Record of the "hottest hot spring" in the surrounding area of Sichuan Basin

Original title: Water from the "hottest hot spring" in the Sichuan Basin AreaHot spring drilling platform operation area. Photographed by reporter Huang XiaoHot spring water outlet platform

Original title: Water from the "hottest hot spring" in the Sichuan Basin Area

Hot spring drilling platform operation area. Photographed by reporter Huang Xiao

Hot spring water outlet platform. Photographed by reporter Huang Xiao

Scientific examination location

Zhougongshan, Ya'an, Sichuan

Scientific examination tasks

Searching for underground hot springs

83Zhougongshan, Ya'an, Sichuan

Where is the hot spring hidden? How was it discovered? Recently, the reporter followed geologists to visit Zhougongshan.

Find the "target": gradually reduce the "encirclement circle" from the surface to the line and then to the point

In the summer of 2021, Zhang Ji, a professor level senior engineer from the First Geological Brigade of Sichuan Province, was tasked with demonstrating the possibility of water from the new well of Zhougongshan Hot Spring.

Hot springs, the professional name is hot mineral water. As the name suggests, geothermal and water must be present here to generate hot springs.

How to find hot springs buried deep underground? Zhang Jihe's team needs to delineate the geothermal target area within six months. From surface to line and then to point, this is a process of gradually narrowing the 'encirclement circle'. This stage is crucial and a double test of experience and understanding.

To find hot mineral water, it can be said that one needs to know astronomy and geography, both observing the earth and listening to the rain. "Xie Dajun, Secretary of the Party Committee of the First Geological Brigade of Sichuan Province, said that the first step is to analyze rock formations, structures, and mineralization models based on existing regional geological data.

These data are based on the accumulation of four generations of geologists. The search for geothermal energy in Sichuan began in the 1950s. As the first unit to research and develop geothermal resources in Sichuan Province, the First Geological Brigade of Sichuan Province has done a lot of basic work for the development and utilization of medium and deep Geothermal energy in Sichuan Province, and has accumulated rich data and valuable experience.

The geological structure of Zhougongshan belongs to the Ya'an concave fold area on the western edge of the Yangtze paraplatform, which is a structural 'depression' and has conditions for the formation of deep geothermal resources. Zhang Ji explained that due to the movement of crustal plates, the surface is uplifted, and there is still uncooled magma below, which continuously releases heat to become a heat source. At this time, if there are pores or fractured aquifers nearby, they will be heated to form hot mineral water.

When the "desk work" is fully prepared, it enters the field investigation stage. The Ya'an area has abundant rainfall, lush vegetation, and a thick topsoil layer. For field investigation teams that need to search for hot spring outcrops, which are exposed areas of strata, it undoubtedly increases the difficulty of their work. A 6-person field investigation team conducted field investigations in an area equivalent to 15 West Lake areas over a period of 2 months, outlining 5 possible target areas.

Choose one out of five target areas and conduct rigorous comprehensive argumentation. To this end, the project team utilized advanced high-density magnetotelluric equipment for geophysical exploration. This step is like doing a "CT" of the earth, by emitting electromagnetic waves into the ground, collecting reflection data, and then analyzing the groundwater direction, geological structure, and terrain cutting through a "CT slice" of the data to determine the optimal location.

Finally, the target area was narrowed down to a place called Songjiashan in Kongping Village, Zhougongshan Town, and a working area covering an area of more than 10 mu was determined, 15 km away from Ya'an urban area.

Surprise "encounter": crossing broken and collapse prone strata and repeating Fracture zone

Once the target area is determined, drilling construction needs to be carried out. Last summer, more than 40 large trucks, loaded with a large number of equipment, arrived at the work area of Kongping Village.

Among them, the hard core "diamond" - intelligent deep drilling equipment is eye-catching, which is a "big guy" specially invited by the project department, with a drilling depth of up to 4200 meters.

In late autumn, the weather turned cold. When drilling into 1600 meters underground, the project team encountered the Xujiahe Formation. This is a coal bearing formation with very complex geological conditions, which is prone to collapse, jamming, and underground accidents.

Not only that, the minimum diameter of drilling is only 24 centimeters, and the drill pipe deep underground is difficult to control, just like a rope. Such a small space poses a great challenge to the accuracy control of drilling.

Work 24 hours a day without stopping, carefully and slowly 'arch' 10 meters forward, "said Xia Minghong, the captain of the deep exploration team." The most afraid is to tilt the well and cause deviation. Only by frequently sending drilling, reducing pressure, and hanging drilling, can the quality of the well be strictly controlled. If encountering sudden increase in drilling speed, venting, loss of circulation, poor drilling, jumping drilling, abnormal gas logging, oil, gas, and water display, etc., immediately stop drilling and observe circulation or shut in the well for observation

It took over two months for the drill bit to cross the Xujiahe Formation at a depth of one kilometer and enter a new formation. Subsequently, the drilling team encountered two repeated formations in a row.

Chen Kebing, the driller of the second shift of the drilling team, still remembers that winter night. As planned, he carried out the construction as usual and saw that the temperature of the mud had increased by 3 degrees Celsius. Excitedly, he quickly woke up Xia Minghong. "Stratigraphic repetition means that there is a deep Fracture zone, a structure with heat conduction and water conduction, which is good news for finding hot springs," Xia Minghong said.

On the drilling platform, 9.6 meters long and 330 kilograms of drill pipes were placed vertically. During the 8-month day and night construction, a drilling team of over 30 people controlled the handle and drilled over 400 drill pipes underground. In March of this year, the drilling entered the Feixianguan Formation of the Triassic system. After comprehensive analysis and judgment by on-site logging experts, the drill bit successfully entered the completed interval, with a depth of 3980 meters.

The deepest record is 4016 meters away from the hot springs around the Sichuan Basin, with a difference of less than 50 meters, "Xie Dajun said.

"The drilling level is high, with a depth of nearly 4000 meters, crossing multiple strata, and there are many applications of advanced technologies," said Ni Huayong, deputy director of the Institute of Exploration Technology of the Chinese Academy of Geological Sciences.

Effluent: Strengthen research, comprehensive utilization, and green development of hot mineral water

Before reaching the hot spring water outlet platform, I could smell a smell of sulfur. On the platform, the spring water continuously gushes, emitting a curl of white air. The reporter placed an egg in the water and it was not long before it was cooked. After measurement, the temperature of the geothermal water outlet from the mineral well ranges from 82 degrees Celsius to 84 degrees Celsius, with an average daily water output of 700 cubic meters. The water temperature and water output both exceed the original target task.

Where does geothermal mineral well supply water source come from? Zhang Ji introduced that the water source comes from the infiltration and replenishment of atmospheric rainfall in the southwestern limestone outcrop area. Through karst karst crevices or pipelines, long-distance runoff and deep circulation are carried out along the catchment structure, continuously exchanging and converging with the surrounding rock through physical and chemical processes, forming hot mineral water. The water source is sufficient and can be used for long-term mining.

Temperature is not the determining factor for the quality of hot springs, mineral content is the key. According to the water quality analysis report of the water samples taken twice during the pumping test, nine minerals and trace elements in the hot spring water, including fluorine, strontium, bromine, iodine, iron, lithium, barium, Metaboric acid and metasilicate, have reached the standard of named concentration.

In other words, Zhougongshan Hot Spring meets the standards of physical therapy and has extremely high therapeutic value. Especially lithium and barium are not commonly seen in hot springs, "said Zhang Ji.

The evaluation expert sighed, "This is the geothermal mineral well with the highest temperature and richest trace elements seen in the surrounding area of the basin

Opening up hot springs is just the beginning of a new phase of work for geologists. Why are there hot springs over 80 degrees Celsius here? How is the geological structure here different from other places? Are there any differences in water temperature and quality between normal and dry seasons? These questions are waiting for geologists to track and answer.

Sichuan's development of mid to deep geothermal energy is relatively lagging behind, and the exploration and development of this hot spring plays a leading role. In the later stage, it is necessary to fully utilize this well, strengthen research on genetic mechanisms and conditions, and produce higher value scientific achievements.

From the perspective of development and utilization, compared with other hot springs, there is a temperature difference of up to 40 degrees Celsius. "If we just dilute and cool down, it will be wasted. We should do a good job in comprehensive development plan and create a model of green development," said Zheng Wanmo, a professor level senior engineer at the China Geological Survey Geological survey Center in Chengdu.

For Ya'an, the hot spring is located in the three mountain tourism loop of Zhougong Mountain, Wawu Mountain and Mount Emei, with prominent advantages. The hot spring well will be used as a hot spring venue for Ya'an cultural and tourism projects such as Zhougongshan Hot Spring Park, driving surrounding residents to enjoy "hot spring meals".

dialogue

dialogue

Reporter: What are the arrangements and deployments for the new round of strategic breakthroughs in mineral exploration?

Xie Bing: We have mainly arranged and deployed three aspects of work. Firstly, we have focused on key mineralization zones, strengthened basic geological work, and implemented exploration blocks and prospecting targets. The second is to focus on strategic and advantageous mineral resources in our province, with the goal of ensuring national energy resource security and local industrial development needs, and increase exploration efforts, mainly in key exploration areas and deep areas of important mines in our province, to promote storage and production increase. The third is to focus on key mineral types and important mineralization zones, and vigorously promote geological technology innovation. The main focus is to strengthen the theory of strategic mineral resource mineralization, exploration methods, and key technological innovation in deep exploration and development.

Reporter: What specific work measures are there?

Xie Bing: Since the launch of the operation, we have formed a new round of strategic breakthrough mining exploration work team and formulated a promotion plan. At the same time, based on regional advantages, 12 regions and one geothermal special leader were identified, and seven strategic and advantageous mineral resource expert teams and technical research teams were established, including vanadium titanium Magnetite, lithium ore, etc.

Reporter: What is the current progress?

Xie Bing: New breakthroughs have been made in the exploration of resources such as phosphorus and geothermal energy. Among them, the geothermal water flow rate of the hot spring development well under construction exceeds 700 cubic meters per day, and the outlet water temperature ranges from 82 degrees Celsius to 84 degrees Celsius, breaking the record for the highest geothermal temperature in the surrounding area of Sichuan Basin. (Reporter Wang Ruoye)

(Source: Sichuan Daily) (Wang Ruoye)

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