With the coming of the new century, what is the new goal of finding oil and gas? How to explore new oil and gas fields? Especially in the vast offshore waters, in addition to continuing to explore the existing conventional oil and gas, it is hoped to open up a large marine field and discover large offshore oil and gas fields. So that one day the focus of oil and gas exploration can be shifted from land to sea. The conjecture of "Remnant Tethys" is nothing more than trying to open the seeker's mind.
Any scientific prediction, conjecture, speculation or hypothesis includes success and failure. However, the creation of the history of human civilization always overcomes all difficulties with perseverance and superb wisdom, so that the world science can develop.
For example, whether the search for cosmic antimatter in the recent space experiment of Alpha Magnetic Spectrometer led by Dr. Ding Zhaozhong will be confirmed immediately remains to be tested by practice, and no one can say that it is 100% successful.
Many Nobel Prize winners have spent most of their lives in the laboratory. They have the courage to walk into the "maze", even after thousands of failures, they still have the courage to walk out of the "maze", and the final success will belong to tenacious people.
Mr. Lu Xun once advocated the spirit of "not ashamed to ask questions". He said, "don't let the last person lose face." Even if he is slow and persistent, he will fall behind and fail, but he will certainly achieve his goal.
As far as exploring geography is concerned, we should also follow this objective law. Looking back calmly, isn't this the way of oil and gas exploration that we have surpassed?
-The discovery of Karamay Oilfield was not inspired by the "rotten mouse in the black pool" in Heiyoushan.
-The discovery of Daqing Oilfield was not because small fishing boats in Songhua River collected source rocks for the first time?
-Will the rise of China's offshore oil industry forget that in the early 1950s, Yinggehai fishermen discovered a "ghost fire" on the sea?
You can also cite many touching examples. History warns people that it is obviously against science to treat science with a scientific attitude and deny it without repeated practice.
The conjecture of "residual Tethys" may become a century problem, or it may be proved by practice that it does not exist, or it may become a reality and be truly successful. This will be related to the development of offshore oil and gas resources in China, as well as the economic interests and strategic needs of China.
I miss it so much. I sincerely hope to get the support and encouragement from the geoscientists in China. I also hope that the younger generation of oil and gas geologists will continue to overcome this problem, and sincerely hope that they will write new oil footprints with genius!
May China's oil and gas geological cause stride forward to 2 1 century with lofty steps!
When I participated in the compilation of Geological-Geophysical Series Map of China Sea Area and Its Adjacent Areas edited by Academician Liu Guangding, Academician Zhu Xia once said that attention should be paid to the marine strata in the southern part of the East China Sea. After a lapse of ten years, the marine geological survey of the continental slope in the northern South China Sea and the oil and gas exploration in Lishui Depression in the southern East China Sea have obtained new data of marine sediments in Mesozoic, Paleocene and even Early Eocene.
In the late Indosinian and early Yanshanian, the Tethys Sea developed at the edge between the western Pacific plate and the Eurasian plate. It enters the South China Sea from the northern side of the Himalayas, crosses the Red River to the north, goes northwest along the Yinggehai, and then passes through the trough on the northern slope of the South China Sea. It is blocked by the Taisheng uplift east of Dongsha, and then divides into two branches: the south and the north. The northern branch enters the southern part of the East China Sea northward through the Taiwan Province Strait; The south branch runs from southwest to east of Taiwan Province Basin and enters Japanese waters.
Scientific conjecture has made extraordinary contributions. As far as earth science is concerned, as early as the beginning of the 20th century, German meteorologist Alfred Wegener put forward the conjecture of "continental drift" at the beginning of this century based on the amazing consistency of coastlines on both sides of the Atlantic Ocean. After the challenges and debates all over the world, it was not until the early 1960s that the Earth Revolution suddenly happened and the theory of plate tectonics appeared that Wei Gena's theory of continental drift was recognized. Of course, Wei Gena is not imagining things, but has mastered a lot of scientific evidence. For example, the migration of paleontology, the global distribution of reptiles and the signs of Carboniferous and Permian glacial deposits between continents 300 million years ago have revealed an intriguing history of earth evolution to mankind.
What is the conjecture basis of "Residual Tethys"?
One of the bases is 1985. Shanghai Marine Geological Survey built Lingfeng 1 well in Oujiang depression in the south of East China Sea shelf basin. The well drilled a set of marine Paleocene below 20 13 meters, which was analyzed by the Institute of Geology of Chinese Academy of Sciences to contain foraminifera, dinoflagellate and calcareous nannofossils. , and confirmed this set by comparing with international standard genera and fossils. There is a group of coal measures strata in the upper part of the series, which may be caused by the rise of sea level at the end of Paleocene, causing a large number of terrestrial plants to drift into the sea and deposit. This shows that there is a vast Paleocene basin in the southern part of the East China Sea shelf and changes in the paleo-marine environment. Shanghai Marine Geological Survey named this stratum "Lingfeng Formation", under which the Late Cretaceous stratum can be seen, but 320m old metamorphic rock series was drilled from below 304 1 m.. Core samples were determined by the Rb-Sr whole rock isochron method by Yichang Institute of Geology and Mineral Resources, Ministry of Geology and Mineral Resources. Its geological age is equivalent to Late Proterozoic,10.68 billion years ago, which can be compared with the old metamorphic rock series. Oil and gas are also shown in metamorphic rock series, which proves that the oil source comes from Paleocene marine strata. Later, when Diamond Gate Beach 1 well was used, the Lingfeng Formation was about 558 meters thick, with good upper caprock and marine source rocks in the lower part.
Secondly, from 65438 to 0985, the Guangzhou Marine Geological Survey cooperated with the lamont-Dougherty Geological Observatory of Columbia University in the United States to conduct geophysical surveys on the northern continental margin of the South China Sea to study the tectonic evolution history of the passive continental margin. On the seismic profile of continental slope, a seismic wave group with continuous reflection, strong amplitude and long-distance traceability and comparison is found (different from Mesozoic continental seismic wave group on continental shelf). )
According to Yao Bochu, a Chinese scientist in Sino-US cooperation, the continental slope is 800 ~ 1400 meters deep, and the seabed is a southerly slope with many gullies, with a relative depth of 100 ~ 500 meters. On the profile, Cenozoic sediments are1800 ~ 4000m. Taking the Eocene top boundary at T6 as the boundary, it is divided into upper and lower structural layers. The upper structural layer is from the seabed to T6, and the lower structural layer is from T6 to Tg (the author suspects that it also includes marine Paleocene). Under Tg, the reflected wave inclines to the north, and the calculated seismic layer velocity is 5.05km/s, and the thickness is 5 ~ 7.8km. Although there are structural changes, the sedimentary layer is still clear, and the top has been eroded to form residual layer, which is confirmed as marine Mesozoic deposition, and it is speculated that the bottom boundary of Mesozoic is Jurassic. It is located in front of the volcanic arc of dongsha islands-Penghu Islands, becoming a pre-arc basin. This is the "residual Tethys" inferred by the author in the late Mesozoic.
During the period of 1995, when studying the tectonic movement in the northern South China Sea, Professor Feng Zhiqiang proposed that "according to a large number of Nanjing in the marine Permian strata exposed in Hainan Island, it is inferred that the water in the Paleotethys is connected with the eastern China. Because there is no clear evidence of petrology or tectonics in the Paleo-Tethys Indosinian suture zone east of Hainan Island, the late Triassic-early Jurassic littoral marine strata distributed in Guangdong and Fujian are interpreted as marginal sea or residual sea deposits in the eastern part of the Asian plate. After the Early Jurassic, there was a Late Tethys between South China and South China Sea, which was similar to aulacogen. The closed geological era lasted from the late Indosinian to the early Yanshan, and continued until the Paleocene and early Eocene. "
Thirdly, the Cretaceous strata seen in Well F 1 in the southwest of Taiwan Province Basin are shallow metamorphic marine shales, containing ultramicro fossils, and the maximum thickness of the strata can reach 5,000m, reflecting the eastward extension trend of residual Tethys deposits.
Fourthly, from 65438 to 0996, two experts, Gong Zaisheng and Wang, chief geologists of China Offshore Oil Corporation, made in-depth and detailed research on the marine Paleocene deposits in Lishui sag, Wendong, south of the East China Sea shelf basin, and made a prediction and evaluation: "Lishui sag has the prospect of finding large and medium-sized oil and gas fields in the near future. The Lishui 36- 1 and Wenzhou 13- 1 structures in the depression are the breakthrough points of oil and gas exploration in Taibei sag.
The dream finally paid off, and the expert's scientific prediction was confirmed by a little exploration and practice. During the period of 1997, Donghai Oil Company cooperated with British Overstandard Oil Company to build Lishui 36- 1 well in block 32 of Lishui Depression in Wendong, and obtained high-yield natural gas in marine Paleocene. This major discovery has opened up a new field of offshore oil and gas exploration in the southern East China Sea and written a new chapter in the history of oil and gas exploration in this area. The spread of this news shocked the Chinese and foreign petroleum circles (because the well 14 has been drilled before), which attracted great attention from scientific research units and aroused people's strong interest in the study of the Paleocene Tethys Sea. Professor Zhao Jinhai from Shanghai Marine Geological Survey and Professor Wang from Tongji University, who have been engaged in oil and gas exploration in the East China Sea for many years, also had a strong response.
Tethys comes from ancient Greek mythology, and Poseidon's sister and wife are called Tethys. After the introduction of natural science, there are two opinions: in astronomy, one of Saturn's eight moons is called Tethys; Geologically, the Mesozoic global geosyncline is called Tethys geosyncline, or Tethys for short. Another way of saying it is closer to history: NoImar proposed that there is an east-west ocean between the Alps and the Himalayas, that is, the middle of the Mediterranean. Later, in memory of the wife of the Greek mythologist Vasinus, Xu Shi named it Tethys.
In the past hundred years, the marine nature and geological age represented by Tethys concept have been expanded, which is no longer limited to Mesozoic oceans, but also includes Paleozoic shallow seas.
1964, when Ganser (1964) divided the Himalayan structural units, it was called the Cambrian-Eocene shallow marine sedimentary belt on the north side of the Himalayas, also known as the Tethys Himalayan belt.
It is reported that the Tethys Sea was also formed in Wadi Nukul, Egypt, and Tolangli, Turkmenistan at the end of Paleocene, where benthic foraminifera became extinct due to lack of oxygen.
To sum up, the "residual Tethys" in the Sea of China mainly consists of three parts from west to east:
(1) Ying Ge trough-Indosinian movement, the Mediterranean oceanic crust subducted into the South China block, which closed the Indosinian block and left the red river suture. Due to the continuous embedding of the Indian plate, the Indo-China block was pushed eastward, resulting in the NW strike-slip fault of the closed Red River fault, which produced new tension and induced the Tethys to continue to activate and accepted half of the deep-sea facies deposits.
At the southeast end of Yinggehai Basin, Well Ledong 30- 1- 1A is the deepest well drilled in the basin, with a final depth of 5026 meters, and Neogene has not been drilled yet. The wave group of nearly 20000 meters obtained from seismic exploration profile has not bottomed out, so it is difficult to determine the properties of deep sedimentary strata and basement. However, the formation of geosyncline is closely related to the activity of the strike-slip fault of the Red River, and this special geological phenomenon is difficult to be explained by "subsidence speed". Professor Zhang Qiming has made an in-depth study on this issue. He called Yinggehai a "unique sedimentary basin".
(2) The continental slope trough in the northern South China Sea-According to the seismic survey data, it is speculated that Mesozoic Tethys still exists. Due to the influence of late tectonic movement, is it connected with the Ying Ge Trough? It is still difficult to determine. It may have been a unified trough, but it was dislocated and separated by a north-south shear fault. This remnant Tethys became a "lost ocean" after the early Eocene.
(3) "Lingfeng Sea"-The East China Sea is affected by NW-trending faults, forming a block-like structural pattern in the north-south direction. In the southern block, that is, the Taibei Depression in the south of the East China Sea shelf basin and its eastern waters, the Paleocene accepted Tethys transgression from the South China Sea, thus forming the Lingfeng Sea and accepting extensive Paleocene marine deposits. Its ancient marine environment: the basement is the "sunken continent" invaded by ancient metamorphic rock series and Yanshanian granite, and on this basis, the marginal sea is formed.
In the 1960s, after the rise of plate tectonics, it was determined that there was Tethys Sea between Eurasia and Gondwana, and it was connected with the Pacific Ocean in the west. This may be the "residual Tethys" mentioned above.
Has the conjecture come true? It has yet to be tested by practice. If conjecture becomes a century problem, I hope someone will explain it later. A similar situation happened in the field of mathematics. After several generations of research, Goldbach conjectures that this world-famous mathematical problem has finally made a breakthrough in the hands of Chen Jingrun.
2 1 century, it is hoped that a group of young geologists will make great achievements in the study of "residual Tethys" in the China Sea and form basic theories. Who will lead the way? We should wait and be optimistic about it.
Learn from Han Yu, a great poet in the Tang Dynasty: "Keep your word!" Overcome the difficulty of guessing in a down-to-earth manner, and as long as you persevere, you will get what you want and achieve new success.
(This paper was published in Geology of China, No.4 1998).
Oil trace history: 50 years of oil and gas exploration