The development of China's continental petroleum geology theory is closely related to the development of oil and gas exploration, and has gone through a process of exploration, establishment and perfection. Before the founding of New China, the petroleum industry foundation in China was very weak, and the petroleum geology theory was mainly introduced from abroad. According to the traditional anticline theory and surface oil and gas display, oil was found. After the founding of New China, the petroleum industry has entered a new stage of vigorous development, and the theoretical system of petroleum geology has been continuously enriched and developed. Corresponding to the exploration development stage in China, the theory of continental petroleum geology has experienced the initial stage in 1950s, the rapid development stage of exploration eastward in 1960s and 1970s, and the rich and perfect stage since 1980s.

(A) the introduction of modern petroleum geology theory and continental oil generation point of view.

In modern China, with the development of petroleum geological exploration, scientific petroleum geological theories were gradually introduced from abroad, mainly anticline oil and gas accumulation theory and exploration methods for tracing oil and gas seedlings.

The modern petroleum industry first developed from the United States and developed rapidly. Petroleum geology also gradually developed from the United States at the end of 19.

1859, American E.L. successfully drilled the world's first industrial oil well in Tilus, Pennsylvania, with a depth of 21.69m and a daily oil production of 0/.817m3, so this well was also named Drake Well.

It was not until the end of19th century that foreign countries combined the search for oil with geology. This gave birth to petroleum geology. In the third year after the completion of the Drake Well, Canadian T.S. studied Ontario Oilfield and pointed out that most of the oil was stored in the porous limestone at the top of the anticline. At the same time, E.B., an American, put forward the same view, but none of them attracted the attention of the oil industry.

After studying the oil and gas wells in Appalachia, USA in 1883, White pointed out that oil accumulation is closely related to anticline structure. In order to prove his point, he chose three anticlines and drew three well locations on their tops. Starting from 1884, the oil and gas flows have been obtained successively. So in 1885, White published the paper "Geology of Natural Gas", put forward the theory of anticline, and began to be concerned by the oil industry. By 19 15, most oil companies have set up geological departments one after another, so 1885 was designated as the year of petroleum geology.

By 19 19, the book Petroleum Geology, published by petroleum geologist Dorsey Wagler in 19 15 and revised in 19 19, is not limited to anticline theory in principle. As far as exploration methods are concerned, it includes surveying and mapping, well location determination, drilling, petroleum production and petroleum geology field methods and tools. The causes of oil in the book can be divided into three types: inorganic theory, marine organic theory and inorganic-organic composite theory.

As for the elements of oil and gas accumulation, five aspects are put forward, namely anticline (including monocline) structure, formation water and extrusion, capillary action, reservoir, caprock and floor. The main aspects of petroleum geology have been covered in the book, but due to the limitation of exploration level and analytical laboratory technology, the understanding is superficial.

The scientific principles of modern petroleum geology in China are basically imported from abroad. 1932, the famous geologist Xie edited and published the book Petroleum, which can be said to be the first petroleum geology work written by China people, and it is very valuable. This book is mainly based on the theory of foreign books and periodicals, and has little to do with China's petroleum geology, but it has become the first Chinese book introduced to China by foreign oil and gas geology science.

In the development of petroleum geology in modern China, the older generation of geologists put forward the viewpoint of continental oil generation under extremely difficult conditions and under the atmosphere of only marine oil generation theory, through field investigation in China. Therefore, the prospect of oil and gas exploration becomes optimistic in China, a land where continental deposits are widely distributed after Indosinian tectonic movement.

First of all, Professor Pan Zhongxiang went to northern Shaanxi for petroleum geological survey from 193 1 to 1934, and went to Sichuan for petroleum geological survey in 1935, and obtained systematic practical data, which was published in 194 1

Then Huang, Weng and others also put forward the viewpoint of continental oil generation in the Geological Survey Report of Xinjiang Oilfield compiled at the beginning of 1943 based on the petroleum geological survey data of Xinjiang in 1942, pointing out that Permian, Triassic, Jurassic and Paleogene in Xinjiang are all possible oil-generating layers. The article said: "At least part of Xinjiang's oil obviously comes from pure continental Jurassic deposits."

Since then, Xie, Li Chunyu (1944), (1945), (1947), Ruan Weizhou (1947), Yin Zanxun (1948) and others have appeared. Yin Zanxun even suggested that due to the volcanic eruption, life in the freshwater lake suddenly died and became the source of Yumen oil. Although these viewpoints are based on regional geological analysis, they are undoubtedly important contributions to the development of petroleum geology in China.

It is precisely because of a clear understanding that continental strata can also generate oil that many geologists are guided to carry out petroleum geological investigation and drilling in China's vast territory, and Yumen Oilfield has been discovered, which points out a good exploration prospect for the development of China's modern oil and gas industry.

China's contribution to modern petroleum geology is to point out the limitations of marine oil generation theory, and put forward a new view that continental deposits can also generate oil, which is a revolutionary change and leap in geological understanding under the absolute advantage of marine oil generation view.

(2) The first breakthrough of modern oil and gas exploration in 1950s, and the initial establishment of China's continental petroleum geology theory.

After the birth of New China, oil and gas exploration began under the condition that the technology left over from old China was very backward and the foundation was extremely weak. The anticline theory guides oil and gas exploration, and the basis for selecting exploration targets is the surface anticline and surface oil and gas seedlings.

In view of the obvious anticline structure of piedmont depression and intermountain basin in northwest China and numerous oil and gas seedlings, the discovery and exploration of laojunmiao and Dushanzi oilfields focus on the west. From 1952, the main force shifted to the west of Gansu, and oil exploration was carried out in the west of Jiuquan, Minhe and Chaoshui basins. At the same time, the ground geological survey was started in the southern margin of Junggar basin in Xinjiang and the piedmont depression of Longmenshan in the west of Sichuan basin. 1954 enters Qaidam basin in Qinghai province.

From 1950 to 1954 * *, a total of 420 wells were drilled, with a footage of 245,000m and an average well depth of 583m. Three small oil fields, namely Yongping, Baiyanghe and Youshi, were discovered successively, with little exploration effect. Part of the reason is poor reservoir physical properties, such as jujube orchard in northern Shaanxi; Some target layers are missing, such as pit water structure in tidal basin; Some surface anticline structures are inconsistent with underground structures, such as Haitangpu structure in western Sichuan. In frustration, people began to realize that the formation of an oil and gas reservoir requires many conditions. Looking for oil and gas fields can not be simply understood as looking for surface anticline structures and oil and gas seedlings, but also studying reservoir changes, stratigraphic distribution, structural development history and coincidence of shallow and deep structures. It is also recognized that oil and gas fields can also be formed in areas with stable regional structure. These new understandings of the formation of oil and gas reservoirs are improvements to the guiding ideology of oil and gas exploration.

In view of the previous understanding, oil and gas exploration in this period gradually expanded to the hinterland of the basin and the area with gentle structure, which was called "Shangtaidi". Under the guidance of this understanding, the first breakthrough was made at the end of 1955, and Karamay Oilfield was discovered. The oil-bearing area in central Sichuan was found in 1958.

Up to 1959, 24 gentle anticlines have been discovered, 10 has been drilled, and 7 oil fields have been discovered in * * in central Sichuan, with oil-producing layers including Middle-Upper Triassic and Jurassic. The reservoir space mainly includes cracks, crystal caves, karst caves and cracks between shells. The two alpine beds are a dual-medium reservoir with both fractures and pores, and the distribution of oil layers is controlled by the occurrence of fractures. Daanzhai layer is not only a source rock, but also a good shell limestone reservoir. It shows that the oil layers in central Sichuan are multi-layered vertically and widely distributed horizontally, and are not limited to anticline traps.

1950 to August 1959 is the initial period of the development of modern petroleum and natural gas geology theory in China. In practice, a set of rudiment of oil and gas geology theory with China characteristics has been initially formed.

After 10 years of oil and gas geological exploration, field geological investigation and reservoir geological environment research, geologists have further established the viewpoint of continental oil generation. Each exploration basin has successively determined the main source rock series and distribution range in this area.

1960 or so, Petroleum Industry Press published several works in this field, which represented the level of petroleum geologists' understanding of continental oil generation at this stage. However, due to various reasons, most of them failed to meet the readers. Essays on Oil Generation and Exploration of Continental Sediments in China (the first episode, 1960 March) is a publicly published book. Some papers in this book discuss the generation of oil from the aspects of structural conditions, sedimentary environment, paleoclimate and sedimentary characteristics of organic matter. Some discuss the oil-generating conditions of continental deposits from the relationship between continental deposits, sedimentary formations and oil generation; Some have proved the continental oil generated from rock characteristics and animal and plant fossils; Some papers also talk about how to find oil in continental deposits, and so on.

As for the geological conditions of oil generation, it was put forward that swamp facies, lake facies (fresh water and brackish water) and even delta facies in inland basins were all sedimentary environments of oil-generating layers, which generally defined the main oil-generating layers in the explored basins in China. Regarding the distribution relationship between source rocks and reservoirs, the book holds that reservoirs are in or near source rock profiles. Terrestrial source rocks are accumulated in expanding sedimentary basins, closed water bodies and humid climate conditions, and their visual signs are gray-green to black clay rocks similar to marine facies.

During this period, Lanzhou Institute of Geology, Chinese Academy of Sciences put forward in 1959 that the geological condition of continental oil generation in China is "inland humid depression". The Ministry of Geology has also systematically done a lot of research work on continental oil generation, with special emphasis on reducing environment when describing the geological conditions of oil-generating layers.

1955 walked out of the piedmont depression for the first time, and the Karamay oilfield with the largest stratigraphic overlap and stratigraphic unconformity in China was found in the monoclinal zone with inconspicuous anticline structure. Later, the metamorphic weathering crust reservoir was discovered in Yaerxia, Yumen, and the fractured reservoir was discovered in the middle of Sichuan, which confirmed that the types of oil and gas reservoirs in China are diverse and the exploration field is very broad.

Hydrogeological conditions have a great influence on the formation of oil and gas reservoirs, and the research in this field in Karamay Oilfield is more in-depth and systematic (Compilation of Petroleum Geological Reports, 1959).

During this period, we began to realize that the distribution of oil and gas reservoirs is not only controlled by a single structure, but also by the whole structural belt. Therefore, the concept of oil and gas accumulation zone has been put forward accordingly. For example, the northern Junggar Basin is divided into three oil-bearing areas and seven oil-gas accumulation zones. Karamay-Wuerhe is a 1 oil and gas accumulation zone.

Regarding the direction of oil exploration, it has been clearly put forward in this period that oil must be searched in basins with source rocks. First of all, we should look for oil storage structures in the whole basin with source rock series.

Oil and gas evaluation gradually abandoned the queuing method of a single anticline and paid attention to the comprehensive evaluation of the whole basin or a certain oil and gas-bearing area. In terms of exploration methods, we have carried out detailed structural contiguous surveys in central Sichuan, southern Sichuan and other areas, and carried out comprehensive exploration of surface geology, drilling and geophysics in Karamay, enabling us to understand underground geological structures more comprehensively and quickly.

(3) The eastward shift of China's oil and gas exploration strategy and the rapid development of continental petroleum geology theory.

The reasons why the focus of oil and gas exploration in China has shifted from the west to the east are as follows: first, the theoretical level of oil and gas geology has improved, and it is recognized that the eastern region has great oil and gas potential; Second, the improvement and development of exploration means, especially the wide application of earthquake and deep well drilling technology, make it possible to explore oil and gas in the vast plain without ground anticline and oil and gas display.

As for the oil-bearing property in eastern China, as early as 1948 1, Professor Weng pointed out in an article in the American Oil and Gas magazine that Songliao, North China, Jianghan, China, Shandong, Jiangsu, Zhejiang, Fujian, Guangdong coastal areas and the western part of Taiwan Province Province are favorable oil-bearing areas. After 1952, some geological experts in China put forward geological exploration in eastern China one after another.

Since 1955, the Ministry of Geology and the General Administration of Petroleum of the Ministry of Fuel Industry have strengthened the petroleum geological survey in the eastern region. 195565438+ 10, the General Administration of Petroleum Management of the Ministry of Fuel Industry held the sixth national petroleum exploration conference and decided to carry out petroleum geological survey in eastern China. In the same year 1 to February, the first oil survey meeting of the Ministry of Geology also decided to explore in the east.

1956, the Ministry of Petroleum Industry set up the North China Petroleum Exploration Brigade, drilled the first oil parameter well-Hua 1, and sent a geological team to Erlian Basin for oil survey.

1958, Songliao Petroleum Exploration Bureau was established in Changchun and East China Petroleum Exploration Bureau was established in Shanghai, which made organizational preparations for the eastward shift of China's petroleum exploration focus.

1. Exploration and development of Daqing Oilfield and gradual establishment of China's oil and gas geological theory.

The oil and gas geological survey and exploration in Songliao Basin began at 1955. First, the Northeast Geological Bureau of the Ministry of Geology conducted reconnaissance of two routes. Through investigation, it is considered that Songliao Plain is a subsidence area with thick Cretaceous and Tertiary sediments, with a total thickness of about 4,000m ... Dark mudstone containing ostracods, which is oily and shows fluorescence, has been found in Songhua River and Heishanzuizi in the west of Gongzhuling, and the possibility of marine strata has been put forward. It is predicted that there may be oil storage structures in the central plain, and it is suggested to carry out geophysical exploration as soon as possible. From 65438 to 0956, the Songliao Petroleum Survey Brigade and the Second Geophysical Exploration Brigade of the Ministry of Geology conducted gravity and magnetic surveys in Songliao Plain, and got a preliminary understanding of the basement fluctuation in Songliao Plain.

The discovery of Daqing Oilfield further proves that continental sedimentary basins can not only generate oil, but also form rich oil, forming a super-large world-famous large oilfield, thus greatly improving the evaluation of the oil and gas potential of continental basins and making China's understanding of oil and gas resources more optimistic.

In the exploration and development practice of Daqing Oilfield, the main contents of petroleum geology in continental basins are systematically studied and summarized, which greatly improves the theoretical level of petroleum geology in China and the corresponding exploration guiding ideology.

(1) Great progress has been made in continental oil generation.

The study of continental oil generation is no longer limited to the simple geological qualitative analysis in the past, but begins to apply a large number of petrochemical analysis data to establish quantitative identification of organic matter abundance and sedimentary environment parameters of source rocks, which is a great progress. Driven by the study of continental oil generation in Daqing Oilfield, this work has been carried out in various oil and gas regions in China, and it is clear that compared with marine crude oil, most continental oil generation in China has the characteristics of high wax, low sulfur, low porphyrin content and low w/(V)/w(Ni) ratio. The salinity of sedimentary water in continental reservoirs is mostly low, with chloride content generally only 65,438+00% ~ 20% of that in marine, iodine content 20% ~ 50% of that in marine, bromine content is also low, and the contents of reduced sulfur, vanadium, nickel, copper, chromium and other elements are generally lower than those in marine, indicating that most continental reservoirs are formed in fresh water and brackish water. Whether the oil-generating layer can be formed depends on the abundance of organic matter and sedimentary environment, not on the salinity of ancient water bodies.

The formation of continental oil layer is closely related to the degree of oxidation and reduction of water body during deposition. The iron reduction coefficient (K) is proposed to determine the reduction degree: oxidation phase K = 0 ~ 0.2 and reduction phase K = 0.2 ~ 0.8, in which weak reduction phase K = 0.2 ~ 0.3, reduction phase K = 0.3 ~ 0.55, strong reduction phase K = 0.55 ~ 0.8 and hydrogen sulfide phase K > 0.8. Based on this standard, the distribution characteristics of source rocks in major oil-bearing basins in China are analyzed, and it is pointed out that terrestrial source rocks are mainly deposited in weak reduction subfacies and reduction subfacies, while marine source rocks are mainly deposited in reduction subfacies, strong reduction subfacies and hydrogen sulfide facies.

The reducing environment is conducive to the preservation of organic matter and the transformation of organic matter into petroleum, and the organic carbon content is the standard to measure the quality of source rocks. The content of organic carbon in continental reservoirs in China is relatively high, with a lower limit of 0.4% and a general value of 1% ~ 2%. The organic carbon content of marine source rocks is generally about 1% or higher. The sedimentary environment of continental source reservoir is a long-term subsidence lake basin covered by deep water, and the uncompensated area is the best place to form a good source reservoir. Climatic conditions are not the most important, and a warm and humid climate is more conducive to the long-term maintenance of water bodies and the reproduction and growth of animals and plants.

(2) It promoted the development of continental sedimentology.

After the discovery of Daqing Oilfield, the understanding of reservoir lithology, physical properties, sedimentary environment and its distribution law has greatly promoted the research and progress of continental sedimentology.

The study of continental sedimentary environment began as early as the end of 1950s and before the discovery of Daqing Oilfield. 1958 In the winter, the Institute of Petroleum Science of the Ministry of Petroleum Industry held a study class on lithofacies palaeogeography in Beijing, which was attended by people from various petroleum administrations. After that, the exploration areas draw lessons from the research methods of marine sedimentology and apply the data of strata, lithology and paleontology to carry out lithologic division and lithofacies paleogeography restoration research. The Petroleum Research Institute of the Ministry of Petroleum Industry set up a lithofacies paleogeography research team in 1959. From 1959 to 1960, the team studied Yanchang Formation (T3y) and Yan 'an Formation (J 1y) in Ordos Basin, Paleogene in Jiyang Depression in Bohai Bay Basin, Songhua Formation in Songliao Basin and Jurassic in Sichuan Basin. Due to the lack of data, the research unit is large, the methods are few, and the characteristics of continental deposition are less reflected. But it has played a certain role in understanding the development history and sedimentary characteristics of the basin.

1960,1/kloc-0 In June, 2006, the Research Institute of Petroleum Science held the "National Conference on Oil and Gas Field Distribution and Lithofacies Paleogeography" to exchange experiences in various oil and gas areas. The lacustrine facies is subdivided into lakeside facies, shallow lacustrine facies, semi-deep lacustrine facies and deep lacustrine subfacies. It is pointed out that deep lake subfacies are beneficial to oil generation, continental deposits have obvious cyclicity, and reservoir-cap assemblages are rich in stratigraphic profile. It is considered that source rocks and caprocks are located in fine-grained section, and reservoirs are located in coarse-grained section, forming a source-reservoir-cap assemblage.

(3) To further understand the formation characteristics of continental oil and gas reservoirs.

After the discovery of Daqing Oilfield, the formation conditions of six oil and gas reservoirs were summarized and put forward, including source rocks (reservoirs), reservoirs (reservoirs), caprocks (reservoirs), migration (migration), sealing (sealing) and preservation (preservation), and the formation and distribution of oil and gas reservoirs in China continental basin were further understood. Generally speaking, there are the following points: ① The distribution of oil and gas reservoirs is strictly controlled by oil-generating depressions because of the great change of continental sedimentary lithofacies and the short migration distance of oil and gas; (2) The secondary structural zone controls oil and gas accumulation; ③ Non-anticlinal oil and gas reservoirs are often formed in slope areas; ④ The central part of the basin is often developed with gentle placanticline, which is the richest in oil and gas, such as Daqing placanticline. Therefore, the guiding ideology of "finding concave and exploring edge" has been formed in exploration. The so-called sag determination means that the oil-generating sag is determined first, and then the favorable reservoir facies belt around the oil-generating sag is explored as a whole with the secondary structural belt as the target. This exploration method has been applied in the initial stage of oil and gas exploration in Bohai Bay Basin and achieved practical results.

2. The exploration progress in Bohai Bay large oil and gas area has promoted the perfection and improvement of oil and gas accumulation theory.

The discovery and development of Bohai Bay oil and gas area is a process of understanding the formation and distribution characteristics of oil and gas reservoirs in extensional rift basins, and it is also a process of leaping development and further improvement of China's continental oil and gas geological theory.

During the period from 1964 to 1977, China's petroleum and natural gas geological theory, including continental sedimentology, continental reservoir evaluation, continental reservoir rock characteristics, continental fluid properties and continental oil and gas field distribution law, has been greatly enriched and developed. The most obvious progress is the formation conditions of oil and gas reservoirs and the emergence of the theory of compound oil and gas accumulation zones.

(1) Development of understanding of hydrocarbon accumulation conditions

As mentioned above, in the early days of Daqing Oilfield discovery, six factors were put forward for the formation of oil and gas reservoirs: source (oil and gas layer), reservoir (reservoir), cap (layer), circle (sealing), migration (migration) and preservation (preservation). After large-scale oil and gas exploration and in-depth research, the understanding of Bohai Bay Basin has been deepened, and the conditions for oil and gas reservoir formation have been supplemented and developed. First of all, it is considered that the source rock is the foundation, and the two conditions of reservoir and cap should not be analyzed separately, but should be linked together, and their functions in the formation of oil and gas reservoirs should be analyzed from the perspective of combining the two. In addition, the situation of oil and gas sources should be analyzed in combination with source rocks and migration conditions. Therefore, in fact, the most basic elements of oil and gas reservoir formation are oil and gas source, reservoir cap rock combination and trap.

The above three conditions are not sufficient conditions for the formation of oil and gas reservoirs. In many areas, these three conditions exist, but some traps become oil and gas reservoirs, some contain little oil and gas, and some even become "empty" traps. Why is this? After in-depth study, it is considered that the three elements of oil and gas accumulation are not interrelated and mutually developed, but change independently. Only when the three elements have the best configuration and combination in time and space can oil and gas reservoirs be formed. Especially, it is more important to allocate the time and space of oil and gas migration and trap formation, that is, traps formed before or at the same time as hydrocarbon generation in time. On the other hand, in space, traps close to oil and gas sources, or far away, but with communication channels, are most conducive to the formation of oil and gas reservoirs. For example, Shengtuo area in Jiyang Depression is a synsedimentary anticline structure, which developed in the third stage of Shahejie Formation (E2-3 s3) and deposited in the middle and late stage of Dongying Formation (E3 d 1-2) when oil and gas migration began. Spatially, this anticline belt is close to the steep edge of Dongying oil-generating sag, and there are many faults communicating with the third member of Shahejie Formation, which leads to the formation of highly enriched oil and gas reservoirs in the second member of Shahejie Formation (E2-3 s2). Kongdian Uplift in Huanghua Depression is not only far away from Qikou oil-generating sag, but also the anticline of Guantao Formation covering this uplift was formed later, but it was still earlier than Minghuazhen period (N 1-2 m), the main generation and migration period of oil and gas. In space, there are unconformities and faults between traps and oil source areas, so oil and gas reservoirs are also formed.

The key to the formation of oil and gas reservoirs is the temporal and spatial configuration and combination of the three major reservoir-forming factors. Under the guidance of this viewpoint, the temporal and spatial relationship of oil and gas generation, migration and trap formation in Bohai Bay Basin is studied, which makes the subsequent oil exploration more targeted and the effect is obviously improved.

(2) The emergence of the theory of compound hydrocarbon accumulation zone.

The understanding of oil and gas accumulation and distribution in Bohai Bay Basin characterized by extensional fault depression has roughly gone through three stages.

The first stage-simple anticline oil and gas reservoir model stage: in the early stage of exploration, it is considered that oil and gas are accumulated in the anticline of North China Plain, just like Songliao Plain. Therefore, a simple anticline oil and gas reservoir model is used to guide exploration, and exploration wells are arranged at equal intervals with large profile to explore the oil and gas range, but many wells have encountered unexpected situations. For example, in the exploration of Jiyang depression, it is found that the exploration wells in the high part of the structure are water layers, but the exploration wells in the low part see oil layers; In a well, there is a water layer above the oil layer and an oil layer below the water layer; The fluid properties, productivity, output and oil-gas ratio of different wells in the same reservoir have changed greatly, and some wells have been hollowed out. For another example, the oil and gas distribution model of Daqing Oilfield was applied in Liaohe Depression to deploy wells in the secondary structural zone of Rehetai in the overall exploration gold belt, which led to the failure of the first batch of exploration wells located in the wings and saddle. There used to be a saying that there is oil only at the structural high point, and that only drilling can determine the oil-bearing area. So there is a completely passive and unknowable situation of "the oil layer expands outward and the water layer contracts inward"

The second stage-exploration of small fault blocks: after preliminary exploration practice, it has been recognized that there are many faults in Bohai Bay Basin, the fault activity time is long, and structural faults and fault blocks control oil and gas distribution. In view of the particularity of fault-block oilfield, some explorers once thought that the oil layer distribution of each fault block must be clearly understood before oilfield development can be carried out. This practice once caused the exploration work to fall into complex small fault blocks, which led to the increasing density of exploration wells and more and more drilling, which made it difficult to keep up with the pace of exploration, so that there was no major discovery in exploration for a period of time. For example, in the early stage of exploration in a depression, two structural zones were explored, and after two years of exploration, they still did not exceed the range of 3 ~ 4km2.

The third stage-the establishment stage of the viewpoint of compound oil and gas accumulation zone: Bohai Bay Basin had 47 depressions during Paleogene deposition. Most depressions are an independent sedimentary system, surrounded by many water systems of different sizes injected into the lake basin, forming a combination of various sand bodies and source rocks generated on the plane and superimposed on the profile. Moreover, due to the continuous migration of the center of the lake basin, the source rocks and reservoir rocks form a good source-reservoir-cap match. This is different from the unified sedimentary basin formed by some large lake basins in China, such as Songliao basin, and it is also much more complicated. In addition, during and after the deposition, the basin experienced many strong fault activities, which made the source beds and reservoirs cut and dislocated by a series of faults in different directions, or staggered, stepped or embedded in buildings. Each oilfield consists of many oil-bearing strata, many types of oil reservoirs and a series of oil-bearing fault blocks with different sizes. Each oil-bearing interval of each fault block is an independent oil-water system. In fact, an oil field is composed of hundreds of oil reservoirs.

Under such geological conditions, after repeated practice and comprehensive and systematic comprehensive research, the theory of compound oil and gas accumulation zone is gradually summarized.

The theory of compound oil and gas accumulation zone has played an important role in oil and gas exploration in eastern China and improved the effectiveness of exploration and development.

Faulted basins have both a complex side and a simple side, which are different and unified. The so-called unity means that a fault structural belt generally has a relatively unified formation history, main target layers and main source-reservoir-cap combinations, and main oil and gas accumulation periods. The distribution of oil and gas is controlled by structural belts, which constitute the basic features of multi-layer system and multi-type oil and gas reservoir combination in a reservoir-forming geological body. The so-called difference is that a fault structural belt is cut by many faults, and oil, gas and water in each fault block are self-contained There are differences in oil-bearing series, oil-bearing interval, oil-water interface, oil-gas-water layer combination, fluid properties, pressure system, drive type and energy among the fault blocks. In exploration, we should proceed from the whole, focus on the whole, make overall arrangements based on the accumulation zone of oil and gas reservoirs, and control and prove the oil-bearing scale. On the other hand, development should be based on fault blocks, treated differently, and strive for high production in sparse wells, early energy supply and timely water injection.

(3) Rolling exploration and development came into being.

As mentioned above, there are a large number and various types of oil and gas reservoirs in the complex oil and gas accumulation zone, which cannot be fully understood through one exploration. Therefore, exploration and development should intersect, resulting in the concrete practice of rolling exploration and development, which significantly improves the effectiveness of exploration and development. This is an effective method described and summarized by oil exploration experts, reservoir engineers and oilfield development experts in China based on their deep understanding of the reservoir characteristics and the complexity of oil, gas and water distribution in fault basins, and it is an important contribution to the practice of oil and gas exploration and development in the world.

(d) The stage of further enrichment and perfection of China's continental petroleum geology theory after1979.

In order to deepen the understanding of petroleum geological characteristics of China petroliferous basin and search for oil and gas reserves more effectively, the former Ministry of Petroleum Industry organized and strengthened the theoretical study of oil and gas geology in China from 65438 to 0979. First, improve and establish research institutions, enrich and strengthen Beijing Petroleum Exploration and Development Research Institute, and successively establish and improve oil and gas geological exploration and development research institutes in various oilfield administrations (companies) in various regions of the country; Second, the coordination and planning management of scientific research work have been strengthened, and advanced analysis and experimental techniques have been widely used; The third is to emphasize the study of basic disciplines, such as structure, sedimentary facies, source rocks, reservoirs, coal-formed gas and natural gas geology, resource evaluation and distribution law of oil and gas reservoirs. After several rounds of systematic summarization by specialty, region and national specialty, China petroleum and natural gas geology has been greatly enriched and improved.

198 1 has promoted the development of oil and gas geological theory. Under the unified research outline and plan arrangement, the work has been carried out for five years. In 1986, the special research on structure, sedimentation, oil generation, coal-formed gas, oil and gas accumulation and distribution, resource evaluation and the national 143 basin resource evaluation were completed. The national oil and gas resources are predicted. This resource evaluation attaches importance to basic research, starting with special research, and has achieved fruitful results. After research work, six special research papers on the structure, sedimentary facies, continental oil generation, coal-formed gas, oil and gas resources evaluation method and oil and gas accumulation and distribution law of China oil and gas area have been summarized and published successively.

Petroleum Geology of China 1985- 1995, including China Offshore Oil Corporation, Petroleum Administration Bureau of China Petroleum and Natural Gas Corporation and Institute of Exploration Bureau (Company), gives a unified overview of petroleum and natural gas geological theories in various oil and gas areas, including strata, sedimentary facies, structures, source rocks, oil reservoirs, oilfield hydrogeology, natural gas geology and crude oil properties. , has been comprehensively and systematically summarized, making the theoretical level of oil and gas geology in China a big step forward.

The second national resource evaluation from 1992 has promoted the further understanding of China's oil and gas geological characteristics.

With the development of oil and gas exploration, many oil and gas geological problems need to be re-recognized and studied. Therefore, from April, 65438 to the end of 1994, China Petroleum and Natural Gas Group Corporation and China Offshore Oil Corporation organized 24 domestic related units to carry out the second national oil and gas resources evaluation and research. Geological evaluation mainly includes basin evaluation and belt trap evaluation. Advanced basin simulation technology is adopted in basin evaluation research. Based on the comprehensive study of petroleum geology in the basin, the geological model and mathematical model are established, and then the software is compiled to quantitatively simulate the formation and development of sedimentary basins and the generation, migration and accumulation of oil and gas in them by computer, thus pointing out the favorable exploration zones in the basin. The study of belt trap evaluation adopts the method of geological risk, mainly carries out the basic geological study of oil-gas bearing property of belt traps, and points out the reservoir-forming conditions and the comparative study of related belt traps.

Compared with the first time, the second resource evaluation study adopted advanced technical methods, unified norms and standards, deepened understanding and significantly improved credibility. The study of multi-layer trap evaluation directly provides exploration targets for the exploration field. In particular, he wrote monographs on the formation conditions and laws of oil and gas reservoirs, continental oil generation theory, immature oil and some new exploration achievements and theories in new fields, which further deepened the geological understanding of China oil-bearing basin.