1) structural system and sedimentary system characteristics and the prototype of the basin.
2) The development and resource richness of source rocks.
3) Discovered oil and gas fields.
4) degree of oil and gas exploration, etc.
6.2.2 Prediction of oil and gas exploration areas
Ordos basin has the characteristics of multi-generation and multi-layer oil generation and storage. Hundreds of oil and gas fields, 6 gas fields and 5 large oil fields have been discovered, and oil and gas resources are very rich. According to the new progress of oil and gas exploration in recent years, the author thinks that the basin is rich in gas and the semi-basin contains oil (south), and the optimization of favorable areas (zones) is determined according to the existing exploration situation (Figure 6- 1).
6.2.2. 1 natural gas
On the basis of comprehensive geological research and zoning evaluation of the basin, combined with exploration degree and resource base, seven exploration targets were selected. Sulige-Hangjinqi area in the north of the basin, Zizhou-Mizhi area in the east of the basin, northwest of the basin, under salt in the east of the basin, southwest and southeast of the basin (Figure 6- 1).
Fig. 6- 1 oil and gas evaluation selection map of Ordos basin
(1) Sulige-Hangjinqi area in the north of the basin
The exploration area in this area is large, and significant progress has been made in the exploration in the east, west and north in recent years. It is suggested that the next exploration target should mainly develop to the west, south and northeast.
1) West: In the past, it was thought that the whole western region was affected by Tian Huan sag and might contain water. Exploration in recent years shows that there is no unified gas-water boundary in the west, and the distribution of the whole gas layer is not controlled by regional structure. Good gas-bearing signs can be seen in the exploratory well drilled to the lower part of the structure. For example, several exploratory wells, such as Well Su 36, Well Su 37, Well Su 38, Well Su 40, Well Qi Tan 1 and so on, which are thrown out in the direction of structural inclination, all encounter the gas reservoir of Member He 8 with a thickness of 6.9 ~12.3m; Gas test production of Well Su 17511.31×104m3/d (AOF). The future goal is to further expand the gas-bearing range in the west and ensure the scale of reserves.
2) The south is an extension of Sulige sedimentary system to the south, mainly located in the delta front sedimentary facies belt, and underwater distributary channel sand bodies are developed. At present, two gas-bearing sand belts, Su 124 and Lian 5, have been implemented in this area as a whole. The lithology is mainly medium-coarse grained timely sandstone, with industrial gas wells 1 1 well. The goal is to expand the scale of reserves.
3) There have been new discoveries in Northeast China recently, so it is necessary to intensify exploration and strive for new discoveries.
(2) Jingbian-Yan 'an area in the middle of the basin.
This area has a large exploration area and is a compound gas-bearing area of upper and lower Paleozoic. The underwater distributary channel sand bodies developed in Shihezi Formation 8 of Upper Paleozoic have the characteristics of large thickness, good lateral continuity and stable distribution. The reservoir is dominated by timely sandstone, and the pore types are mainly dissolution pores and intergranular pores, with common gas. There are 28 industrial gas wells with a gas-bearing range of over 6000km2. Lower Paleozoic Mawu 1+2 and Mawu-4 gas reservoirs are stable in distribution and have similar karst reservoir characteristics to Jingbian gas field. Gypsum is the main pore type, with good physical properties and gas-bearing property, with an average porosity of 4.4% and a permeability of 0.58× 10-3μm2. There are 9 industrial gas wells, and the favorable exploration area exceeds 1000km2.
Through further exploration, the gas field scale can be formed in this area.
(3) Zizhou-Mizhi area in the east of the basin.
The eastern part of the basin is a multi-layer gas-bearing system with an exploration area of 15000km2 and 62 industrial gas wells. The main target strata are Shihezi Formation, Shanxi Formation and Taiyuan Formation.
The intensity of hydrocarbon generation in this area is high and the supply of hydrocarbon sources is sufficient; Many sets of reservoir sand bodies with different genesis and types are developed. Natural gas mainly migrates vertically, and gas layers are distributed in all layers of Upper Paleozoic, which has the characteristics of multi-layer compound gas.
In view of the characteristics of shallow burial and many gas-bearing layers in the Upper Paleozoic in the east of the basin, in order to further improve the efficiency of single well production and exploration and give full play to the productivity of each gas layer, it is appropriate to carry out fracturing reconstruction technology experiments in multi-layer large intervals, so as to provide a backup site for the next step of natural gas productivity construction.
Through further exploration, the eastern region is expected to form a reserve scale of 6000× 108m3.
(4) Northwest of the basin
This area is located in the north of Tianhuan sag, with a favorable exploration area of 6000km2. The main target beds are Ordovician Christen Formation, Permian Shihezi Formation and Shanxi Formation. The degree of natural gas exploration in this area is relatively low. The 2D earthquake completed 9 10km, and five Paleozoic exploratory wells were drilled, among which Qitan 1 well obtained gas-bearing indications in Christen Formation and Upper Paleozoic, and Tiekou 1 well obtained good gas-bearing indications in Upper Paleozoic.
Reef-beach facies deposits are developed in Christen Formation of Ordovician, and it has been confirmed that the distribution area of reef-beach bodies is 437km2. Pore types such as dissolved pores, intergranular pores and reef skeleton pores are mainly developed, which can form good reservoirs and have good exploration prospects.
In Upper Paleozoic, reservoir sand bodies controlled by NW provenance developed, with the thickness of the sand body in He 8 member being 15 ~ 40m and the thickness of the sand body in Shan/kloc-0 being 1 0 ~ 20m ~ 20m. The lithology is mainly timely sandstone and cuttings timely sandstone, with an average porosity of 5% ~ 1 1% and an average permeability of.
By deepening exploration, it is expected to open up a new field of carbonate exploration, form a certain reserve scale and an important exploration replacement field.
(5) Huating area in the southwest of the basin.
The exploration area in this area is 16000 km2, and the exploration degree is low. Among them, Zhentan 1 Jingshan 1 gas test obtained the industrial gas flow. The main target strata are the Upper Paleozoic Permian Shihezi Formation and Shanxi Formation.
Delta plain and front sand bodies controlled by southwest provenance are developed in Permian Shan 1 He-8 member. The sand body is large in scale, mainly composed of timely sandstone, and the pores are mainly intergranular pores and granular dissolved pores, with good physical properties and gas-bearing properties. In contrast, the mountain 1 sand body has a stable plane distribution, and the thickness of the main reservoir sand body is 7 ~ 10m, with good gas-bearing property. The gas test in Zhen 1 Jingshan 1 section has obtained industrial gas flow, indicating that the southwest of the basin has a good exploration prospect and is expected to form an atmospheric field.
(6) Subsalt target area in the east of the basin
This area is located in the middle-east of Ordos Basin, with the structural position on Yishan slope and the exploration area of about 10000km2. Six wells (Yu 9, Mi 1, Zhenchuan 1, Longtan 1, Fu 5, Shank 1) have been drilled in this area, of which Longtan 1 well has been tested in Mawu 7 section, and the gas flow rate is 407m3/d..
There are many sets of source rocks in Lower Paleozoic in this area, with a cumulative thickness of more than 20m. The reservoir is mainly dolomite with intergranular pores and intergranular dissolved pores. The Ordovician salt rocks cover an area of over 4× 104km2 and are well preserved. After further exploration, a new exploration field of carbonate rocks can be formed, and the estimated reserve scale is (3000 ~ 5000) × 108m3.
(7) Fuxian-Yichuan area in the southeast of the basin.
This area is located in the southeast of Ordos Basin, with an exploration area of1.2000 km2. The exploration degree in this area is low, and there are only 5 Paleozoic exploration wells (Iraq exploration well 1, Yi 2, Luo 1, Yi 5, Yi 6) and 5 Paleozoic exploration wells (Hong 3, Fu exploration well 1) around the exploration area.
This area is located at the southern end of the hydrocarbon generation center of Upper Paleozoic, with the thickness of Carboniferous-Permian coal seam of 3 ~ 8m, dark mudstone of 30 ~ 70m and Carboniferous limestone of 2 ~ 18m. Among them, the organic carbon content of coal seam is 73.6% ~ 83.2%, which is the main hydrocarbon source bed in this area. The thickness of CAMBRIAN-Ordovician carbonate rocks is above 500 ~ 1000 m, and the residual organic carbon content is 0. 13% ~ 0.20%, which has certain hydrocarbon generation potential. At present, the cumulative hydrocarbon generation intensity is (15 ~ 45) × 108m3/km2, and the cumulative hydrocarbon generation amount is 24.4×10/2m3, so the hydrocarbon source conditions are good.
The southeastern part of the basin was mainly supplied by the ancient Qinling Mountains in the Late Paleozoic, and the river flowed into the lake area from south to north on the Fuxian-Yichuan line. Favorable reservoir sand bodies are mainly developed in the 8th member of Shihezi Formation and Shanxi Formation 1 member of Lower Permian. The thickness of the 8th member of Shihezi Formation can reach 10 ~ 20m, the porosity is 8% ~ 1 1%, and the permeability is (0.2 ~ 0.6) × 10-3 μ m2. The thickness of mountain 1 sand body can reach 5 ~ 12m, and the lithology is light gray lithic sandstone and grayish white feldspathic lithic sandstone, with porosity of 5% ~ 10% and permeability of (0.1~ 0.4) ×10-. The gas production of well 1 well box 8 should be 0.44 1× 104m3/d, and the industrial gas flow rate is 3.500× 104m3/d, which is obtained by well testing in the underground stone box group of well Fugu 5 in Zhongyuan Oilfield in the north of the exploration area. The Luo 1 well, which was drilled in 2004, encountered 19m cuttings sandstone in the 8th floor of Lower Shihezi Formation in Upper Paleozoic. 6.6 m sandstone was drilled in the eighth member of Upper Paleozoic Lower Shihezi Formation in Well Yi-5, and 7. 1.6 m sandstone was drilled in the second member of Shanxi Formation. The gas-bearing layer in logging interpretation is 1.6m. The analysis shows that the Upper Paleozoic in this area has great exploration potential.
The Ordovician Majiagou Formation is located on the northern slope of the central paleouplift in the southern margin of Mizhi Salt Lake, and the Caledonian weathering crust is located in the development area of constructive karst reservoirs in karst terraces. Gypsum-bearing dolomite and algal dolomite at the top of Majiagou Formation have been transformed into dolomite karst reservoirs with large distribution through multiple transformations such as quasi-syngenetic interlayer karst, weathering crust karst and acid water karst during burial. The types of reservoir pores in 1 well and adjacent exploration wells are intergranular pores, intergranular dissolved pores, dissolved pores (holes), gypsum mold pores, micro-fractures, etc. Generally, the porosity is 3% ~ 6% and the permeability is (0.10 ~ 2.48) ×10-3 μ m2. Mawu 6 interpretation of Ordovician Majiagou Formation in Well Yi-2 has two gas reservoirs, both of which are ***5.0m, with an average porosity of 3.27% and an average permeability of 0.24× 10-3 μ m2. The top horizon of Well I6 is Ma 6 member of Majiagou Formation of Ordovician, Ma 5 member 1+2 interpretation gas layer 4, ***9.6m, with an average porosity of 2.4 1%, an average permeability of 0.1×/kloc-0-3 μ m2, and a gas test output of 2.0822. Further deepening geological research is expected to form the reserve scale of large gas fields.
6.2.2.2 Petroleum Company
(1) northern Shaanxi
Northern Shaanxi is located in the middle of Ordos basin, and the main target layer is Chang 6 oil layer. In the process of large-scale delta construction, multi-stage underwater distributary channel and estuary dam overlap each other, forming a large-scale delta group, which effectively guides the fine exploration in northern Shaanxi and realizes the compound contiguous oil area. In recent years, on the basis of previous research and exploration results, the research on sedimentary microfacies, distribution law of reservoir sand bodies and oil migration and accumulation mechanism has been further deepened, and new progress has been made in fine exploration. At present, seven oil-rich areas have been discovered in Chang 6 1 and Chang 62 reservoirs, covering an area of 450km2, with proven reserves exceeding 2.0×m8t.
Chang 8 oil layer is a newly discovered oil-bearing series in the old area of northern Shaanxi. At present, 26 wells have drilled into oil layers with an average thickness of 5.6 m, an average porosity of 8.6% and a permeability of 0.43× 10-3μm2. There are 0/5 industrial oil flow wells/kloc-,and the average oil testing output of a single well is 6.44t/d, with a maximum of 20.66.
In recent years, in order to solve the problems of shallow reservoirs in northern Shaanxi, such as shallow burial, low pressure and temperature, and difficulty in flowing back after fracturing, fracturing technology has effectively improved the gel breaking effect and made important progress in shallow oil exploration in northern Shaanxi. In the past three years, 68 industrial oil flow wells have been obtained in shallow oil layers in northern Shaanxi, with an average oil production of 12.5t/d and a maximum oil production of 7 1.66t/d (sickle 4 1 well). At present, five favorable areas have been found in this area, with a reserve potential of 2.0× 108t, which will become another important way for Changqing Oilfield to achieve the resource development goal of 5,000×104t.
(2) Xifeng Oilfield and its surrounding areas
This area is located in the southwest of Ordos basin, and the proven Maling oilfield in this area in the 1970s is mainly Jurassic reservoir. In recent years, on the basis of deepening the study of sedimentary system and reservoir distribution scale in this area, oil exploration has made great discoveries with the goal of "finding Maling under Maling" and based on the main target layer of Chang 8 and Chang 3 oil layer. Eight oil-rich areas, including Zhen 83, Li 47 and Huan 42, have been found in Chang 8 oil layer, with a favorable oil-bearing area of about 800km2 and a reserve scale of 4.0× 108t. 2 1 Chang 3 oil-bearing favorable area was found in Chang 3 oil layer, with an area of about 200km2 and a reserve scale of 9000× 104t. Through further exploration and evaluation, it is estimated that the reserve scale will be more than 10× 108t, which sets a new production target for Longdong area to achieve the annual output of 800× 104t.
Chang-7 is the oil layer in the maximum lake invasion period, with turbidite sand body and good reservoir-forming conditions. Well Li 17 and Well Cheng 7 1 tested in Longdong area in 2009 obtained industrial oil flows of 2 1.08t/d and 10.46t/d in Well Chang 7, respectively, and great progress was made in exploration. At present, there are 79 industrial oil streams, and the average well testing output is 8.58t/d, with a maximum of 50. 1t/d (Li 47). Six oil-rich areas were discovered, and the replacement of new strata in the lower part of the old area of Maling Oilfield was realized.
At present, Chang 7 in the basin has drilled 122 wells, completed well testing 108 wells, and obtained industrial oil flow of 7/kloc-0 wells. The average oil testing output of a single well is 8.50t/d, and the highest is 56.45t/d, making it a series of exploration worthy of attention.
(3) Jiyuan area
This area is located in the middle and west of Ordos basin, and it is a multi-layer compound oil-rich area. While looking for large lithologic reservoirs, we should pay attention to paleogeomorphology and small reservoirs. Chang 4+5, Chang 6 and Chang 8 reservoirs in Yanchang Formation are mainly developed, and some blocks are composed of Chang 4+5, Chang 6, Chang 8, Chang 2 and Jurassic multilayer systems. In recent years, the area has insisted on three-dimensional exploration, continuously deepened the study of sedimentary system and oil and gas migration and accumulation mechanism, intensified the overall exploration and evaluation, and quickly implemented the scale of reserves.
Chang 8 oil layer is a shallow water delta deposit, with multi-stage distributary channels superimposed on each other, stable sand body distribution and long extension distance, which is beneficial to the formation of large lithologic reservoirs. At the same time, this area belongs to the development area of Chang 7 high-quality source rocks, with large thickness of source rocks and high abundance of organic matter. In the main hydrocarbon generation period and hydrocarbon expulsion period, the hydrocarbon generation amount is the largest, which has strong migration force for hydrocarbon expulsion, and has the characteristics of hydrocarbon expulsion up and down and large-scale episodic charging.
Chang 4+5 oil layer belongs to regressive delta deposit, which developed under the background of short-term lake invasion. Estuary dam and distributary channel are superimposed, and reservoir sand bodies are developed. The establishment of this sedimentary model plays a key role in the exploration breakthrough of Chang 4+5 oil layer in Jiyuan area, and provides a new idea for the basin to find new oil-bearing strata.
Chang 7 oil layer is the exploration replacement series in this area. Through the exploration in 20 10 years, two oil-rich areas, An 88 well area and Yuan 140 well area, were discovered.
Chang 2 and Jurassic are the old strata explored in this area. In the 1970s, a number of small oil fields were discovered through the exploration of Jurassic paleogeomorphic reservoirs and small structural reservoirs. In recent years, with the stereoscopic exploration and fine exploration of shallow oil layers in Jiyuan, 17 high-yield oil layers have been newly discovered, which has become a favorable target for production and construction.
(4) Huaqing District
This area is located in the middle of Yanchang Lake Basin in Ordos Basin, and the main target layers are Yanchang Chang 6 oil layer and Chang 8 oil layer. Early exploration in this area mainly focused on reservoirs above Chang 4+5, and found Yuancheng, Cheng Hao, Huachi and Nanliang reservoirs. In recent years, by deepening the study of sedimentary characteristics in the middle of the lake basin, a new understanding of "delta distributary channel and gravity flow compound reservoir sand body developed in the middle of the depressed lake basin" was obtained for the first time, which changed the traditional understanding that "the middle of the lake basin is dominated by argillaceous rocks". This theory has effectively guided exploration, expanded the exploration field and made a major breakthrough in Chang 6 oil layer. In recent years, around the overall exploration and overall evaluation of Chang 63 oil-bearing main sand belt, four reserve areas with complete scale, such as Yuan 284, Bai 209, Bai 255 and Shaanxi 139, have been quickly delineated, and the proven geological reserves have been submitted to 2.63× 108t, and the controlled geological reserves are 2.01×/Kloc. 20 10 actively carried out exploration on its east and west sides, and newly discovered two oil-bearing sand belts, Wu 58 and Wu 69, forming a new reserve replacement area.
While paying attention to the exploration of Chang 6 oil layer and insisting on three-dimensional exploration, Chang 8 oil layer has made great discoveries. At present, there are 50 industrial oil flow wells, and 6 oil-rich areas have been found, with a favorable oil-bearing area of about 400km2, and the estimated reserves can reach 1 100 million tons.
Pay special attention to the new class. The Yanchang 10 oil layer is the one with the lowest exploration degree in Mesozoic. Up to now, there are 40 wells1well, 40 appraisal wells1well and 5 development skeleton wells1well in Chang 10 reservoir, totaling 4 16 wells, with an average exploration well density of 0.0042 wells /km2. In the past, Chang 10 reservoir was only found in Majiatan oilfield in the western margin of the basin. In recent years, with the continuous improvement of exploration degree and drilling depth, people gradually realize that Chang 10 oil layer is an oil-bearing series that cannot be ignored, especially in the distribution area of Chang 9 source rocks in the northeast of the basin. Chang 10 oil layer has the necessary conditions to form oil reservoirs, and it is expected to form upper and lower reservoirs driven by reservoir overpressure. Up to now, 65,438+04 industrial oil flow wells have been obtained in Chang 65,438+00 reservoir, with an average reservoir thickness of 9.4m, an average porosity of 65,438+00.7%, and a permeability of 65,438+09.96× 65,438+00-3 μ m2, which has reached 20t/m.. The industrial oil flows of Well Wang 526 and Well Wang 527 completed this year are 3 1.54t/d and 2 1.77t/d respectively. At present, nine favorable oil-bearing targets have been preliminarily implemented, with an area of about 150km2.
Chang 9 oil-bearing formation is the second cycle of lake basin evolution in the extended period. In recent years, Chang 9 oil layer has been discovered by deepening the research on the sedimentary evolution and sand body distribution law of the lower strata of Yanchang Formation in the basin, and intensifying the exploration, which has become an important reserve replacement layer. Up to now, 958 drilling and evaluation wells have been completed and 34 skeleton wells have been developed in Chang 9 reservoir, totaling 992 wells, with an average exploration well density of 0.0099 wells /km2. The reservoir type belongs to structural lithologic reservoir, and the nose uplift zone and small-amplitude structure have obvious control over the formation of the reservoir. At present, the average reservoir thickness is 14.5m, the average porosity is 13.0%, the permeability is 5.04× 10-3μm2, the highest oil test is 34.34t/d (well Huang 2 19), and the average single well oil test output is/kloc-0.
(5) western margin fault fold belt
This belt refers to Majiatan section and Shajingzi section (controlled by Liupanshan arc structural system), and it is a reserve exploration field worthy of attention. The exploration in this area began in 1970s, and mainly targeted at structural reservoirs, Majiatan Oilfield, Lizhuangzi Oilfield, Dashuikeng Oilfield and Baiyanjing Oilfield were successively discovered, with proven oil-bearing area of 20.4km2 and proven geological reserves of1151.97x104t. In recent years, through the study of the tectonic evolution history, the temporal and spatial relationship of basin-mountain evolution and the conditions of oil and gas migration and accumulation in the western margin fault-fold belt, it is considered that this area is a worthy exploration field. ① Although the area underwent multi-stage structural transformation during the formation of Mesozoic basin, the oil-bearing target layer in the middle and lower part of Yanchang Formation and the target layer of Jurassic Yan 'an Formation are well preserved; (2) At the peak of hydrocarbon generation and expulsion in the basin, this area is in the direction of oil and gas migration, adjacent to the hydrocarbon generation area, and oil reservoirs have been discovered in the north, middle and south of this section; ③ This area is dominated by structural oil reservoirs, which are easy to form multi-layer composite oil bearing, improve the reserve abundance, and shallow burial is also conducive to saving exploration costs; ④ The progress of seismic exploration technology, the fine processing and interpretation of various logging data and the improvement of oil testing technology make it possible to find and describe local structural traps and identify oil and gas reservoirs. The exploration breakthrough in this area is of positive practical significance for finding the reserve exploration battlefield, broadening the exploration field and deepening the understanding of the western marginal structural belt.
The low exploration degree area north of Yanchi and Jingbian refers to the exploration range of Yanchi-Chengchuan in the north of Mafang and Youfangzhuang old oilfields. The exploration degree in this area is low. In the past exploration and production, because this area is far away from the hydrocarbon-generating area, the exploration effect of shallow oil layers is not ideal, the input workload is less, and the exploration work lags behind for many years. In recent years, with the continuous extension of oil exploration to the north and the discovery of Mesozoic oil layers in Paleozoic natural gas exploration, this area has become a field worthy of further exploration. Up to now, many exploration wells in this area have obtained industrial oil flow, of which well Chi 8 10 extends to 4.59t/d and produces water18.3m3; . Well Ding 24 in Yanchang 9 has a daily output of 26.44 tons, without water; Well An 79 obtains 20.83 tons/day in Well Yan 9, without water; Well Ding 27 is 6 1 long, with daily oil production of 4.3 1t and water production of 7.8 1m3. The discovery of these industrial oil flow wells shows that this area has the conditions for reservoir formation. The problems that need to be studied now are: ① the oil supply conditions in this area, whether the source rocks were formed during the development of Chang 4+5 and Chang 7 lake basins in this area, and if so, what is the hydrocarbon generation capacity? That is to say, the oil source of reservoir formation comes from there, whether it is autogenous or accumulated by oil and gas migration in the south of the basin; ② The distribution and influence of micro-cracks in this area belong to the splicing zone of the north and south basement of the basin with 38 north latitude, which has been clearly shown on the surface, forming two landforms: loess gully in the south and saline-alkali Gobi desert in the north. However, in the later tectonic movement, what influence did the concealed movement of the basement splicing zone have on the overlying Mesozoic strata, and what regularity does the time and plane distribution of the fault system have, which needs further study. At present, Jurassic oilfield in the middle of the basin has been discovered.
(6) Southeast of the basin
The area starts from Ganquan in the north, reaches Fuxian in the south, reaches the junction of Shaanxi and Gansu in the west, and reaches Linfen in the east, spanning south-central Shaanxi and southwest Shanxi. This area is adjacent to Weibei Uplift, with strong tectonic activity and developed faults and cracks in different periods. The strata change is complex, with Cretaceous-Jurassic-Triassic outcrops and Permian, Carboniferous or Ordovician outcrops in the south and east. Petroleum exploration in the southeast of the basin began in the early 1950s and can be roughly divided into four stages. In the first stage, in the 1950s and 1960s, geological surveys and gravity surveys were conducted in Huangling and Tongchuan, and a number of structures and oil seedlings were found. The structures of the Silangmiao and Qigezhen anticlines were carefully investigated, and some exploratory wells were drilled, only a small amount of oil and gas flow was obtained. The second stage refers to the 1.17m3/d industrial oil flow, Miaowan, Wufangchuan, Malan, Silangmiao and Jier in the early stage of the "campaign" (early 1970s). The third stage is 1998 ~ 2004. From 1998 to 200 1, under the guidance of "three new understandings", the reservoir-forming conditions in Weibei area were re-evaluated, and the structures such as Miaowan, Nianziyuan, Laoye Temple and Silang Temple were optimized. Already drilled 1 1 well, and the length of 9 drilled horizons is 8- 9. The commercial oil flow of 1.7t/d (well depth 222m) was obtained by fracturing and testing in Chang 2 well of Miao 38 well. At this stage, the newly-increased proven reserves are 32× 104t, the controlled reserves are 459× 104t, and the predicted reserves are 448× 104t. From 2000 to 2004, Chang 2 reservoir in Miao 38 well was developed. Exploration at this stage shows that the upper reservoir of Yanchang Formation in Weibei area is shallow buried, with developed fractures, poor physical properties (Chang 2 average porosity 1 1.0%, permeability 0. 12× 10-3μm2) and small reservoir scale. The exploration field should span Weibei uplift, from structural-lithologic oil and gas reservoir exploration to lithologic oil and gas reservoir in the basin. In the fourth stage, from 2005 to now, under the guidance of the idea of "throwing out and drilling out", 34 exploratory wells and 25 exploratory wells were drilled in the exploration target layer in the lower part of Yanchang Formation in Weibei low exploration degree area, and the drilling length was 10. It is found that there are three industrial oil flows (Zheng 25, Wang 9, Wang 18) and five low-yield oil flows (Zheng 10, Zheng 12, Wang 1, Wang 19 and Dian 4) in the lower reservoir of Yanchang Formation. The proven rate of Mesozoic resources in southeastern Ordos Basin is less than 1%. Through the analysis of the reservoir conditions of each oil layer in this area, it is considered that there is still great exploration potential in this area.
(7) Southwest area of basin
That is, the northern part of Zhen Jing-Binxian area is close to oil source and sand bodies are developed. At present, many oil fields and natural gas have been discovered in Triassic, which indicates that it is possible to further expand the oil-bearing area in this area. We should pay attention to the exploration of new strata, increase reserves and discover new oil fields.