Four major technological breakthroughs make up the industry's shortest board China's gas storage construction ushered in a golden period
Our reporter Qu Jian
PetroChina announced on April 19 that the national key energy construction project and the first gas storage group in western China, the Wenjisang gas storage group in the Tuha Oilfield, officially started construction. This move opened the curtain on the construction of six major gas storage centers in the Northeast, North China, Northwest, Southwest, Midwest, and Mid-East during the “Fourteenth Five-Year Plan” period, making it the ultimate solution to alleviate winter gas shortages in local areas. The gas storage ushered in a golden period of construction.
It is reported that the Wenjisang gas storage group is located in Shanshan County, Xinjiang. It is reconstructed from three depleted gas reservoirs, with a total designed storage capacity of 5.6 billion cubic meters and a working gas volume of 2 billion cubic meters. It is expected to be completed and put into operation in 2025. This is China's first low-porosity, low-permeability, low-yield and strong heterogeneous complex gas reservoir type gas storage group, and it is also an important supporting project for the West-East Gas Pipeline. After the project is completed, it will build a gas storage center such as Xinjiang Hutubi Gas Storage and Tarim Gas Flooding Cooperative Construction and other gas storage together to form a 20 billion cubic meter gas storage center in northwest China.
The latest data from the National Development and Reform Commission shows that China's apparent natural gas consumption in 2019 was 306.7 billion cubic meters, an increase of 9.4% year-on-year; as of now, 27 gas storages have been built nationwide, with peak shaving capacity exceeding 12 billion cubic meters. Compared with the previous requirement of the National Development and Reform Commission that "natural gas sellers should build a 10% peak shaving capacity supporting sales volume", the peak shaving gap for the year exceeded 60%. The lack of peak shaving capacity due to the lagging construction of gas storage is the shortest board for the development of China's natural gas industry, and also the "mystery" of the "gas shortage" in local areas in winter.
On April 10, the National Development and Reform Commission, the Ministry of Finance and other five departments jointly issued the "Implementation Opinions on Accelerating the Construction of Natural Gas Reserve Capacity", which is the key issue, and called for the acceleration of the construction of gas storage infrastructure, from land, finance, taxation, finance, and investment. A number of supporting policies have been proposed to encourage enterprises to speed up the shortcomings of gas storage infrastructure construction.
According to PetroChina, China's existing gas reservoirs and salt caverns are two types of underground gas storage spaces, which are converted from depleted gas reservoirs and mine holes left after salt mining. Among them, the construction of salt caverns is still not widely used due to technical reasons such as site selection and cavity creation, and gas reservoir-type gas storage is currently the mainstream.
Before 2000, China's underground gas storage was in a blank state, in fact, "there is no gas". For its root cause, PetroChina said that there are four world-class problems in terms of "injection, survival, and recovery".
What can only be "complaint" but not "extraordinary" is that foreign gas storages are generally simple in structure, high permeability and buried depth less than 1500 meters; while China's main reservoir construction is complex fault block gas reservoirs, broken structures and reservoirs Low permeability, strong heterogeneity, complex fluid and deep burial. "The location of foreign countries basically excludes the possibility of building such gas reservoirs."
Such complex geological conditions bring huge theoretical and technical challenges to the location, design, construction and operation of gas storage, including: there is no theoretical guidance for the evaluation of complex fault block dynamic seals, and almost no reservoirs are available; low permeability and strong heterogeneous reservoirs The mechanism of high-speed injection and production seepage is unclear, and the design of foreign methods cannot achieve the efficient use of gas storage space; engineering construction technology and equipment cannot meet the needs of high-quality well construction and high-pressure and large-flow injection and production; It is difficult to operate wells safely and manage risks.
After nearly 20 years of continuous research, PetroChina has made major key technological breakthroughs in complex gas storage: it has created a complex geological body dynamic seal theory, broke through the complex fault block storage selection area, and guided 65 billion cubic meters of working gas storage site selection ; Created storage capacity utilization theory and optimized design method of complex gas storage type gas storage, solved the problem of efficient utilization of gas storage space, storage capacity parameter design error was reduced from 26% of foreign methods to 6%, and storage utilization rate was increased from 70% to More than 90%; Innovative key technologies for the construction of gas storage projects with complex conditions have been solved, which has solved the difficult problems in the development of key equipment for long-term sealing of cement rings under alternating loads, leak-proofing with large differential pressure drilling and high-pressure and large-volume injection and production. Geological conditions gas storage project construction technology system; innovated long-term operation risk early warning and management technology of complex gas storage, formed a geological body-wellbore-ground trinity risk management and control system, and has built a gas storage operation with zero accidents so far.
PetroChina disclosed that using this set of technical guidance, 22 gas storages have been built, forming 11.1 billion cubic meters of peak shaving capacity; peak shaving has produced 22.5 billion cubic meters of gas in the past three years, creating direct economic benefits of 23.8 billion yuan; The peak shaving of the reservoir has accounted for 45% of the total gas peak shaving in cities and towns across the country, benefiting nearly 400 million people in more than 10 provinces and cities. It has played a key role in emergencies such as reducing the supply of imported gas in Central Asia and the interruption of the West-East Gas Pipeline due to natural disasters.
It is estimated that by 2030, the demand for peak shaving capacity of natural gas in China will exceed 100 billion cubic meters. PetroChina said that on the basis of the existing database building model, it began to explore two new models of building a database in a gas-producing field and cooperating with a gas drive to produce oil. During the "14th Five-Year Plan" period, six major gas storage centers will be built in Northeast, North China, Northwest, Southwest, Midwest, and Mid-East, and 23 new gas storage centers will be constructed. The total working gas volume will reach 27 billion cubic meters. The investment is nearly 100 billion yuan. (Technology Daily Beijing, April 19th)