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The current status and methods of exploration in the world’s offshore oil industry: http://www.oilnews.com.cn/bk/images/070821/A012007011.jpg China Petroleum News Center: http://www.oilnews.com.cn/bk/images/070821/A012007011.jpg The exploration and development of offshore oil and gas is a continuation of onshore oil exploration and development, having evolved from shallow waters to deep seas, and from simple methods to more complex ones. In 1887, the world’s first offshore well was drilled in waters several meters deep off the coast of California, United States, marking the beginning of oil exploration in the ocean. Marine oil and gas reserves: The world’s oceans are rich in oil and gas resources. Marine oil resources account for about 34% of the world’s total oil resources, with an exploration rate of around 30%; thus, exploration is still in its early stages. According to the Oil & Gas Journal, as of January 1, 2006, the world’s proven oil reserves amounted to 175.7 billion tons, while the proven natural gas reserves were 173 trillion cubic meters. The global reserves of marine oil amount to approximately 135 billion tons, of which about 38 billion tons have been identified ； Marine natural gas resources amount to approximately 140 trillion cubic meters, with proven reserves of around 40 trillion cubic meters. Distribution of oil and gas resources: Marine oil and gas resources are primarily found in the continental shelf, accounting for about 60% of the world’s total marine oil and gas resources. However, the oil and gas potential in the deep waters of the continental slope and in ultra-deep waters is also significant, accounting for around 30%. Among the world’s proven reserves of marine oil and gas, shallow seas still play a dominant role at present; however, with advances in oil exploration technology, exploration will gradually extend to deeper seas. Water depths of less than 500 meters are considered shallow seas, those greater than 500 meters are deep seas, and depths over 1500 meters are ultra-deep seas. Between 2000 and 2005, the world saw an increase of 16.4 billion barrels of oil equivalent in proven oil and gas reserves, of which deep-sea areas accounted for 41%, shallow seas for 31%, and land-based areas for 28%. Regionally, offshore oil exploration and development have taken on a pattern of three bays, two seas, and two lakes. “The “three bays” refer to the Gulf of Persia, the Gulf of Mexico, and the Gulf of Guinea ； “The “two seas” refer to the North Sea and the South Sea ； “The \"Two Lakes\" refer to the Caspian Sea and Lake Maracaibo. Among them, Saudi Arabia, Qatar, and the United Arab Emirates in the Gulf of Persia, Kazakhstan, Azerbaijan, and Iran along the Caspian Sea, the UK and Norway along the North Sea, as well as the United States, Mexico, Venezuela, Nigeria, and others, are all important countries in the world for offshore oil and gas exploration and development. Offshore oil and gas production began in the 1940s; it was 1 million barrels per day in the 1960s, and 25 million barrels per day in 2005. In terms of global marine oil production, the oil output from the North Sea and its rate of growth have always been at the top among all marine regions. Production reached its peak in 2000, at 320 million tons, and then gradually declined. Oil production in the Gulf of Persia is growing slowly, with annual output remaining between 210 and 230 million tons. In contrast, oil production in regions such as the Gulf of Mexico, Brazil, and West Africa is increasing at a faster pace, with an average annual growth rate of over 5.0%. The Gulf of Mexico is likely to surpass the North Sea as the world’s largest oil-producing region in the coming years. Investments in offshore projects: With the continuous rise in international oil prices, the total global investment in oil and gas exploration and development (E&P) is increasing steadily. For the exploration of marine oil and gas resources, the drilling depths involved are quite significant: there are 15 drilling ships capable of operating at depths exceeding 3,000 meters, with a drilling capacity of up to 10,000 meters. The lifting capacity for offshore construction tasks is 14,000 tons, the depth at which underwater welding can be carried out is 400 meters, the length of pipelines that can be laid in deep waters is 12,000 kilometers, and the depth at which underwater repairs can be performed is over 2,000 meters. There are more than 204 oil extraction units designed for use in deep-water areas. In 2003, there were 2,100 underwater production systems, and this number increased to 5,700 by 2007. Characteristics of offshore oil and gas exploration; Environmental characteristics of the work area. Compared with onshore oil and gas exploration, the huge waves and strong winds caused by typhoons at sea affect the progress of exploration activities and pose a threat to the lives and property of exploration personnel. Characteristics of exploration methods: The methods and techniques used for oil and gas exploration on land are applicable to oil and gas exploration in the ocean as well. However, due to the harsh marine physical geography and the physicochemical properties of seawater, many exploration methods and techniques are limited. Characteristics of drilling projects: The equipment used in offshore drilling projects is much more complex, and offshore drilling requires the use of drilling platforms. Due to the influence of the natural marine geographical environment, offshore drilling projects must take into account the effects of wind and waves, tides, ocean currents, sea ice, tsunamis, storm surges, and coastal sediment movement. Factors such as ocean depth and towage for offshore relocation are taken into account, whereas drilling projects on land do not need to consider these factors. Investment and Risk Characteristics: Investment in offshore oil and gas exploration has increased significantly, typically being three to five times that of onshore oil and gas exploration. Exploration investment is primarily reflected in the design and manufacturing of offshore drilling equipment, the transportation and towing of such equipment, the collection and transport of oil and gas at sea, logistical support during offshore drilling operations, as well as the salaries and insurance for engineers involved in offshore drilling projects. These exploration investments are much larger than those on land. Advantages of offshore oil exploration: Oceanic geophysical exploration enables very high efficiency in offshore oil and gas exploration, thanks to convenient transportation and the use of specialized instruments and equipment. In marine seismic exploration, the seismic vessel moves along the survey line while carrying out measurement tasks, and its efficiency is higher than that of land-based seismic exploration. Stages of offshore oil and gas exploration: Offshore exploration in the United States is divided into the preliminary exploration stage and the further exploration stage. The preliminary exploration phase includes basin evaluation, block evaluation and trap evaluation, as well as the discovery of oil and gas reservoirs. The further exploration phase focuses on drilling wells and evaluation wells in order to expand the oil and gas-bearing area and increase and identify geological reserves of oil and gas. During the basin evaluation phase, seismic surveys with a sparse grid spacing of 40–80 km are carried out; regional tectonic analysis is conducted by combining these seismic data with gravimetric and magnetic data. The structure of the basin is studied in depth, its tectonic patterns and sedimentary models are established, and analogical analyses of the basin are performed ； Evaluate the oil and gas potential of the basin, calculate its prospective resource volume, and make a decision on whether to continue exploration. During the block and trap evaluation phase, the exploration blocks are divided and evaluated through enhanced seismic data and high-precision non-seismic geophysical methods. It mainly focuses on blocks, classifies and ranks traps, calculates the resource volume of these traps, and conducts risk analysis. After conducting a new round of evaluation through detailed seismic surveys, preliminary drilling is carried out on the traps to discover oil and gas fields and initially assess the commercial value of the reserves. The further exploration phase primarily involves carrying out additional drilling to expand the oil and gas-bearing area, as well as calculating the proven reserves of the oil and gas field. In the early stages of offshore oil and gas exploration in the United States, great emphasis was placed on analogical analysis with oil and gas-bearing basins around the world. In exploration work, the importance of resource evaluation is given special emphasis, making it the core of the entire exploration process. Strive for excellence in the preparation of local structures and conduct risk analysis. World ocean seismic vessel survey: As of 2006, there were 22 companies worldwide engaged in offshore seismic exploration operations, with a total of 125 vessels. Of these, 51 were capable of carrying out operations in shallow waters or transitional areas, while 74 were suitable for deep-water seismic exploration. Oceanic exploration drilling: Offshore drilling requires the use of platforms and drilling ships. Jacked-up drilling platforms are used for drilling at depths generally less than 180 meters; they have good mobility and low construction costs, but are difficult to tow and require complex operations for positioning. Semisubmersible drilling platforms, operating in water depths of 60 to 2000 meters, with depths reaching up to 3100 meters; they offer good stability and can cope with harsh sea conditions. Their self-propulsion speed is low, and their cost is high. Deep-water drilling rigs, for water depths of 300–6000 meters, feature high mobility and dynamic positioning; they are highly affected by wind and waves, and have a limited deck area. Deep-water oil and gas exploration: The exploration and development of oil and gas resources in deep-water areas are constrained by harsh and complex environmental conditions as well as specific reservoir characteristics. This field is characterized by the \"four highs\": high technology, high risk, high-skilled personnel, and high returns. According to the World Deep Water Report, 44% of oil and gas reserves will be found in deep waters in the future, compared to only 3% at present, which demonstrates the great potential involved. Deep-sea oil and gas exploration and development in waters 500 meters deep or deeper began in the 1970s, and by the end of 2002, 47 billion barrels of oil had been discovered. According to estimates by the U.S. Geological Survey and the International Energy Agency, the ultimate potential oil reserves in the world’s deep-sea areas could exceed 100 billion barrels. In 2004, deep-sea oil production covered about 5% of the world’s oil demand, while by 2010 deep-sea crude oil production could reach 8.5 million barrels per year (430 million tons per year), satisfying 9% of the world’s oil demand. Oil and gas exploration at depths of 500–1500 meters worldwide has become an integral part of the important strategic assets of most offshore oil and gas operators. In the Gulf of Mexico, for example, the share of oil and gas in its deep-water areas rose rapidly from 4% and 1% in 1990 to 64% and 36% ten years later, showing a fast pace of development. The period from 2004 to 2008 will be a period of active exploration for deep-sea oil and gas. According to Offshore Resources, between 2001 and 2007, 434 offshore oil and gas development projects were planned worldwide, of which 48% were deep-water projects with depths greater than 500 meters, and 22% were ultra-deep-water projects with depths exceeding 1200 meters. The number of projects using floating production systems has reached 209. Development activities in the Asia-Pacific region still focus mainly on shallow waters within the continental shelf, while in other parts of the world, such activities have extended beyond the continental shelf and are concentrated in waters with depths of over 500 meters. As oil and gas resources on the continental shelf become increasingly depleted, moving into deeper seas is an inevitable trend, and deep-sea platform technology has become a hot topic of research in the international offshore engineering community. The Barents Sea, the Gulf of Mexico in the United States, and the waters off Angola and Nigeria are the four major deep-sea oil regions in the world that attract much attention. It accounts for almost all of the world’s deep-sea drilling and newly discovered reserves. According to statistics at the end of 2003, among the deep-sea reserves that had been discovered, Brazil had 14.6 billion barrels, with the 5 largest discoveries accounting for over 10 billion barrels. The Gulf of Mexico had 140 discoveries, totaling 11.5 billion barrels, while off the coast of Angola there were 41 discoveries amounting to 9.5 billion barrels. Nigeria has 25 offshore oil fields with reserves of 8.3 billion barrels. World deep-sea and ultra-deep-sea investment forecasts from 2004 to 2008. It is expected that oil production in the four major deep-sea oil fields will grow rapidly over the next five years, with production reaching its peak by the beginning of the next decade. Compared to the Atlantic Basin, deep-sea oil and gas activities in Southeast Asia are on a smaller scale; it does not exert as much influence on large multinational companies as West Africa, Brazil, and the Gulf of Mexico. However, the potential benefits in Southeast Asia offer opportunities for oil companies looking to explore deep-sea fields. From 2005 to 2008, Malaysia and Indonesia were set to become the main regions for deep-sea oil and gas activities in Asia over the next five years. Currently, companies such as BP, Petrobras, Statoil, ExxonMobil, Shell, Husky, and Unocal are engaged in deep-water exploration and development activities, possessing the core technologies for such operations. Patterns of deepwater oil and gas exploration: Currently, the areas where deepwater oil and gas exploration yields good results are mostly found in passive continental margin basins or rift basins associated with passive continental margins, and they often represent extensions of shallow-water and onshore exploration areas. Oil and gas reservoirs are often from the Cretaceous or Tertiary periods, and are mostly deep-water turbiditic sandstones from the Tertiary period. Deepwater oil and gas exploration often aims to discover large and medium-sized oil and gas fields as well as to find large and medium-sized traps. Most of the discoveries in deep-water areas are oil reservoirs. Hotspot exploration areas all possess a set of salt rocks that are closely related to oil and gas accumulation. Salt rocks and salt-related structures have become hot topics in current research on tectonics and oil and gas reservoir formation. Prospects for the exploration of marine oil and gas resources: With the development of the world economy, energy demand continues to rise. Driven by market demand and high oil prices, global offshore oil and gas exploration and development is set to continue growing at a rapid pace in the future, with increasing investment, rising production volumes, and an expansion of the areas and depths where such exploration and extraction activities take place. Organic carbon in global natural gas hydrates accounts for about 53.3% of the world’s total organic carbon, while coal, oil, and natural gas combined account for only 26.6%. Among them, the maximum geological reserves of natural gas hydrates located on land are approximately 5300×108 tons, while those in the oceans are about 1.61×1015 tons. The reserves alone in the oceans can meet human needs for over 1,000 years. To date, natural gas hydrates have been discovered in 122 locations around the world, including 33 on land and 84 in the oceans; core sampling has been conducted in more than 20 of these sites. Japan has discovered large amounts of combustible ice in the deep seas of the continental shelf on the southeastern slope of the Japanese archipelago. More than 30 wells have been drilled, and partial pilot production has been successful; a plan for commercial exploitation by 2015 has been established. The United States has discovered large amounts of methane clathrate in the deep waters of the Gulf of Mexico and has set a plan for commercial exploitation by 2016. The biggest challenge in currently extracting seabed gas hydrates is maintaining stable bottom-hole pressure to prevent methane leaks and avoid triggering the greenhouse effect. Natural gas hydrates may become a new source of energy for humanity, and will gradually become a new focus in the exploration and development of offshore oil and gas. Conclusions and Insights: Marine oil resources account for 34% of the world’s total oil resources, with a cumulative proven reserve of about 40 billion tons; the proven rate is around 30%, indicating that exploration is still in its early stages. Due to the special conditions of the ocean, investment in offshore oil and gas exploration has increased significantly, typically being three to five times that of onshore oil and gas exploration. Offshore oil and gas exploration primarily relies on marine cable seismic surveys. The offshore exploration phase is divided into the preliminary exploration phase and the further exploration phase. The preliminary exploration phase includes basin evaluation, block evaluation and trap evaluation, as well as the discovery of oil and gas reservoirs. The further exploration phase focuses on drilling wells and evaluation wells in order to expand the oil and gas-bearing area and increase and identify geological reserves of oil and gas. Areas such as the Gulf of Mexico, West Africa, and Brazil will continue to drive global trends in offshore oil and gas exploration. New offshore regions with promising prospects, including those in the continental shelves of Southeast Asia and Australia, the Bay of Bengal, the Caspian Sea region, and the polar continental shelves, will gradually begin to be explored. Advanced exploration technologies are becoming increasingly mature