Identification of potential CCUS clusters and its pipeline network optimization in China

. Climate change is a huge challenge facing the world. Carbon Capture, Utilization and Storage (CCUS) is an important technology that is expected to ensure the continued safe and large-scale use of fossil energy under the pressure of climate change in China. However, the current CCUS project has a large initial investment, and it is difficult to realize the commercialization of CCUS technology. The development of CCUS cluster centers can effectively reduce the overall investment of CCUS projects, which is the development trend of CCUS projects. This study identified 20 coal-fired power plant cluster centers and 6 oil and gas field gathering and transportation centers by utilizing Chinese coal-fired power plant data and oil and gas field data. Finally, the CO 2 pipe network between the cluster centers is planned. This study provides data and research methods for identifying potential CCUS clusters and storage and transportation centers in China. It can provide a theoretical reference for further research on the matching site selection of CO 2 transport pipelines and CO 2 sources and sinks in China.


Introduction
Climate change is a huge challenge facing the world.The United Nations Intergovernmental Panel on Climate Change (IPCC) believes that CCUS technology plays a vital role in the scenario of achieving a 450ppm CO 2 equivalent concentration in 2100 (the target of controlling the temperature rise by 2 °C) [1].The 450 ppm scenario suggests in IEA statement that implementation of CCUS would reduce required emission reductions by 12% [2].As the world's largest CO 2 emitter, it actively implements the national strategy for mitigating climate change, and proposes the goal of "strive to achieve carbon peak by 2030 and carbon neutrality by 2060" in China.CCUS is an important technology that is expected to ensure the continued safe and large-scale use of fossil energy in China under the pressure of climate change.Large-scale commercial promotion of CCUS is faced with the development obstacles of high investment and operating costs, especially after the implementation of CCUS in power plants, the levelized power cost will increase by 29%-32% [3].CCUS project cluster planning and development has many advantages.Amortize CCUS investment and operating costs by utilizing shared infrastructure.Studies have shown that in CO2-EOR oilfield clusters, the construction of public CO 2 storage and transportation centers can significantly reduce the initial investment [4].Lowering the entry barriers for participating in CCUS projects, providing opportunities to participate in CCUS for emission sources with small CO 2 emissions, as well as emission sources that do not have CO 2 storage or have limited storage capacity.At the same time, it can also provide sufficient and reliable CO 2 sources for CO 2 -EOR and other CO 2 utilization projects [5].In order to identify potential CCUS clusters and storage and transportation centers in China.The clusters and storage and transportation centers identified in this study can provide a theoretical reference for further research on the matching of CO 2 transportation pipelines and CO 2 sources and sinks in China.

Methods
The research method of this paper is shown in Figure 1.The identification method of cluster center and gathering center is divided into three modules.The first part is the CO 2 cluster center identification module.It is determined that the power plants that meet the implementation of CCUS are screened for suitability of power plant data, imported into ArcGIS software, and the function of Kernel density estimator is used to further confirm the power plant cluster center.In the second part, the suitable oil and gas field screening criteria are used to determine the suitable oil and gas fields for CO2 storage, and the Kernel density estimator function is also used in ArcGIS software to realize the storage and transportation center of the storage site.The third part is the identification module of the shortest CO2 transmission pipeline, which links the power plant with the oil and gas field cluster center, and determines the main pipeline network of CO2 transportation.
Fig. 1 Power plant and oil and gas field cluster identification method

Data
Screen the power plants suitable for deployment of CCUS and calculate the CO2 emissions of the power plants.
From the surveyed power plant data, obtain the name, address, installed capacity, annual power generation, construction time and steam turbine type of each power plant, and screen out the power plants suitable for CCUS implementation according to the CCUS retrofit suitability specification for coal-fired power plants [2].The power plant was built after 1995, with an installed capacity of more than 300 MW and within 800 kilometers of the storage basin.After the screening was completed, there were 591 power plants meeting the above rules, with a total installed capacity of about 664 GW.
The reservoir database comes from China Petrochemical Corporation [6].The reservoir database contains 4386 reservoirs.The database has detailed statistics on oil reservoirs.There is the location of each oil field, including the name, location, and topography of the oil reservoir, as well as the basin and affiliated oil company of each oil reservoir.In terms of recoverable reserves, there are details of the time when the oil field was discovered, the proven recoverable reserves of the reservoir, and the amount of oil that has been extracted.

Identification results of power plant cluster centers
From the power plant cluster results, a total of 20 large coal-fired power plant cluster centers were identified, and these 20 collection centers covered a total of 580 large coal-fired power plants, with a total annual CO 2 emission of about 2.2 billion tons.The total emissions of the 20 coal-fired power plant cluster centers account for about 25% of the country's total emissions from coal-fired power plants.There are 3 cluster centers whose CO 2 capacity exceeds 2% of the total emissions of coal-fired power plants, namely Nanjing, Jiyuan and Shenyang.There are a total of 9 cluster centers with CO 2 capacity exceeding 1% of total emissions, as shown in Figure 2. According to the analysis of power grid area, the East China Power Grid Regional Collection Center is the largest, which is the Nanjing Gathering and Transportation Center, covering 42 power plants with an annual emission of about 200 million tons.In the Northeast Power Grid region, the Shenyang collection center covers 65 power plants with an annual emission of about 180 million tons of CO2, making it the largest collection center in the Northeast region.In the North China power grid area, the number of collection centers is at most 7, involving a total of 138 power plants and an annual CO 2 capacity of about 570 million tons.The Shijiazhuang collection center is the largest cluster center in North China.The Central China Power Grid Regional Collection Center has a total of 3 large-scale collection centers.Among them, Jiyuan Collection Center is the largest cluster center in Central China, involving 49 coalfired power plants, with an annual CO 2 storage capacity of 190 million tons.There are 3 large-scale coal-fired power plant cluster centers in the coverage area of Northwest Power Grid, namely Shuozhou, Changji and Wuzhong cluster centers, involving a total of 82 power plants.The largest coal-fired power plant cluster center is Wuzhong cluster center, involving 41 power plants.The CO2 capacity can reach 140 million tons.

Identification results of cluster centers of electric oil and gas fields
From the analysis of oil and gas field clusters, a total of 6 large oil and gas gathering and transportation centers have been identified, as shown in Figure 3.They are Daqing Oil and Gas Gathering and Transportation Center in Songliao Basin, Karamay Oil and Gas Gathering and Transportation Center in Junggar Basin, and Shengli Oil and Gas Gathering and Transportation Center in Bohai Bay Basin.Oil and gas gathering and transportation center in Yanchang in Ordos Basin, Changqing oil and gas gathering and transportation center in Ordos Basin, and Jianghan oil and gas gathering and transportation center in Hanjiang Basin.The six oil and gas gathering and transportation centers cover a total of 81 large oil and gas fields, with a total CO2 storage capacity of 2.3 billion tons, of which about 190 million tons of CO 2 can be stored through CO 2 -GAS, and the rest need to be stored and transported through CO 2 -EOR.The sum of the CO 2 storage capacity of the six potential storage and transportation centers is about a quarter of the country's total annual emissions.The potential CO 2 storage and transportation capacity of Shengli, Karamay and Daqing accounts for about 5% of the country's total annual emissions.
Fig. 3 Identification results of oil and gas field gathering and transportation centers

Cluster Center Matching
The matching results of the direct shortest distance pipeline network between the coal-fired power plant cluster center and the oil and gas gathering and transportation center are shown in Figure 4.There are a total of 6 matching pipeline paths.The transportation distance of the main network is basically distributed between 200-300km, and the longest between the Shenyang power plant cluster area and the Daqing storage and transportation area is 518km.The gathering and transportation center of Changji coal-fired power plant is matched with the pipeline network of Karamay oil and gas gathering and transportation center.The actual distance of the pipeline network is 213 kilometers, and the transportation volume is expected to be 390 million tons.The CO2 pipeline network is 170 kilometers long from the gathering and transportation center of the Wuzhong coalfired power plant to the Yanchang oil and gas gathering and transportation center.The transportation distance from the gathering and transportation center of the Wuzhong coal-fired power plant to the Changqing oil and gas gathering and transportation center is 153 kilometers.
From the Shenyang coal-fired power plant cluster center to the Daqing oil and gas gathering and transportation center, the transportation distance is 518 kilometers, and the transportation volume is about 720 million tons of CO2.The Tianjin coal-fired power plant cluster center is matched with the pipeline network of the oil and gas gathering and transportation center of Shengli Oilfield, with a transportation distance of 217 kilometers and a transportation volume of about 400 million tons of CO 2 .
From the Pingdingshan coal-fired power plant cluster center to the Jianghan oil and gas gathering and transportation center, the CO 2 transportation pipeline network is 371 kilometers long, and the transportation volume is about 50 million tons.The CO 2 -EOR storage capacity of oil and gas fields is limited, and other CO 2 utilization projects need to be added, such as deep saline aquifer storage, CO 2 -ECBM, CO 2 -EGS, etc.

Conclusions
From the power plant cluster center, the total CO 2 emissions in the power plant clusters in Nanjing, Jiyuan and Shenyang all account for more than 2% of the national annual CO 2 emissions.The CCUS clusters with the highest average power plant emissions are distributed in the Ningbo cluster area, with an average annual CO 2 emission of about 8Mt per power plant.From the perspective of oil and gas field storage and transportation centers, the amount of CO 2 -EOR storage used in oil and gas field storage and transportation areas is only a quarter of the country's annual CO 2 emissions.In the storage and transportation areas of the Daqing, Karamay and Shengli CCUS oil and gas fields, the combined CO 2 storage potential accounts for 70% of the total CO 2 -EOR storage capacity.From the perspective of the proportion of public pipelines, the power plant cluster areas in Tianjin, Jiyuan and Shantou share more than 30% of the pipelines.In the storage and transportation areas of Yanchang and Changqing oil and gas fields, the pipeline sharing ratio is about 25%.From the perspective of the power plant cluster center and the oil and gas field storage and transportation center, Wuzhong power plant cluster center and Yanchang, Changqing oil field storage and transportation center, Shenyang power plant cluster center and Daqing oil field storage and transportation center, Tianjin power plant cluster center and Shengli oil field storage and transportation center, The development of CCUS cluster is more suitable.This is also the area where the CCUS demonstration project currently carried out is located in China.Based on the above research, this paper puts forward corresponding policy recommendations.On the basis of the existing CCUS demonstration projects, especially the CCUS demonstration projects distributed in Yanchang, Changqing and Shengli Oilfields, the CCUS storage and transportation center is planned to prepare for the future CCUS cluster development and CO2 transportation network construction.Utilize the advantages of its shared infrastructure, as well as its flexible and reliable operation, to verify the feasibility of reducing the construction and operation costs of CCUS projects.Explore new business models suitable for the development of CCUS clusters in China.

Fig. 2
Fig. 2 Power plant cluster center identification results

Fig. 4
Fig. 4 Identification results of oil and gas field gathering and transportation centers