Using the "pen" as a guide to identify mineral resources, this biostratigraphic team is looking for "blue gold" in the cracks of rocks

In 1735, Swedish taxonomist Carl von Linnaeus recorded a strange fossil that looked like a pen scribble on a rock in his book Systema Naturae, and named it "Graptolithus". Linnaeus at that time probably never thought that one day, this tiny ancient life would not only become a "vernier caliper" for paleontologists to divide geological time, but also a "compass" and "great contributor" to oil and gas exploration, bringing new vitality to the main battlefield of the national economy - the exploration and development of new energy.

▲Group photo of some members of the biostratigraphy team

So how exactly does this tiny creature connect to energy exploration?

On this blue planet, the Earth, energy has been inseparable since humans first picked up fire. When the Industrial Revolution began, it brought about earth-shaking changes, but also brought increasingly prominent environmental and energy problems. In recent years, in order to improve the environment in which humans live, my country has proposed a "dual carbon" goal. Compared with coal and oil, new energy - natural gas has become a key transition energy source because of its obvious low-carbon emission advantage, and unconventional natural gas represented by shale gas is becoming an important source of natural gas in China. It is known as the "blue gold" underground.

In the past decade, more and more scientific research teams in my country have embarked on the journey of searching for "blue gold" in the cracks of rocks. Among them, there is a very "special" team - the Biostratigraphic Group of the China Petroleum Exploration and Development Research Institute (hereinafter referred to as the "Biostratigraphic Group"). It was voluntarily initiated by academicians such as Chen Xu, Rong Jiayu, and Zou Caineng, and strongly organized by backbones such as Wang Hongyan and Zhao Qun of the China Petroleum Exploration and Development Research Institute. It has gathered a group of like-minded elite talents in multidisciplinary fields such as China Petrochemical Corporation, China Geological Survey, and Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences. In their work, these team members have unanimously felt the importance of paleontology to shale gas exploration and development. With the "pen (penstone)" as a guide and breaking barriers, they spontaneously embarked on a new path of interdisciplinary, cross-directional, and multidisciplinary deep integration, setting an example for the combination of basic research and production application.

What specific work did the biostratigraphic team do? How did they use their "pens" to identify mineral resources? What touching stories happened behind this? With these questions, this magazine takes you into the magical world of this team and their research.

Origin: Spontaneously formed biostratigraphic group

In the oceans between 500 million and 300 million years ago, there lived a mysterious small marine invertebrate - Graptolites. They lived in groups like today's coral polyps, and liked to build neat and delicate "small houses" called cell tubes, which were round, square, straight or curved, and lived in them. Therefore, they are often praised as the hardworking "construction workers" in the ancient oceans, and also the "little artists" who kept improving.

▲Academician Chen Xu teaches on-site shale graptolite identification

Graptolites lived in the Cambrian period of the Mesozoic Era and the Ordovician period of the Paleozoic Era. If you travel to the oceans of the Ordovician period, you will find that any object that can allow graptolites to firmly fix can become their thriving home. They thrive on the surface of the sea rich in oxygen and food, and fall to the bottom of the sea and be buried after death.

Because of the rapid evolution of graptolites, the large number of fossils, and their wide distribution around the world, they have been selected by scientists as standard fossils for studying strata. Scientists use the time when specific types of graptolites appear and disappear to mark the age of strata and establish the "Tang, Song, Yuan, Ming and Qing" in geological history, so graptolites are called the "vernier caliper" of geological time; and because they mainly feed on organisms such as microorganisms and algae in seawater, which are the main source of oil and gas. In the oceans of the Ordovician and Silurian periods, a large number of graptolites often lived in places where microorganisms and algae flourished. Therefore, looking for oil and gas in rock strata with a high content of graptolite fossils has become the golden rule of oil and gas exploration.

As described by Academician Chen Xu, one of the initiators of the biostratigraphy group and a researcher at the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences: If the strata are "hundreds of pages of books", geological changes have torn and crumpled these hundreds of pages and thrown them everywhere. What they have to do is to find the dozens of pages with "minerals" in these hundreds of pages - find the specific combination of organisms and rocks in each page, distinguish which layer is which, and then recognize which place belongs to the "page" with minerals in different places, which will indicate the direction of exploration. It can be said that in the exploration and development of shale gas resources, not only high-end drilling technology is needed, but also the precise calibration of the stratigraphic positions of black shale. In this process, graptolites play an irreplaceable role as a golden caliper, which is currently the simplest, fastest and most accurate method to determine biostratigraphy at the drilling site. With only a magnifying glass of about 10 times, biogeological research scientists can identify the genus and species of graptolites in the rock strata on site, and thus determine the age of the strata in which they are located.

In China, shale gas exploration and development research has only been going on for a dozen years, but shale gas has become a major growth pole for my country's natural gas. Such a rapid development is due to the unremitting efforts of a group of researchers in related fields.

In 2006, a group of geologists represented by Academician Zou Caineng, another initiator of the biostratigraphy group, began to venture into a new field of oil and gas exploration. They conducted special research and comprehensive geological evaluation on shale gas, and preliminarily identified the shale gas resource potential, favorable strata and favorable zones in Weiyuan and southern Sichuan. Since then, the China Petroleum Exploration and Development Research Institute has organized personnel to conduct on-site technical inspections and indoor joint research in Changning, Weiyuan and other places in Sichuan Province many times. They first discovered rich organic nanopores in my country's marine shales, confirmed the gas storage capacity of the Longmaxi Formation shale, and unveiled the mystery of the shale gas in the Wufeng Formation-Longmaxi Formation in southern Sichuan. Not only that, they also determined that there are deeper and higher-quality shale gas target layers to the north of the Changning structure and the east of the Weiyuan structure.

Hardships and difficulties will eventually lead to success. What everyone sees is the brilliance of fruitful results, but only those who are deeply involved in it understand the hardships and sweat behind these achievements. China's shale gas exploration is actually a process from "0 to 1". Many basic work has no precedents before, especially in the initial exploration period of combining paleontological research with shale gas exploration. Difficult problems have come one after another, such as the problem of inconsistent stratification of black shale in the Wufeng Formation-Longmaxi Formation, which has made scientific researchers anxious. There is also a lack of effective means for the fine division of shale gas reservoirs, and there are disputes over the determination of shale gas horizontal well development boxes. The main problems focus on the inconsistency of the original multiple schemes, the many names, and the inconvenience of communication; the research is not in line with the international biostratigraphy, the division is mainly based on lithology and sedimentary phases, and there are time-diachronic phenomena. There are numerous problems to be faced, and it is urgent to re-establish a stratigraphic division scheme in line with international standards.

With the mission on our shoulders, we move forward with a heavy burden. The Biostratigraphy Group was born. It can be said that it was built on the in-depth understanding of the urgent needs of the frontline by the team of academicians such as Chen Xu, Rong Jiayu, and Zou Caineng, as well as the backbone of oil exploration and development such as Wang Hongyan. It is precisely because of this understanding that their calls have received positive responses from people of insight in many units. When it was first launched, all the members of the group voluntarily joined and learned out of interest.

The power of example guides us forward. As the organizer and manager of the Biostratigraphy Group, Wang Hongyan has won unanimous praise from everyone over the years for his strong organizational ability, uncompromising execution, and superb mastery of oil exploration and biofossil identification technology. In the early days of the Biostratigraphy Group, he and several academicians systematically carried out multiple training sessions on fossil systems such as graptolites, and organized and carried out many representative joint surveys, including the Guizhou-Chongqing model joint survey, the Meishan Golden Nail joint survey, the Changshan Golden Nail joint survey, and the Sichuan Yuanyangyan profile joint survey. Under his strong call and cohesion, the Biostratigraphy Group, a spontaneous and originally loose organization, has achieved a high degree of multidisciplinary integration. A group of cross-disciplinary, cross-unit, and cross-age scientific researchers, with their love for scientific research, have developed one basic theory after another to support my country's shale gas exploration and development, and have won one hard battle after another, becoming a banner in the field.

If you want to do your work well, you must first sharpen your tools. After the establishment of the biostratigraphic team, the first thing Wang Hongyan led everyone to do was to clarify the stratigraphic division and comparison plan for the entire southwest.

The Changning and Weiyuan blocks in the southern Sichuan Basin are one of the main shale gas producing areas in my country. The main gas-producing layers, the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation, are rich in organic matter, with shale thickness ranging from 20 to 40 meters, which is well comparable. However, after analyzing from the perspective of graptolite stratigraphy, the researchers found that there are obvious differences in the deposition time and deposition rate of the black organic-rich shale in the above two blocks. Taking full advantage of the multidisciplinary team, the members of the biostratigraphy team applied sedimentology, biostratigraphy, geochemistry, mineralogy and other research methods to carry out core description and graptolite biostratigraphic division of the eight wells in the above-mentioned two blocks. For example, through the identification of important biological fossils such as graptolites and trilobites in the Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation of Wei 202 well in Weiyuan shale gas field, they divided it into the graptolite belt in combination with the regional stratigraphic characteristics, and determined that the graptolite belt in the lower part of the Wufeng Formation and Longmaxi Formation was the optimal reservoir. The concept was proposed that the Wufeng Formation, Guanyinqiao Formation in the late Ordovician and Longmaxi Formation sections in the early Silurian in the Wei 202 well area could be compared with the Wangjiawan section in Yichang, Hubei, thus laying a solid foundation for exploring the comparison and sedimentary characteristics of the graptolite belt.

Similarly, in order to conduct an in-depth study of the shale gas reservoirs and gas content of the Wufeng Formation-Longmaxi Formation in the Wuxi area in northeastern Chongqing, members of the biostratigraphy team, based on the drilling data of Wuxi Well 2 and using the graptolite biostratigraphy as a "ruler" for the division and comparison of black shale formations, conducted a systematic stratified study of the organic geochemical characteristics, petrological characteristics, reservoir space types and characteristics of organic-rich shales.

The research results show that the thickness of the organic-rich shale of the Wufeng Formation-Longmaxi Formation in Wuxi 2 Well is 89.8m, and the graptolite sequence is complete and continuous; the organic-rich siliceous shale and clay siliceous shale have the characteristics of "both sweet and brittle", which are the dominant lithofacies for the development of shale reservoirs; the nanopore morphology is mostly open parallel plate-like pores on four sides, with good connectivity; and the Henantian LM1 zone is found to be the best layer, with the characteristics of "the sweetest and the most brittle", which can be used as the "sweet spot" of the best target position for horizontal wells, etc. These achievements have laid a solid foundation for further improving the stratigraphic division and comparison plan in the southwest.

In general, since its establishment, the biostratigraphic team has not only systematically carried out the work of fine stratigraphic division, established a stratification marker fossil system, but also established paleostratigraphic and logging response markers, and achieved regional promotion and application. They innovatively combined multiple methods to establish a scientific and industrial stratification plan for shale gas. Under the guidance of the biostratigraphic framework, they established three shale deposition models, restored the paleogeographic pattern of five peaks, three uplifts and one depression based on the paleontological database, accurately identified the paleogeographic characteristics of southern Sichuan, and avoided the development risks of shale gas. "A tree that can be embraced by two people grows from a tiny seed; a nine-story tower starts from a pile of earth." It is precisely with this series of basic theoretical innovations and breakthroughs that the biostratigraphic team has made a series of breakthroughs in the field research of rock gas reservoirs.

▲Academician Yin Hongfu (center) and Academician Xie Shucheng (second from right) took a group photo with key members of the biostratigraphy team

The achievement of these research results has important stratigraphic comparison significance and provides important theoretical support for shale gas research. Today, driven by the biostratigraphy team, people have become convinced that tiny ancient life can not only serve as a "ruler", but also "probe for oil". The biostratigraphy team has also entered the industry's field of vision in a very short period of time due to a series of major discoveries. Due to its authority and professionalism, it has attracted research institutions and companies related to shale gas exploration and development to come with questions, thus giving birth to many new stories.

Crossing: Collision from different disciplines

When one basic theory after another becomes a bridge for the development of related fields in the future and leads China's shale gas exploration and development research to the right track, few people understand that the process of building the bridge is actually extremely difficult.

In fact, when the biostratigraphic team was first established, it encountered an important problem - unlike other fossils, there are many types of graptolites. So far, scientists have probably identified less than half of the species. Although there are many species, some of them are not of scientific research value. Although graptolites that are hundreds of millions of years old look beautiful, they are basically useless. Only those that have been deposited for millions or even hundreds of thousands of years are useful, and the faster the evolution, the more valuable they are. It is very difficult to accurately identify key and valuable graptolites from the complex categories. Usually, the preservation conditions of graptolites are not very good, and it is likely that only a small broken limb can be seen, and the characteristics are not obvious. Only with a deep understanding of the relevant knowledge and characteristics of graptolites can we overcome all difficulties and make accurate judgments - even if there is only one section, it is possible to determine what kind it is.

Achieving accurate identification of graptolites is a long process of accumulation. This work is difficult even for scientific researchers who specialize in this profession, not to mention other non-professionals in the biostratigraphic team.

"Many people in the group are not paleontologists, especially many of them are geologists, who only have a general understanding of paleontology and do not understand the specific details. Therefore, a lot of basic knowledge needs to be learned from scratch and accumulated step by step before it can be used freely." According to the recollections of the group members, although many training sessions were organized after the group was established, it is difficult to confirm the characteristics of graptolites because learning is one thing and seeing them on site is another. Therefore, in order to deepen everyone's deep understanding of graptolites, the academicians in their 80s in the team often took the trouble to lead everyone to travel thousands of miles to conduct on-site inspections. The wise are like lamps, illuminating the way forward. The selfless dedication and profound knowledge of the predecessors have built a ladder of progress for the rapid growth of the members of the biostratigraphic group.

It is worth mentioning that the members of the biostratigraphy team faced not only challenges in professional learning, but also had to face doubts - at that time, there were very few researchers on graptolites in the industry in my country, and many people were skeptical about the role of this technology.

"From the perspective of the research on graptolites at that time, the most critical layer was only 20 to 30 meters. Even within these 20 to 30 meters, it was all 'black' rock and soil, and it had to be divided into many layers." This was harder than climbing to the sky for many people, but the team members chose to persist and not give up. They listed all the various evolutions of graptolites and analyzed the entire area clearly. People engaged in geological research can generally understand the laws involved. Now everyone has accepted this stratification, and no one questions the guiding value of the "golden caliper" anymore.

Another thorny problem faced by the biostratigraphy team is the fine stratification of biostratigraphy. Gamma logging and graptolite zones are two different ways of recording sedimentary environment and geological events. The gamma curve records sedimentary environment and geological events, while graptolite evolution reflects ecological environment and geological events. When the biostratigraphy team was exploring and studying the main shale gas producing areas in my country, "At first we thought that the high-quality shale in southern Sichuan was deposited in the Rhuddanian Stage. But in reality, we found that half of the shale in the Rhuddanian Stage in Changning is high-quality; and in the Weiyuan area, the shale of the entire Rhuddanian Stage is of high quality." As the research deepened, members of the biostratigraphy team found that in southern Sichuan, the sedimentary differences between the south and the north are relatively large.

▲Academician Zou Caineng and the biostratigraphic team inspected the shale profile of the Wufeng Formation-Longmaxi Formation in Wuxi area of ​​Chongqing

Why is the difference so big? Everyone was confused. "At that time, we thought that this deposit might be related to the ancient topography and did not take into account the structural factors. Later, under the guidance of Academician Chen Xu, we went to many places and learned that in southern Sichuan, due to the squeezing of the Yangtze Plate by the South China Plate, the entire stratum gradually rose from south to north. This event seriously affected the deposition of high-quality shale: in the middle of the Rhuddanian deposition, the southern stratum had been lifted, resulting in a decrease in the quality of the deposited shale." After finding this relationship, the biostratigraphy team carried out a lot of complicated work, compared the data of many wells, and finally successfully explained the differences in logging curves in different regions. "It is because of such an uplift that there is a peak inside that has no deposition." It is precisely because the theoretical framework has been straightened out that the team members can analyze the deposition clearly. This undoubtedly created a "Thunderbolt Sword" for the breakthrough of the difficulties. In the end, the biostratigraphy team established paleobiostratigraphy and logging response markers and successfully promoted and applied them in southern Sichuan.

The three-foot-thick ice does not form overnight. The reason why the experts of the biostratigraphy group can build bridges over water and cut roads across mountains is inseparable from their careful accumulation.

Many team members remember this incident - once the biostratigraphy team was meeting in another place, a company manager came to the team with a large set of black shale. It turned out that when they drilled the well, they looked at a large pile of shale but could not distinguish the layers. The biostratigraphy team had already made a name for itself in the industry, so the executives of this company drove hundreds of kilometers to the hotel where they were meeting to ask for advice. Seeing the eager and sincere look of the manager, several academicians and team members immediately studied the black shale on the carpet of the hotel.

"Every time we look at a core and find a marker, we will make a mark on the standard line of the well logging curve to see how many key geological strata can match the peak of the measured gamma curve." Zhao Qun, a core member of the biostratigraphy team, found through careful observation that there were exactly four peaks that were wrong. The gamma peaks of the biostratigraphy and the well logging curve had a particularly good correspondence. "This is because in the process of geological sedimentation, it was affected by the uplift of different regions. The north of the entire southern Sichuan region is complete, but the south is incomplete." But at the time, these statements were just guesses. After returning from the meeting, Zhao Qun and everyone worked together to sort out all the wells they could find. The hard work paid off, and they finally found the rules. These rules also became one of the basic bases for researchers to successfully distinguish shale stratification.

Many breakthroughs that come suddenly seem accidental, but are in fact inevitable. Many members of the biostratigraphy group have a deep understanding of the value of persistence in accumulation and comprehensive innovation and breakthroughs.

In recent years, under the guidance of Academician Chen Xu, the team has formulated a sub-layer division scheme for the Wufeng-Longmaxi shale reservoirs based on multiple factors to address the problem of inconsistent stratification schemes for the Wufeng-Longmaxi shale formations in the southern marine facies. Four logging gamma response modes have been established, forming a logging identification method for biostratigraphy with distinctive characteristics. Special technologies such as shale reservoir microscopic characteristics and gas content testing methods have been developed, making positive contributions to the detailed evaluation of the Wufeng-Longmaxi shale in the Sichuan Basin. These achievements have also promoted the revolutionary leapfrog development of unconventional oil and gas in my country.

Now, the members of the biostratigraphy team are focusing on sedimentary research in southern Sichuan. Many problems have occurred in the production process of shale gas in related areas. For example, the shale storage changes in Dazu, Zigong and Da'an areas have exceeded expectations. "We need to calibrate fossils and find some other sedimentary evidence to determine why it has changed so much and how far the change has affected it." This is actually the most concerned issue in the oil field, but only by analyzing why it has changed can we predict how far it has changed. Based on key issues, the biostratigraphy team embarked on a journey again.

Passion: The self-driving force born from love

"More than 400 million years ago, you flourished and frolicked in the ocean, then fell into the black seabed like a snowflake. Your flesh was gradually devoured, leaving only the marks of pencil writing, but the fire of life refused to burn out. Over time, your story has not been forgotten. Let's follow the master to write your legend, search for you in the shale, and explore the secrets of shale gas."

In the biostratigraphic group, a poem written by the team leader Wang Hongyan, "You of Yesterday", was sung. They even made a video, which was read by some team members, telling their stories and emotions with the graptolites and the exploration business, word by word, full of affection. It can be felt that they are a group of like-minded colleagues with ideals and ambitions. While shale gas exploration and development continue to make major breakthroughs, this group of earliest scientific researchers engaged in related research are preparing to conquer new heights with full enthusiasm. Behind the continuous attack is their endless self-driving force generated by love.

Although the biostratigraphy group is a spontaneous and loose organization, a series of research projects have made rapid progress. The reason for this is that it has benefited from the strong promotion of talent training.

In 2009, Wang Hongyan, then director of the New Energy Research Institute of the China National Petroleum Exploration and Development Research Institute, reported to the China National Petroleum Exploration and Production Company on the development of shale gas at home and abroad and the understanding of domestic shale gas research on behalf of the team. After listening to the report, the company decided on the spot to launch shale gas exploration and development tests, and in accordance with the goal of "implementing resources, evaluating production capacity, conquering technology, and developing benefits", it was determined to implement the first shale gas well in the Weiyuan structure. This well also became the foundation for a series of subsequent research and exploration.

▲The biostratigraphic team is investigating the Huangying section in Wulong District, Chongqing

Since then, the world's top scientists have joined one after another, adding fuel to the authority and rigor of the research work of the biostratigraphic group. For example, Academician Chen Xu once said that his greatest wish is to apply the paleontology he has studied for a lifetime to actual production. Today, his wish has been realized through a wonderful way of combining the stratigraphic division of graptolite fossils with oil and gas production, becoming a model of interdisciplinary integration. Whenever talking about this career, the old academician's eyes always reveal excitement, and his words are full of satisfaction that the research can continue. It is because of his love that he works tirelessly and selflessly, teaches carefully during training, and pours out his knowledge of graptolite identification for many years; when investigating, he travels thousands of miles to go in and out with young people, and never makes special arrangements.

In fact, every core member of the biostratigraphy team has his or her own story about his or her interest and passion for this career.

Wang Hongyan, the organizer of the group, has many responsibilities, but he is thorough and thoughtful in handling all matters in the group. Although he has a lot of official duties, his knowledge accumulation and special skills are still the best among the young people in the group. In everyone's eyes, "he not only has superb organizational skills, but also has a strong learning ability. He knows many kinds of graptolites, and he can tell them in detail not only their Chinese names, but also their Latin names." In June 2018, the delegation of China National Petroleum Corporation fully demonstrated its thinking and understanding of the sustainable development of the natural gas industry at the 27th World Gas Conference (WGC2018), making a loud "Chinese voice". Wang Hongyan won the WGC Exploration and Production Technology and Innovation Award for his research on "Ten Years of Development and Innovation of Shale Gas".

Another key member of the team, Zhao Qun, majored in geology. He has been rooted in the Langfang Branch of the former China Petroleum Exploration and Development Research Institute since his graduation internship. After the establishment of the New Energy Research Institute (now the Unconventional Research Institute) of the China Petroleum Exploration and Development Research Institute, he naturally became one of its key members. "I found that shale gas is very promising and I am full of confidence in it," said Zhao Qun. Although he studied it as an amateur most of the time, his interest made him study it more and more deeply and reluctant to leave. He found that the parameters of the total organic carbon (TOC) content in shale were similar in many places. They were all shale, but in fact, there were beddings in it, and each was different. If you just study it in general, you can't reveal the mystery at all. "And I really like to do research in this area from the bottom of my heart. This is a very meticulous job." Zhao Qun said, so when the biostratigraphic group was formed, he decisively joined it and became one of the founding members of the group.

In the biostratigraphy group, there are many stories about passion and people who are willing to contribute, including Qiu Zhen, winner of the National Natural Science Foundation of China Outstanding Young Scientist Fund, Zhou Tianqi, winner of the 2022 Top Ten Young Scientific and Technological Advances of China Petroleum Exploration and Development Research Institute, and Shi Zhensheng, Sun Shasha, Wu Jin, Zhang Leifu and other outstanding representatives in their respective professional fields. The team's important results "Gravity flow sedimentation of the Wufeng Formation-Longmaxi Formation of the Ordovician-Silurian System in the Sichuan Basin and its significance to unconventional oil and gas" were published in the international oil and gas journal "American Association of Petroleum Geologists Bulletin" (AAPG Bulletin). Walking into this special team, you will find that their members come from all corners of the country, with different backgrounds and personalities; they have different disciplinary backgrounds, interdisciplinary, but they have their own specialties and clear division of labor... But they all have a common wish: to come together to contribute to my country's oil exploration cause. Where there is a collective effort, there is no victory; where there is collective wisdom, there is no failure. What makes everyone happy is that, through everyone's joint efforts, the team's talent training mechanism and system have been gradually improved, and a group of ambitious and capable young people have grown up. As long as there is continuity, there is a future, and the grand plan of turning the shale gas blueprint into blue gold has slowly begun.

Vision: Turning shale gas blueprint into blue gold

According to the plan, by 2030, my country's shale gas production is expected to reach 80 billion to 100 billion cubic meters, accounting for one-third of the country's total. Shale gas has become the main force for increasing natural gas reserves and production in my country in the future.

▲Zhao Qun, a member of the biostratigraphic team, is investigating the Huangying section in Wulong District, Chongqing.

After thinking, summarizing and planning all the way, the biostratigraphy team has now determined the direction of future development. At present, the team is studying several forward-looking and basic projects of China National Petroleum Corporation, including key technologies for marine shale gas exploration and development. According to the "Shale Gas Development Plan (2016-2020)" released by the National Energy Administration, my country will improve and mature the exploration and development technology of shallow marine shale gas at a depth of 3,500 meters, and break through the exploration and development technology of deep marine shale gas, continental shale gas and marine-continental transitional shale gas at a depth of 3,500 meters. This is the layout direction of the entire China Petroleum Exploration and Development Research Institute in new fields in the future, and it is also the key technology that the team will increase its efforts to break through.

At the same time, establishing a system of marine shales, i.e. deep-water deposits, is also the focus of future research by the biostratigraphic team, in order to establish a deep shale gas sedimentology system under an isochronous framework. This is of great significance to the entire discipline. Fortunately, the team has made a good start: four hierarchical objects have been drawn, and some evidence has been found. For example, through large thin sections and large argon ion polishing slices, the biostratigraphic sublayers have been found to have sand-mud transitional horizontal bedding, transitional horizontal bedding, book-page horizontal bedding, sand-mud interbedded horizontal bedding and massive bedding in the deep-water area of ​​the Wufeng Formation-Longmaxi Formation in southern Sichuan, which may indicate the development of fine-grained turbidity current deposits, muddy isobath deposits, pelagic-semipelagic deposits and silty isobath deposits in deep-water areas.

Although the prospects are promising, the long road of combining research and practice is still full of challenges for the biostratigraphy team. The only way is to move forward steadily: "After establishing the theoretical system, we are still faced with the problem of how to promote it. China's shale gas development areas can be divided into four major regions, namely the south, central and eastern, northwest and Qinghai-Tibet, which roughly correspond to the plates. They all have good shale gas exploration prospects. It is a difficult problem whether this theoretical system can be used to clearly divide the stratigraphic dimensions of each region. We believe that the great discovery of shale gas in southern Sichuan is not an accident. Our ultimate goal is to make breakthroughs in all parts of the country." We should take a long-term view and move into deeper and broader fields. There is a lot of room for development waiting for the biostratigraphy team.