Development and contribution of natural gas industry under China's carbon neutrality goal

1. The role of natural gas in carbon neutrality

The concrete ways to achieve the goal of carbon neutrality mainly include reducing carbon emissions and increasing carbon absorption. At present, the main source of carbon dioxide in the environment is fossil energy combustion. According to the statistics of the International Energy Agency (IEA), the global energy-related carbon emissions have dropped to 315×108 t in 2020, but the global energy-related carbon dioxide emissions have continued to rise in the past decade (Figure 1) [5]. As the world's largest consumer of fossil energy, China also ranks first in the world in terms of carbon emissions, with the total carbon dioxide emissions exceeding 100×108 t in 2020 [6]. China has a special energy consumption structure due to its advantages in coal resource endowment, and the carbon emissions from coal combustion account for nearly 80% of the total emissions, far exceeding the world average. In 2020, China's coal use accounted for 56.8% of the primary energy structure, which also indicates that China's energy system is bound to usher in major structural adjustment and resource integration. The most fundamental way for China to achieve the goal of carbon neutrality is to reduce carbon emissions, that is, while expanding the renewable energy supply, reduce the consumption of high-carbon fossil energy such as coal and oil, especially control coal power and terminal coal use, and increase the use of clean fossil energy represented by natural gas [7-8]. Cultivate natural gas to gradually replace coal, increase the proportion of natural gas in power, industry and other industries, and become one of the main energy sources of China's modern clean energy system.

Increasing carbon uptake is also closely related to the gas industry. Carbon uptake includes natural carbon uptake and anthropogenic carbon uptake, the former mainly refers to carbon sink, carbon sequestration by plants through photosynthesis; The latter is mainly geological carbon sequestration through carbon capture, carbon utilization and carbon storage (CCUS) technology. Specifically, in the process of natural gas development, carbon dioxide is used to strengthen the exploitation of conventional natural gas, shale gas, coal bed methane and other resources, including carbon dioxide fracturing and displacement, to improve recovery efficiency and complete long-term effective storage of carbon dioxide. In addition, the natural geological environment such as the depletion of oil and gas reservoirs is used as a large-scale biochemical reactor to produce artificial methane, and it is stored in underground space on a large scale to realize the recycling of carbon resources and the synthesis and storage of natural gas. CCUS, combined with natural gas storage and pipeline network, is a key supporting technology to promote the clean utilization of fossil energy, and will play an important role in the development of renewable energy.

China's plan to complete the 30 years from carbon peak to comprehensive carbon neutrality faces great challenges. The author believes that China's current carbon neutral road should promote the diversification of energy development, gradually reduce the proportion of coal, greatly increase the proportion of natural gas and other low-carbon energy and renewable energy, and finally establish a sustainable energy system with natural gas, renewable energy and hydrogen energy as the main body.

2. China's natural gas development prospects

2.1 Research and judgment by major institutions at home and abroad

In 2020, China's natural gas consumption is about 3 240×108 m3, an increase of about 130×108 m3 over the previous year, accounting for 8.7% of the total primary energy consumption. Compared with 32.2% in the United States, 20.8% in Japan and 24.2% in Germany in the same period [9], the proportion of natural gas in China's energy consumption market is still relatively low.

In the context of carbon neutrality, the medium and long-term development trend and prospect of natural gas in China's energy market are more worthy of attention. This paper summarizes the medium and long-term forecasts of China's natural gas consumption by many domestic and foreign institutions and scholars based on different development scenarios, as shown in Table 1[1-3, 10-14]. The projections fall broadly into two categories: a peak year before the carbon neutrality target and a subsequent decline; Carbon neutrality targets have been increasing for years. The International Energy Agency, BP, Tsinghua University and other institutions predict that China's natural gas consumption will peak between 2030 and 2040, and the peak level is expected to be between 5 110×108 and 7 500×108 m3, which is a significant increase compared with the current level. The largest consumption appears in the 2.0 ° C scenario in the report "Research on China's Long-term Low-carbon Development and Transformation Path" [13] of Tsinghua University. Between 2050 and 2060, gas consumption is around 5,000 ×108 m3 in most scenarios. According to relevant reports and studies by petrochina and China University of Petroleum (Beijing), under various scenarios, China's natural gas consumption will still increase after the carbon peak. In the reference scenario of petrochina's World and China Energy Outlook 2050 [12], China's natural gas consumption in 2050 is about 6 700×108 m3, and in the scenario of hydrogen energy society and carbon neutrality, the natural gas consumption is 5 900×108 m3 and 5 500×108 m3 respectively. Research by Li, Children, et al., China University of Petroleum (Beijing) [3] shows that under the extreme conditions of their scenario A (0 coal and oil consumption), natural gas consumption in 2060 is 14 000×108 m3, the largest of all projections. There is a big gap in the predicted natural gas consumption of various institutions, mainly due to the different scenario selection. Some scenarios meet the needs of carbon emission and theoretical temperature control from the data perspective, but do not take into account the needs of national development and the actual safety operation of the energy system. In addition, the structure of energy consumption projected by different agencies is different, resulting in significant differences in consumption. In general, the importance and cleanliness of natural gas are becoming increasingly prominent, and the proportion of natural gas in China's energy consumption structure has a large room for increase, and the development potential is considerable.

2.2 Multi-scenario prediction based on fixed-base energy consumption elasticity coefficient method

According to China's economic development trend, and with reference to The State Council's "Action Plan for Carbon Peak before 2030" : Strictly and reasonably control the growth of coal consumption during the "14th Five-Year Plan" period, gradually reduce during the "15th Five-Year Plan" period, as well as the implementation of the ban on the sale of fuel vehicles by the Ministry of Industry and Information Technology, this paper predicts that coal and oil consumption will peak in 2030-2040, considering the service life of ordinary coal-fired power plants and fuel vehicles, coal and oil will still occupy a certain proportion of primary energy before 2060. But overall usage has shrunk dramatically. Gas-fired power generation will develop into the main peak power supply, so there is still a large room for natural gas consumption to rise. Based on this theory, this paper tries to establish the benchmark scenario, low-speed scenario and high-speed scenario corresponding to different economic growth rates. Through comparative analysis of the relationship between energy consumption and economic growth in China in recent years, based on quantitative prediction and research assumptions, the fixed-basis energy consumption elasticity coefficient method [15] is adopted to calculate the total medium and long-term primary energy consumption in China, and the natural gas consumption is forecasted and analyzed by setting the proportion of natural gas in the future primary energy consumption.

The elasticity coefficient of energy consumption is the ratio of the growth rate of energy consumption in a certain period to the growth rate of gross domestic product (GDP) in the same period, which usually reflects the relationship between energy consumption and national economic development. The traditional non-fixed-base energy consumption elasticity coefficient data is convenient to obtain and simple to calculate. As shown in Figure 2, the mismatch between China's energy consumption growth rate and economic growth rate is poor, resulting in large fluctuation of the non-fixed-base energy consumption elasticity coefficient and fuzzy law (Figure 3), which is not conducive to quantitative analysis.

The elasticity coefficient of fixed-base energy consumption in China is relatively stable on the whole (Figure 3), and has shown a slow rise since 1979. In 1998, the growth rate of China's GDP and energy consumption reached the lowest value in the same period (Figure 2), resulting in a significant decline in the elasticity coefficient of fixed-base energy consumption. However, with the rapid development of China's manufacturing industry, the growth rate of GDP and energy consumption has increased significantly, and the elasticity coefficient of energy consumption has gradually recovered. Compared with developed countries, China's energy consumption elasticity coefficient is significantly higher than that of developed countries in Europe and the United States in the same period due to its energy structure with a high proportion of coal, industrial structure dominated by heavy industry and manufacturing, and extensive economic growth mode with high energy consumption, as shown in Figure 3. In the past few decades, the economic growth rate of the major developed countries in Europe and the United States is generally higher than the growth rate of energy consumption, and some of them have negative growth in energy consumption, and the elasticity coefficient of fixed base energy consumption has decreased to a negative value. After 2006, the elasticity coefficient of China's fixed energy consumption showed a slow downward trend, and after the establishment of the "double carbon" goal, China's energy utilization efficiency will continue to improve, and the energy consumption per unit GDP will continue to decline, there is reason to believe that the coefficient will continue to maintain a steady decline. According to the trend extrapolation method, the forecast of the elasticity coefficient of fixed base energy consumption from 2021 to 2060 under the base scenario in this paper is shown in Figure 3, which predicts that the coefficient will decline to 0.18 in 2030 and 0.08 in 2060.

In addition, it has become a general consensus that the proportion of natural gas in the primary energy consumption structure will increase in the future, and the mainstream forecast is between 10% and 12% [16]. In this paper, the ratio of natural gas consumption to primary energy consumption is assumed to be 12%.

In the baseline scenario, countries emerge from the COVID-19 pandemic in a timely manner, trade recovery accelerates, and domestic and international cycles continue to generate momentum. It is expected that the average annual economic growth rate in the period from 2021 to 2060 will remain at about 3.5%, in which the average annual economic growth rate in the period from 2021 to 2030 will be 5.5% in the early period, and will be reduced to 2.83% in the period from 2031 to 2060 in the later period, but the economic quality will be higher and the green and low-carbon carbon will be more prominent. It is predicted that the total primary energy consumption in 2030 will increase from 49.80×108 t (tons of standard coal) in 2020 to 60.78×108 t, and then the growth rate will slow down and reach 62.23×108 t in 2060, as shown in Table 2. According to this calculation, natural gas consumption in 2030 and 2060 is about 6 006×108 m3 and 6 150×108 m3, respectively.

In the low-speed scenario, the world will be affected by the COVID-19 epidemic for a long time, international relations will remain tense, trade frictions will not improve significantly, and the Chinese economy will maintain steady growth with more reliance on the domestic cycle. It is expected that the average annual economic growth rate in the period from 2021 to 2060 will remain at about 2.5%, with an average annual economic growth rate of 4.5% in the first 10 years and 1.83% in the next 30 years. In the short term, the elasticity coefficient of fixed base energy consumption fluctuates less, and is still predicted to be 0.18 in 2030. Subject to the slowdown of economic growth, the elasticity coefficient is predicted to be 0.10 in 2060, which is slightly higher than the base scenario. Under the influence of various factors, China's total energy consumption will grow steadily in the short term. In 2030, the total primary energy consumption will reach 55.14×108 t, and then enter the plateau period, which will drop to 53.43×108 t in 2060. Natural gas consumption in 2030 and 2060 will be about 5 449×108 m3 and 5 280×108 m3 respectively. It is worth noting that under the conditions of relatively low economic growth, the total energy consumption and natural gas consumption in the target year of carbon neutrality have decreased compared with the average year of carbon peak.

In the high-speed scenario, countries around the world benefit from the effective role of COVID-19 vaccines and stable and improving international relations, as well as various regional investment and trade protection agreements, and the global economy accelerates its recovery from the epidemic, while China's economy is efficiently driven by a development pattern dominated by domestic cycles and reinforced by domestic and international cycles, and maintains medium-high growth for a long time. It is expected that the average annual economic growth rate will remain at about 4.5% from 2021 to 2060, 5.5% from 2021 to 2030, and slightly drop to 4.16% after 2030. In this scenario, the elasticity coefficient in 2030 is 0.18, and due to the high economic growth rate, the elasticity coefficient is expected to decline to 0.06 in 2060, which is slightly lower than the base scenario. The total consumption of primary energy will reach 60.78×108 t in 2030, and will continue to increase to 68.20×108 t in 2060, and the consumption of natural gas in 2030 and 2060 will be about 6 006×108 m3 and 6 740×108 m3, respectively.

In order to ensure the accuracy of the model prediction results, the backward inference method was used to calculate the proportion and consumption of natural gas consumption. According to the latest research results of Nature magazine, the average annual carbon absorption of China's terrestrial ecosystem from 2010 to 2016 was about 11.1×108 t[17]. The data of the ninth National forest resources inventory show that the total carbon sink of China's forests is 4.34×108 t, equivalent to 15.91×108 t of carbon dioxide [18], and China's terrestrial ecological carbon sink will be maintained at about 15×108 t in the future. In addition, China's CCUS technology is developing rapidly, and it is estimated that the emission reduction that can be achieved by 2060 is 10×108 ~ 18×108 t of carbon dioxide [19]. Therefore, China's terrestrial carbon sink capacity in 2060 is close to 25×108 ~ 33×108 t. Using this as the carbon emissions allowed in the target year of carbon neutrality, the amount of fossil energy that can be used is 9×108 ~ 12.5×108 t (one ton of standard coal is estimated to emit 2.66 ~ 2.72 t of carbon dioxide), accounting for 13% ~ 24% of the predicted total primary energy consumption. Considering that the main fossil energy in 2060 is natural gas, oil will still be used in a small amount in transportation, and coal will be used in other ways, which proves that the proportion of natural gas in 12% is relatively reasonable, and the prediction of natural gas consumption to reach 5 280×108 ~ 6 740×108 m3 is also relatively accurate.

In general, the decline of fossil energy consumption under the guidance of carbon neutrality goal is an inevitable trend of energy development. In the process of the transformation of energy structure from high-carbon fossil energy to low-carbon and renewable energy, natural gas, as a clean fossil energy, has a relatively optimistic development prospect compared with coal and oil. In the long term, even if carbon neutrality is achieved, natural gas will become a strong support for renewable energy, ensuring a stable supply of energy systems. The above discussion provides a reference case for the future development of natural gas, that is, the proportion of coal and oil consumption in primary energy is very low, and natural gas consumption will continue to grow under the basic conditions of achieving carbon neutrality.

2.3 Main source of natural gas in China

2.3.1 Conventional natural gas, shale gas and coalbed gas

In 2020, China's domestic production of natural gas is 1,888.5 ×108 m3 (excluding coal bed methane), an increase of 9.8% compared with 2019, among which shale gas output is about 200×108 m3, an increase of 39.3% compared with the previous year, accounting for 10.6% of the total annual output [20], becoming the main growth point of natural gas output. In recent years, China's oil and gas exploration and development has continued to increase, and the new reserves and production of natural gas have reached a record high. In 2019, the country's new proved geological reserves of natural gas were 15 800×108 m3, an increase of about 6 000× 108 m3 year-on-year. Among them, the new proved geological reserves of conventional natural gas and shale gas are 8 091×108 m3 and 7 644×108 m3, respectively, and the new technical recoverable reserves are 3 521×108 m3 and 1 838×108 m3, respectively. At present, China's proved geological reserves of conventional natural gas are about 17.64×1012 m3, and that of shale gas is about 2×1012 m3. The Sichuan Basin, the main production area of shale gas, is increasing its development efforts, and its output will continue to increase significantly, becoming the main force of natural gas production increase. In addition, China is also rich in CBM resources, with proven reserves of about 3 040.7×108 m3 in 2019. In 2020, China's coalbed methane production will be 102.3×108 m3, an increase of 13.5×108 m3 and an increase of 15.2% over the previous year [21]. To ensure the stable supply of natural gas, conventional natural gas, shale gas and coal bed methane will all play a fundamental role.

2.3.2 Imported Pipeline Gas and liquefied Natural Gas (LNG)

In 2020, China's import volume of natural gas will reach 10 166×104 t (about 1 400×108 m3), of which the import volume of LNG will be 6 739.45×104 t (about 930×108 m3), and the import volume of pipeline gas will be 3 453.11×104 t (about 480×108 m3). Total imports increased by 5.3% year on year, of which LNG imports increased by 11.4% from 2019 and pipeline gas imports decreased by 4.9%[20-22]. China has completed the construction of Central Asia, China-Myanmar and China-Russia natural gas pipelines, with a total designed annual gas transmission capacity of more than 1 100×108 m3. Meanwhile, by the end of 2020, China has completed 22 LNG receiving stations, with an annual receiving capacity of 9 045×104 t. At present, the capacity of coastal LNG receiving stations under construction exceeds 2,000 ×104 t/a[20], which will be put into operation this year and next. At present, China's imported pipeline gas mainly comes from Central Asia and Russia, and the main sources of imported LNG are Australia and Qatar. In 2020, China's LNG import from the United States increased significantly, reaching 320.44 ×104 t, while in 2019, the LNG import from the United States was only 27.6×104 t[22-23]. On January 15, 2020, with the signing of economic and trade agreements between China and the United States, China will also expand imports of energy products from the United States in the future. On March 27, 2020, China and Iran officially signed a 25-year cooperation agreement to strengthen all-round cooperation between the two countries in the fields of economy, trade, energy and security, which represents a more diversified choice of natural gas import sources for China.

2.3.3 Coal-to-synthetic Natural Gas (SNG)

Coal has long been the main source of energy in China, mainly used for power generation and heating. With the goal of carbon neutrality, the use of coal will gradually decline, and it is expected that by 2060, coal will be completely withdrawn from the power generation industry, so there is an urgent need to expand the use of coal and promote the clean use of coal. As a kind of synthetic natural gas, coal-to-gas can not only enrich the consumption of coal, but also alleviate the tight situation of domestic natural gas supply to a certain extent. Especially for the provinces with good coal resource endowment, coal-to-gas is the key and important development direction for coal to get rid of the single fuel attribute and realize the efficient and clean utilization of coal. Different from oil and gas resources, China has abundant coal reserves and large resources, with proven reserves of about 10 000×108 t and proven recoverable reserves of 1 145×108 t[24]. According to the current standard of producing about 300 m3 of natural gas from 1 t of raw coal, the output of coal-to-gas can exceed 30 000×108 m3. In 2019, the national coal-to-gas production has reached 36.8×108 m3 [22], and there is huge potential for coal-to-gas production in the future, especially in coal-rich areas.

2.3.4 Synthetic (man-made) natural gas

Using "electricity to gas +CCUS" to achieve artificial natural gas, while completing the conversion and storage of renewable energy. Green hydrogen (H2) and oxygen (O2) are prepared through renewable electricity electrolysis technology. Hydrogen can be used to synthesize methane, and oxygen can be used to enrich oxygen for power generation. At the same time, the use of underground space such as underground depleted oil and gas reservoirs, injection of industrial by-product impurities hydrogen and carbon dioxide, through microbial catalysis and other ways to produce biomethanes, to complete the large-scale conversion of renewable energy into methane and other clean energy. As a promising CCUS and energy storage technology, this technology has completed preliminary research and laboratory tests in Germany, and has been carried out field tests, with wide application prospects.

2.3.5 Natural gas hydrate

Gas hydrate, also known as combustible ice, is a kind of ice-like crystalline substance formed under high pressure and low temperature. The main components are methane and water molecules. It is widely distributed in deep sea or land permafrost. Research shows that the decomposition of natural gas hydrate per cubic meter can produce 160 times the volume of methane, and its combustion product is only water and a small amount of carbon dioxide, which is a new type of high calorific value clean energy. The investigation shows that the natural gas hydrate in China is mainly distributed in the South China Sea and the Qinghai-Tibet Plateau, with a potential resource of 12.15×1013 m3 and great potential for development. In May 2017 and March 2020, China has successfully conducted two test mining of natural gas hydrate in the Shenhu area of the South China Sea, of which the cumulative gas production of the second round of test production exceeded 86×104 m3 [25-26]. Although the development of natural gas hydrate is at an early stage and full of challenges, its advantages of cleanliness, high energy, wide distribution and large reserves provide a new development direction for China's energy strategy, and it is an important energy technology reserve.

2.3.6 Biological natural gas

Biogas is produced by purifying biogas, one of the products of anaerobic fermentation of biomass, to natural gas grade quality, and can be used for power generation, or directly as building heating or industrial boiler fuel for heating, and can also be used for cogeneration. In China's townships and rural areas, biogas can not only effectively increase the supply of clean energy, but also provide ancillary value (the fermentation process produces organic fertilizer), which has strong development potential. Bio-natural gas can also be transported by relying on the existing natural gas pipeline network, which greatly improves the convenience of use and transportation. According to the guidance of the National Development and Reform Commission, the National Energy Administration and other ministries, China will accelerate the development of bio-gas industry. It is expected that the annual output of bio-gas in China will exceed 100×108 m3 by 2025, and exceed 200×108 m3 by 2030 [27]. At that time, bio-gas will also become a favorable supplement to China's natural gas market.

2.4 Main use scenarios of natural gas in China

2.4.1 Gas-fired power generation

With the in-depth promotion of electrification in the process of carbon neutrality in China and the significant increase in the proportion of renewable energy generation, renewable electricity, mainly solar power, will become the main power source in the future. However, the volatility, intermittency and other drawbacks of wind and solar power generation can easily lead to problems such as frequency instability of the power system, which affects the safe and stable operation of the system. At present, the proportion of renewable energy generation in Germany has exceeded 50%, and the high proportion of installed renewable energy access has led to increased fluctuations in the power grid, and the German power grid has been unable to independently complete the adjustment task, and it is necessary to participate in peak regulation with the help of neighboring countries to ensure the stability and security of the power grid. It can be seen that when the scale of renewable energy generation in China reaches a certain level, more adequate power supply is needed to achieve independent grid regulation.

Gas-fired power generation has the advantages of rapid response, stable operation and flexible deployment, and will become an important regulating power supply, shouldering the tasks of peak load and valley filling, frequency and phase regulation and emergency black start of power system. By the end of 2020, the installed capacity of gas power generation in China will be 9 751×104 kW, accounting for only 4.4%[28]. In 2019, China's natural gas power generation was 2 365×108 kW·h, accounting for 3.2%, which was much lower than countries such as the United States and Japan (38.6% and 35.0%) in the same period [9]. It is expected that in 2060, the national power consumption is 15×1012 ~ 20×1012 kW·h, only calculated according to 15×1012 kW·h, according to relevant experience, the peak load reserve power accounts for 20% (3×1012 kW·h), if it is borne by gas power generation, It consumes 5,010 ×108 m3 of natural gas (60% thermal efficiency). It can be seen that in the future, gas-fired power generation will become the main force of natural gas consumption.

2.4.2 Industrial use

Industry is the most important area of energy consumption and carbon emissions, in 2019, China's industrial energy consumption accounted for more than 60%, and industrial carbon emissions accounted for 70% of the total carbon emissions in the year. Coal is the main fuel of China's industry, especially in steel, building materials, non-ferrous metals and other energy-consuming industries, therefore, the industrial field of carbon emission reduction needs to vigorously promote the "gas instead of coal", reduce the burning of high-carbon fossil energy, increase the use of natural gas and other clean energy. In 2019, China's industrial gas consumption reached 1 060×108 m3, accounting for 34.8%[29], but it was still low and not enough to significantly reduce industrial carbon emissions. Therefore, in the future, it is still necessary to increase the market share of natural gas, as well as the coverage in the high-energy manufacturing industry, and actively promote the clean development of the industry.

3. Coupling development of natural gas and renewable energy

3.1 Basis of coupling development

According to the white paper "China's Energy Development in the New Era" [30], by the end of 2019, China's consumption of clean energy such as natural gas, hydropower, nuclear power and wind power accounted for 23.4% of the total energy consumption, and non-fossil energy accounted for 15.3%. China's total installed capacity of renewable energy power generation is 7.9×108 kW, accounting for about 30% of the global total, among which the installed capacity of hydropower, wind power, photoelectric and biomass power generation reaches 3.56×108 kW, 2.10×108 kW, 2.04×108 kW and 2 369×104 kW, respectively, ranking first in the world. In addition, China is also rich in geothermal resources, and only the total dry hot rock resources are preliminarily estimated to be about 856×1012 t of standard coal [31]. In general, China has abundant reserves of renewable energy resources and broad prospects for development. Remarkable achievements have been made in the development of some renewable resources, but there is still huge potential for exploitation and utilization. Natural gas has the characteristics of high combustion efficiency, diverse ways of development and utilization, convenient transmission, distribution and storage, and less external restrictions, so that it can be used to make up for the disadvantages of renewable energy, both of which also have the resource base and development conditions of high-quality coupled development and support for energy green transformation. Under the strong drive of low-carbon energy structure, the coordinated development of natural gas renewable energy will become one of the important directions of China's energy development.

3.2 Coupling development scenario

The coupled development scenario refers to the cooperative layout of natural gas and renewable energy resources such as photovoltaic, wind power, hydropower, hydrogen energy and geothermal energy. Through the joint innovation of energy utilization technology and information and communication technology, natural gas can be flexibly and efficiently embedded with renewable energy in the upstream, middle and downstream links of production and development, storage, transmission and distribution, consumption and utilization, and in accordance with local conditions. We will promote a new development model in which various energy sources complement each other.

With the rapid development of energy Internet and information technology, 5G, artificial intelligence and other information technologies will accelerate the penetration and integration of the energy industry, natural gas and renewable energy deep coupling development conditions are becoming more mature, and the coordination of energy system operation and resource utilization efficiency will be greatly improved.

3.2.1 Upstream Production

In the process of natural gas development, the utilization of new energy can be strengthened, and the transformation of traditional oil and gas production mode to green energy production mode can be promoted. Specifically, more electric drilling and electric drive fracturing technologies can be used, and wind, solar, and geothermal energy can be used as power sources according to local conditions. The oil and gas field station can also give priority to the use of wind power, photovoltaic power, and mains power as a supplement to achieve energy greening.

In the process of unconventional natural gas development, CCUS technology is introduced, as shown in Figure 5, to strengthen the promotion and application of carbon dioxide intensive development shale gas technology, improve the development effect of tight gas reservoirs, complete the storage and utilization of carbon dioxide, and achieve zero carbon emission or even negative carbon emission. In addition, methane itself is an important greenhouse gas, and its greenhouse effect is much higher than that of carbon dioxide, so it is necessary to effectively control methane emissions in the process of natural gas exploitation to ensure the high-quality development of the natural gas industry.

3.2.2 Storage and transportation

Develop "electricity to gas + natural gas pipeline network" and other related technologies. With the increasing distribution of energy, energy transmission will face increasing challenges, compared with electricity transmission, gas network transmission losses are lower. The technology of hydrogen production from renewable energy combined with hydrogen transportation in natural gas pipeline network is an effective way to solve the utilization and transportation of hydrogen energy and overcome the problem of large-scale wind and electricity absorption. Since 2004, many countries around the world have studied the relevant application technologies of natural gas mixing hydrogen. In 2012, Germany established the world's first "wind power hydrogen production - natural gas pipeline hydrogen transport" application demonstration project, Uniper energy storage company in Falkenhagen, Brandenburg combined wind power and alkaline electrolysis technology to produce hydrogen, the green hydrogen directly into the natural gas pipeline, the proportion of hydrogen mixing is 10%. In 2018, the company used PEM electrolysis (polymer electrolyte membrane electrolysis) technology to deliver higher purity hydrogen into the natural gas network in Hamburg, Germany. In 2019, the German state of Saxony-Anhalt launched a natural gas pipeline transportation project with a hydrogen content of 20% in Schopsdorf [33]. The construction of China's natural gas infrastructure and transmission and distribution network has been relatively complete. As of 2019, the mileage of China's natural gas trunk pipelines exceeded 8.7×104 km, and the gas transmission capacity exceeded 3 500×108 m3/a. With the establishment and operation of the National Oil and Natural Gas Pipeline Network Group, the construction and management of pipeline networks are expected to reach a new level. It is suggested that some existing natural gas infrastructure and pipeline network should be reformed to adapt to the transportation of hydrogen-doped natural gas.

Using "electricity to gas + gas storage" to achieve the conversion and storage of renewable energy. As an important energy conversion technology and energy storage means, electricity to gas technology (such as electrolysis of water to produce hydrogen) can realize the purpose of "storing" wind energy and solar energy. At the same time, using depleted oil and gas reservoirs, underground salt caverns, etc., carbon dioxide collected through carbon capture technology and hydrogen produced from renewable energy through microbial catalysis, etc., to achieve carbon dioxide hydrogenation and methanation, produce biomethane, and complete large-scale conversion of renewable energy into low-carbon clean energy such as methane. In addition, carbon dioxide and hydrogen can also be used to produce methanol, methanol chemical characteristics are stable, easy to transport, is a clean and efficient high-quality fuel, but also an important chemical raw material.

3.2.3 Downstream consumption

China's inland natural gas resources are mainly concentrated in the northwest, southwest and other central and western regions. With the continuous improvement of pipeline construction, natural gas will be able to flexibly flow to cover major energy consumption areas in China. Therefore, gas-fired power generation can be deployed in areas with relatively concentrated renewable energy distribution and poor grid flexibility. We will promote the integrated development of gas power generation with wind, solar, biomass and other new energy power generation. For the three northern areas of inland wind power optoelectronics, southwest hydropower and other areas to provide sufficient support for gas and electricity peak regulation. In addition, through heat storage, electrolytic water hydrogen production and other ways, to deal with the uncertainty of renewable energy, reduce the abandonment of wind and light, improve the utilization efficiency of renewable energy. In addition, distributed gas-fired power stations can rely on communication technologies such as 5G networks, Internet of things and monitoring networks, combined with control technologies such as new power grids, big data and artificial intelligence, to realize multi-energy complementaries between natural gas and renewable new energy sources such as water, light, wind, biology and geothermal, and provide a variety of energy services such as "cold, heat, electricity and gas". Vigorously develop energy intelligent control technology, use the information exchange and monitoring functions of the digital intelligence energy network, achieve a balance between energy supply and consumption, achieve on-demand supply, and improve comprehensive energy utilization efficiency.

4. Conclusion

1) The "dual carbon" goal will have a profound impact on China's energy consumption structure, but unlike coal and oil, natural gas still has a large development potential and space due to its relative cleanliness and convenience, and is an important part of the energy system.

2) According to the multi-scenario analysis, by 2030, under the low-speed scenario and high-speed scenario (the same baseline scenario), China's total primary energy consumption will be 55.14×108 t and 60.78×108 t respectively, and the natural gas consumption will be about 5 449×108 m3 and 6 006×108 m3 respectively. In 2060, under low-speed, baseline and high-speed scenarios, the total primary energy consumption is 53.43×108, 62.23×108 and 68.20×108 t, and the natural gas consumption is about 5 280×108, 6 150×108 and 6 740×108 m3, respectively. Compared with the current level of 3 200×108 m3, the consumption of natural gas in the carbon neutral period has nearly doubled the room for growth.

3) It is suggested that while expanding the production of conventional natural gas on the supply side, the exploration and development of unconventional natural gas such as shale gas and coal-bed methane should be intensified. At the same time, the high-quality development of natural gas hydrate, artificial natural gas and bio-natural gas should be promoted, and the trade of imported LNG and pipeline gas should be expanded to enhance China's natural gas guarantee capacity and technical reserves; Gas power generation will be the main use of natural gas in the future, as a regulating power supply to ensure the stability and reliability of the new power system; In the industrial field, we will increase the substitution of gas for coal, increase the proportion of natural gas used in industrial production, and promote clean industrial energy.

4) Carbon neutral stage natural gas is a strong complement to renewable energy, the two should complement each other, synergistic development. It is suggested to invest more power and electric drive equipment in the natural gas industry, vigorously develop carbon dioxide, and strengthen negative emission technologies such as shale gas extraction and CCUS; Promote the construction of infrastructure such as natural gas pipeline networks and gas storage facilities, especially emergency peaking capacity, and realize the deep integration of technologies such as electricity to gas, hydrogen storage and carbon sequestration; Combined with the new power grid, the management and control mode is transformed by digital and intelligent technology to realize the intelligent storage, transportation and consumption of natural gas.