basin of the USA, the RECOPOL project that started in 2001, the Yubari project in Japan, and the Qinshui basin project in China that started in 2002 [53].

2.4. CCUS: CO₂-EGR

Studies on injecting CO₂ into depleted gas reservoirs to enhance gas recovery started in the 1990s [54]. Unlike the CO₂-EOR technology, CO₂-EGR technology is still at the pilot-scale stage. Its efficiency is highly dependent on reservoir type, temperature and pressure conditions, heterogeneity, production strategy, and so on [55–60]. For some CO₂-EGR projects, the gas recovered can reach 10%, while other projects have seen less or no enhancement [61–63]. The rapid breakthrough of CO₂ in a production well, resulting in a high concentration of CO₂, restricts the production of pure natural gas [64]. Since 1999, the USA has carried out a pilot project of CO₂-EGR in Rio Vista. The Netherlands injected 60 kilotonnes of CO₂ into a depleted gas reservoir in the K12B project during 2004 and 2009 [7]. The CLEAN project in Germany started a CO₂-EGR project in the Altmark gas fields in 2009; however, public protests have prevented CO₂ injection on the site [65]. Many other countries including Australia and Norway are also positively developing this technology [64, 66–74].

2.5. CCUS: CO₂-ESG

The USA has been carrying out shale gas desorption since 1821. However, limited development of the technology made this process procedurally cumbersome and substantively difficult to apply before the 21st century. In 2000, shale gas contributed only 1% of the whole natural gas supply, while, by the end of 2011, this proportion had increased to 30% due to a breakthrough in horizontal drilling and horizontal multistaged fracturing technology. The revolution of shale gas in the USA is changing the energy structure of the world [75].

Encouraged by the successful application of CO₂ in oil and gas recovery, its application in aiding the production of shale gas began in recent years [76–81]. There has also been progress in replacing water by supercritical CO₂ as the injection fluid in the fracturing technology [82–86]. However, this process is still in the very early exploration stages.

2.6. CCUS: CO₂-EGS

The first study of EGS technology started in Fenton Hill, USA, in 1970 [87]. Since then, many other countries, including France, Germany, Austria, Italy, Japan, and Australia, have paid attention to the development of this technology. The conventional EGS technology uses water as the injection fluid and circulation media. Based on the research in [88], CO₂ is now regarded as a more favorable circulation fluid compared with water because of its large compressibility and expansibility. This idea has already been supported by many studies (e.g., [89–93]).

The application of CO₂ in a geothermal system is not restricted to the hot dry rock reservoirs but also includes the conventional hydrothermal reservoirs [38, 91, 94]. The injection of CO₂ can enhance the efficiency of reinjecting the hot wastewater by improving the porosity and permeability through the activated water-rock geochemical reactions [95]. Besides being the main circulation fluid, CO₂ can also be regarded as a pressurized hydraulic fluid in the reservoir. Injection of CO₂ in a hydrothermal or hot dry rock reservoir can maintain the reservoir pressure, promoting the flow rate of the in situ water towards the production well, thus enhancing the heat recovery and even the recovery of the CH₄ dissolved in the aquifer water [96–99]. Reference [38] described this process as the CO₂-AGES (CO₂-aided geothermal extraction system) in which three stages are involved: () the production of hot water when CO₂ is used as the pressurized hydraulic fluid; () two-phase fluid flow in the production well after the CO₂ breakthrough; and () and as a circulation fluid, when CO₂ fills the production well, which is similar to CO₂-EGS.

3. CCS and CCUS Engineering Projects Worldwide

By the end of 2016, based on the statistics of Global Status 2016, there were 38 large-scale CCS + CCUS projects in operation or under construction and planning. Among them, 17 projects are located in North America (12 projects in the United States and 5 in Canada); 12 projects in Asia (8 in China, 2 in South Korea, 1 in Saudi Arabia, and 1 in United Arab Emirates), 5 in Europe (2 in Norway, 2 in United Kingdom, and 1 in the Netherlands), 3 in Australia, and 1 in Brazil. Among the 15 projects that are in operation, 12 projects are related to CO₂-EOR and the other 3 projects are pure CO₂ sequestration. There are 66 pilot-scale CCS + CCUS projects of which 22 are in operation, 5 under construction, 5 at the planning stage, and 34 have just been completed.

Among the 70 pilot-scale engineering CCUS projects worldwide, based on their distribution by regions or countries, 22 are located in North America, 1 in South America, 22 in Europe, 20 in Asia, 4 in Australia, and 1 in South Africa; see Figure 3 for more details.

Figure 3: Global distribution of pilot-scale CCUS engineering projects based on project purpose and reservoir types, data sourced from http://www.globalccsinstitute.com/.

There are still no concrete CO₂-ESG and CO₂-EGS projects anywhere in the world. Only a few countries, including the USA, Canada, China, and Argentina, can commercially produce shale gas. At the end of 2015, the daily shale gas output in the USA, Canada, China, and Argentina had reached 37, 4.1, 0.5, and 0.07 Bcf, respectively [100, 101]. Shale gas production in the USA abruptly increased after 2000, while Canada and China successfully produced shale gas for the first time in 2008 and 2012, respectively. There are now more than 100,000 shale gas drilling wells in the USA. In China, however, only about 600 wells have been drilled in the last few years [102]. The EGS technology is still at the research and development stage. Nevertheless, there are some experimental EGS plants and pilot projects, for example, at Fenton Hill, Coso, and Desert Peak in the USA, Bad Urach, Neustadt-Glewe, Bruchsal, Landau, and Unterhaching in Germany, and Soultz-sous-Forets and Bouillante in France [87]. Substantially higher research, development, and demonstration efforts are needed to ensure EGS technology becomes commercially viable in the near future.

4. Current Status of CCS and CCUS Technologies in China

Since 2005, CCS has been listed as a frontier technology in China’s mid-long term technical development program in order to realize the goal of zero emissions from fossil fuel energy [103]. Meanwhile, more attention has been paid to CCUS technology, especially CO₂-EOR and CO₂-ECBM [104–107]. Between 2006 and 2015, the Ministry of Science and Technology of China (MOST) funded eight National Basic Research Programs (also known as the 973 Program) and State High-Tech Development Plans (commonly known as the 863 Program). Three of these programs were related to CO₂-EOR and the others to the CO₂ capture technology, shale gas recovery, and the hot dry rock systems. The National Natural Science Foundation of China (NSFC) also generously funded basic research related to CCS and CCUS.

Based on the incomplete statistics of the research projects funded by MOST and NSFC during 2005–2016 (Figures 4 and 5 and Table 1), the distribution of funding for different aspects of CCS and CCUS is shown as follows: () CCS (32 projects), of which all the 7 projects funded by the MOST were related to CO₂ capture technology. The 23 projects funded by the NSFC and 1 project funded by the Ministry of Land and Resources were concerned with CO₂ storage; () CCUS: CO₂-EOR (18 projects), of which 6 projects were funded by the MOST and 10 by the NSFC; () CCUS: CO₂-ECBM (22 projects), of which 3 projects were funded by the MOST, and 17 by the NSFC; () CCUS: CO₂-EGR (4 projects); () CCUS: CO₂-ESG (4 projects); and () CCUS: CO₂-EGS (7 projects).

Table 1: The research projects of CCUS funded by China Ministry of Science and Technology (MOST) and National Natural Science Foundation of China (NSFC) and so on during 2005–2016 (amount unit: 10,000 RMB or 1,450 US$).

Name of the research projects
Responsible institute
Funding sources
Amount

Type 1: CO ₂-EOR

Utilization of CO₂-EOR and geological storage of CO₂
Research Institute of Petroleum Exploration & Development (CNPC)
973 Program 2006–2010
3500

Key technologies of CO₂-EOR and sequestration
863 Program 2009–2011
—

Basic research on CO₂ geological sequestration, reduction in CO₂ emission and utilization
973 Program 2011–2015
—

Key technologies of CO₂-EOR and storage
Major Science & Technology 2011–2015
—

Microscopic mechanism of oil-water-rock multiple surface system of the porous media and their application
NSFC 2016 confirmed
20

CO₂ capture and storage technologies
Tsinghua University
2008–2010
—

Basic studies on the transportation of supercritical CO₂, water and oil in the low permeable porous media
Dalian University of Science and Technology
NSFC 2008–2011
180

Studies on microscopic flowing mechanism of supercritical CO₂, oil and water in the low permeable oil reservoir
NSFC 2013–2015
25

Studies on the CO₂ diffusion and mass transfer processes in oil and water bearing porous media
NSFC 2013 confirmed
25

Factors affect the CO₂ diffusion in the porous media and its mechanism studies
China University of Petroleum
NSFC 2009–2011
20

QSAR studies on the thermodynamics and transportation properties of CO₂-EOR system
Tianjin University
NSFC 2012–2014
—

CO₂-EOR and its damage mechanism to the reservoir
China University of Geosciences
NSFC 2012–2015
59

Studies on the surface properties using alkylol amine capture CO₂ and processes of CO₂-EOR
North China Electric Power University
NSFC 2012–2016
—

Microscopic mechanism, quantification and optimization of injection-production scheme of CO₂-EOR and CO₂ sequestration in the oilfield
Southwest Petroleum University etc.
NSFC 2014–2016
25

CO₂-EOR pilot project in Jilin oilfield
Jilin oilfield etc.
2007-
—

CO₂-EOR process and pilot project in Songliao basin
Major Science & Technology 2011–2015
—

CO₂ capture and CO₂-EOR pilot project in Shengli oilfield
Shengli oilfield etc.
2010-
—

Technical development of CO₂ capture from the flue gas of the large-scale coal-fired power station, EOR and storage and pilot projects
Major Science & Technology 2012–2016
—

CO₂ capture from coal gasification and EOR
Independent project
—

Type 2: CO ₂-ECBM

CO₂ storage and enhanced coalbed methane recovery
China United Coalbed Methane Corp., Ltd. etc.
International 2002–2007
—

CO₂ injection and storage in the deep coal seam and enhanced coalbed methane recovery
International 2011–2015
—

Test project of deep coalbed methane production technology of China United Coalbed Methane Corp. Ltd. (CUCMC)
Major Science & Technology 2011–2015
—

CO₂-ECBM potential in China and related basic scientific research issues
Institute of Rock and Soil Mechanics (CAS)
One hundred talent program 2005–2009
—

CO₂-ECBM potential in China and the suitability evaluation
GSC 2011
—

Mechanism of using mixtures of CO₂/N₂ displace coalbed methane in situ geological conditions and the best ratio of gas composition
NSFC 2012–2014
26

Impacts of coal matrix on the coal expansion and permeability changes of CO₂/CH₄ during the CO₂-ECBM process
Institute of Coal Chemistry (CAS)
NSFC 2007–2009
—

Solid-gas interaction during CO₂ sequestration in the deep coal seam and simulation of the sequestration experiment
Institute of Process Engineering (CAS)
NSFC 2007–2009
32

Advanced models of CO₂-ECMB
China University of Mining and Engineering
NSFC 2007-2008
6

Adsorption and desorption mechanisms of multiple gases during CO₂-ECBM process
NSFC 2003–2005

Experimental study of coal matrix on expansion effects during CO₂-ECBM process
NSFC 2008–2010
—

Two-phase gas and solid coupling effect and dual porosity effect during the CO₂ sequestration in the deep coal seam
NSFC 2011–2013
20

THM coupling mechanism of CO₂-ECBM
NSFC 2012–2014
25

Dynamic model of multiphase fluid CH₄-water flow in porous media of heterogeneous coal seam
NSFC 2012 confirmed
25

Fluid-solid coupling response and mechanism of supercritical CO₂ and minerals in the coal
NSFC 2013 confirmed
25

Theoretical study of CO2 sequestration in the deep coal seam and the efficiency of CH₄ recovery
NSFC 2014 confirmed
300

Interaction of supercritical CO₂ and organic matter in the coal and their responses to the coal structure
NSFC 2014 confirmed
25

The construction of 3D model of reservoir structure in the high grade coal and the geochemical response to the injection of CO₂
NSFC 2014 confirmed
23

CO₂ enhances CH₄ adsorbed by the coal, the permeability characteristics and mechanisms
NSFC 2015 confirmed
70

Multiphase gas-liquid-solid coupling mechanisms of CO₂ sequestration in the porous coal media
NSFC 2016 confirmed
62

Interaction of supercritical CO₂ and coal during CO₂ sequestration in the deep coal seam and its impact on the CO₂ storage
Shandong University of Science and Technology
NSFC 2012–2015
60

Transportation mechanisms of supercritical CO₂ injection into the stress partition residual coal pillar and its displacement of CH₄

NSFC 2015 confirmed
20

Basic research on the mechanism of CO₂-ECMB in the deep low permeable unmineable coal seam under THM coupling effect
Liaoning Technical University
NSFC 2009–2011
33

Microscopic mechanism of supercritical CO₂ on the recovery of CH₄ in the coal
NSFC 2014 confirmed
25

Type 3: CO ₂-EGR

Safety production of the CO₂ bearing gas reservoir and the utilization of CO₂
Research Institute of Petroleum Exploration & Development
Major Science & Technology 2008–2010
—

Pilot project of the production of the CO₂ bearing volcanic gas reservoir and utilization
Jilin oilfield etc.
CNPC 2008–2010
—

CO₂ sequestration mechanism in the depleted gas reservoir and the transportation rules
Southwest Petroleum University
NSFC 2013 confirmed
80

Phase behavior of supercritical CO₂ displacing CH₄ in the porous media and the seepage characteristics
Dalian University of Technology
NSFC 2015 confirmed
64

Type 4: CO ₂-ESG

Basic research of supercritical carbon dioxide enhanced shale gas development
Wuhan University
973 Program 2014–2018
—

Basic research of the supercritical CO₂ in the production of unconventional oil and gas reservoirs
China University of Petroleum
NSFC 2011–2014
258

CO₂ sequestration in the shale gas reservoir and mechanisms of CO₂-CH₄-shale interaction
Chongqing University
NSFC 2013–2015
25

Damage mechanism of using supercritical CO₂ as the hydraulic fluid in the shale reservoir
NSFC 2014 confirmed
25

Studies on the solid-fluid coupling mechanisms of CO₂ sequestration in the shale reservoir and its effect on the recovery of shale gas
NSFC 2014 confirmed
80

Brittle fracturing mechanism of supercritical CO₂ used as the hydraulic fluid in the shale reservoir and the transportation rule of the suspended sand
Qingdao University of Science & Technology
NSFC 2014–2016
80

The propagation evolution of the hydraulic fracture network induced by the supercritical CO₂ in the shale reservoir
Institute of Geology and Geophysics (CAS)
NSFC 2015–2017
85

Type 5: EGS/CO ₂-EGS

Simulation and prediction of CO₂-EGS
Jilin University etc.
Ph.D. program 2011–2013
—

Comprehensive utilization and production of hot dry rocks
863 Program 2012–2015
—

The flowing characteristics of the man-made fractures in the hot dry rocks and the mechanisms of multifield coupling heat and mass transfer
Tianjin University
NSFC 2013 confirmed
76

Large scale CO₂ utilization and storage in the innovative EGS technology
Tsinghua University
International 2012–2014
—

Mechanisms of the production of geothermal energy in the high temperature depleted gas reservoir using CO₂ as the circulation fluid and the evaluation of potential
China University of Petroleum
NSFC 2016 confirmed
54

Heat transfer using supercritical CO2 enhances the geothermal recovery and the mechanisms of induced sliding of fractures
Institute of Rock and Soil Mechanics (CAS)
NSFC 2016 confirmed
54

Multiphase dynamic characteristics in the CO₂ plume type geothermal system and the optimization of the energy conversion
Jilin Jianzhu University
NSFC 2016 confirmed
20

Type 6: CO ₂ capture technology

R&D of the new type O₂/CO₂ circulated combustion equipment and the optimization of system
Huazhong University of Science and Technology
863 Program 2009–2011
—

Key technologies of CO₂ capture by using 35 MWth oxy-fuel combustion technology, R&D in equipment and pilot projects
National Sci-Tech support plan 2011–2014
—

R&D in key technologies of CO₂—oleaginous microalgae—biodiesel
Xin’ao Group etc.
863 Program 2009–2011
2070

IGCC-based CO₂ capture, utilization and sequestration technologies and pilot projects
Huaneng Group etc.
863 Program 2011–2013
5000

CO₂ capture and purification technology using high gravity method
Shengli oilfield etc.
National Sci-Tech support plan 2008–2010
—

Capture of high concentration of CO₂ in 0.3 million tons coal to oil industry, geological sequestration technology and pilot scale project
Shenhua Group etc.
National Sci-Tech support plan 2011–2014
—

Development of key technologies of reduction in CO₂ emission from the blast furnace iron making and their utilization
China Association of Metal
National Sci-Tech support plan 2011–2014
—

Research on key technologies related with large-scale CO₂ capture from the flue gases of the coal-fired power station
Tsinghua University
NSFC 2012 confirmed
230

Type 7: CO ₂ storage in the saline formation (CCS technology)

Potential assessment of CO₂ geological storage in China and pilot projects
China Geological Survey
Ministry of Land and Resources 2010–2014
—

Multiphase multicomponent reactive transportation mechanism of the sequestration of impure CO₂ and numerical simulation
Institute of Rock and Soil Mechanics (CAS)
NSFC 2016 confirmed
20

HMC coupling mechanism of CO₂ sequestration in the saline formations, stability of rock and the transportation rules of CO₂
NSFC 2011 confirmed
20

Geochemical studies on the supercritical CO₂-rock-saline water system
China University of Geosciences
NSFC 2011–2013
50

Mechanisms of the water-rock-gas interaction of the CO₂ sequestration in the saline aquifers in the pressurized sedimentary basin
NSFC 2012–2014
70

Experimental geochemical studies on the interaction of supercritical CO₂-water-basalt
Nanjing University
NSFC 2013–2015
85

Surface characteristics of supercritical CO₂-saline water in CO₂ geological sequestration
Dongnan University
NSFC 2012–2014
25

The diffusion mechanism of CO₂ in porous media and its quantitative relationship with the propagation rate of the CO₂ front
China University of Petroleum
NSFC 2013 confirmed
80

Factors affect the diffusion and mechanism of CO₂ in porous media
NSFC 2009 confirmed
20

Numerical simulation of the multiple field coupling processes in CO₂ geological sequestration using numerical manifold method
Beijing University of Technology
NSFC 2012 confirmed
62

Evolution of the damage in the near-field neighboring rocks of the CO₂ storage site in the rock salt and the integrity studies
Sichuan University
NSFC 2012 confirmed
25

Transportation rule and trapping mechanisms of CO₂ geological sequestration in the multiscale heterogeneous saline formations
Hehai University
NSFC 2012 confirmed
58

Impacts of reservoir heterogeneity on the capacity of CO₂ in the saline formations
Wuhan University
NSFC 2013 confirmed
25

Flowing characteristics and mechanism of the supercritical CO₂ in the low permeable porous media
Qingdao University of Science & Technology
NSFC 2014 confirmed
80

Mechanism studies on the physical and dissolution trapping of the supercritical CO₂ in the microscopic porous aquifer
Tsinghua University
NSFC 2010 confirmed
20

Interaction of CO₂-saline water-caprocks in the CO₂ geological sequestration and the risk of CO₂ leakage
NSFC 2014 confirmed
84

Mechanisms of the difference in the distribution of the CO₂ saturation based on the high reliable saline formation model
GSC Hydrogeology & Environmental Geology
NSFC 2016 confirmed
18

Physical property measurements on the CO₂-saline water system in the CO₂ geological sequestration
Dalian University of Technology
NSFC 2011 confirmed
20

Impacts of the physical properties of the porous media on the two-phase (CO₂, saline water) fluid flow and the trapping mechanism of CO₂
NSFC 2014 confirmed
80

Two-phase CO₂-water fluid flow characteristics and trapping mechanism of CO₂ at the porous scale in the multiple porous media
NSFC 2015 confirmed
64

The convective mixing of CO₂ sequestration in the saline formations and its development characteristics
NSFC 2015 confirmed
21

Basic studies on the transportation of supercritical CO₂ in the geological sequestration in the saline formations
NSFC 2012 confirmed
25

Basic research on the wettability of CO₂-saline water-rock equilibrium system during the CO₂ sequestration in saline formations
NSFC 2013 confirmed
25

Viscous behavior and mechanism of the supercritical CO₂ on the rock surface in the geological sequestration condition
NSFC 2016 confirmed
60

Figure 4: Research projects of CCS and CCUS in China during 2005–2016 based on Table 1.

Figure 5: Different types of CCUS research projects in China during 2006–2016 based on Table 1.

Several international cooperation research projects were also developed, including NZEC between China and Europe, CAGS between China and Australia, and CCERC between China and the USA; see Table 2 for further details.

Table 2: China’s international collaboration on CCUS projects during 2005–2016.

Name of projects
Main responsible institutes in China
Funding sources
Funding

China-EU Cooperation on Near Zero Emissions Coal (NZEC)
The Administrative Center for China’s Agenda 21 (ACCA21) etc.
MOST, EU, UK Environment, Food and Rural Affairs (DEFRA) 2007–2009
4.5 million US$

China-Australia Geological Storage of CO₂ (CAGS)
MOST, Australian Department of Resources, Energy and Tourism
2010–2018
>4.0 million US$

China-Italy CCS project
MOST, Italian Ministry of Environment 2010–2012
—

China-Netherlands CO₂-ECBM and CO₂ saline aquifer storage exchange center
Institute of Coal Chemistry (CAS) etc.
Ministry of Economic Affairs
2008-
—

China-U.S. low emission technology of IGCC
Institute of Engineering Thermophysics (CAS) etc.
MOST, U.S. DOE
2010–2012
—

China-U.S. Clean Energy Research Center (CCERC)
Huazhong University of Science and Technology
MOST, U.S. DOE
2010–2015
2 million US$/year

China-Germany CCUS project
Sichuan University etc.
NSFC, DFZ
2010–now
—

4.1. CCS

China’s Geological Survey compiled a series of atlases relating to the storage capacity and suitability evaluation of China and its main sedimentary basins [25, 108–112]. Combined with a selection indicator evaluation system for potential storage sites, the standardization of the CCS in China has a good foundation [20, 21, 113, 114]. A preliminary evaluation of the CO₂ storage potential in the saline formations at a depth of 1–3 km showed a capacity of 1.435 × 10¹¹ tonnes, and most parts of the Huabei plain and Sichuan Basin can be regarded as favorable storage sites [115, 116]. Based on the studies on CO₂ sequestration in saline formations [117–124], the first full chain CCS project in China was successfully launched in the Ordos Basin with a storage target of 0.1 million tons of CO₂ injected in 2010 [125–130].

4.2. CCUS: CO₂-EOR in China

The theoretical CO₂ storage capacity of depleted onshore oil reservoirs is estimated to be 3.78 gigatons of CO₂ [131]. Conservative estimates reveal that about 70% of the oil production comes from nine oilfields, that is, Changqing, Tarim, Daqing, Shengli, Yanchang, Bohai, Liaohe, Zhongyuan, and Jilin. However, most of them are facing or will soon be depleted after many years’ production. Under these circumstances, CO₂-EOR technology may become an effective option to produce more oil from the depleting reservoir. In fact, China started the development of CO₂-EOR technology in the 1960s in several districts of the Daqing oilfield including Ta #112, Fang #48, and Shu #16 and #101 [132]. Several CO₂-EOR field tests have also been carried out in other fields including Jilin, Dagang, Shengli, and Liaohe (see Figure 6), with recovery increasing to about 10% [118, 121, 132–137]. Compared with the status of CO₂-EOR technology in the US, extensive application of CO₂-EOR in most oilfields of China may be difficult as the geologic structure of most reservoirs is characterized by many faults and low permeability [138]. Besides, a lack of policy and regulatory incentives, high commercial uncertainty, and technical challenges affect the rapid development of the CO₂-EOR technology in China.

Figure 6: Development of CO₂-EOR pilot tests in several oilfields in China since the 1960s.

4.3. CCUS: CO₂-ECBM in China

While studies on CO₂-ECBM technology first started in the 1990s, China began its basic research in this field (including adsorption, desorption and swelling mechanisms in the coal matrix, and the two-phase gas flow of CO₂ and CH₄ in different types of coal rocks) at the end of 20th century [139–145]. This research was further extended to include the CH₄ displacement mechanisms by using a mixture of CO₂ and N₂ [41, 146–151]. Based on the well test data for coalbed methane production in China, the recovery is in the range of 8.9%–74.5%, with an average value of 35%. By using CO₂-ECBM technology, the recovery can be increased to 59% [152]. Based on the preliminary evaluation of [153], the recoverable coalbed methane can increase to 1.632 × 10¹² m³ with CO₂ storage amount of about 120.78 × 10⁸ tonnes for the coalbed at a depth ranging from 300 to 1500 m.

4.4. CCUS: CO₂-EGR in China

According to the results from the third oil and gas reserve investigation, if 75% of the porous volume derived from gas production is used for CO₂ sequestration, there will be a potential for a CO₂ storage capacity of 5.18 billion-tons [9, 154]. However, the gas industry in China started late and gas production is low, which means that there will not be many depleted gas reservoirs in the short term, limiting the possibility of a commercial scale application of the CO₂-EGR technology. From the maturity point of view of this technology, very few research institutes in China are working on the improvement of CO₂-EGR at the present. Furthermore, the early breakthrough of CO₂ in gas production wells makes it difficult to attain good production efficiency from the application of CO₂-EGR technology [47]. A means of reducing the costs of separating the mixed gases, CO₂ and CH4, is required to attain the widespread application of the CO₂-EGR technology in China.

4.5. CCUS: CO₂-ESG in China

Encouraged by the successful exploitation of shale gas in North America, China joined the exploration of shale gas in 2005 [155]. The published data from the Ministry of Land and Resources in 2002 confirms that China had a shale gas reserve of 25.1 × 10¹² m³. By the end of 2015, China had a technical shale gas reserve of about 1.3 × 10¹¹ m³ including the increased proved technical reserve of 1.09 × 10¹¹ m³.

In December 2010, China drilled its first shale gas exploration well, Wei201 in Weiyuan gas field [155]. In May 2012, the first shale gas horizontal well in China was drilled and operated by Yangchang oilfield, demonstrating a great breakthrough in the hydraulic fracturing technology for shale gas reservoirs. By the end of 2012, China’s total shale gas production was 2.5 × 10⁷ m³, which increased to 2.0 × 10⁸ m³ in 2013, 1.3 × 10⁹ m³ in 2014, and 4.47 × 10⁹ m³ in 2015. The production of shale gas in China has increased greatly during the last few years, especially from the Peiling shale gas field in Chongqing with a proved reserve of more than 1.0 × 10¹¹ m³. It has produced shale gas of about 1.03 × 10⁹ m³, becoming the largest commercial shale gas field in China.

However, high production costs, a large amount of water consumption and a breakthrough in some key technologies related to shale gas production will restrict large-scale production in the near future [102]. In 2012, the National Energy Administration of China set a target for shale gas production of 6 × 10¹⁰–1.0 × 10¹¹ m³ by 2020. But after a two years’ practical experience during 2012-2013, it revised this target to 3.0 × 10¹⁰ m³ by 2020. Using CO₂ to enhance the recovery of shale gas is now at an early exploration stage [156].

4.6. CCUS: CO₂-EGS in China

The 863 plan project that aims at investigating EGS was initiated by Jilin University in 2012 [157]. There are now several other projects in the country using CO₂ in geothermal production (see Table 1). This demonstrates that China is interested in developing EGS to exploit the deep geothermal resources from the hot dry rocks. Many Chinese researchers (e.g., [143, 158–162]) have already studied the operation mechanisms of the CO₂-EGS system and its optimization designs. A preliminary site selection system considering the role of CO₂ in the geothermal production was set up by [26]. Research in this technology is still at the very early stage and requires detailed work to attain pilot scheme status.

5. Status of CCUS Engineering Projects in China

The CO₂ emission sources are mainly located in the middle-eastern regions of China; see details in Figure , [34]. Therefore, pilot-scale CCUS (mostly CO₂-EOR) engineering projects in China are also located in these regions (Figure 7, Table 3). Based on published government and industrial reports and personal communications, the progress of pilot-scale CCUS engineering projects in China is as follows:

(1)A CO₂-EOR field test was executed for the first time in Daqing oilfield in 2003. In recent years, the industrial injection of CO₂ and the production of oil with the help of CO₂-EOR technology operated by the Daqing oilfield are mainly located in the Yushulin and Hailaer oilfields.(2)A CO₂-EOR project with a CO₂ injection amount of 0.8–1 million tons/year in Jilin oilfield (still in operation) since 2005 for the exploitation of the CO₂-rich (21% CO₂ concentration) Changling gas field. A CO₂-EOR experiment has been carried out by Jilin oilfield in 2006 and oil recovery enhanced by 8%–10%. The Changling gas field was the first project to integrate natural gas production, CO₂ sequestration, and EOR technology [7]. As the conventional water injection method does not provide good production efficiency in low permeable oilfields, CO₂-EOR has played a large role in increasing production, such as in the Fuyang oilfield [137]. By March 2017, oil production increased to 100 kilotons by injecting 1.1 million tons of CO₂ underground.(3)A full chain pilot-scale CO₂-EOR project has been injecting CO₂ at a rate of 40,000 tons/year in the Shengli oilfield (still in operation). The Sinopec Shengli oilfield cooperated with the Shengli power plant to install the largest equipment for capturing exhaust gases in a coal power plant [163]. Its purpose is to reduce CO₂ emission by 30 kilotons/year and enhance oil recovery by 20.5%. This project started in 2008 and about 251 kilotons of CO₂ had already been injected in the ultralow permeable oil reservoir through 11 injection wells by April 2015.(4)A CO₂-EOR project operated by Zhongyuan oilfield (still in operation) injected CO₂ at a rate of 30,000 tons/year and managed to increase oil production by 3600 tons after injection of 2170 kilotons of CO₂ and 827 kilotons of water [7]. By February 2017, a total amount of about 553 kilotons of CO₂ was injected underground. As a result, oil recovery is proved to have enhanced by 10% in the Zhongyuan oilfield and by 60% in the Shayixia oilfield after the pilot-scale test.(5)The CO₂-EOR project led by the Yangchang oilfield company was carried out in 2013 using captured CO₂ during the production of methanol and acetic acid. At present, the capture equipment designed for 360 kilotons/year of CO₂ is under construction. Pilot-scale CO₂-EOR field tests have been done in some districts of Jinbian and Wuqi, with a total of 90 kilotons CO₂ injected.(6)As the first demonstration of IGCC power station in China, the first stage of the IGCC project at Tianjin combined with the CO₂ capture and EOR technology, with an installation capacity of 265 MW, has been in operation since November 2016.(7)The CO₂-ECBM project located in the Qinshui basin of Shanxi Province operated by China United Coalbed Methane Corporation, Ltd (completed) [7, 164]. It is the only pilot-scale CO₂-ECBM field test in China and operates at an injection rate of 40 tonnes/day of CO₂. This is a cooperation project between the Zhonglian coalbed methane Ltd and Canada which aims at studying the feasibility of CO₂-ECBM in China [53].(8)The full chain CCS project in the saline formations located in the Ordos of the Inner Mongolia (completed). This is the first full chain CCS project in China, with a capital investment of more than 28.6 million US$. The drilling of one injection (with a completion depth of 2826 m) and two monitoring wells (31 and 70 m away from the injection well) started in 2010. Since September 2011 until 2015, a total amount of 300,000 tons CO₂, produced by the coal liquefaction factory of the Shenhua Group, has been transported by oil tankers and injected in four saline formations and one carbonate formation [165]. The first stage of injection test started in 2011, with the wellhead injection pressure ranging from 6.79 to 8.63 MPa. The second production test started in 2012 with varying injection rates of 6 m³/h, 9 m³/h, 12 m³/h, and 15 m³/h and constant wellhead injection pressure of 5.7 MPa and temperature of 5°C. Another large-scale CO₂ sequestration in the deep saline formations located in Lianyungang of Jiangsu Province is in preparation.(9)A CO₂ storage project in the rock salt at Yingcheng in Hubei Province, where CO₂ will be captured by the oxy-fuel combustion technology, is in preparation [166].(10)CO₂ sequestration by microbe algae has also been identified an effective means to reduce CO₂ concentration in the atmosphere. The two representative CO₂ sequestration projects using microbe algae are the Xin’ao and Qinghua groups both from China.

Table 3: Main engineering CCUS projects in China.

Projects
Location
Scale tons/yr
CO₂ capture method
Storage/utilization
Status

() CO₂-EOR project by Daqing oilfields
Yushulin, Hailaer
—
—
EOR
Operation

() CO₂-EOR project by Jilin oilfield
Songyuan
0.28 million
Liquefaction of FCC flue gas
EOR
Operation

(2-1) Second stage of EOR project in Jilin oilfield
Songyuan
Planned for 0.5 million
Precombustion from the separation of natural gas production
EOR
Operation

() CO₂-EOR project by Shengli oilfield
Dongying
40,000
Postcombustion
EOR
Operation

() EOR project by Zhongyuan oilfield
Puyang
100,000
Post-combustion
EOR
Operation

() EOR project by Yanchang oilfield
Yanchang
400,000
Coal liquefaction plant
EOR
Operation

() First stage of Huaneng greengen IGCC in Tianjin
Tianjin
—
Pre-combustion
Planed for EOR
Operation

() CO₂-ECBM by China United Coalbed Methane Ltd.
Jincheng
40/day
Purchase of CO₂
ECBM
Completed

() Full chain CCS project by Shenhua Group
Ordos
100,000
Coal liquefaction plant
Saline formation
Completed

() Pilot project of IGCC clean energy in Lianyungang
Lianyungang
1000,000
Pre-combustion
Planed in saline formation
Preparation

() 35 MWt oxy-fuel combustion in Zhongyan Yingcheng of Hubei
Yingcheng
100,000
Oxy-fuel combustion
Sequestration in the salt rock
Preparation

() CO₂ capture and storage pilot project by China Resources Power
Dongguan
1 million
Pre-/post-combustion from power station and oil refinery
Planed for EOR or saline formation
Prefeasibility study

() Coal-to-liquids project in Ningxia by Shenhua Group
Ningxia
2 million
Pre-combustion from the coal-to-liquids process
Undefined
Opportunity study

() Third stage of Huaneng greengen IGCC in Tianjin
Tianjin
2 million
Pre-combustion from the power station
Planed for EOR saline formation
Not start

() Second stage of coal-to-liquids project by Shenhua Group
Ordos
1 million
Pre-combustion from the coal-to-liquids process
Saline formation
Prefeasibility study

() CCS project by Sinopec Qilu Petrochemical
Dongying
0.5 million
Pre-combustion from oil refinery
EOR
Preliminary design

() CCS project of Shengli power station by Datang Group
Dongying
1 million
Post-combustion from the power station
EOR
Prefeasibility study

() CO2 capture and EOR in coal chemical industry by Yangchang Petroleum Co. Ltd.
Yanchang
5,0000
Pre-combustion from coal chemical industry
EOR
Operation

(17-1) Second stage of CO₂ capture and storage project by Yanchang Group
Yanchang
1 million
Pre-combustion from coal chemical industry
EOR
Not start

() CO₂ capture and storage pilot project in Daqing oilfield by Datang Group
Daqing
1 million
Oxy-fuel combustion from the power station
Planed for EOR + saline formation
Prefeasibility study

Coal-to-gas project by CNOOC Datong
Datong
1 million
Pre-combustion from coal-to-gas process
Planed for EOR + saline formation
Prefeasibility study

Coal-to-gas project by CNOOC Ordos
Ordos
1 million
Pre-combustion from coal-to-gas process
Planed for EOR + saline formation
Pre-feasibility study

Coal-to-olefin Ordos project by CPIC and TOTAL
Ordos
1 million
Pre-combustion from coal-to-olefin process
Planed for EOR + saline formation
Prefeasibility study

CCUS project by Shanxi international energy group
Shanxi
2 million
Oxy-fuel combustion from the power station
Undefined
Prefeasibility study

Industrial conversion of the captured CO ₂, not for underground geological sequestration

() Pilot project of CO₂ sequestration by microalgae of Xin’ao Group
Dalate qi
320,000
Flue gas of the coal chemistry factory
Microbe sequestration
Construction

() SNG project in Qinghua of Xinjiang
Yili in Xinjiang
—
Pre-combustion
Microbe sequestration
Operation

() Geothermal power station in Gaobeidian of Beijing by Huaneng
Beijing
3000
Post-combustion
Food and industry use
Operation

() Shidongkou project in Shanghai by Huaneng
Shanghai
120,000
Post-combustion
Food and industry use
Operation

() Shuanghuai power plant project
Chongqing
10,000
Post-combustion
N/A
Operation

() CO₂ project in Hainan
Dongfang
2100
Separation from natural gas
Biodegradable plastics
Operation

() CO₂ project in Jiangsu
Taixing
8000
Alcohol factory
Chemical material
Operation

() CO₂ pilot project in Tianjin
Tianjin
20,000
Post-combustion
Food
Preparation

Note. Projects marked with threaten cancellation in the near future for unknown reasons.

Figure 7: Distribution of CCUS engineering projects in China excluding the South China Sea Islands (numbers defined in Table 3) superimposed on the provincial CO₂ emission map for the year 2010 (from [34]).

In the next few years, CO₂-EOR engineering projects will still be the most important CCUS technology in application. After the successful experience attained from the pilot-scale CCUS projects so far, China is now planning to run 13 large-scale CCUS projects. Based on the stages of the engineering projects, the project will be divided into the following study phases: opportunity preliminary prefeasibility feasibility construction drawing design construction operation completed. All the stages before the construction drawing design phase, that is, preparation of the engineering projects, could be lumped together and called the “evaluation” stage. Due to the current low oil price and a lack of the motivation policy, the progress in developing most of these large-scale planning CCUS projects lags far behind the schedule. Most of these projects are still at prefeasibility or feasibility stages and some may even be cancelled.

Although capturing and industrial utilization of CO₂ in China are not the key aims of this paper, the related projects in operation include () Huaneng Beijing thermal power plant; () Huaneng Shanghai Shidongkou; () China Power Investment Corporation Chongqing Shuanghuai; () CO₂ project in Hainan operated by China National Offshore Oil Corporation (CNOOC); () CO₂ project in Jiangsu province operated by the Zhongke CO₂ Jinlong company. The CO₂ pilot-scale project in Tianjin organized by China Guodian Power is in preparation.

At present, China does not execute any CO₂-EGS field tests. However, a few engineering EGS projects exist at their early scientific field test stages. These include () the hot dry rock scientific drilling project in Zhangzhou Fujian province, in operation since May of 2015, with a drilling depth of 4000 m and a water temperature high enough for geothermal power generation and () a hot dry rock scientific drilling project in Qinghai Province, with a water temperature of 200°C at a depth of 3000 m [157]. Studies on power generation in traditional hydrothermal fields located in Yangyi, Xizang, and Tengchong in Yunnan Province are also undergoing. However, there are no active engineering projects related to CO₂-EGR and CO₂-ESG in China.

6. Challenges in the Widespread Application of CCUS in China

6.1. Tackling Problems in Key Technologies

The injection of CO₂ underground for the CCS and CCUS purposes involves multiple physical-chemical coupling interactions of multiple components in porous fractured media, especially the transmission and migration of fluids between porous media with a low/ultralow permeability and complex fractured network.

(a)There are mature commercial CO₂-EOR technologies in the USA and Canada. In China, however, because of the strong heterogeneity in oil reservoirs, the CO₂ channeling effect is serious [138]. Therefore, improving the sweep efficiency is the key to attaining widespread application of CO₂-EOR in China. Other efficient methods include the alternating injection of water and CO₂ (WAG) and the addition of foaming and gelling agent [132].(b)There are currently no commercial scale CO₂-ECBM engineering projects being developed anywhere in the world. In China, studies on CO₂-ECBM technology are at a very early stage of exploration. More research is required to tackle key problems like the adsorption-desorption process between CH₄ and CO₂ in the coal seam [46, 146, 147], the mechanisms of the interaction between CO₂-CH₄-H₂O at molecular scale [150], the impact of the coal grade, water content and composition of coal, and so on on the diffusion and migration of mixed gases in the coal seam, the dynamic changes of phase behaviour during the process of CO₂ injection, and CH₄ production and so on.(c)In the application of the CO₂-EGR technology, more effort is required to prevent the early breakthrough of CO₂ into the production well, thus enhancing the sweep efficiency of CO₂. Thus more studies are needed like the understanding of migration processes of the CO₂ after its injection into the depleted gas reservoir, phase behaviour, the mixing mechanism of CO₂ and CH₄, and so on [48, 60].(d)Multistage hydraulic fracturing in the horizontal wells has been widely used in shale gas production in China. However, this technology is still not mature enough for the production of shale gas at depths >3500 m. The large amount of water consumed in the production of shale gas is a big challenge for its large-scale production, especially in southwestern China, where the existing water resources are very poor. Using CO₂ as the fracturing fluid has become a research hot spot in China [167]. Injection of CO₂ to extract brine or methane energy from the aquifers was also studied recently [168]. While the feasibility of using CO₂ to enhance shale gas recovery still requires more research and field tests.(e)The direct use of geothermal energy in China has been the priority during the last few years, while its use for power generation largely lags behind that of several countries, such as the USA, the Philippines, Japan, and Indonesia. Technologies including CO₂-AGES, EGS, and binary cycle power plants may have a positive effect on the development of China’s geothermal power system. However, before obtaining mature engineering experiences, China needs to enlarge its investment in human, physical, and financial resources in these technologies.

6.2. Negative Impacts on the Environment and Resources

The risk of leakage of the injected CO₂ in the injection/production wells may have a serious environmental impact [169–173]. The groundwater quality may deteriorate if the CO₂ in the injection layer leaks into the freshwater aquifer through microfractures or faults [174, 175]. When hydraulic fracturing is applied to shale gas or geothermal energy production, it will induce microseismic events. In addition, the toxic chemical additives in the hydraulic fluid may have a serious negative impact on freshwater aquifers when they leak into the shallow layers because of possible geological hazard. Therefore, a long-term environmental monitoring activity should be carried in parallel with the CCUS engineering project to ensure its safety [104]. The dynamic migration process of CO₂, chemical interaction among CO₂ -reservoir fluid-rock, the deformation or eruption of injection/overlying caprocks, and temperature and pressure changes in the reservoir should be monitored for a long time after the injection [29, 176].

6.3. Storage Capacity Data Is Not Clear

The total amount of resources and the distribution of depleted oil and gas fields, deep unmineable coal seams, deep saline formations, shale gas, and rock salt reservoirs are not clearly known because of the inadequacy of the geological data. Thus to attain a widespread application of CCUS technologies, more accurate evaluation work should be done based on geological, geophysical, geochemical, rock mechanics data, and so on.

6.4. Policy Factor

The positive effect of China’s involvement in CCUS technologies in recent years has been to focus on developing CO₂-EOR, the capture of CO₂, the shale gas and hot rock geothermal energy production, and especially shale gas production with a subsidy of 4 US¢/m³ during 2016–2018 and 3 US¢/m³ during 2019-2020. However, other fields of CCUS also need to be supported by the government.

6.5. High Investment Costs

The cost of a CCS or CCUS project mainly includes CO₂ capture, transportation, drilling, injection, and monitoring. Costs for the capture of CO₂ produced by the technologies of precombustion, postcombustion, or oxy-fuel combustion take the largest proportion in the investment of a specific CCS or CCUS project. Taking a coal-fired power station as an example, if 80% of the CO₂ emitted is captured and compressed to a certain pressure, its energy consumption will increase by 24%–40% [177]. In the US, the price of electricity generated from a coal-fired power station is 82–99 US$/MWh and 83–123 US$/MWh without and with the CO₂ capture technology, respectively, [178]. Depending on different situations and technologies in US, the capture cost is 42–87 US$/ton CO₂, transportation costs range from 4.3 to 7.2 US$/ton CO₂/250 km, while injection and storage costs are 1–12 US$/ton CO₂ based on the prices in 2013. In China, the cost of electricity generation by coal-fired power station increases by 30%–50% using CO₂ capture technology due to the extra consumption of electricity and steam. Taking the Huaneng Beijing coal-fired power station as an example, the capture price is about 24.3 US$/ton CO₂, with the CO₂ capture efficiency of 80%–85% [179]. On the other hand, simulation results of the IGCC coal-fired power station with the CCS technology in Tianjin show the capture price to range from 21.3 to 24.8 US$/ton CO₂, accounting for 80% of the price of a full-scale CCS project [180, 181]. However, the uncertainty in the CO₂ capture price is high depending on different capture technologies including precombustion, postcombustion, and oxy-fuel combustion at various stationary point sources including coal-fired power stations, cement factories, and coal chemical industries. From the aforementioned point of view, the uncertainty in the investment of a specific CCS or CCUS engineering project is determined by the cost of CO₂ capture. Therefore, a reduction in the cost of CO₂ capture is the key to the widespread application of CCS or CCUS technologies. Besides, drilling costs are large for all types of CCUS engineering projects and hydrocarbon/geothermal production, taking a shale gas well as an example, it costs 5.8 million US$ for a drilling length of 2500–3000 m, and 0.72 million US$ for a general gas well. The drilling cost of a geothermal production well in a hot dry rock will be much higher. The corrosion property of CO₂ requires a high quality of pipelines and ground equipment, increasing the production costs of oil, gas, and geothermal energy [182, 183].

6.6. Energy Price

The slump in the international oil price has greatly affected the investment in the oil/gas production and CCUS projects. Shale gas production in Peiling shale gas field in southwestern China with good geological conditions and large reserves is just above the breakeven point. If the oil/gas price remains low in the future, many industries will be unwilling to invest in these kinds of projects. With the exception of CO₂-EOR, it is difficult to profit from other CCUS projects. Due to completion from the increased installation capacity of wind and solar energy that have been much easier to make an economic return in recent years, the development in geothermal power generation will be continuously limited because of the difficulty in returning an economic benefit.

6.7. Social Acceptance

This is the biggest challenge for any CCS or CCUS project. It has a substantial impact on political decision makers and the implementation of energy projects such as nuclear power and wind energy programs [184]. It is the same for CCS and CCUS projects, and some CCS exploration activities in Schleswig-Holstein and Vattenfall Janschwalde in Germany, the Belchatow project in Poland, and so on were postponed or cancelled because of the lack of public acceptance over the exploration of storage sites [185, 186]. As the most unfamiliar technology to the general public in China, CCUS technology has been reluctantly accepted when compared with other low carbon technologies including wind power, solar power, energy efficiency, or biomass for reasons of climate change mitigation [10, 187]. However, there is now a positive attitude towards CCUS policies in China. In order to stimulate public acceptance, the uncertainties regarding safety and environmental risks involved in CCUS will have to be reduced at the beginning of the development stage of any CCUS technology [188]. However, this will be largely dependent on the innovation of long-term monitoring techniques in both operating and planned pilot projects [189, 190].

7. Conclusions

() Many countries have participated in activities to tackle global climate changes during the last few years. The total CO₂ emissions for China in 2005 were 59.76 × 10⁸ tonnes, accounting for 80.03% of the greenhouse gas emission of China in 2016. To perform its social responsibility, China plans to reduce its CO₂ emission per unit of GDP by 40%–45% in 2020 compared with the 2005 level. Therefore, on one hand, China needs to change its current energy framework by reducing the consumption of fossil fuels like coal energy, or applying a clean coal program, capturing the CO₂ produced by the combustion of coal. On the other hand, China needs to develop the renewable energy sector, including wind energy, solar energy, and geothermal energy.

() The serious air pollution problems in recent years are forcing the government of China to pay more attention to the development of green and clean energy aimed at saving energy and reducing the emissions of greenhouse gases. Some local governments have increased their investment in modern coal-fired power station coupled with the CCS technology. The CCUS engineering projects, especially those related to EOR, are also developing fast.

() Traditional CCS projects can store a large amount of CO₂, captured from large-scale point source emission sites, deep underground, thus effectively decreasing emissions in the atmosphere. CCUS is more attractive than the CCS technology in China because of the economic benefits accrued by using the CO₂. China has large reserves of low permeable oil and gas reservoirs. The conventional water injection methods cannot achieve good production efficiency in such reservoirs; therefore the CO₂-EOR and CO₂-EGR will have a great potential in enhancing the recovery of oil and natural gas in low and ultralow permeable reservoirs, as well as storing CO₂ in the underground space. The CCUS technology will play a considerable role in controlling the reduction of CO₂ emissions related to coal-fired power stations and the coal chemical industry. For a long period of time, coal will remain the main energy source in China; thus CCUS technology is very important for cleansing the coal-based industry. CO₂ has the potential to be used in the production of geothermal energy because of its favorable physical properties including large density and small viscosity. In addition, studies on replacing water by supercritical CO₂ as the fracturing fluid in the oil/gas/shale gas reservoirs are currently being carried out by many researchers. If this method is proved to be feasible, it will greatly decrease water consumption in the production of shale gas. This is particularly meaningful in the western regions of China where there is lack of groundwater resources.

Nomenclature

ACCA21: | Administrative Center for China’s Agenda 21
ADB: | Asian Development Bank
CAS: | Chinese Academy of Sciences
CCERC: | China-U.S. Clean Energy Research Center
CCS: | Carbon capture, sequestration, or storage
CCTV: | China Central Television
CFHEG: | Center for Hydrogeology and Environmental Geology of Chinese Geological Survey
CCUS: | Carbon capture, sequestration, and utilization
CLEAN: | CO₂ Large-scale Enhanced Gas Recovery project in the Altmark Natural Gas Field
CNOOC: | China National Offshore Oil Corporation
CNPC: | China National Petroleum Corporation
CO₂-AGES: | CO₂ aided geothermal extraction system
CO₂-ECBM: | CO₂ enhanced coalbed methane recovery
CO₂-EGR: | CO₂ enhanced gas recovery
CO₂-EOR: | CO₂ enhanced oil recovery
CO₂-ESG: | CO₂ enhanced shale gas recovery
CRS: | Chromium Reducible Sulfur recovery technology
CSLF: | The Carbon Sequestration Leadership Forum
CUCMC: | China United Coalbed Methane Corporation, Ltd
DFZ: | Deutsche Friesenpferdezuchter
DEFRA: | UK Department for Environment, Food and Rural Affairs
FCC: | Fume from Catalytic Cracking
GCCSI: | Global Carbon Capture and Storage Institute
GDP: | Gross Domestic Product
IEO: | International Energy Outlook
IGCC: | Integrated Gasification Combined Cycle (IGCC)
IPCC: | Intergovernmental Panel on Climate Change
K12B: | K12B gas field located at the North Sea
MOST: | The Ministry of Science and Technology of China
NSFC: | The National Natural Science Foundation of China
NZEC: | China-EU Cooperation on Near Zero Emissions Coal project
RECOPOL: | Reduction of CO₂ emission by means of CO₂ storage in coal seams in the Silesian Coal Basin of Poland
SNG-EOR: | Synthetic Natural Gas-Enhanced Oil Recovery
USDOE: | United States Department of Energy.

Conflicts of Interest

The authors hereby declare that there are no conflicts of interest regarding the publication of this paper.

Acknowledgments

The authors would like to extend their gratitude to the National Natural Science Foundation of China (Grant no. NSFC51374147) and China CDM Fund “Update of China’s CCUS Technical Roadmap” (Grant no. 2013085) for funding this work. Q. Li acknowledges financial support from the China-Australia Geological Storage of CO₂ (CAGS) Project funded by the Australian Government under the auspices of the Australia China Joint Coordination Group on Clean Coal Technology.

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