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Oil & Gas Storage and Transportation2022 09
WANG Zhechao1,ZHANG Bin2,QIAO Liping1,YANG Sen3
As the underground water-sealed storage is one of the important ways of oil and other energy storage in China, the development and innovation of basic theory and key technologies is of great importance. In the construction of the second phase of National Petroleum Reserve Projects in China, the entities involved in construction of those projects carried out the extensive scientific research and key technology research with reference to the actual construction conditions. However, the construction of the underground water-sealed oil storage in rock caverns with millions of cubic meters of reserves is a complex systematic project, which is still a new technology field in China. Thus, many key technologies related to the construction of large-scale underground water-sealed oil storage in rock caverns need to be studied in depth. Herein, the important research progress in the basic theory and key technologies of underground water-sealed storage in China in recent years was summarized. For the basic theory, the progress in water seal efficiency evaluation, water seal reliability analysis, and water inflow prediction method of storage caverns was introduced. For the key technologies, the progress in water sealing monitoring and evaluation technology, support design and stability monitoring technology was reviewed. Finally, five challenges and countermeasures in the construction of underground water-sealed storage were analyzed and summarized in combination with the development trend of underground water-sealed storage in China. The research results are expected to play a positive role in promoting the scientific and technological progress and high-quality development of underground water-sealed storage industry in China. (1 Figure, 50 References)
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GUO Jieqiong,ZHOU Tao,LI Gang,ZHANG Jiahong,Meng Lingyun,GE Lingzhi,JIANG Senjue
The construction and market-oriented operation of underground gas storages (UGS) form a positive correlation of mutual promotion. The economic and social benefits brought by market-oriented operation can promote more social capital to be invested in the UGS construction, which can improve the gas storage capacity of the whole market, and in turn, promote the competition and transactions in the gas storage market. On the basis of learning from the business modes of foreign UGS, the business modes in China were discussed in combination with China’s current regulatory policies on UGS and the degree of fairness and openness, and classified into four modes from the prospective of UGS products under the management of traditional gas storage companies, including “binding lease”, “price difference in low and peak seasons”,“deposit and loan gas”, and “remote access” modes. It is suggested that the first two modes be promoted as the main and the “deposit and loan gas” mode as the auxiliary to increase the profit space for the gas storage companies. In addition, the“remote access” mode is suitable for the joint operation of several gas storages or gas storage clusters in close distance. Further, the proposal of the four business modes provides practical reference for the marketization of gas storages, and the business modes could be directly promoted in the gas storages, which are conductive to activating the commercial value of gas storage services in China, thus promoting the realization of openness and fairness. (7 Tables, 31 References)
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PU Hongbin,WANG Xin,JIAO Jian
The wellbore of Jintan Gas Storage faces more failure risks than conventional natural gas wellbore due to its salt rock creep, frequent fluctuations of injection-production pressure, and abundant groundwater, which makes their safety evaluation and control requirements hard to be met by the conventional evaluation methods and conclusions. Herein, 10 specific risk factors of the wellbore of Jintan Gas Storage, including frequent fluctuation of injection-production pressure, alternating load, abundant groundwater and salt rock creep, were identified based on the geographical conditions of Jintan Gas Storage and the actual operation state of the wellbore. Meanwhile, the fault tree of Jintan Gas Storage wellbore was established with consideration of the possible failure modes caused by various risk factors, and the structural importance of wellbore was calculated and ranked. The results show that the maximum risk factor of wellbore failure in Jintan Gas Storage is the frequent fluctuation of injection-production gas pressure, which is significantly different from the sour environment of conventional natural gas wells. Among the 10 identified risk factors specific to the wellbore of Jintan UGS, 5 unique risks are ranked in the top 10 of the structural importance of the bottom event, which indicates that the failure risk of the wellbore of Jintan Gas Storage mostly comes from its own operating characteristics and geographic location. Finally, targeted measures for wellbore risk control of Jintan Gas Storage were put forward based on the management of conventional natural gas wellbore. (8 Figures, 3 Tables, 20 References)
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ZHENG Yali1,2,QIU Xiaosong1,2,LAI Xin1,2,ZHAO Yanjie3,SUN Junchang1,2,HUANGFU Xiaohong1,2
The geological body management of gas storage is essential for the integrity management of Underground Gas Storage (UGS). However, the integrity management of geological body of gas storage is unclear in concept with fuzzy interface and incomplete system at present, and it is also limited to the integrity evaluation of gas reservoir UGS. Therefore, the concept of geological body of salt-cavern gas storage was defined based on the analysis of research results related to the geological body of gas reservoir UGS, and an integrity management system for geological body of salt-cavern gas storage was established. The results indicate that (1) the integrity management system for geological body of gas storage comprises 4 items, which are based on the hazard identification and data analysis and centered on the risk evaluation and integrity evaluation. (2) The risk analysis for geological body of salt-cavern gas storage focuses on the analysis of the 3 indicators, i.e., salt cavern shrinkage, gas leakage and land subsidence. (3) The salt-cavern storage integrity evaluation is composed of 3 major evaluation technologies, i.e., stability evaluation of salt cavern and surface, fault stability evaluation, and integrity evaluation of interbed and caprock. In conclusion, the establishment of the integrity management system for geological body of salt-cavern storage complements the shortage of geological body management in UGS integrity management, and also provides technical support and new application direction for the safe operation management. (1 Figure, 2 Tables, 31 References)
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YANG Yuehui1,GAO Guangliang2,WANG Fang2,LI Chaofeng2,WAN Wenjin2,SUN Dongsheng1,CHEN Qunce1
In-situ stress is an important basic data for determining the top and bottom limit of operating pressure of underground gas storage, evaluating the stability of geological body and analyzing the fault activity in the storage area. Herein, the layered in-situ stress measurement method, test equipment and construction process of perforated interval were briefly introduced, and the minimum principal stresses of 2 reservoir sections and 3 mudstone caprock sections in the depth range of 4 150.0 m to 4 338.0 m of Well NP36-X in Pugu-2 Block of Jidong Oilfield were measured with this method. As shown by the results, the tests were repeated over 3 times for each section, and the fracture shut-in pressure in multiple tests had good consistency with the relative error less than 5%. Besides, the minimum principal stress in the mudstone caprock of Well NP36-X was determined to be 72.40 MPa to 74.27 MPa with various fracture shut-in pressure analysis methods. Moreover, the minimum principal stress of high permeability formation was comprehensively determined to be 54.89 MPa to 60.25 MPa with the fracture extension pressure and the injection flow. As an exploration based on the in-situ stress measurement method for the perforated interval of old wells, this method, especially the field application test based on the fracture extension pressure and the injection flow, can partly compensate the insufficiency that the classical in-situ stress measurement method of hydraulic fracturing is not applicable to the high permeability formation. (5 Figures, 4 Tables, 29 References)
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LIU Zhong1,ZHANG Yejin2,ZHANG Lide2
It is in strong demand to construct the underground water-sealed oil storage in rock caverns, but there are problems such as difficult control of water seepage during the construction of water-sealed cavern storage, insufficient attention to the water sealing conditions of cavern storage, and immature methods for water sealing control at present. Herein, the water sealing criteria of cavern storage were analyzed by reviewing domestic and foreign researches on the water sealing of underground oil storage in rock caverns, and it was found that the vertical hydraulic gradient greater than 1 in the surrounding rock of caverns was the essential condition for the underground oil storage in rock caverns to meet the requirements of water sealing. Besides, it was also revealed that the goal of water sealing regulation in the cavern storage was to achieve the lowest full life cycle cost and the highest benefit under the premise of meeting the requirements of water sealing. Meanwhile, study was also carried out to the mechanism of different regulation means, such as seepage reduction by grouting, artificial water curtain system adjustment and cavern storage pressure adjustment. On this basis, the multi-factor combined regulation mechanism of water sealing in cavern storage was analyzed, and a multi-factor combined regulation strategy based on iterative optimization was proposed. Finally, the multi-factor combined regulation strategy based on iterative optimization was applied through case analysis. Generally, the research results could provide theoretical and technical support for the efficient construction and safe operation of cavern storage projects. (6 Figures, 33 References)
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ZHANG Jian1,2
In the traditional gas storage construction, due to the effect of on-site construction environment, it is difficult to control the project quality and the construction progress, and the risk of safety management is high, thus the urgent needs of the project owner for the construction period is hard to be satisfied. In order to improve the construction quality of gas storage, shorten the construction period and reduce the safety risk, modularization technology was adopted for the division of module units, comparison of road transportation schemes, three-dimensional design of modules and analysis on structural stability. At the same time, the modules were processed, manufactured, tested and packaged in the prefabrication plant, and then were assembled on site according to the reassembly scheme upon arrival, so as to realize the rapid completion and commissioning of gas storage. The results indicate that the construction mode with modularization technology can minimize the impact of on-site adverse factors on construction quality and progress. Moreover, the safety risk of the project site is reduced and the construction period is shortened due to the transfer of a large number of construction operations to the prefabrication plant. The research results could provide design ideas for the gas storage projects to be constructed in modular mode. (5 Figures, 2 Tables, 22 References)
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ZHU Rongqiang1,DING Hao2,3,JIANG Xinghong2,3,PENG Zhenhua1,HU Xuebing2,3,ZHU Jiong2,3
Underground gas storage is an important guarantee for the national energy strategic reserve, and its construction is being accelerated. The stability of surrounding rock during the construction of Underground Gas Storage (UGS) cavern is the key factor determining the feasibility of gas storage. As a case study, research was performed to a single UGS cavern. Specifically, the influence law of different surrounding rock conditions, different depth-span ratios and different buried depths on the stability of surrounding rocks during excavation of UGS cavern with large section was studied by establishing a three-dimensional finite element model based on the rock yield process and plastic flow rule. The results indicate that the deformation of surrounding rocks of cavern increases exponentially with the reduction of surrounding rock grade after excavation, and the plastic zone also increases gradually. Besides, the deformation of surrounding rocks of the cavern increases with the increasing of the buried depth, and the surrounding rock deformation at the waist of cavern increases exponentially. The maximum vertical deformation of surrounding rocks decreases generally with the increasing of depth-span ratio, while its maximum horizontal deformation increases with the increasing of depth-span ratio. Moreover, the gas storage cavern should be constructed in the area with good conditions such as grade Ⅱ and grade Ⅲ surrounding rocks within the buried depth of 200 m, and the surrounding rock is more stable when the depth-span ratio of the cavern is 2.5 to 3.0. In general, the research results could provide reference for the structural design of UGS cavern with large section. (13 Figures, 2 Tables, 29 References)
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KANG Yanpeng1,2,JIAO Yujia1,2,WANG Jianfu1,2,ZHANG Ling2,WU Zhangfan2
The salt rock resource in China is characterized with multiple interlayers, thin salt formation and poor purity. Meanwhile, the conventional single vertical cavern has small volume and low utilization rate of salt formation, which cannot meet the requirements of rapid and efficient storage construction. Multi-step horizontal leaching can improve the utilization rate of salt formation and is suitable for constructing large gas storage in thin salt beds, and the cavern shape is a key factor affecting its volume and stability. Therefore, a physical simulation experiment was performed for the characteristics of horizontal leaching herein. Meanwhile, the effect of leaching parameters such as leaching rate, brine discharge position and back-step length on cavern shape and brine discharge concentration was explored. The results show that the large leaching rate and the high brine discharge position can reduce the brine concentration, and the effect is more significant in the early leaching stage. The small step length will form a hump cavern roof, while the large step length and use of blanket will form a flat cavern roof, and the alternate injection by two wells will form large body at both ends and small body in the middle. The cavern shape obtained by experiment is basically consistent with the numerical simulation result, which verifies the accuracy of experiment result. In addition, reference values were provided for such parameters as leaching rate and step length of multi-step horizontal leaching on site based on the experiment results, so as to build a hump-shaped horizontal cavern, further improving the stability and gas storage capacity of cavern. (5 Figures, 3 Tables, 24 References)
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With the rapid development of China’s economy and society in recent years, the demand for oil and natural gas is growing day by day, and a large number of underground energy reserves have begun to be built in salt rocks. Under the engineering background of a proposed underground oil storage group in bedded salt rocks in a salt mine in Jiangsu Province, a numerical simulation model of horizontal oil storage group was established with the finite element analysis method, using FLAC3D software as the platform. Meanwhile, the stability of storage group with different pillar widths in rectangular and diamond-shaped well layout was simulated and analyzed. In addition, the variation laws of the displacement distribution of surrounding rock, the volume shrinkage, the volume of plastic zone and the maximum vertical displacements of roof and floor after 30 years of operation of the storage groups were analyzed. The result shows that it is a reasonable layout to ensure the stability of the horizontal oil storage groups by adopting diamond-shaped well layout and setting the pillar widths not less than 1.75 times of the storage diameter. In addition, the results were verified according to the stability criterion, which shows that the stability conditions are satisfied. Generally, the research results could provide reference to the construction of underground oil storage groups in bedded salt rocks in China in the future. (10 Figures, 3 Tables, 30 References)
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XIAO Kaixi,HOU Lei,HUANG Ya'nan,LI Yanhao,CHAI Chong,ZHANG Rui
The leakage of tank oils, once occurred, will bring about adverse effect to ambient environment, social economy and safety of tank farm, and even cause safety accident. Herein, the leakage diffusion process of oil and gas was simulated with the improved Gaussian puff model to find out the concentration distribution law of oil and gas in tank farm under different environmental wind speeds and atmospheric stability. Meanwhile, the tank farm was divided into the explosive hazardous area, flash fire hazardous area and suffocation hazardous area according to the risk level of oil and gas concentration. By analyzing the influence of environmental wind speed and atmospheric stability on migration and diffusion of oil and gas puff, the influence law of environmental conditions of tank farm on concentration distribution of oil and gas, as well as the scope of hazardous area, was obtained. Specifically, the migration and diffusion of oil and gas puff is intensified with the increasing of environmental wind speed, but the concentration of oil and gas in the tank farm is reduced, and the hazardous areas of different grades are reduced accordingly. With the increase of atmospheric stability, the diffusion of oil and gas puff becomes weaker, the influence range of concentration along the downwind direction increases, but the influence range along the crosswind direction decreases. Because of the fluctuation of wind speed, the oil and gas puff may gather and form an oil and gas accumulation area at high concentration. Generally, the lower the environmental wind speed and the more stable the atmosphere, the easier the oil and gas puff to gather. The improved Gaussian puff model may more accurately reflect the leakage diffusion law of oil and gas, and predict the concentration distribution of oil and gas, which could provide guidance to the safe operation and management of tanks. (7 Figures, 1 Table, 26 References)
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BAO Wenhong1,ZHANG Yinglong1,BAN Tao1,ZHAO Xilong2
The baffles of some road tankers for liquefied gas (hereinafter referred to as liquid tankers) are found to be cracked or fallen off during the regular inspection. If the failed baffles are not repaired and replaced in time, the safe operation of the liquid tankers will be seriously affected. According to the actual service conditions of the liquid tankers, the liquid sloshing within the liquid tankers that brake at different accelerations was simulated with Fluent software, and in this way, the impact force of each baffle was obtained. In addition, the changing law of impact force applied to the baffles at different positions over time under the action of different inertial loads was analyzed. The results show that the maximum impact force applied to the baffles is generated in the deceleration stage of liquid tankers, and the impact force of baffles increases with the increasing of the braking acceleration. In addition, the baffle subjected to the maximum positive and negative impact force is located at the same position among the many baffles within the tanker, which has nothing to do with the braking acceleration of liquid tankers. The research results could provide some guidance for the inspection and design of baffles of liquid tankers. (8 Figures, 1 Table, 26 References)
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ZHAO Zhenxue1,SHI Yongjie1,ZHANG Lifeng2,YU Huichao1
Accurate and efficient prediction of outbound volume of product oil is the source and basis of scientific management for product oil inventory. In order to increase the inventory efficiency and lower the inventory cost of product oil, 166 product oil depots of a company in the western region were studied to analyze the influencing factors of inventory management on the base of the related research results of inventory management and sales prediction. Thereby, the multi-stage prediction algorithm of dual-time granularity was designed, and the algorithm was integrated with the time series model algorithm library of multi-model as well as Mamdani’s fuzzy inference systems to predict the monthly and daily outbound volume of product oil and conduct the quantitative analysis. As indicated by the results, the proposed algorithm and the algorithm designed by the model library could automatically select the appropriate model according to the data characteristics of the outbound volume, as well as match and predict the outbound volume of the oil depot on large scale with high quality in short time. Generally, the median of the average absolute percentage error of the prediction results is higher than 85%, the prediction confidence is close to 95%, and the average accuracy of the monthly outbound volume prediction of the application cases can reach 90%. Conclusively, the research results could provide scientific recommendations for the decision-making on inventory management of oil depot, and have practical significance for establishing a scientific and efficient modern oil supply and logistics system. (5 Figures, 3 Tables, 24 References)
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WANG Menghao1,2,LI Sensheng3,2,4,XIE Wenjie5,2,4
In the context of promoting the market-oriented reform of natural gas and the transformation of gas storage to independent operation, it is necessary to design gas storage products that meet the conditions of natural gas industry in China. Herein, the design modes of gas storage products suitable for the conditions of China were proposed from the point of the degree of freedom for injection/withdrawal by analyzing the basic theory on design and the desired form of gas storage products in China. Meanwhile, the premium mechanism of gas storage products and the physical constraints were discussed. Due to the financial value given by the capacity of capturing gas price fluctuation, the gas storage products should have a premium rate controlled by their quantified financial values. A series of gas storage products with different degree of freedom for injection/withdrawal were designed from temporary product to day-ahead product. With the increasing of degree of freedom for injection/withdrawal, the premium rate and the deployment difficulty are also increased. The results show that diversified products should be provided for high marketization degree while relatively simple products should be provided for low marketization degree. Salt cavern storage has the advantage of financial value due to its flexibility, but such advantage could not be presented in the market with low marketization degree. The ratio of various products should be determined by prediction of the gas storage on customer requirements. Generally, this research results could provide a theoretical basis for the gas storage product design during natural gas marketization. (2 Figures, 26 References)
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ZHANG Bo1,WU Yuhang1,CHEN Kaiyan1,GAO Yan1,JIA Jianchao2,WANG Lu2,LIU Tuanhui1,XI Zengqiang1
Some achievements have been made in a province of China for old cavern reconstruction of salt-cavern gas storage, but some of the reconstructed caverns are not suitable to be used as underground gas storages for peak sheaving of pipeline network due to small working gas capacity and high cost of cushion gas. However, underground salt caverns are still very important strategic resources. Specifically, these salt caverns, if constructed as a compressed air energy storage power station, can be used to store power resources in the valley power stage. Based on successful foreign cases and the given situation of these underground salt caverns, specific parameters for reconstruction of the energy storage power station were calculated, and the economic analysis was carried out for the energy storage power station reconstructed with old salt caverns. The results show that X1 old cavern can store 3.07×106 kW·h of energy and generate 17.49×104 kW·h power in a single injection production cycle according to the actual situation. The reconstruction of salt cavern gas storage would have a good development prospect under the background of “carbon peaking and carbon neutrality” if it could explore to establish a suitable business mode while improving the technology. (3 Figures, 1 Table, 20 References)
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About Journal
Administrator: China National Petroleum Corporation
Sponsor: PetroChina Pipeline Company
Editor and Publisher: Oil & Gas Storage and Transportation Journal Agency
Address: Oil & Gas Storage and Transportation Journal Agency, No.51, Jinguang Rd., Langfang City, Hebei Province, 065000, P.R. China
Post code: 065000
Tel: +86(316)2176173
Publication No: ISSN 1000-8241,CN 13-1093/TE
Periodicity: Monthly
Book Size: 16-mo
Establishment Year: 1977