(China Petroleum Xinjiang Oilfield Company, Urumqi, Xinjiang 830000)

Junggar basin is an old oil area with large-scale exploration and development for nearly half a century. The task of research work is to carry out research from two aspects according to the existing and proposed problems at this stage: first, to solve practical problems in production; The second is forward-looking to solve the long-term expected development problems. The purpose is to ensure the long-term, stable and sustainable development of exploration.

1 In terms of thinking methods, exploration and research need to deal with several aspects.

1. 1 While trying to keep pace with the world's advanced development level, we should pay more attention to studying reality and solving this problem.

Substantive issues

It is necessary to absorb foreign advanced academic ideas, methods and technologies in time to promote the improvement of China's research level; But what is more important is to make foreign things serve China, combine with reality and focus on practicality. Only in this way can our work keep up with the world trend and catch up with the world level in some aspects. This is what is often said: "Only the national is the world's".

Nowadays, international communication is very active, and we have introduced and learned many new concepts, ideas and theories from abroad, such as plate tectonics, petroleum system, foreland basin and so on, which is very necessary. It is important to analyze the essential differences and similarities between these theories or terminology concepts and those we have used for a long time, such as trough theory, source-reservoir-cap combination, piedmont depression and marginal depression, and absorb their essence instead of simply replacing them. Simple substitution is fashion, not improvement and progress. Therefore, we should strongly advocate making more specific analysis at any time.

Whether Junggar is an oceanic crust or a continental crust is a purely academic issue, and it is desirable as long as it is justified. However, since overseas scholars put forward the theory of ocean crust, domestic scholars have followed suit, but most of the evidence is to the contrary. There is no ocean crust with a thickness of more than 40km in the world, and the mechanism of the direct evolution of ocean crust into inland lake basin is not clear.

For example, the trough theory is a tectonic theory based on continental geology. Because I didn't know much about marine geology before, when the results of marine geological survey came out, it seemed very helpless. So the idea of continental drift was revived on the basis of marine geology, and the plate theory appeared. But the plate theory is not perfect, and it has been constantly improving and developing. For example, in Africa, there are passive continental margins on both sides, and there is no reduction zone. Still drifting? Is it drifting east or west? In addition, the Great Rift Valley in East Africa is still expanding. It can be seen that whether the plate completely repels the trough platform has not been seen for decades. When Zhu was alive, he found it difficult to apply plate theory to Paleozoic. Both the mainland and the ocean are on the same earth, and it is impossible to completely exclude and deny each other. The earth can neither become a continent nor an ocean completely, but must be in a unity, so the two must be coordinated with each other. Therefore, the groove and the disk are not absolutely opposite. The practice after the plate landed shows that it is far more difficult to form * * * knowledge than the ocean, especially the ancient plate before Paleozoic. On the mainland, some people have turned all the fold zones into collision zones. In fact, the collision zone can't be painted everywhere on the mainland. Ultra-basic rocks are not necessarily signs of collision zones, especially those without "nesting". So it can't be simply substituted. How the plates on the mainland evolved is now being explored by everyone.

The core problems of source-reservoir-cap assemblage and petroleum system are all around oil source, so they are all source-controlled. Without source rocks, assemblages and systems would not exist. Some people say that the combination is static and the system is dynamic, which is incorrect. The combination is not all simple one-to-one, and the system is not all simple relationships. Sometimes an oil source can form several sub-combinations in different regions and horizons, showing the dynamic change of time-space relationship, just like a subsystem can be divided in an oil-bearing system. The combination emphasizes the vertical relationship and the system emphasizes the plane change, which can complement each other.

It seems promising to talk about the foreland basin now, but old comrades all know that the oil exploration in the piedmont depression in the 1950s and 1970s was criticized and denied at home. Of course, this is because its benefits are not as good as platform area and stable units, and often get twice the result with half the effort. Although this is one-sided, it is also one-sided to say that there is oil in foreland basin. Now, the new packaging of "foreland basin" has been reintroduced into the piedmont depression and marginal depression, which has become a hundred times more valuable and very undesirable. Moreover, there are not many standard foreland basins in China, all of which are concentrated in the west. The focus of the work should be on the specific analysis of the depression, not limited to model comparison. Two years ago, I had the honor to participate in the evaluation of a project in northern Tibet, and paid deep respect to the fruitful achievements made by workers in filling the gap through hard work in the alpine region. Unfortunately, when evaluating the prospect, the foreland nature of the depression area is mainly emphasized, but the preservation conditions are not discussed enough. The existence of source rocks can be determined by geochemical research. Without preservation conditions, it is also a problem to enrich the oil source. The source rocks, reservoirs and caprocks in this area are all late paleomarine carbonate rocks. On Kunlun Mountain, the relationship between reservoir and caprock has become the main contradiction, which should be paid attention to.

Prototype pots are very popular now. Last year, our oilfield originally planned to set up a big project for the prototype basin research of Junggar basin, and planned to adopt the way of technology introduction and cooperation to obtain basic results. If we solve the prototype of the basin, it is impossible to get a definite solution. It is better to organize a small theoretical team to do some appropriate research. If we try to obtain the oil and gas distribution information of Junggar basin by simulating the oil and gas evolution and distribution model of the basin prototype, we can't reach the level of detail we have now anyway. Therefore, it is not worthwhile to make great efforts to carry out large-scale research, and it is also flashy to include productive research. The competent department asked me for advice. I was puzzled and cut the project. Of course, you can do it again if you cut it wrong.

As the name implies, prototype basins should be classified according to their original state. However, the views on the original state of most existing basins, such as boundaries, often vary from person to person. As for sedimentary bodies and their thickness, facies characteristics, structural styles and metallogenic conditions, etc. This should also be included in the connotation of the basin, and the damaged part cannot be recovered. Jones, a famous structuralist, believes that the whole Tianshan Mountain was completely covered by Mesozoic and Cenozoic, and then the Mesozoic and Cenozoic overburden collapsed from the mountain to the north and south sides, forming an extension to the mountain. Accordingly, Tarim and Junggar in Mesozoic and Cenozoic, as well as Tuha and Yili, are all a unified basin. This is also the prototype of the basin. How credible is it? I'm afraid it will only add some unnecessary pen and ink lawsuits.

In fact, most basins in relatively stable structural areas, especially some large basins, basically preserve all the elements of each stage of basin development. It is basically enough to analyze and understand the basin itself, its history and its existing metallogenic laws. However, those basins located in strong tectonic activity areas, especially small basins, are more difficult to understand the whole picture of the basin because of the serious incompleteness of later reconstruction. Obviously, it is of little practical value to pursue those parts that no longer exist and originally belonged to the basin. Of course, it is also necessary to extract the most essential characteristics of the original state type of the basin from the high-level theory to guide the exploration of oil and gas resources strategically (only strategically). This is the task of professional theoretical teams and professional theoretical researchers, and production research work can't be so lively.

Although there are many existing prototype basins, few of them are qualified to become oil-bearing basins. China is probably only the Quaternary oil-bearing basin in Sebei, the middle part of Sanhu Lake in Qaidam Basin, Qinghai Province. Most of the remaining oil-bearing basins have undergone different degrees of transformation. It is troublesome to call all these "transformed basins".

I think our way of thinking should be like this.

1.2 summing up experience should not separate the stage connection, let alone absolutize the stage experience.

In the past, we first focused on locating the sag, exploring the edge and finding favorable units, that is, turning around the sag, actually turning around the oil source area, taking the source control theory as the guiding ideology, such as the northwestern margin of Junggar Basin and the southern slope of Lvliang. Later, some people summarized this as a resounding slogan: "Look for big oil fields around the Great Depression". This is in strategic decision-making. In the early days of oil and gas exploration, this is generally the only way to choose the main target. But not all of them are successful, such as the exploration of Wulungu sag, because the sag or large sag may not have enough hydrocarbon generation potential. But it is also controlled by the source code. After the successful belt selection in the early stage, when the exploration is further deepened, the source control mechanism alone can no longer guide the exploration decision of the selected belt. For example, the oil-bearing property of the southern slope of Lvliang was initially determined according to the source control theory, which has been proved to be correct in practice. However, it is impossible for the southern slope of Lvliang to contain all oil. The controlling factor is a series of NE-trending and nearly EW-trending structural high belts on the south slope, which used to be called "tertiary structural belts". Now everyone says this is beam control theory. However, it cannot be considered that the source control theory is outdated and invalid. Beam control only exists on the premise of source control; If there is no source control, beam control cannot be established. For example, there are many structures in Wulungu sag, but there is no oil control. For another example, both of them are NE-trending structural high zones with different oil-bearing properties. Not all the same structures contain oil. For example, the Jurassic at the top of Xishi structure does not contain oil, but the wing contains oil, which Kong Liang could not answer. The explanation is not omnipotent, and the application is selective. This shows that there are deeper factors that determine the distribution of oil and gas under structural control, such as lithology or physical properties. Therefore, it should be "lithologic control" or "physical control" to solve the problem of uneven distribution of oil and gas in the structure. Therefore, whether it is source control, beam control, lithology control or physical property control, there is (and can only be) relative correctness. They are not mutually exclusive, but interrelated and complementary, serving strategic decision-making, tactical action design and campaign arrangement respectively. It is harmful to isolate or absolutize a role.

1.3 We should carefully analyze the effects and application conditions of high-tech production, and seek advantages and avoid disadvantages.

We now use many high-tech production technologies and means, which are undoubtedly correct and necessary and an important symbol of modernization. But every high-tech technology is not a panacea, nor a magic weapon, and it has its own adaptive environmental conditions. Only by fully understanding and grasping these conditions can we gain advantages and avoid disadvantages and be in an invincible position. There is such a lesson in the exploration of Xiaoguai Oilfield. Xiaoguai oilfield is a footwall fault block with deep burial. The reservoir is thick and complex, and it is impossible to find and prove the oil field without the investment of high-tech means. Without modern digital seismic technology, it is impossible to find out the closed shape of the fault block. Although the well 147 drilled according to the "flat point" information obtained oil flow in the early 1980s, it was not until the mid-1990s that the oil field was discovered and put into development. The use of high-tech means has both positive and negative aspects. At present, we use a reservoir description that integrates drilling, logging, oil testing and seismic information in one furnace. The seismic information is calibrated by drilling, recording, measuring and testing data of oil layer, and then extrapolated, so as to delineate the oil-bearing range, which has great certainty for oil and gas reservoirs in conventional reservoirs, and can save many wells in the exploration stage and obtain high benefits. For example, only one of the more than 400 development wells in Cainan Oilfield fell into the waters on the edge of small fault blocks, which was a great success. However, for the dry alluvial fan conglomerate with huge thickness and no stable interlayer in Xiazijie Formation, due to its inherent shortcomings, the lithology and physical properties of the reservoir with low porosity, low permeability and dual media characteristics change dramatically in vertical and horizontal directions. Correspondingly, the change of oil content is also amazing. Because of this, the oil-bearing height of massive reservoir may reach 402 meters, but there is no massive oil-bearing within this height of 402 meters. Under the control of insufficient exploration wells, it is difficult to fully reflect this drastic change in reservoir description, and the reliability of the results is relatively low. It is not surprising that due to underestimation and over-optimism of the description results, the development has intervened too hard in advance, resulting in low efficiency and many wells have been hollowed out. If the exploration speed is appropriately delayed and the reservoir is further described according to the situation of new wells, the understanding of the reservoir will be more accurate and the development will be more secure.

This is another example. A few years ago, Comrade Lai Zhongkang started the AVO research of hydrocarbon detection in seismic data, which is a successful innovation. After Lao Lai retired, Zou Yuping, who worked with him, continued to study and found that the overlying strata of the reservoir are high-speed calcareous mudstone. No matter what the fluid properties in the reservoir are, AVO phenomenon will be formed, and it is impossible to distinguish whether it is oil, gas or water. This is another progress, which shows that the application of AVO technology in oil and gas detection is conditional, not absolute. If you don't realize this, you may fall into a trap.

1.4 Attention should be paid to carefully identifying contradictory information.

The oil test results of exploration wells are often inconsistent with logging data, and the oil test results should not have absolute veto power.

During the exploration in Yamakaji, the oil test results of two wells are still fresh in our memory, one is Pingsan 2 in 2A, Huo Nan, and the other is Pingsan 10 in Dong Yi Huo 1 0 well. According to Yamakaji standard, the electrical characteristics are oil layers in any case, so it is reasonable to produce water during oil testing, which is based on the results of oil testing. The suspended sand body of Well Huo 10 is still lower than the oil-water interface, so it is natural to draw a conclusion. However, if the oil test is not complete and the result is inaccurate due to the influence of engineering process factors, the oil layer will not be released. In the Ping32 reservoir of Well Huo-2, the production test water above the oil-water interface has caused a lot of troubles, which has been proved by history to be an engineering technology problem.

Another example is that after the discovery of Cainan Oilfield, according to the geochemical index of crude oil, it is considered that the oil source comes from Jurassic itself and is a self-generating and self-storing reservoir. However, this is contrary to the result that the Jurassic near Cainan has not reached the mature window and Jurassic oil has not been found in many underground wells in Wucaiwan-Anshan area. The local Jurassic can't generate oil, and the oil source moves far from the south without being intercepted, which makes Cainan's Jurassic oil source theory very puzzling. However, the Jurassic oil source theory must have a comparative basis, and the problem lies in the standard. Later, some people put forward the evidence of mixed source with Permian, and the contradiction was eased, but the master-slave problem remained unsolved. Until recently, the Jurassic oil source has been in a secondary position, but the Carboniferous-Permian oil source is the main one. This sign of Carboniferous source rock should be the same thing originally thought to belong to Jurassic source rock, but it is actually caused by "similarity". This is progress. If we blindly follow the Jurassic oil source, we will not move forward. In fact, judging the oil source of biomarkers depends on the accumulation of data. During the quasi-Eastern Conference, a graduate student of East China Normal University (who should be an associate professor or professor now) took samples at Xiaoquangou Group (T2-3xq) in Well Bei 25. This atlas is very similar to Lucaogou Group (P2l), but it is obviously different from Jurassic. This fact shows that the difference of kerogen is essentially the difference of sedimentary facies, which can be changed in plane. Therefore, the kerogen model of a certain stratum cannot be fixed. For example, the dry asphalt near the bottom of Permian in Taoshuyuan, Turpan-Hami basin, the correlation between oil and source is caused by the unification of Triassic in Heiyingshan, Kuqa Depression. The subtext is that it is different from both Permian sapropelic source rocks and Jurassic sapropelic source rocks, but it is a transitional type between them. Huangshanjie Formation in Heiyingshan is characterized by mud-free and carbon-free argillaceous deposits, and the Permian in Aiweiergou is dominated by carbon-like and carbon-free black argillaceous deposits, so the source rock of Taoshuyuan dry asphalt is actually a variant phase of Permian. For Lukeqin Oilfield, I am afraid it will return to Permian sapropelic source rocks.

Two forward-looking topics

2. 1 should be paid attention to, and physical trap research should be carried out immediately.

We all know that non-structural lithologic seal, but physical seal is not mentioned much in our literature. Exploration in the belly of the basin has put this problem on the agenda. The discovery of Shinan Oilfield was initially aimed at some small traps with local low amplitude, and as a result, the oil-bearing area mostly exceeded the scope of small traps, indicating that the oil-controlling factor is not structure, but lithology. However, the oil-bearing area is not completely consistent with the distribution of sand body, which also shows that the distribution of oil and gas in sand body is affected by the change of physical properties. Jurassic reservoirs in Xishi oilfield are all in the two wings, and there are many sandstone reservoirs at the top, but they do not contain oil. Why? Among them, there should be poor physical properties. In the deepening exploration of oil and gas basins, non-structural trap factors are becoming more and more prominent, and physical plugging will become more and more important. Therefore, we should study the physical seal as soon as possible, including the identification of seal and the formation mechanism of seal. The former aims at application, the latter aims at prediction, and the latter aims at better application. How to study? It's up to everyone to find a way. This has the nature of tackling key problems, and it may not be successful soon, but if you persist, you will certainly get something. There are many examples of physical traps in the West Siberian Basin, but they often appear in descriptive reports. As for how to determine the physical trap, few people mention it and it is difficult to learn from it. It seems that our problems are others' problems, and our own problems have to be solved by ourselves.

The influence of physical properties is nothing more than the innate factors of sedimentation and the epigenetic changes of diagenesis after sedimentation. The congenital conditions of continental reservoirs in Junggar are very unfavorable, and most of them are the products of rapid reservoir formation, poor sorting, mixed cements and skeletons, and many and complicated clay minerals. The Jurassic sedimentary rate is relatively slow, but the skeleton is still dominated by cuttings, which is not dense. With the increase of buried depth, the primary pores disappear obviously. The increase of porosity is often related to the development degree of epigenetic cracks. In the supergene changes of continental strata, acid hydrothermal solution and cement recrystallization are the main factors, and the sooner or later oil and gas enter the pores, it has a significant influence on this. In this way, the collocation of hydrocarbon expulsion period and reservoir will affect the change of reservoir physical properties. How to study and master these internal relations and predict the lateral changes of reservoir physical properties is still an urgent task to be explored.

2.2 We should seriously face the problem of gas-based exploration in the basin and abdomen.

With the increase of buried depth of hydrocarbon source beds in the hinterland of the basin, thermal evolution tends to be over-mature, and hydrocarbons will mainly be gaseous. This sends a very clear message to the discovery of oil and gas in the lower assemblage system and the oil ring condensate gas field in Mobei area. Unless the oil and gas entering the overlying reservoir in the early stage may be liquid, a large number of oil and gas that will continue to migrate in the future may be mainly gaseous. For this gas reservoir dominated by condensate oil, exploration and development are facing many difficulties, so it is necessary to make preparations in advance now.

For Triassic Jurassic coal measures strata, whether the thermal evolution has reached the stage dominated by gas remains to be determined by oil generation research. However, in the southern half of the basin, the buried depth is nearly 8000 meters, and the possibility of gasification is great. However, Jurassic is basically in a gentle syncline state, lacking local traps and large faults, and its accumulation is only in two directions: one is the secondary gas reservoir of Cretaceous tertiary epidermis structure in deep depression; The second is the deep basin gas reservoir in the depression slope area. The first one depends on the clarity of the deep traps in the skin structure of mountain earthquakes, and the second one is that engineering technology has to overcome many problems. The second type is a water-sealed gas reservoir when the formation water above the slope and the gaseous hydrocarbon below are in dynamic stability, which can only appear under the conditions of low porosity and permeability. How to understand this accumulation and explore it effectively is still a brand-new topic for us, so we should make preparations early.

3. Deepening exploration of the influence of basic research

3. 1 Relationship between basement age, evolution process and hydrocarbon formation in the basin

The basic structure of Junggar basin, such as unit division, sedimentary distribution and other important issues, is now relatively clear, which is no different from the general pattern of the past 20 years. Different researchers have different local corrections based on different angles, which is a normal phenomenon and does not affect the overall situation. It is difficult to study the formation and evolution of the basin before a large number of new data are accumulated. General large-scale research is not urgently needed. If we want to do it, we should focus on the very important actual data collection that we didn't have in the past, that is, we should have new means. However, this does not prevent some data accumulation and exploration in time. There are two problems that need special attention: first, we should seriously face and analyze the two opposing aspects of all information, and we should not take the attitude of replacing it in the right direction and abandoning it in the opposite direction in order to make an objective evaluation; Second, we must abide by the "rules of the game." No matter what viewpoints, methods and theories researchers adopt or agree with, they must operate according to the conditions and logical systems required and assumed by the selected theoretical system in order to justify themselves. The absolute age values of underground rhyolite and basalt, such as Xi Shi, Heather and Xia Yan, obtained not long ago are very valuable. This is the first time that the Carboniferous basement volcanic rocks in Junggar Basin have recorded the absolute ages of many specimens. As for how to use this information, it needs careful analysis and research. This age value confirms the existence of Precambrian basement in Junggar basin. Volcanic rocks are not Carboniferous, and the theory of basement double-layer structure is self-defeating. This is a rule of the game that must be observed. Although I put forward the double-layer structure, it was really denied by the actual data, and I am also very happy. Because of progress, the problem has been solved. But correspondingly, firstly, the rock sample must be metamorphic; Second, if it is the original rock, it is only possible as Singapore dollar occupied the Sinian suberathem in northern China; Third, all Paleozoic sediments covered on it must be stable platform-type structures. This is also a rule of the game that must be observed. However, none of these three conditions can be met. This is a bit of a problem. Of course, if the data measurement is not accurate, it is another matter. Naturally, we cannot judge the accuracy of the data, but we have the right to use it. Whether it is used or not depends on whether it can be justified.

In fact, the most remarkable feature of the evolution of Junggar Basin is that some basement rock series under the caprock still have considerable hydrocarbon generation potential. Except for the regenerative basin, the basement rock series as a sedimentary basin is generally trough-shaped, which has undergone intense folding, extrusion, deformation and different degrees of metamorphism and assimilation of magmatic rocks, and the hydrocarbon generation potential of sedimentary protoliths has long since disappeared. Some bedrock in Junggar basin not only has considerable hydrocarbon generation potential, but also has been proved to be helpful to hydrocarbon accumulation, and there are examples of industrial oil and gas reservoirs. Obviously, its evolution process is different from the general model. This feature is of great research value.

3.2 Formation problems

Conventional exploration in Junggar basin has been going on for half a century. Due to various reasons and new problems in production, there are still some stratigraphic problems closely related to oil and gas to be solved.

3.2. 1 Dishuiquan Formation (C 1d)

The drip spring profile measured by petroleum system is limited to a set of dark argillaceous rocks hundreds of meters thick on the downhill slope of the spring. The top and bottom are unclear, which does not conform to the stratigraphic code, so it is difficult to form an independent stratigraphic unit, and the age is unclear. It is probably a part of Nanming Water Formation (C 1n). In the past, the relationship between Dishuiquan Formation and oil and gas production was far away, and transportation was extremely difficult. Although we had the technical ability to solve this problem in the 1960s and 1970s, we didn't have any safety equipment, so we didn't do any further work. After the discovery of Wucaiwan gas field, Dishuiquan Formation was identified as a source rock. The deep part of Cainan Oilfield also reached Nanmingshui Formation, and gradually established itself as an important source rock. The problem of drip spring formation is more prominent and urgent. One is to solve its position on the regional stratigraphic table, and the other is to clarify its distribution range. This needs considerable field work to solve, and it's time to make up your mind.

3.2.2 Does Jiamuhe Formation belong to Carboniferous or Permian?

Jiamuhe Formation, established in the early 1960s, refers to a set of variegated tuffaceous conglomerate, a small amount of sandy mudstone and the interbedding of massive andesite porphyry and basaltic porphyry exposed in the upper reaches of Jiamuhe River. There is no obvious boundary between its bottom and Carboniferous volcanic rocks in Hala Alat mountain area, which does not meet the formation criteria. After that, a large number of volcanic rocks and conglomerates were seen in the layers corresponding to the reflection wave groups of earthquakes Ct2 and Ct3 underground in the oil region. People thought it was the underground Jiamuhe Formation, and it was determined as Permian according to sporopollen fossils. However, the relationship between the outcrops of volcanic rocks on the surface of Jiamu River and Hassan Mountain has not been seriously studied. The outcrop of Jiamuhe Formation can be traced eastward to the wellhead of Well Ha 1, and the volcanic rocks of Well Ha 1 are recognized as Carboniferous, so the age of the surface Jiamuhe Formation should also be Carboniferous. In this way, either the underground Jiamuhe Formation is not, or the underground Jiamuhe Formation is not Permian, so there is no room for reconciliation.

3.2.3 Division and correlation of Jurassic system

This is the most detailed and mature unit in the basin, but some new problems and new schemes have been put forward in production in recent years. According to the tracking of seismic wave groups in the whole basin, it is found that Badaowan Formation (J 1b) in the east of the basin is equivalent to the sum of Badaowan Formation, Sangonghe Formation (J 1s) and Xishanyao Formation (J2x) in the footwall of Wu Ke fault. Therefore, according to this idea, the division between the ground and the underground is generally adjusted and redrawn. The deepening of research and division of labor should be more and more detailed. If it doesn't taper gradually and return to roughness, it means that the contrast is wrong and it is a retrogression. A more reasonable solution should be to be able to deal with and solve various problems, rather than leaving more problems.

There are two key problems: first, it is unreliable to define Jt2 wave group as the upper coal-bearing section of Badaowan Formation; Second, there is an error in dividing the underground footwall of faults in the oil region. The lacustrine deposits in the middle and lower part of Badaowan Formation and the coal-bearing strata in the middle and upper part are divided into Sangonghe Formation and Xishanyao Formation respectively. If the thinking is wrong, the more work you do, the longer the detour you take, and the greater the waste.

3.2.4 Boundary between Cretaceous and Tertiary

This is far from the past oil and gas production, and it has become a hot topic in production since the release of gas from Ziniquanzi Formation. In the past two decades, dinosaurs, dinosaur egg skins and other related fossils have been found in the Paleogene Honglishan Formation and Wulunguhe Formation (established by Zhu equals in the mid-1950s) in the northern part of the quasi-basin, and dinosaur egg skins have also been found in the middle of Ziniquanzi Formation in recent years. It seems that these rocks should be classified as Cretaceous. According to the laws of paleontology, times can change with dinosaur fossils. However, in different places, Honglishan Formation also contains Paleocene dicotyledonous flora, Wulunguhe Formation also contains a large number of Eocene mammals, and Ziniquanzi Formation also finds rodent gum. However, these contradictory facts cannot be simply engaged in. Therefore, great efforts are still needed to find and study the stratigraphic relationship of these fossils. Is there a * * * background, or is it just a pure relationship? Until the final solution is reached, it is better to temporarily maintain the original plan or deal with it across the times.

4 About the exploration target

4. 1 The source of oil and gas in Mosuo Bay area in the middle of the basin needs to be determined as soon as possible.

Is oil and gas from Permian alone or from Jurassic mixed source oil and gas? When determining Jurassic oil and gas, it is necessary to pay attention to the difference between Jurassic oil and gas and Carboniferous oil sources, so as to be accurate and learn from the troubles and lessons encountered in the study of Cainan oil source. Different oil and gas sources will have different considerations on exploration emphases and methods. If it is Permian oil source, it may be mainly oil that entered Jurassic in the early stage, and only gas that entered in the later stage. If it is the oil and gas of Jurassic itself, if it is dominated by oil, it means that the gas that oil arrived before has passed; If gas is dominant, oil is still behind, and the southern slope area has greater prospects.

4.2 The exploration of secondary oil and gas reservoirs in the southern margin should be strengthened.

The Homatu structural belt has been proved to be an epidermal fold, and Cretaceous and Tertiary participated in the deformation. Important reservoir systems include Caraza Formation, Qingshuihe Formation, Donggou Formation and Ziniquanzi Formation. The first two are unlikely to be drilled, and the gravel porous reservoirs of the latter two are unstable, but they are realistic target beds that can be drilled. There are two urgent topics in geological research. One is how to find out the internal structure of folds and the stratigraphic distribution of fault blocks as much as possible in mountain earthquakes. The second is to study the conditions of oil production and reservoir formation in Tugulu anticline.

The discovery of Hutubi gas field has prompted people to speed up the exploration of gentle anticlines such as Anji Sea and West Lake.

The exploration engineering technology of piedmont structure in the southern margin has always been a big problem. One is how to pass through the thick mudstone layer of Haihe Formation in Anji, and the other is how to pass through steep structural passes such as Homatu and Dushanzi.

4.3 The scale of Becky overthrust fault should be ascertained as soon as possible.

The epidermis structure of Paleogene in piedmont is related to the pushing and deformation balance from the south. At present, only in the northern wing of Guqi anticline, there is obvious overthrust dislocation in Mesozoic and Cenozoic, and there is no obvious sign of reaching the sky in the shallow part; No faults were found in Tertiary system on the surface. It is reasonable that the fault should occur in the main curtain of Himalayan period at the end of early Pleistocene, and which layer is the highest fault should be carefully studied. This breakpoint is by no means an isolated phenomenon, it should extend far from east to west, at least within the scope of Homatu; It may even extend to the west. Is there any connection with the Tusi Chengbei fault? Where does it end in the east? Is there any exploration value in some parts of the upper wall of the fault? What are the hidden traps and favorable areas in the footwall? These all need to be carefully studied.

4.4 The exploration of Sikeshu sag should be further deepened.

This is a large area in the west of the basin. A lot of work was done in the middle and late 1980s and early 1990s, but it stopped because there was no breakthrough. There should be Permian source rocks suitable for hydrocarbon generation in the depression, and the surface oil and gas seedlings indicate that the oil source is guaranteed. The target layer should be mainly Mesozoic, and the field should be located in the ultra-fault zone in the northern margin fault step area. We should focus on the deep layer of Ka Indyk and its north side and choose the breakthrough point of deep well drilling.

Well Ka-6 drilled according to this idea in 2000 obtained high-yield oil and gas in Cretaceous and Paleogene. The oil production of Ka-Indyk structure has transformed the "golden body" explored in the southern margin of Junggar Basin for half a century.