(1) After the founding of New China, a large number of systematic petroleum geological surveys and explorations began. 1950 to 1954, the former General Administration of Petroleum of the Ministry of Fuel Industry (predecessor of PetroChina) entered the basin for the first time. Why northern Shaanxi, south of Qingjian and north of Tongchuan, has become the first choice, naturally has historical origins. There are not only Yanchang Oilfield that has produced oil, but also several rows of anticline belts in the southern margin of Tongchuan-Huangling Basin (Figure 3- 1).
Figure 3- 1 Structural Outline of Weibei Flexural Fold Zone in Ordos Basin
In the picture, Weibei is divided into seven secondary areas. What is really meaningful is that the two areas north of Ma Jiahe-Sujiadian indicate the location of the coal mining tunnel (Upper Shijie) from J 1f to T3.
Following the custom spread from the former Soviet Union in the early days of the founding of New China, the Northern Shaanxi Brigade explored the Triassic Yanchang Formation (T3y) and Huangling, focusing on Zaoyuan, Qiaoergou and Tsinghua in Yan 'an, extended Ganguyi, Hujiacun and Zichang Qingjian, Shimenzi in Ganquan, Silang Temple in Yijun and seven towns in Huangling. Firstly, the above points were investigated and surveyed in detail at the ground elevation1:50000-1:kloc-0/0000, and Yongping, Zaoyuan, Silangmiao and Qizhen were selected for drilling verification (142 exploration wells). Besides drilling, it is further confirmed that Yongping is a small oil field (T3y4), including 9 wells in the Silangmiao structure. Although the oil and gas display of T3y can be seen everywhere, the test was finally abandoned because it was worthless. By the end of 1954, PetroChina withdrew from northern Shaanxi and shifted its focus to Majiatan area on the western edge of the basin.
(2) The general survey of the former Ministry of Geology in the basin started with 1955 and the whole country. At the beginning of the work, there were two teams. Under the guidance of the idea of "platform margin", the Liupanshan area with Guyuan as the center in the western margin of the basin was optimized in the work area of Team 633 led by Guan Shicong. Under the guidance of "bedrock uplift", the preferred work area of Team 206 headed by Wang Yongyan is Wulange (uplift) in the north of the basin. During the period of 1955 ~ 1957, Team 633 took the Cretaceous Liupanshan Formation (K 1l) as the main target stratum, taking into account the tertiary evaluation. In the south, it reaches Jingchuan and Longxian counties, and in the north, it reaches Tongxin and Haiyuan K 1l bare land for1:200,000 census. The discovered structures such as Sikouzi, Fengchuanli and Wangdasitao were investigated in detail, and shallow wells were drilled. Oil and gas show is only found at the depth of 30 ~ 40m in structural well No.61of Miaoshan structure in the southwest of Guyuan, and a small amount of gas show is found at the depth of 20m drilled by hand in Sikouzi. It should be said that due to the limitation of means, there is no in-depth understanding of the deep Liupanshan, including the Qingshui River basin coverage area (low gravity) in Guyuan-Tongxin area.
Team 206, dedicated to "Dongsheng bedrock uplift", conducted a general survey of the top of Yimeng uplift in 1 year .20,000. In the second year, the scope of the census was expanded to Daqingshan in the north, Zhungeer Banner in the east, Table Mountain in the west, Hanggin Banner in the south and Otog Banner in the south. The main achievement is the discovery of "oil sands" (audible but invisible) in the early Cretaceous strata at the top of the "bedrock uplift" 56 kilometers long from east to west, and the delineation of four local structures (true knee bends) represented by Liugou and Changshengyuan. During this period, a total of 8 shallow wells were drilled, and the early Cretaceous oil and gas show was seen in wells Wu 1 to Wu 5, and the oil sands of Shihezi Formation (P 1-2sh) were also seen in wells Wu1,Wu 6 and Wu 7. It is also shown above and below the Lower Cretaceous/Archaean unconformity at the depth of Wu 1 Well 107.9 m..
According to the instructions of the Ministry of Geology, Liupan Mountain was put down, and Team 633 and Team 206 merged at 1957 to establish Ordos Petroleum Survey Brigade in Dongsheng. During the period of 1957 ~ 1960, the team focused on the northern part of Ordos, and continued the general survey of1:200,000 and the detailed investigation of1:50,000 under the idea of "bedrock uplift". Drilling work has been systematically carried out in the east and west of bedrock uplift, and oil and gas displays have continued to be found in the Lower Cretaceous and Permian Shihezi Formation. The Permian Shanxi Formation is also found in Well Wu 6, and a small amount of gas injection is found in the geotechnical test of Well Wu 19.
According to the decision of the Ministry of Geology, Shaanxi Petroleum Team led by Shaanxi Geological Bureau was established in Yan 'an on 1959. From 1959 to 1960, the investigation and detailed investigation were carried out in Yi 'an County in the south, Suide in the north and the Yellow River basin in the east. At the same time, it entered Duigoumen and Ganquan areas, drilled into Jurassic, and found the oil and gas display of Jurassic Yan 'an Formation.
(3)1960 65438+In February, the Ministry of Geology decided to merge the Ordos Petroleum Survey Brigade and Shaanxi Petroleum Team to form the third survey and exploration brigade (hereinafter referred to as San Pu), and the team headquarters was moved from Dongsheng to Yan 'an. Although the technical guiding ideology at this time began to pay attention to the overall study of the basin, the scope of work was the whole Ordos and its periphery. However, due to the influence of the thought of "Placanticline" at that time, in the design thought of San Pu 1960 ~ 1963, the thought of "Secondary Placanticline Structure" focusing on the gravity and magnetic anomalies in Zhidan-Qilingou was written into the design of San Pu. In the past four years, San Pu has cooperated with the Third Geophysical Exploration Brigade of the Ministry of Geology, deployed three regional profiles, concentrated its advantages to fight annihilation and dissected anomalies. This paper attempts to understand the inheritance of Mesozoic basement "uplift" At the same time, a detailed survey of1:50,000 ground area was carried out in the east of the abnormal zone, trying to find out the nature of the abnormal zone and evaluate the oil and gas prospect in this area according to the relationship between local structures and drilling.
Just like Ordos seen on the published geological map, from 196 1 to 1962, 2 1 wells were drilled in the eastern part of the anomaly zone, which confirmed that the gravity and magnetic anomaly zone of Zhidan-Qilingou did not reflect uplift in Mesozoic, and the whole northern Shaanxi was a big dip less than 1.
While denying the idea of placanticline, oil sands are generally found in wells Zhi 2 1, 22, 23 and 25 in the east of gravity and magnetic anomalies, and oil sands in wells Zhi 5, 6 and 8 in the middle are also found in Yanchang Formation of Upper Triassic. The total thickness of oil sands in Well Zhi-8 is 3 1.8 m, and oil sands of middle-upper Jurassic Yan 'an Formation are also found in Wells Zhao-4, 6, Gong-8 and Liu-kloc-0/west of Yan 'an, which are well displayed in Yanchang Formation and Yan 'an Formation of Wushen Well.
(4) In the overall study of surface geology, drilling, basin and basin mapping, the following understandings have been obtained:
Based on the overall study of the basin, the structural units of the basin are clearly divided for the first time, and it is pointed out that northern Shaanxi, which accounts for 2/3 of the basin area, is a monocline without local structure, that is, the "east slope" in Figure 3-3.
Through mapping (the whole basin), it is recognized that the line 38 north latitude, or line 2- Road 4, that is, the boundary between the loess plateau area in the south of the basin and the desert area in the north, is not only the oil-bearing northern boundary of the Upper Triassic Yanchang Formation-Middle-Upper Jurassic Yan 'an Formation in this area, but also the boundary between the fluvial facies area and the lake facies area of Yanchang Formation, and the line to the south of the boundary-the north of Yan 'an is the gentle slope estuary delta area of Yanchang Formation.
The reservoir characteristics of the upper member of Dadianxie, Yanchang Formation and Yan 'an Formation are typical lithologic reservoirs, which are "block by block" in plane and "banded" in profile. Because the porosity and permeability of Yanchang Formation are extremely low, there is no conventional fracturing (drilling and oil testing were not done at that time), and it can only be "oil is seen in the hole, but there is no flow in the hole".
Figure 3-2 Distribution Map of Paleozoic Gas Fields in Ordos Basin
A large monocline inclined to the west
1- basin boundary; 2- extend 6 isobath; 3- Lower Paleozoic gas field; 4- Upper Paleozoic gas field
During this period, through the overall study of the basin, several important achievements that should still be paid attention to are put forward.
Figure 3-3 Division and Distribution of Structural Units in Cenozoic Graben System around Ordos Basin
—— According to the study of Paleozoic sediments and tectonic palaeogeography in the east and west of the basin, especially in the Upper Paleozoic, there is an "ancient central palaeouplift" in the center of the basin (Figure 3-4).
-On the basis of studying that the sedimentary subsidence centers of Yanchang Formation and Yan 'an Formation are inconsistent and migrate every time, the concept of Mesozoic sedimentary migration from west to east is put forward.
The team of PetroChina left northern Shaanxi on 1954, took Majiatan as its stronghold, entered Lingyan work area to the west, took Yinchuan as its stronghold, and attacked the central part of Majiatan fault fold belt, and also went north to Wulange and Liupanshan areas on 1964 ~ 1965. At the same time, the Lingyan (Lingwu-Yanchi, the same below) work area was extended eastward to the trilateral area, and exploration was also carried out in Yinchuan Graben where the station was located, with the emphasis on Tertiary. The main achievement is that small oil (gas) fields such as Yimatan, Yuanyang Lake, Liujiazhuang, Lizhuangzi and later Dashuikeng and Mafang have been discovered in Lingyan area, that is, in the middle of Majiatan fault fold belt on the movable wing of the western margin of the basin and in the west wing adjacent to Tian Huan syncline (Figure 3-5).
Figure 3-4 Schematic Diagram of Upper Paleozoic Thickness in Ordos Basin
At the later stage of this stage (1964 ~ 1968), the team of geological and mineral system (San Pu) left Ordos as the main body of the basin for the first time and entered the Weihe River (Wei Fen Basin) graben on 1964.
Deny the Zhidan-Qilingou gravity and magnetic high zone as a placanticline; The phenomena of "oil in the hole", "no flow in the hole" and "three lows and none", together with the understanding that the basement in northern Shaanxi is too stable, the cover is too flat and the rocks are too hard, were influenced by the breakthrough of Cenozoic rift basin in East China and North China at the end of 1963 (at this time, PetroChina discovered the gushing layer of Shahejie in Well Hua 8), and the team attended the national meeting of the Ministry of Geology.
During the period of 1964 ~ 1968, the Weihe work area passed from north to south and from east to west, including 7 deep wells and 2 shallow wells. The seismic team worked for nearly 12 years (including the seismic team and drilling rig sent to the northern Hetao basin in the later period), which proved that the characteristics of Weihe basin were as follows:
Figure 3-5 Distribution Map of Oil and Gas Fields in Ordos Basin
1- drilling; 2- Building partition lines; 3- Oilfield; 4- Paleozoic gas field; 5- Ancient river course; 6— Yanchang Formation (T3y) Oil-generating Area
It denies the previous understanding of shallowness, smallness, fragmentation and redness, and proves that this is a new deep semi-graben attached to the North Qinling in Cenozoic (Figure 3-6a-b) (the main sedimentary body of Tertiary is Miocene-Pliocene, the bottom boundary of Quaternary reaches 2,400 m in WC-4 well, and the bottom boundary of Neogene reaches below 5,200 m in the southwest of the basin).
The basin was formed on the uplift background of Mesozoic "North Qinling" axis. The Ordovician in the northern part of the basin is below Miocene-Pliocene, and the Precambrian in the southern part of the basin is below Miocene or local Eocene-Oligocene.
Lacustrine source rocks similar to Shahejie Formation in North China have not been found, and the Paleogene (Bailuyuan Formation and Honghe Formation) seen locally are all red beds. The only dark lacustrine deposit (Yongledian Group 1 ~ 3 Group) is actually the simultaneous heterogeneity of Sanmen Group of Quaternary (Figure 3-7).
Fig. 3-6a Simplified Schematic Diagram of Weihe WH-ⅸ Line Interpretation
Figure 3-6b Schematic Diagram of the Central Section of Weihe Graben
Fig. 3-7 Lithofacies Profile of Sanmen System (Yongledian Group 1 ~ 3 Group) passing through the south and north (surface-underground) of Weinan.
2. The second stage (1969 ~ 1975)
—— "Going home", ushered in the battle of Changqing Oilfield, broke through the Qing, Hua and Wu Dynasties, and reached the first step of petroleum geological reserves of the Lower and Middle Jurassic Yan 'an Formation (J 1-2y) in the south of the basin.
The petroleum exploration work of the geological department of Ordos Basin has gone through 1964 ~ 1968 and 1968 in Weihe area for 14 years. During this period, "I used the oil exploration theory of platform margin depression (referring to Liupanshan Mountain) and platform margin uplift (referring to Wulange), and then used the oil exploration experience of Daqing placanticline and Cenozoic fault depression (referring to northern Shaanxi and Weihe River) to make a big turn in the basin ... Although I have accumulated a lot of geological data and experience and lessons in oil and gas exploration, I have not found industrial oil gas flow, nor submitted an oil and gas field to the country, and none of them can be sure. The whole team is caught in a dilemma (Exploration and Discovery of Oil and Gas in China, page 289).
At the end of 1968, Wang Lin, the brigade commander, and Sun, the engineer, launched a big discussion on the direction and how to find oil in order to deploy the next phase of oil and gas exploration. The focus of discussion: first, whether to stay in Weihe River and Hetao to continue working; The second is to return to which area of Ordos basin; The third is to choose a new district, where is the new district ... (ditto) ". The brigade sent Sun and workers' representatives back to Beijing to report to Minister Li Siguang. After listening to Sun's opinions on the Weihe River and the Hetao Basin, the Minister said according to his consistent theory on the three subsidence zones in eastern China: "Songliao, North China and Jianghan have all produced oil in the second subsidence zone, then the Shaanxi-Gansu-Ningxia Basin (Ordos Basin) and Sichuan Basin in the third subsidence zone, as well as the two basins from the north to the Mongolian People's Republic (referring to the oil-producing East Gobi and Qiao Balsam Basin)." The situation in the Shaanxi-Gansu-Ningxia basin is somewhat similar to that in the Sichuan basin ... There is no problem with the existence of source rocks here, so we should return to the Shaanxi-Gansu-Ningxia basin. As Yishan shield, the middle part of the basin is worth doing, so we should be close to it. After the minister finished speaking, Comrade Li Haiyun asked the minister, "Shall we go back to our hometown?" ? "The priest said," Yes, I just want to go back to my hometown! (For details, please refer to Minister Li Siguang's conversation record 1968 of February 23rd, Oil and Gas Exploration and Discovery in China, page 289). The opinions of the broad masses of workers in San Pu and Li Siguang's instructions were supported by the leaders of the geological department who listened to the report together. San Pu 1969 Petroleum Survey Area was transferred from Weihe River and Hetao to the south-central Ordos Basin.
Going back to Ordos, where the breakthrough is chosen is the key to opening up the situation. Through the overall analysis of the basin area, we think that Ordos was a large inland depression when the Upper Triassic Yanchang Formation (T3y) was deposited, and it was an overlying depression (foreland) basin based on the inland platform. Qing, Hua and Wu areas are at the junction of stable area (northern Shaanxi) and active area (western margin), which is a thick and thin sedimentary zone. According to this rough idea, combined with the old electrical method and new earthquake results in Qingyang-Huachi area, Qingshen Well and Huashen 1 Well were boldly deployed in Qingyang and Huachi Mountain Villa. Among them, the well Huashen 1 drilled on Huachi Dianlong was flooded in summer. Although 10 oil sands with a total thickness of 74.5 meters were seen in the upper part of Yanchang Formation, they still had to be abandoned. According to the "uplift" of San Pu 342 Geophysical Exploration Team on the SH-Z survey line, Huashen 2 well was drilled in the villa.
The 19 oil and gas reservoir was discovered in Yanchang formation and Yan' an formation in Qingshen well. In the process of oil testing, the well learned the lesson that "the hole does not flow" because of low permeability. The author and Li Binggang went to Yumen Oilfield together and invited the fracturing team of Yumen Oilfield of CNPC. 1August, 970, two groups of four-layer fracturing sand blasting tests were carried out on this well (the first fracturing well in the Ministry of Geology and Mineral Resources), which made the well "from non-production to production, from production to intermittent spontaneous flow (spontaneous flow is 40m higher than that of the 823 wellhead, 1970)", thus breaking through the Longdong oil outlet and causing Lanzhou Military Region and PetroChina.
In May, 1970, Huashen 2 well in Huachi Mountain Villa. Because good oil sands were discovered in the Lower Jurassic and Middle Jurassic Yan 'an Formation for the first time, drilling and oil testing were completed in advance at the well depth 1367.6m, and the daily production reached the record of 30.3m3/ day at the beginning of August 28th.
The breakthrough of Qingshen well and Huashen 2 well has accelerated the exploration pace in Longdong area. 1In September, 970, the Ministry of Fuel Chemical Industry submitted a report to the Central Committee, requesting the Lanzhou Military Region to organize the Shaanxi-Gansu-Ningxia Petroleum Battle. 165438+1October 5 ~ 10, a campaign cooperation meeting was held in Lanzhou, which was hosted by Lanzhou Military Region and attended by the military divisions of the three provinces of Shaanxi, Gansu and Ningxia and more than 40 units. On behalf of San Pu, the author gave a report on oil and gas exploration in Wu Qinghua to Tang Keji, Vice Minister of the Ministry of Fuel and Chemical Industry. Tang Ke suggested that San Pu withdraw from the breakthrough areas of Qingyang and Huachi, and return to northern Shaanxi with the task of "reconnaissance of Wuqi with strength and reconnaissance of Zoumawan with firepower".
From February 197 1 year, San Pu first broke through Well Wu L 14 m3/d, and in August of the same year, Well Wu 2 1. 1 m3/d and Well Wu 8 (Zhangping)108. 1974, San Pu moved to Zhidan, and the output of Yong 2 well reached 23.7 m3/d, breaking through the oil outlet of Zhidan county.
From 1969 to 1973, 22 wells were drilled in Qingyang, Huachi, Wuqi and Zhidan areas, and almost every well showed oil and gas, mainly in Yan 'an Formation. Of the 16 wells tested, 13 wells obtained industrial oil flow.
This is the origin and context of the two concepts of "going home" and "celebrating China and Wu". "Because of the breakthrough in Wu Qinghua, at the Xi Petroleum Geology Symposium held by the Geological Bureau of the State Planning Commission in June 1973, the author introduced the experience of breaking through the Ordos Basin on behalf of San Pu, which was valued by the delegates. 1April, 980, at the national geological system awards conference held by the Ministry of Geology, San Pu was rated as an outstanding contribution unit in geological prospecting. In order to summarize the petroleum geological survey in Ordos Basin in the past 20 years, Sun, Xie, Sun Guofan and Li Longyun completed the compilation of 1974 Summary Report on Geological Achievements in Petroleum Exploration Stage in Shaanxi-Gansu-Ningxia Basin. Starting from the whole basin, focusing on Triassic and Jurassic, and focusing on the discovery of Wu Qinghua, this report summarizes the law of oil and gas occurrence in Wu Qinghua area and puts forward the direction of oil and gas exploration. The exploration mode of bottom exploration of Jurassic sandstone oil and gas fields with the connotation of "two grids" and the occurrence law of stratigraphic lithologic oil and gas reservoirs with the ancient river channel and lakeside delta as the main body enrich the geological theory and exploration methods of continental oil and gas fields in China. The Discovery of Oil and Gas Fields and Lithofacies Paleogeographic Features in the Shaanxi-Gansu-Ningxia Basin, People's Republic of China (PRC) Petroleum Atlas (Ordos Part) and 5200m Open Hole Drilling Technology won the National Science Conference Award in 1978 (Oil and Gas Exploration and Discovery in China, 29 1 page).
During the same period, the main fighting forces affiliated to PetroChina successively organized campaigns such as "encircling Maling, expanding the city (ditch) and the middle pool", "developing Wuqi, attacking Jiyuan", "marching into the border" and "opening up two rivers (Luohe and Hulu)". "Six oilfields, including Maling, Cheng Hao, Huachi, Nanliang, Wuqi and Mafang, have been proved, and there are 16 oil production points in Shanzhuang, Liu Ping, Wujiao, Shang Liyuan, Hechuan, Heihe, Yanwu, Qingyang, Jiyuan, Xuecha and Shunning". "A new Jurassic paleogeomorphic river sand-oil area stands tall in China Loess Plateau" (Yang Junjie, 2002, P 166) (Figure 3-8, Figure 3-9).
3. The third stage (1975 ~1982)-going down the Weihe River and breaking through Inner Mongolia.
Go down the Weihe River again.
1970 September 17, the Geological Bureau of the State Planning Commission assigned San Pu to the Geological Bureau of Shaanxi Province and renamed it Shaanxi Petroleum Survey Brigade. Therefore, in the previous stage of the battle, when accepting Minister Tang Ke's "Power Reconnaissance Wuqi, Fire Reconnaissance Zoumawan", according to the requirements of the province, the author added some words with local color to the geological design of San Pu in 197 1. In this way, San Pu has a team from northern Shaanxi to Guanzhong and then to southern Shaanxi.
Second, the steps to the Weihe River are west first and then east. Focus on Paleogene in Xi 'an sag. By 1975, the Xi 'an sag had an earthquake of 2546km, with a controlled area of 5700km2. Five deep wells were drilled, and the footage was19501m. Among them, Shen Wei 10 well, with a depth of 5,205 m and an open hole interval of 49 13m, set three records of the deepest systematic drilling, the longest open hole drilling and the deepest coring at that time. The well is located near Qinling Mountains, and 52 10m does not penetrate the Neogene (it is reported that it is the top of Oligocene). Later, five deep wells were drilled in Gushi sag in the east, with footage 14369m and an earthquake of 2270km. In addition to the comment that "three-month-old hens can't lay eggs" (which means the source rocks are immature), Shangweihe's exploration conclusion is a further supplement to a round of negative conclusions.
Ershang Weihe River entered Sanmenxia eastward due to geological and drilling work. In a series of small northeast grabens attached to Xiaoqinling, dark strata, represented by the Paleogene Xiangcheng Formation, were found, thus linking Xiangcheng Formation with the northeast Walnut Garden Formation in Nanxiang Basin across Qinling, and calling the small northeast grabens distributed on the western Henan uplift "western Henan Graben System" respectively, including the near east and west sides of Zhoukou and Hefu Basin or the first one in NWW direction.
Figure 3-8 Early Jurassic Paleogeomorphic Zoning Map of Southern Ordos Basin
1- Oilfield; 2- Palaeogeomorphic zoning; 3-oblique angle; 4- water collection triangle; Five-finger mound; 6— Slope of lateral erosion; 7-Yan 10 deletion region
Break through inner Mongolia
1975 After the establishment of the State Geological Bureau, San Pu returned to the State Geological Bureau and resumed its name. 1976,1/At the first Changsha meeting held in June, 2000, the General Administration gave San Pu the task of 1977 to go north to Inner Mongolia, striving to break through the oil export barrier of the Upper Paleozoic in that year. In the design book of San Pu 1976, the design content of "focusing on Yimeng, preparing for Hetao, grasping the ancient times and developing the ancient land and sea simultaneously" is written. Of course, the focus of 1977 is to strive to achieve the task of "trying to break through the oil export barrier in Inner Mongolia" entrusted by Su Yunshan, deputy director of the Petroleum Bureau of the State Geological Administration, at the Changsha meeting.
Figure 3-9 Relationship between Oilfield Distribution of Yan 'an Formation in Southern Basin and Early Ancient Channel of Yan 'an Formation
(According to Changqing Oilfield data)
1- Oilfield; 2- Ancient river course; 3-There is a far-off scenic spot; 4- Delete extension 10 or pinch-out area
There are more than four completely different opinions on the choice of breakthrough well location in the north, which is also the first well location in Inner Mongolia. The author was inspired by the report of the Shen Shi 1 well drilled by China Petroleum and Natural Gas Corporation in the north of Shiguhao. "Why not try the Permian Shihezi Formation 18m oil sands?" "Isn't it a copy of Wu Shenjing from Wuqi in northern Shaanxi?" Thirdly, with the support of Wang Qingbin, the team leader at that time, and Li Haiyun, the person in charge of Inner Mongolia work area, the author arrived at the site in the winter of ice and snow in Inner Mongolia on 1976, and set up a new Yishen 1 well at the "stone trough nose high point" less than 100m from the old well. The well was started in June 1976, and it was completed after drilling to 22,962 meters of pre-Sinian gneiss in the basement. The Permian Shihezi Formation is directly unconformity covered on Archean metamorphic rocks. Oil and gas show is common in the 6-8 sand layer of Shihezi Formation of Permian, which was tested on July 1977. The bottom four layers are tested together, and the daily production 15920m3 natural gas flowing is obtained without fracturing technology, while the upper sand layer obtains 10000m3 natural gas and 1m3 condensate oil.
Figure 3- 10 Schematic Diagram of Graben System in Western Henan Province
Sanmenxia belongs to Wei Fen Graben.
Although the work of Yishen 1 well was not smooth for a period of time, Ordovician weathering crust and its interior (I 13 and I 15), Middle Carboniferous, Upper Carboniferous and Permian Shanxi Formation (I3 and I 16) were still seen in some wells. The exhibition scope expanded from the east side of the north to the south section of Table Mountain in the west.
1In May, 982, after the establishment of the Sino-Japanese cooperation team (earthquake), the combined well (Damiao Township, Otok Banner) determined by both parties produced 20,700 cubic meters of gas per day and 0.4m3 of condensate oil. At the same time, low production or low production indications from Shihezi Formation to Ordovician were also found in wells I 17, I 13 and Yi Bei 24 in Yulin area. Among them, the initial production of Well Yi 17 is only 2006 m3/d, and it reaches 37 m3/d after fracturing. Four layers of gas were discovered in Ordovician in Well Yi-24, with a daily production of 267 m3.
At the end of this period, Changqing Oilfield made a breakthrough in the exploration of Yan 'an Formation in the battle. The annual output of crude oil in Changqing Oilfield exceeds 6,543,800 tons, and the total annual output is close to 2 million tons. During this period, three oil pipelines with a total length of nearly 500 kilometers to Lanzhou were completed.
4. Since 1990s (1983 to present)-The great development period of oil and gas in the basin led by China Petroleum and Natural Gas Group Corporation (abstract)
Under the guiding ideology of "pressing Yanchang Formation, taking large oil fields" and "grasping the delta in the east and looking for lake bottom fans in the west", PetroChina has taken Ansai large oil field with geological reserves of105160,000 tons.
In the late 1970s, after the peak of Jurassic reserves in basin exploration passed, it became a top priority for PetroChina to expand oil and gas reserves. Yanchang Formation "is not only an ideal replacement layer to make up for the oil and gas production of Yan 'an Formation in this area, but also a risk object that needs to be tackled emphatically". On the basis of summarizing the unsuccessful experience of 1973 to 1975, they added the idea of "grasping the eastern delta" this time (1983), taking Yanchang formation delta in northern Shaanxi as the object and Ansai as the breakthrough first. As a result, the first batch of exploration wells were successively successful, in which the daily oil production of Well L (Chang 2) was 64 tons, and that of Well Sai 5 (Chang 2 and Chang 6) was 18.3 tons ... Later (1985 ~ 1986), Well Sai 37, Sai/kloc. Therefore, it is proved that Ansai Yanchang Formation is a large oilfield in lake delta, with proven oil-bearing area of 206km2, geological reserves10156x104t, controlled reserves of 3300x104t and associated gas of 50x108m3 (attached figure 3
Breakthrough period of northern Shaanxi gas field (1986 ~ 1994)
In the early 1980s, PetroChina withdrew from the Hetao because of its "thick skin and deep flesh" and entered the central part of the "Shrinking Salt Pottery" basin and the western part of Shanxi, and then drilled Qishen 1 well and Zhou 1 well in northern Shaanxi. The natural gas output of weathering crust at the top of Majiagou Formation of Lower Ordovician is 65438 0.73 and 40000 m3/d respectively. The field 1 well located on the syncline Tianchi structure also obtained the flow of160,000 cubic meters/day in the middle Ordovician Cremorie Formation.
1988, PetroChina Research Institute cooperated with Changqing Oilfield to drill a scientific exploration well in Jingbian. At the same time, from June 27th, 1989 to July 27th, 1, Changqing Oilfield held a seminar on natural gas development strategy and tactics in Qingyang. After discussion, the following four questions were clarified:
Firmly confident to find large and medium-sized gas fields in the middle of the basin.
Unified search for the main direction of gas field-the understanding of ancient uplift in Central China (see below for details).
The function and significance of the top erosion surface of Ordovician are emphasized.
Make clear the guarantee function of exploration strategy (especially fracturing technology).
In 1989, high-yield natural gas flows of 28.3× 104m3 and 13.8× 104m3 were obtained in the weathering crust at the top of the lower Ordovician, respectively. Through exploration practice and comprehensive research, the weathering crust at the top of the middle Ordos Basin was successfully discovered.
Up to now, starting from 1969, China Petroleum Group Company has developed 22 oil fields for the early and middle Jurassic ancient rivers, with the cumulative proven oil field area of 156.8km2 and the petroleum geological reserve of 2.33x108t. ; With the discovery of large delta oilfields in Yanchang Formation of Ansai, five oilfields, namely Jing 'an, Anzhenbei, Xiasiwan and Zhiluochaiyao, have been discovered one after another. Accumulated proven oilfield area 1002. 1km2, and petroleum geological reserves of 5. 1077× 108t. In addition, five small oil fields (Yanchang and Yongping) in Yanchang oil mine have been discovered. Eight gas fields have been discovered (Liujiazhuang, Shengli Well, Zhenchuanbao, Zhongbu Gas Field, Shenmu, Yulin, and Sulige in Uxin Banner), and the accumulated proven natural gas reserves are 7504× 108m3. Among them, Sulige gas field, which was discovered more than two years ago in the middle part of the northern basin, has drilled 2l wells within the range of 20000km2 and obtained natural gas wells 1 1. The main gas reservoir is He 8, with sand body width 15~40km, length 15 ~ 40k m, thickness of 20 ~ 45m and thickness of 65 ~ 45m. Porosity 12% ~ 14%, permeability10×10-3-62.7×10-3 μ m2, and the average open flow of a single well is 25×104m3. Controlled reserves 1000× 108m3 (proven reserves in autumn 2002 are 6000× 108m3) (Figure 3- 13, Figure 3- 14).
Figure 3- Late Triassic Paleogeographic Map of Ordos Basin +0 1
Pay attention to the location of the delta
Fig. 3- 12 regional anatomy and drilling effect map of late Triassic delta system in northeast Ordos basin
1- well location; 2- oil well; 3— sand body contour; 4- Lake shoreline; 5- Delta front; Liuduan line
If you draw the work and election experience of the Ministry of Industrial Geology in Ordos since 1949 on a map, you can see the following characteristics (Figure 3- 15).
1968 The end of reporting to Minister Li Siguang's history after returning to his hometown is an important dividing line in the history of oil and gas exploration in this basin. In the first 20 years, although the scope of small oil fields in northern Shaanxi was expanded and several anticline small oil and gas fields were discovered in Lingyan area, there was no leap in the development of petroleum industry in terms of ideology, output and reserves. Twenty years after "going back to my hometown", it's different. First, with the idea of "get out of the way, occupy both sides", we won six Jurassic oil fields represented by Qing, Hua and Wu in "Old Jurassic is not enough friends". Then, under the concept of Triassic delta, five 100 million-ton oil fields north of Yan 'an-Wuqi, represented by Ansai, were won. After oil flow was found in the weathering crust at the top of the Lower Ordovician in Well Yu 3 and Well Shenshan 1 in northern Shaanxi, the Ordovician northern Shaanxi (Changqing) gas field in the middle of the basin was discovered under the background of realizing the idea of "ancient central uplift".
Figure 3- 13 Natural gas exploration results of Upper Paleozoic in Ordos Basin
It took less than five years from the investigation of Songliao Basin to the discovery of Daqing Oilfield (1955 ~ 1959). It took only six years for North China to start oil production in Well Hua 8 from 1955, including a low tide and a period of "south first and then north" ... Why did the exploration work in Ordos go through a tortuous history of decades from discovery (1907) to real breakthrough?
Figure 3- 14 Isothickness Map of Sandstone of Lower Shihezi Formation of Middle Permian in Ordos Basin
According to the law of oil and gas field scale discovery in a region (basin), large oil (gas) fields are always discovered in the early stage. Why are the discoveries of large oil and gas fields, such as the gas field in central Ordos, all in the later stage of exploration?
On the basis of introducing what I know about the landscape of Ordos Basin, the author wants to focus on the idea of guiding exploration and summing up historical experiences and lessons to start with some understanding and discussion.
Fig. 3- 15 schematic diagram of petroleum survey work area in Ordos basin (1955 ~ 1969)
(See Qiu et al. in PetroChina Work Area, 1999)