Oil and gas are demanded from the ocean because of the rise of tracing the extension of land oil fields on the seabed. 1890, people began to explore marine oil and gas. At that time, according to the trend of land oil and gas fields extending to the ocean, people built trestles along the coast of California and drilled oil in shallow waters by the sea. 1920, the United States conducted oil exploration drilling in Lake Maracaibo, Venezuela. Subsequently, according to the mud volcano theory, the former Soviet Union began to explore and develop offshore oil and gas fields from Baku to Upsilon in the Caspian Sea. At that time, it was connected with the land shore through a wooden fixed trestle. By the end of 1960s, many European countries had started oil and gas exploration in the North Sea, making this area the most active area for oil and gas exploration and development in the world. In the early 1970s, 75 countries in the world were looking for oil at sea, among which 45 countries were drilling and 30 countries were producing oil at sea. By the 1980s, there were more than 65,438,000 countries or regions engaged in offshore oil exploration and development. At present, the activities of searching for oil and natural gas at sea are developing in depth, and the investigation and exploration of offshore oil and gas are expanding. On the continental shelf adjacent to coastal countries, there are derricks and platforms everywhere, which is a prosperous scene. The exploration and development of submarine oil and gas resources has become an important economic activity of coastal countries.
Among the four oceans and dozens of offshore waters, the Persian Gulf is the richest in oil and natural gas, accounting for about half of the total reserves. The second place is Lake Maracaibo in Venezuela. The third place is Beihai. The fourth place is the Gulf of Mexico. Followed by the coastal areas of China, Southeast Asia, Australia and West Africa. At present, 58 1 oil fields have been formed in the world's oceans, including 25 in Europe and the Mediterranean, 20 in the North Sea 1 10, 20 in Italy and North Asia, 43 in South America, 27 in Africa, 85 in West Africa, and 60 in the Persian Gulf and India. Offshore of India and Malaysia 15, offshore of eastern Australia and New Zealand 3, offshore of Australia's northwest continental shelf 12, offshore of Ghips 19, offshore of North Sea 44, offshore of US Gulf of Mexico 16.
The development of offshore oil and natural gas has brought economic prosperity to some coastal countries. As we all know, the Gulf region was once a relatively poor and backward region in history. Since the discovery and exploitation of offshore oil in the Gulf in 1960s, the oil industry has promoted the economic development of the region and greatly enhanced the strength of the Gulf countries. Among the world's eight largest oil storage countries, Saudi Arabia, Iraq, Kuwait, United Arab Emirates and Iran occupy five seats, and oil has become the main source of foreign exchange income of these countries, accounting for more than 85% of their fiscal revenue. For example, Kuwait, a small oil-rich country, has accumulated assets of $85 billion just by investing overseas. For another example, Norway was a poor country in Europe before the Second World War, and now it has entered the ranks of rich countries in the world, with a per capita GNP 1.4 million US dollars. The key reason for the great changes in this country lies in the development of offshore oil. Norway was originally a country without oil. After the discovery of oil and natural gas in the North Sea in the mid-1960s, 197 1 began to produce oil, and 1975 became the first oil exporter in Western Europe. 1977, Norway's income from oil exploitation in the North Sea only accounted for 0.2% of the gross national product, accounting for 0.5% of the country's total exports, while in 1984, it had produced more than 59 million tons of oil with an output value of 9.74 billion US dollars, accounting for 20% of Norway's gross national product, compared with 1977. The rapid development of offshore oil industry has also brought vitality to the development of other industries in the country. The once depressed machinery and shipbuilding industry turned to produce oil platforms, ships and other oil industry equipment. The development of offshore oil industry has also increased the employment opportunities of domestic personnel. Although Britain is an old capitalist power, before the mid-1960s, there was no offshore oil industry in Britain, and the oil needed was basically imported, which consumed a lot of money. 1968, the cost of importing oil in Britain alone reached 125 billion pounds, which brought heavy financial pressure to the country. After 1970, Britain discovered Sithole gas field and fortes oil field in the south and middle of the North Sea. 1975 was put into development and production, and 1978 ~ 1980 entered the peak production period, with a daily output of 68,000 tons of crude oil. To 1982, the cumulative output is1370,000 tons. Since 1980s, Britain has exploited about1.200 million tons of crude oil from the North Sea every year, which fundamentally changed the situation of British oil import. The British government's offshore oil revenue in the North Sea alone reached 654.38+00 billion pounds. It can be seen that the oil and gas development in the North Sea has a great influence on Britain's economic and social life.
It should be noted that the breadth and depth of marine oil and gas resources investigation and exploration are not enough compared with land. Except for the favorable offshore waters, most of the continental shelf areas are still blank or only roughly investigated, far from commercial development. Submarine oil and gas development has just started, and offshore oil and gas development has bright prospects and attractive situation.
Some people may ask, how did submarine oil come into being? How can we find oil and natural gas at the bottom of the sea, and how to exploit it after finding it? Here are some introductions.
The generation of oil is a long-standing debate, but it is generally believed that oil was formed by the chemical and biochemical changes of biological remains in the past geological period. There are three conditions for the formation of oil: first, there must be a large number of biological remains; Second, there should be an oil reservoir and a cover to protect oil from escaping; Third, it is necessary to have a geological structure conducive to oil enrichment. Some petroleum geologists believe that the seabed of continental shelf is usually a thick marine deposit in Mesozoic and Tertiary and after Tertiary, and this geological structure is a good place for oil generation and storage. The continental shelf is closely connected with the offshore, and there are a large number of plankton such as algae and fish in the offshore, which are the raw materials for forming oil. When these creatures are quickly buried by sediments brought by rivers, the buried biological remains are isolated from the air and are in an anoxic environment for a long time. Coupled with the pressure of thick rocks, high temperature and bacteria, they began to decompose. After a long geological period, these biological remains gradually became dispersed oil. In shallow waters, especially bays blocked by island headlands, the waters are in a calm and semi-closed state, which is most conducive to the accumulation of organic matter. With the deposition of a large amount of sediment, good conditions are created for oil storage. Oil is stored in the pores of sandstone, just like water in a sponge, and will not be lost, but will slowly precipitate in the shallow sea area of the continental shelf for a long time. Those basins with large subsidence and thick subsidence strata are often the most favorable areas for oil generation. In these large sedimentary basins, some structures that stand out because of compression are often the places with the largest oil reserves. Therefore, in order to find oil at sea, we must find those oil-bearing structural areas with both source and reservoir beds and well-protected caprocks.
In the vast ocean, there are hundreds of meters and thousands of meters of water above and thousands of meters of rock below. You can't see or touch it. How can you find oil? In practice, people have created unique petroleum exploration methods, such as geological exploration, geophysical exploration and geochemical exploration. Among them, physical exploration is a widely used method. Physical exploration of offshore oil is generally equipped with special instruments and equipment on marine survey vessels to find strata and structures conducive to oil accumulation. The most commonly used methods are gravity exploration, magnetic exploration and seismic exploration. The so-called seismic exploration method is to use explosives to explode in seawater or compressed air, and sparks instantly release a lot of energy to produce artificial seismic waves. Based on the principle that sound waves travel at different speeds in different substances, we can find strata and structures that are beneficial to oil storage. The so-called gravity exploration is to measure the gravity value of seabed rocks with gravimeter to obtain the density, geological age and depth of rocks. Through the observation of the gravity field in the sea area, we can understand the thickness of sedimentary rocks and the fluctuation of bedrock, divide the structural units of the survey area, study the properties of uplift, and thus delineate the oil and gas area. The so-called magnetic exploration is to determine the magnetic strength of the sea area where the ship or aircraft passes through through the magnetometer placed on the survey ship or special aircraft, so as to determine the thickness and geological structure deposited on the magnetic basement under the seabed, and then to find oil and natural gas. The above methods can only indirectly determine the position of offshore oil in the ocean. Whether there is oil on the seabed and how big the reserves are must be confirmed by the direct method of offshore drilling. Therefore, offshore drilling is an important link in oil and gas exploration and development. Core samples obtained from drilling can accurately grasp the situation of submarine oil and gas resources. Offshore drilling is much more difficult than onshore drilling. First of all, because the sea surface is unstable, in order to maintain the stability of drilling, it is necessary to build a workbench or drilling platform higher than the sea surface, and then carry out drilling activities on the platform. Offshore drilling platforms generally include fixed drilling platforms and mobile drilling platforms. Of course, some countries have made drilling ships and installed drilling equipment on them for drilling operations. The United States has the largest number of offshore drilling in the world. There are also Britain, Indonesia, Malaysia, India, Russia and many other countries. 1965, Exxon Oil Company of the United States used the "Cass-1" drilling rig in the offshore waters of Southern California to drill the world's first deep water well with a water depth of193m. Later, the number of deepwater oil drilling increased and the technical equipment became more and more advanced. At present, there are 18 drilling vessels with drilling depth exceeding 1000m in the world, of which the maximum drilling depth is 2,600m and the maximum drilling depth is1000 m. Judging from the future development trend, offshore oil drilling will develop to the deep sea.
With the development of offshore oil and gas industry, offshore oil and gas exploitation and equipment are also developing. Fixed production platform has formed the basic characteristics of modern offshore oil fields. Most of these platforms are steel pile platforms, which are generally composed of superstructure, jacket and steel piles. Superstructure is generally composed of one or several blocks, which is the base camp of production facilities, living facilities and power equipment. The superstructure is installed at the top of the jacket, which is integrated with the jacket through leg connectors and cement slurry. The jacket rotates on the seabed and is immersed in the water. The lower part of the jacket is a steel column, which is driven into the continental shelf. The whole platform and natural environment loads, such as wind force, wave force, ice force, flow force and earthquake force, are supported by the friction between the pile wall and soil and the bearing capacity provided by the pile end. 1947, the United States built the world's first offshore steel and oil platform with a depth of 6 meters in the Gulf of Mexico, and China also built a modern drilling platform in the Bohai Sea in 1966.
In order to cooperate with offshore oil and gas exploitation, many countries have also built corresponding supporting devices in oil and gas storage and transportation. 1988 In May, Japan completed the construction of the world's first oil storage base on Wushang Island near Nagasaki, and built five giant oil storage tankers at a cost of 190 trillion yen.