From 65438 to 0975, he served as the chief engineer of Jiangsu Petroleum Exploration Command, and Xu served as the deputy commander. On August 24th of the same year, the headquarters held a report meeting on geological achievements in the first half of the year. At the meeting, Zhu Xia made a report on "A Corner of the Subei-South Yellow Sea Basin from the Perspective of Structural Analysis", and pointed out on what structural basis the Subei-South Yellow Sea Basin developed according to the basin attributes. What is the process of its occurrence and development? Why is there such a geological structure today? How is oil and gas formed? His main argument is:
Since (1) 10, in the exploration of Mesozoic-Cenozoic oil-bearing basins in China, tectonic stresses with different layouts have acted on local media (including basement and caprock) again and again. Because of the different stress distribution, physical and mechanical properties of media and internal structure, different basins have different characteristics. Even basins belonging to the same historical stage and the same movement system have their own particularity due to the specific differences between internal and external factors. For example, the same Cenozoic basins, North China and Jianghan are different from Subei-South Yellow Sea.
"To expose the essence of the development process of things, we must expose the particularity of contradictions in all aspects of the process." In order to analyze the sum mentioned above, it is necessary to correctly handle the relationship between stress (including direction, nature, strength, layout …) and medium (including physical and mechanical properties, internal structure, boundary conditions …). Do you know which is the main aspect of contradiction? I once pointed out: "Only on the premise of understanding the whole basin and its history can we correctly and concretely analyze the characteristics of each part of the basin, especially the oil and gas bearing property, thus guiding the practice of general survey and exploration." According to our understanding, a large oil-bearing basin almost always develops evenly on two or more structural units. It is the unity of construction and transformation. Architecture, represented by a certain substance, has a certain time limit and is a historical concept; Transformation is the expression of motion, reflecting the combination and distribution of space, and it is a mechanical concept. To analyze the whole process of the occurrence and development of an oil-bearing basin as a whole, we must consider these two aspects, namely, the interdependence and mutual restriction of motion and matter, space and time, history and mechanical evolution.
Considering the relationship between stress and medium, whole and local, when analyzing a basin, we should first find out the structural pattern represented by each structure (group) in this period, so as to determine the stress distribution in this period, and then discuss the evolution of the structural pattern and stress distribution from this period to the later period and the historical origin of its inheritance and transformation, and discuss the temporal and spatial ownership of local structures or structural belts in combination with the oil and gas conditions of this structure, so as to evaluate its oil and gas prospects.
This method can be said to be "geomechanical analysis based on geological history analysis". The comrades of the geotectonic mapping group of the Institute of Geology, Chinese Academy of Sciences once put forward "geological history analysis based on geomechanical analysis". Due to the different objects, according to the above analysis of the main contradictions, it is necessary to consider that most of our objects are covered with huge thickness, and it is difficult to obtain direct observation data on the tensile, compressive and torsional structural planes. Moreover, with the different stages of the earth's historical development, it is not allowed to engage in "north-south extrusion as the leading factor"
(2) A major problem of historical analysis is to distinguish different stages of oil development from the long process of oil development.
In the long-distance development of the earth's material movement form, it is inevitable and obvious to distinguish different development stages. In the past, we called the sum of material movement forms in different stages (including the nature of movement, historical interaction and the whole or partial reflection of the affected crustal blocks) as "movement system", and pointed out that "the change of movement system is the primary condition for the formation of oil and gas basins." "The movement system of the earth's crust changes with the development of geological history. Therefore, the classification of basin types according to the movement system also contains the significance of historical stages or times. " On this basis, it is suggested that it is necessary to distinguish between basins belonging to the Alpine stage and those belonging to the pre-Alpine stage. When discussing the basis of division, it has been pointed out many times that "if the development of marine basins around the world is considered", that is, "the vast majority of marine basins in the world were formed in Mesozoic and its later period", then the necessity of this division is "more clear".
During the period of 10, especially since 1968, the theory of plate tectonics generated from marine geology and marine geophysics developed rapidly, which gave us a new understanding of the division of crustal development stages. Hayin (1972) called the Mesozoic-Cenozoic stage of crustal development the fourth stage, that is, the plate tectonic stage, to distinguish it from the previous third stage, that is, the Paleozoic geosyncline-platform stage (the other two stages belong to Archean and Proterozoic), which is completely consistent with the Alpine stage and the pre-Alpine stage of the new regional cycle (since Sinian). In view of the dominant position of Indosinian movement in East Asia relative to Hercynian movement, it is reasonable to calculate the plate movement here from the late Triassic.
Subei-South Yellow Sea Basin is a Mesozoic-Cenozoic basin belonging to Alpine stage. It is located in the front of Eurasia facing the Pacific plate, and its "attributes" in time and space are very clear. Therefore, it is necessary not to recognize plate movement. If we believe in the reality of this movement, then we can't deny that the whole process of the occurrence and development of the Subei-South Yellow Sea Basin will inevitably be branded with the relative movement between the Pacific plate and the Eurasian plate, and this point can never be ignored in the historical and mechanical analysis of this basin.
(3) In our example, on what basis does plate movement work? As we all know, the basement of Subei Basin includes two structural units, namely, Lusu Shield and Yangtze paraplatform. There is no obvious boundary between them, which is due to the thickening of Paleozoic-Middle-Lower Permian caprock. Before the deposition of Huang Ma Formation, the crustal movement changed fundamentally.
The Tancheng-Lujiang fault is the most remarkable structural sign, which has obviously moved northward along the Qinglong Group on the east side and its lower strata, indicating that the fault may have existed a long time ago, but in this movement, there has been a significant left-lateral horizontal displacement from the east side to the north.
Another feature of the basement is that the Upper Triassic Huang Ma Formation and the Middle and Lower Jurassic Xiangshan Formation deposited after the movement reflect a new subsidence center zone. The distribution of these strata is basically a NE-trending belt, from near Anqing, along the banks of the Yangtze River to Ningzhen area, and then through Jiangdu uplift to Xiaohai Sheyang (possibly from Ningzhen branch to Nantong). This early subsidence zone later "returned" to a uplift zone, which deposited less Pukou-Chishan Formation strata than its two sides. At the end of Cretaceous, the "fault depression" formed by tensile stress in Gaoyou and Qintong was different from the "depression" in Jinhu and Hai 'an on both sides of Gaoyou and Qintong, and inherited the settlement in the late Cretaceous.
(4) On this basis, the geological history entered the Alpine stage, and plate movements were carried out. The historical development of the whole stage, as pointed out in the past, is also wave-like, so it is periodic. Each cycle includes the transition time for producing new quality products, the preparation period before the transition and the adjustment period after the transition. The material movements inside the earth, including differentiation, migration and transformation (phase change) ... prepare conditions for every change from quantitative to qualitative, and adjust with each change. This form of material movement in the earth is obviously not limited to the basin itself, but must involve a wider range of fields. Reflected in the form of surface material movement, it also includes differentiation, migration and phase change, which is naturally related to a series of phenomena such as uplift, subsidence, erosion and deposition far outside the basin. Therefore, the analysis of basin history should focus on a much larger "overall situation" and understand the relationship between relevant parts in time and space. Of course, the "overall situation" mentioned here also has its certain "boundary conditions".
The relationship between the position and function of the Pacific plate and the Eurasian plate during the Yanshan cycle is not clear, but the eruption of large-scale intermediate-acid volcanic rocks in eastern China from late Jurassic to early Cretaceous is undoubtedly related to this relationship. At that time, there was no marginal sea, and the combination surface of plates was much closer to the present continental margin. This large-scale volcanic eruption is controlled by a series of NE-NE and NW faults, such as the NE fault on the syncline side of Ningwu and the NW fault between Ningwu and Ningzhen. However, these faults do not show opening, on the contrary, they are accompanied by metamorphism in some places (such as Fujian), which is more closely related to magmatic intrusion. They are likely to rise under compressive stress like volcanic island arcs. The discovery of acidic volcanic rocks in Ningwu area shows that the contents of K2O and K2O+Na2O and their unsaturation relative to SiO2 _ 2 may also increase to the mainland.
After a large number of magma erupts, the crust must have a balanced adjustment. As a result of adjustment, the thickness of Si-Al layer increases, Moho surface decreases, and the corresponding large-scale regional increase occurs in areas where volcanic rocks accumulate along the coast of Fujian and Zhejiang. In Jiangsu, where volcanic activity is much weaker, especially in northern Jiangsu, the crust thickness decreases, the Moho surface rises, and large-scale continuous subsidence occurs. I remember that the crustal thickness map compiled by the State Seismological Bureau shows that the crustal thickness in Fujian-Zhejiang area and the area south of the Tan-Lu fault is more than 35 kilometers, while that in the central Jiangsu area is less than 35 kilometers, which reflects the boundary between uplift area and subsidence area. It is under this background that the long-term subsidence of the Subei-South Yellow Sea Basin was formed. It rose from Lusulong and formed a flying goose with another large-scale subsidence area (North China-Bohai Sea).
Therefore, it can be considered that the formation of Subei-South Yellow Sea Basin is the inevitable result of early plate activity and the response of the material movement form on the earth's surface to the material movement form inside the earth.
For a long time, there is a popular view that the North China Basin belongs to the subsidence zone, while the North Jiangsu Basin occurs on the background of the uplift zone, so the oil and gas prospects are very different. This view does not affect the confidence and determination to find oil in northern Jiangsu at all. Facts have proved that this prejudice should be corrected. Comrade Meng said it in his speech at the meeting, and Comrade Cai Ganzhong also said it in an article. I totally agree. "
I listened to Zhu Xia's report and had a theoretically advanced course on petroleum and natural gas geology. Based on the law of the earth's material movement and the theory of plate tectonics, he comprehensively analyzed the geotectonic properties of the Subei-South Yellow Sea Basin, and clearly pointed out that the basin belongs to another subsidence zone of the Bohai Bay Basin in North China-the Yanling subsidence zone.
In fact, the Subei-South Yellow Sea Basin is a whole and belongs to the basement of the Yangtze Platform. The tertiary deposits have been basically the same since the late Cretaceous, except that transgression occurred since the late Pliocene-Pleistocene, and the South Yellow Sea appeared. Therefore, there is obviously not much geological basis for dividing northern Jiangsu in the uplift zone and the southern Yellow Sea in the subsidence zone. Even the Yellow Sea, the East China Sea and the South China Sea can not be divided into a subsidence zone, because it will involve the continental shelf, continental slope, subduction zone, marginal sea and small ocean basins that may exist in the middle of the South China Sea. Tectonic units with such complex and different properties cannot be divided by geomorphic types. All the participants supported Zhu Xia's viewpoint and fully affirmed the oil and gas prospect of Subei Basin.
Oil and gas exploration in Jiangsu involves many geological problems, but it is a different world in southern Jiangsu. Here, the Paleozoic strata of the lower Yangtze platform, especially the carbonate strata, have been partially exposed.
1In the spring of 982, Guan Shicong, Zhang Yonghong, Li Dodge and others conducted a four-day field geological observation in Maoshan, southern Jiangsu Province, in order to understand the relationship between the geological structure of Maoshan and oil exploration.
Maoshan is the floorboard of low hills among Dantu, Jurong, Jintan, Su Yang and Sushui counties in southern Jiangsu. It is a NE-trending mountain range between Ningzhen Mountain and Tianmu Mountain, which winds intermittently for nearly a hundred miles and is several to ten miles wide. It is a natural paddock in the southeast of Nanjing.
Maoshan was called Qushan in ancient times. According to legend, in the Western Han Dynasty and Yuan Dynasty, three brothers, Mao Ying, Mao Gu and Mao Zhong, came to Maoshan from Xianyang, Shaanxi Province to practice the way of "Ascending Immortals", so later generations called it Maoshan. After the Tang and Song Dynasties, Maoshan Mountain was listed as the eighth cave of Taoism, with three palaces and five views on the mountain and numerous Taoist views, which became the center of Taoism in southeast China. "Other peaks stand out from the crowd, separated by dust and sand. Look down at the clouds and you can't move forward. " Wang Anshi, a poet in the Song Dynasty, described the majestic posture of Maoshan.
Guan Shicong and others inspected six sections, including Dinggong, Fangshan North Highway, Wild Boar Pond, Xiaojianshan, Zhu Qing Coal Mine and Fangshan. It can be summarized as follows: ① Maodong fault is overthrusted from west to east at a high angle, not from east to west, not at a low angle; ② Overthrust faults involve Paleozoic and Paleozoic Qinglong limestone, but not directly related to Cretaceous Pukou Formation; ③ Paleozoic strata are not napped on the Jurassic volcanic rocks of the fault on the east side of Maoshan Mountain; ④ The main body of Maoshan fault fold has inclined positive anticlines, but not all of them are inverted; ⑤ imbricate faults in Maodong fault zone are not developed.
In addition to field observation, the seismic profile of 10 1 and the cores of two wells (sentence 10 and sentence 12) were also examined. It is considered that the erosion surface of Lower Paleozoic is integrated with that of Indosinian.
After observing Maoshan Mountain, Guan Shicong and others published "Maoshan Structural Geology and Petroleum Exploration" (published in Volume 3, No.4, Petroleum and Natural Gas Geology), and thought that the petroleum exploration targets in the lower Yangtze region were: Lower Paleozoic, Upper Paleozoic, Mesozoic and Cenozoic. As far as Maoshan geological structure is concerned, several problems related to oil exploration are:
(1) Maoshan is not a Feilai peak, so the gentle and broad oil storage structural potential in the deep (especially in the Lower Paleozoic) is difficult to appear, and it will not exist like the oil reservoir under the American Rocky Mountain overthrust belt. But as far as Jiangnan is concerned, it is still a shortcut to find suitable structural oil and gas reservoirs in Mesozoic and Cenozoic overthrust faults of Indosinian fold.
(2) Because Maoshan is not a nappe, the Mesozoic Jurong Basin and Changzhou Basin, which were divided by Maoshan, are wide basins with certain sedimentary thickness, while the middle and late Cretaceous wide basins in southern China are mainly thick red beds, which are not suitable for a large amount of oil generation.
(3) Early and Middle Jurassic Xihongshan Formation and Early Cretaceous Gecun Formation basins formed on both sides of Maoshan main body in southern Jiangsu Province on the basis of Indosinian fold still have oil and gas exploration prospects.
(4) The overlapping area of Cenozoic basins at the end of Yanshan cycle is much smaller than that of Upper Cretaceous. That is, according to geomechanics, there are relatively stable structural conditions in the horseshoe shield between Maoshan Ridge and Ningzhen Arc, but its sedimentary thickness and lithology are not conducive to oil generation.
There is a comment in the book: The oil and gas geology and exploration prospect in southern Jiangsu will involve the overall evaluation of carbonate areas in southern China. Since 1979, at the symposium on oil exploration and deployment held in Changsha, the southern marine carbonate sedimentary area was taken as the key selection area in the second round of census, and a large-scale scientific and technological breakthrough was organized during the Seventh Five-Year Plan, but there is still no breakthrough in oil and gas exploration, including the lower Yangtze area in southern Jiangsu. Due to the special complexity of geological structure, it needs long-term exploration practice and advanced theory and exploration technology to solve it.
However, the reality also reminds people that the Su 174 well in Huangqiao structure in northern Jiangsu obtained 1.4 cubic meters of light crude oil from the Silurian Fentou Formation, Maoshan Formation and Devonian Wu Tong Formation. High-yield carbon dioxide gas was obtained in limestone of Lower Permian, with a daily output of 200,000 cubic meters. What will this mean? How to face up to the evaluation of oil and gas prospect in the lower Yangtze region with an area of about 50 thousand square kilometers from Huangqiao? We expect this unknown to be solved as soon as possible.