Global oil and gas exploration investment development can be divided into two stages in the past five years. During the first stage of 2017 to 2019, the global oil and gas exploration investment stayed at the investment level of (430-440) × 10⁸ US dollars, gradually walking out of the global recession in oil and gas exploration investment caused by the sharp fall of international oil prices in 2014. However, with the spread of COVID-19 at the end of 2019 and the decline of international oil prices, global oil and gas exploration investment decreased again in the second stage from 2020 to 2021 by more than 125 × 10⁸ US dollars. In 2021, the global oil and gas exploration investment was 313×10⁸ US dollars ^[9], the same as in 2020. Among them, the exploration investment in the Americas and the Asia Pacific region was the largest. Exploration investment in both regions was more than 100×10⁸ US dollars, far higher than in other regions (Table 1).

The global exploration and drilling workload remained steady, with a slight decrease. In 2021, 1235 exploratory wells were drilled, showing a year-on-year decrease of 39. There were only 644 wildcats, showing a year-on-year decrease of 26. In 2021, the distribution of global exploratory well basins continued to follow the trend of 2020, mainly located in Oman, West Siberia, North Sea, Sureste, and other mature exploratory basins, with a total number of 25-60 wells (Table 2). The Guyana basin in the Americas has been a global exploration hotspot since 2015 and continues to maintain an exploration scale of more than 10 exploratory wells per year.

The distribution of wildcats onshore and offshore worldwide is uneven, and the success rate of exploratory wells varies year on year. In 2021, 423 wildcats had been drilled onshore, with a slight increase compared to 2020. The success rate of exploratory wells is 44.9%, with a slight decrease compared with 2020. Two hundred twenty-one offshore wildcats were drilled, showing a year-on-year decrease of 38. The success rate of offshore wildcats was 49.3% (Table 3), higher than 39.4% in 2020. It takes a trend of increase in the past three years. Sixty-six wildcats have been drilled in the deepwater and ultra-deepwater fields, accounting for 29.8% of the offshore wildcats. The deepwater basin in the Gulf of Mexico and the Guyana basin took the lead in the number of completed wildcats, 21 and 11, respectively, far more than that of other basins. Although the number of wildcats in deepwater and ultra-deepwater fields accounts for a low proportion, the recoverable reserves of newly discovered oil and gas fields are generally higher than those of mature exploration basins in onshore/shallow water areas, and they are the main body of global new reserves in 2021.

In 2021, a total of 230 oil and gas fields were discovered in the world (excluding North America onshore) (Fig. 1), including 214 conventional oil and gas fields, with recoverable reserves of 20.8×10⁸ t oil equivalent ^[9-10], showing an increase in both quantity and the reserve volume. In addition, there were 16 unconventional oil and gas fields with recoverable reserves of 2590×10⁴ t oil equivalent, showing a year-on-year increase in quantity but a year-on-year decrease in reserves. The large-scale reserves of newly discovered conventional oil and gas fields worldwide are unevenly distributed. The American regions continue to lead in the discovery of global oil and gas exploration reserves, with recoverable reserves of 11.42× 10⁸ t oil equivalent, accounting for about 55% of the total global conventional oil and gas reserves, far higher than the other regions (Table 4). Central Asia - Russia region ranks second, with recoverable reserves of 4.11×10⁸ t oil equivalent. The newly discovered oil and gas reserves in the Asia Pacific, Middle East, and Africa are in third place, with recoverable reserves of (1-2)×10⁸ t oil equivalent. The resource in Europe is relatively poor, and exploration is also the most mature. The newly discovered reserves are the smallest, of only 8139×10⁴ t oil equivalent.

In the past three years, the newly discovered conventional oil and gas fields have maintained the reserve level of 20×10⁸ t oil equivalent, much higher than the average level of 12.7×10⁸ t oil equivalent from 2016 to 2018.

Among the 214 conventional oil and gas fields newly discovered in the world in 2021, 33 were large and medium-sized oil and gas fields (with recoverable reserves and oil equivalent greater than 1×10⁸ bbl (1370×10⁴ t) ), accounting for only 15.4%. The recoverable reserves are 17.55×10⁸ t oil equivalent, accounting for 84.4% of the reserves (Fig. 2), mainly distributed on both sides of the Atlantic Ocean, the Gulf of Mexico, the Black Sea, the South Caspian Sea, and the Arctic (Fig. 1). Among them, 10 and 3 large and medium-sized oil and gas fields have been found in the onshore and shallow water fields, with recoverable reserves of 6.23×10⁸ t oil equivalent and 4332×10⁴ t oil equivalent, respectively. 20 large and medium-sized oil and gas fields have been discovered in deepwater/ultra-deepwater fields (Table 5), with recoverable reserves of 10.9×10⁸ t oil equivalent, with a year-on-year increase of 3.4%.

In 2021, the reserves of large and medium-sized oil and gas fields were mainly natural gas, and the recoverable reserves of natural gas are 1.25×10¹² m³ (Fig. 2), accounting for 57% of the total reserves of large- and medium-sized oil and gas field, 52% higher than in 2020. The reserves are mainly found in the Americas, Central Asia and Russia, and the Middle East, with a total of 4989×10⁸ m³, 4555×10⁸ m³, and 1814×10⁸ m³, respectively. Among them, the recoverable reserves of the Im. Ye. Zinicheva gas field of Russia’s Yenisey-Khatanga Basin ranked first in the world, and the recoverable reserves of natural gas amounted to 4054×10⁸ m³. The Sakarya North gas field discovered in Türkiye’s Black Sea area is another significant discovery after the Sakarya gas field in 2020, with recoverable reserves of 1360×10⁸ m³. The Mairare and Urissane oil and gas fields in Campos Basin, Brazil, are the two largest natural gas discoveries in the Americas. Their recoverable reserves of natural gas were 1479×10⁸ m³ and 811×10⁸ m³, respectively.

Large- and medium-sized oil and gas fields are mainly distributed in the deepwater/ultra-deepwater fields of passive continental margin basins such as Guyana, Campos, Santos, Cote d'Ivoire, and Esprito Santo basins on both sides of the Atlantic Ocean and the Gulf of Mexico. The recoverable reserves amounted to 9.3×10⁸ t oil equivalent, accounting for 85% of the total reserves in deep water and ultra-deep water (Table 5). Among them, 12 oil and gas fields have been discovered in the ultra-deepwater area with a water depth of more than 1500 m, accounting for 60% of the total, with recoverable reserves of 8.65×10⁸ t oil equivalent, accounting for 80% of the total reserves in deepwater and ultra-deepwater, showing good exploration prospects.

In recent years, the reserve contribution of large- and medium-sized oil and gas fields mainly came from the Mesozoic Cenozoic reservoir (Table 6), of which the Cretaceous oil and gas reserves were the largest. The total Cretaceous reserves discovered in 2021 were 13.34× 10⁸ t oil equivalent, accounting for 76.0% of the total reserves of large- and medium-sized oil and gas fields, 56.8% higher than in 2020. Cretaceous reservoirs are mainly distributed in Santos, Campos and Esprito Santo basins in Brazil, Yenisey-Khatanga basin in Russia, Guyana basin, Venezuela basin and Sureste basin in Mexico, North Slope basin in Alaska, and Cote d'Ivoire basin in West Africa. The recoverable reserves account for 74.7% of the total reserves of large and medium-sized oil and gas fields.

In 2021, a total of 17 onshore deep conventional oil and gas fields were discovered, accounting for 7.9% of the total number of newly discovered oil and gas fields; total recoverable reserves amounted to 1.34×10⁸ t oil equivalent, accounting for 6.4% of the total reserves, mainly distributed in Mexico, Saudi Arabia, Columbia, Russia, Pakistan, Ukraine, China, Oman, and other countries. Four Cretaceous oil and gas fields were discovered in Mexico's Sureste and Veracruz basins. The buried depth of the top of the trap is 5270-6990 m, and the total recoverable reserves amounted to 9881×10⁴ t oil equivalent, accounting for 53% of the total reserves of newly discovered onshore oil and gas fields in Mexico. In recent years, Saudi Arabia has attached great importance to oil and gas exploration at Khuff and pre-Khuff strata. The reservoir of Shadoon gas field in the Central Arabian Basin discovered in 2021 contains sandstone of the Lower Permian Unayzah Formation. The recoverable reserves are 2402×10⁴ t oil equivalent, accounting for 99.8% of the recoverable reserves in the Middle East. Independent oil companies of Russia, such as Lukoil, Tekhn Komp, and Yugraneft, have discovered four Jurassic sandstone oil fields and one Permian-Triassic weathered basement reservoirs of the western Siberian Basin, with total recoverable reserves of 311×10⁴ t oil equivalent.

In 2021, unconventional oil and gas exploration was characterized by the trend of multi-point flowering. In Saudi Arabia, China, Mongolia, Australia, Oman, Argentina, and Russia, 16 unconventional oil and gas fields were found (Fig. 1 and Table 7), which doubled compared to 2020. Take Saudi Arabia as an example. In recent years, Saudi Arabia has actively deployed unconventional oil and gas exploration. Due to the relatively low proportion of clean energy, such as natural gas, Saudi Aramco plans to increase its share of gas in its energy structure by 2030 and continue strengthening unconventional gas exploration. Saudi Aramco expanded its exploration scope following the discovery of unconventional oil and gas in the Central Arabian Basin in 2020. In 2021, while finding unconventional oil and gas in the Central Arabian Basin, it discovered unconventional gas fields in the Widyan-Mesopotamia basin for the first time (Table 7). The reservoir of the Samna gas field in the Central Arabian Basin is the Upper Ordovician Sarah Formation sandstone. The reservoir thickness is 150 m, the top burial depth is 5500 m, and the daily gas production is 16.4×10⁴ m³. The reservoir of Umm Khansar gas field in the Widyan-Mesopotamia basin is sandstone of Ordovician Qasim Formation, with a top burial depth of 310 m, a daily gas output of 5.65×10⁴ m³, and condensate output of 43.3 t. It has been confirmed that these two wells embraced total recoverable reserves of 87×10⁸ m³, indicating good exploration prospects for Paleozoic tight oil and gas in the Middle East region.

National oil companies refer to the companies established with government investment and endeavor to implement national strategical goals. They are characterized by representing the country, protecting the interests of the country, and serving the overall interests of the country. In recent years, considering the low-carbon transformation of global energy and energy security, national oil companies have vigorously strengthened domestic resource exploration and development, especially gas exploration, and continuously expanded the proportion of gas production. They also actively promoted the international bidding and exploration of domestic resources, including unconventional resources, taking oil and gas exploration as the core business to drive the transformation of national energy. For example, Brazil's national oil company, the United Arab Emirates national oil company, and China's three major national oil companies continue to increase domestic exploration efforts to ensure energy supply security actively and seek long-term sustainable development. In recent years, the United Arab Emirates national oil company has increased the international bidding of local resources. For example, in 2022, it launched a batch of unconventional block bidding for the first time.

In the past two years, Qatar National Oil Company has continued to cooperate with major international oil companies to enter overseas exploration blocks, adhere to the strategy of the non-operators following, and actively improve the allocation of overseas oil and gas assets. Their main international partners include ExxonMobil, Shell, Eni, and Total Energies. The international assets are distributed in Morocco, Brazil, Oman, Mexico, South Africa, Argentina, and other countries. In April 2017, the company and ExxonMobil obtained the license of 20 blocks in Cyprus; In November 2017, it acquired 52 blocks in Oman with Eni, holding equity of 30%; In December, together with Total Energies, it obtained 25% of the interests of block 11B/12B in South Africa.

Independent oil companies are companies whose operating income mainly comes from oil and gas exploration business development. The oil and gas industry only engages in exploration and development, and its operations do not include marketing and refining. A few independent companies have international business, and more independent companies focus on domestic oil and gas business. Compared with international and national oil companies, changes in the market environment have a more significant impact on the development of independent oil companies. In recent years, the upstream independent oil companies have gradually changed from increasing debt to prudent development by reducing debt, and from scale development to survival development, with more merging and integration to take advantage of synergistic benefits. Independent oil companies represented by North America’s unconventional oil and gas enterprises focused on creating profits, paying dividends, and reducing debts. They were conservative in the upstream exploration business. Before 2019, with the improvement of the international market environment and the steady recovery of oil prices, independent oil companies had achieved rapid development by focusing on advantageous fields and expanding and strengthening core assets. However, the COVID-19 epidemic and the sharp drop in oil prices in 2020 had once again changed the development strategy of independent oil companies, pushing them to shift from pursuing core asset scale development to substantial cost reduction for survival. For example, the exploration activities of ConocoPhillips mainly focused on unconventional oil and gas. It resolutely withdrew from the exploration activities in Austin Cretaceous in central Louisiana in the USA, continued to focus on the major onshore unconventional oil and gas production areas such as Delaware and Eagle Beach, and at the same time made a large-scale acquisition of Shell's unconventional resources in the Permian Basin to expand its regional scale advantage.

With lower degrees of exploration and greater resource potential, offshore will be the essential exploration area in the future, including mainly the passive continental margin and back-arc basins. Eight major basin groups (Table 9) are included: (1) The passive continental margin basin groups in the southern part of the South Atlantic Ocean, with the target of Jurassic-Cretaceous structure in Colorado basin, Upper Cretaceous submarine fan, and other plays in Rio Salado basin. The yet-to-find recoverable resources of oil and gas are estimated to be 23.7×10⁸ t oil equivalent. (2) The passive continental margin basin group in the middle part of the South Atlantic mainly targets the deepwater gravity flow on salt and the carbonate rocks under salt in Santos, Campos, and Kwanza basins. The yet-to-find recoverable resources of oil and gas can be 327.6×10⁸ t oil equivalent. (3) The passive continental margin basin group in the northern part of the South Atlantic, including the Cretaceous-Miocene slope fan and basin-floor fan in the basins of Foz do Amazonas, Suriname, Guyana, Etc. The yet-to-find recoverable resources of oil and gas are 26.1×10⁸ t oil equivalent. (4) The passive continental margin basin group in the mid-Atlantic Ocean is targeted at the plays such as USA Mexico Bay, Paleogene-Neogene lithologic assemblage in the Sureste basin, and the plays such as the Cretaceous submarine fan on the east coast basin of Senegal and USA. The yet-to-find recoverable oil and gas resources are 281.3× 10⁸ t oil equivalent. (5) The passive continental margin basin group in the North Atlantic mainly includes the Jurassic-Cretaceous fault block structure and structural-stratigraphic plays in the east coast basin of Greenland. The yet-to-find recoverable resources of oil and gas are 38.3×10⁸ t oil equivalent. (6) The passive continental margin basin group in the East Africa offshore is targeted at various types of as the Cretaceous-Paleogene slope fan/ basin-floor fan in the basins such as Somalia, Zambezi Delta, and Tanzania coast. The yet-to-find recoverable oil and gas resources are 99.5×10⁸ t oil equivalent. (7) The passive continental margin basin group in the Arctic, including the Jurassic Cretaceous fault block structure in the Kara Sea and the Barents Sea basin, has a yet-to-find recoverable resource of 364×10⁸ t oil equivalent. (8) Southeast Asia back-arc basin group, including Paleogene-Miocene structure/reef flat/submarine fan and bedrock buried hill, Etc., has a recoverable resource of 36.8×10⁸ t oil equivalent ^{[2,19⇓ -21]}.

Due to the relatively high degree of conventional oil and gas exploration in onshore basins, the future favorable exploration fields are mainly located in the deep formations of cratons, rifts, and foreland basins, including mainly 6 basins (Table 10): (1) Arabian/Zagros foreland basin, of which Arabian basin mainly includes the Paleozoic deep structural reservoir forming assemblage and Jurassic-Cretaceous stratigraphic lithologic traps. It is predicted that the yet-to-find recoverable resources are 415.4×10⁸ t oil equivalent. In the Zagros Basin, the main target is the deep structural traps below Jurassic in the thrust structural belt, and the yet-to-find recoverable resources are 236.7×10⁸ t oil equivalent. (2) The West Siberian rift basin aims at many large-scale structural traps in the Cretaceous of the South Kara Sea in the North and deep structural and stratigraphic traps in the Jurassic in the south-central part of the basin. It is predicted that the yet-to-find recoverable resources are 261.1×10⁸ t oil equivalent. (3) Amu Darya foreland basin, the target is the reef flat of pre-salt Upper Jurassic and the deep stratigraphic trap of middle and lower Jurassic. It is predicted that the yet-to-find recoverable resources are 151.9×10⁸ t oil equivalent, mainly gas. (4) In the eastern Siberian craton basin, the target is the carbonate rocks of the rift system and the Vendian clastic rocks. It is predicted that the yet-to- find recoverable resources are 113.7×10⁸ t oil equivalent. (5) Precaspian foreland basin, the target mainly includes subsalt Permian clastic rock, Devonian-Carboniferous deep play, Etc. It is predicted that the yet-to-find recoverable resources are 48.4×10⁸ t oil equivalent. (6) In the Ghadames foreland basin of North Africa, the targets mainly include Paleozoic low amplitude anticline structural traps and stratigraphic lithologic composite traps. The yet-to-find recoverable resources are predicted to be 12.2×10⁸ t oil equivalent ^{[2,19⇓ -21]}.

In recent years, unconventional oil and gas have shown a differentiated development trend due to technology and production cost. Among them, the exploration and development of tight oil and gas and shale oil and gas have made rapid progress and will remain an important exploration focus in the future. The favorable exploration fields for shale oil (including tight oil) in the future are mainly distributed in seven basins (groups) (Table 11): (1) North American foreland basin group, in which Devonian-Carboniferous plays dominate Permian, Appalachian and Williston basins, while Cretaceous plays dominate Gulf, Denver and Powder River basins. The technically recoverable resources of shale oil are 313×10⁸ t. (2) The Andean foreland basin group mainly includes Llanos-Barinas, Putumayo, Maranon, and Neuquen basins. The favorable play is Jurassic-Cretaceous, and the technically recoverable resources of shale oil are 89×10⁸ t. (3) The North African foreland basin group mainly includes the atlas fold belt, Triassic-Ghadames basin, and other basins. The favorable play is Silurian and Devonian. The technically recoverable resources of shale oil are 43×10⁸ t. (4) The rift basin group in Central West Africa mainly includes the Bongor Basin, South Chad Basin, Muglad Basin, Melut Basin, and other basins. The favorable play is Cretaceous lacustrine shale oil, and the technically recoverable resources of shale oil are 20×10⁸ t. (5) Russia foreland/rift basin group and West Siberia Basin are favorable plays of Upper Jurassic Bazhenov Formation. In contrast, Timan-Pechora and Volga-Urals basins are Devonian Domanik Formation. The technically recoverable resources of shale oil are 130×10⁸ t. (6) The Arabian/Zagros foreland basin is mainly the Zagros basin and Arabian basin. The favorable play is Jurassic and Cretaceous marine shale oil. The technically recoverable resources of shale oil are 52×10⁸ t. (7) Southeast Asia back-arc basin group mainly includes North Sumatra, middle Sumatra, and South Sumatra basins. The favorable play is Cenozoic lacustrine shale oil, and the technically recoverable resources of shale oil are 13×10⁸ t ^{[21⇓⇓-24]}.

The key exploration fields of tight gas and shale gas in the future are mainly distributed in seven basins (groups) (Table 12): (1) North American foreland basin groups, in which the favorable plays for Permian, Appalachian, and Williston basins are Devonian-Carboniferous. Cretaceous dominate Gulf Basin and Powder River Basin, and the technically recoverable shale gas resources are 79×10¹² m³. (2) The craton basin group in Central South America mainly includes Amazon, Chaco-Parana, and other basins. The favorable plays are Devonian-Carboniferous. The technically recoverable resources of shale gas are 19×10¹² m³. (3) The Andean foreland basin group mainly includes Neuquen, Magllanes, and other basins. Jurassic-Cretaceous is favorable play, and the technically recoverable shale gas resources are 21× 10¹² m³. (4) The North African foreland basin group mainly includes the atlas fold belt, Triassic Ghadames, and other basins. The favorable plays are Silurian and Devonian. The technically recoverable resources of shale gas are 26×10¹² m³. (5) Russia foreland/rift basin group and the favorable play in West Siberia Basin is upper Jurassic Bazhenov Formation; Timan-Pechora and Volga-Urals basins belong to Devonian Domanik Formation, and the technically recoverable resources of shale gas are 14×10¹² m³. (6) The Arabian/Zagros foreland basin mainly includes Zagros and Arabian basins. The favorable plays are Jurassic, Cretaceous, and Silurian. The technically recoverable resources of shale gas are 16×10¹² m³. (7) Australia’s central craton basin group mainly includes Canning, MacArthur, and Eromanga basins. The favorable play is the Devonian-Carboniferous system. The technically recoverable shale gas resources are 12×10¹² m^{3 [21-24]}.

In 2021, large and medium-sized oil and gas discoveries in the global deepwater and ultra-deepwater fields continued to dominate global oil and gas discovery, further revealing the good exploration prospects in the frontier field of deepwater on the passive continental margin. Therefore, it is inevitable for international oil companies to continuously expand gas exploration in the deepwater area^[25]. Based on the fact that the foreign cooperation of frontier basins in resource countries mainly adopts the way of bidding, the cooperation opportunities that can be obtained through active bidding in recent years will include the following: (1) The sixth round of bidding for exploration blocks in East Africa Mozambique offshore includes two favorable oil and gas bearing basins, the Angoche and Zambezi deltas. The former mainly develops two sets of favorable reservoirs forming Upper Cretaceous and Paleogene submarine fan assemblages. The latter develops a reservoir forming an assemblage of Cretaceous delta sandstone. (2) The first round of sea area block bidding of East Africa in Somalia mainly includes the coastal basin of Somalia, which consists of three sets of favorable reservoirs forming combinations of Jurassic reef flat and Cretaceous/Paleogene slope fan. (3) The second round of offshore block bidding in Argentina focuses on the deep water Upper Cretaceous submarine fan in the coastal basin of Argentina. (4) The first round of bidding blocks in the Greenland Sea area focuses on Jurassic structural traps in the eastern coastal basin.

After entering the discovery stage, the Eni "dual exploration model" operation and management method is suggested. Since 2006, Eni has obtained 74 deepwater blocks in the Circum African region mainly through bidding. The obtained area is 38×10⁴ km. Since 2011, Eni has successively obtained five large gas fields. Before the first gas production, only the two major discoveries of Zohr and Mamba have helped Eni earn more than US $100×10⁸ through equity transfer. In this way, not only can the cost be recovered quickly, but the exploration project can also achieve good economic benefits before development and construction.

Since 2015, large oil and gas fields have been discovered while exploring the upper Cretaceous deepwater fan in Guyana basin, the Cretaceous under the salt reef flat in Santos basin, and the Jurassic Cretaceous structure in the South Kara Sea in the West Siberian Basin. These discoveries further confirm that once a breakthrough is made in exploring a frontier basin, it will generally become a hot spot of exploration and lead to the growth of reserves in the next 5-10 years or even more extended periods ^[7]. Considering this feature, international/independent oil companies usually quickly seize exploration blocks with similar geological backgrounds or the same play. At present, it is suggested to actively enter the hot basins such as the pre-salt reef flat of Santos-Campos Basin in Brazil offshore, the Neogene submarine fan of deep water in Mexico bay, the Jurassic-Cretaceous structural trap in the South Kara Sea in West Siberia, the deepwater submarine fan in the coastal basin of Southwest Africa and the Miocene submarine fan in the Black Sea basin.

As the same play in the same basin has been confirmed, the geological risk of the surrounding undrilled blocks is low, with considerable potential but a higher entry cost. If the government opens the surrounding blocks through bidding, the bidding companies will generally win with a high-profit oil sharing ratio for the government and a high signing fee. For example, from 2006 to 2012, after continuous breakthroughs in the subsalt core area of Brazil's Santos–Campos Basin led by Brazil's national oil company, the government started external bidding in 2013. The winning block’s government profit oil sharing ratio is between 65% and 75%, and the signing fee is up to US $13×10⁸. If the oil company introduces partners before drilling, the entrants often have to pay a relatively high price to enter under conditional payment. Take the 58 blocks in Suriname of the Guyana basin that Total Energies entered in 2019 as an example. In 2015, Apache invited bids to enter the 58 blocks in Suriname, Guyana basin. From 2015 to 2019, great discoveries continued to be made in Guyana. Total Energies paid the exploration cost proportion after entering with 50% of the operator's equity, plus conditional payment. After the commercial success, it paid the US $1×10⁸ in cash and 75% of the development investment.

In 2021, new oil and gas, especially gas, were discovered continuously in the deep-layer fine exploration in the onshore Arabian, western Siberian, Sureste, and other basins. These discoveries further confirm that the deep-layer oil and gas, especially gas, in the onshore oil and gas- rich basins still has great potential for fine exploration ^[9-10]. After more than 60 years of exploration and practice in domestic on-shore basins, a relatively mature theoretical and technical system of fine exploration has been formed in the eastern rift basin, the central and Western Craton, and the foreland basin. By actively giving play to the technical advantages, and combined with advanced joint research, CNPC can transform the technical advantages into the development advantages in overseas exploration and improve the overseas exploration benefits through more cooperation in onshore deep-seated oil and gas exploration with oil companies of resource countries. The onshore deep oil and gas fields are mainly distributed in the foreland thrust belt, the mid-lower combination of the craton basin, and the deep formation of the rift basin. The strata are mainly Paleozoic and Mesozoic Cenozoic. The areas worthy of special attention include Paleozoic carbonate rocks and Jurassic clastic rocks in the four oil and gas rich basins of Volga-Urals, Timan-Pechora, West Siberia and East Siberia, Middle East Arabian-Zagros foreland basin, Paleozoic in Northwest African foreland basin, Mesozoic in the slope belt of Andean back-arc foreland basin group, Etc.

Although carbon neutralization promotes the acceleration of energy transformation, it is predicted by many domestic and foreign institutions that, even under the most radical scenarios, oil and gas will still account for more than 20% of the world's primary energy consumption in 2050. The oil and gas industry will not quickly withdraw from the historical stage. Unconventional oil and gas resources are still an adequate replacement for conventional oil and gas resources ^[21,26]. With the improvement of unconventional oil and gas theory and the progress of production technology, the global industrial production of unconventional oil and gas enjoys a firm foundation. The theory of fine-grained sedimentology and continuous oil and gas accumulation with organic shale as the core has been formed, and advanced technologies such as geophysical "sweet spot" prediction, horizontal well volume fracturing, micro-seismic monitoring, and bench top "factory" mining have been developed. The continuous development and improvement of unconventional oil and gas theory and technology have made the exploration and development of tight oil and gas in China increasingly mature daily^{[27⇓⇓-30]}. Compared with the utilization of conventional oil and gas resources, the utilization of unconventional oil and gas resources in many parts of the world has just begun. Chinese oil companies can make use of the mature and supporting tight oil and gas technologies as the point of breakthrough and select necessary fields with special geological conditions such as Jurassic in western Siberian rift basin in Russia, Silurian in Triassic-Ghadames foreland basin in North Africa, and Jurassic/Cretaceous/Silurian in Middle East Arab foreland basin to obtain relatively high-quality resources based on cooperation with the national oil companies of resource countries. By steadily promoting the transnational exploration and development of unconventional oil and gas and by taking domestic drilling and fracturing engineering technologies to the international market, oil companies of China can thus give full play to the integrated advantages.