The progress of technology makes drilling deeper and deeper. The offshore oil industry, which started in the 1940s, spent nearly 30 years producing oil and gas in the deep water area of 100 meters, and more than 20 years in the sea area of nearly 2000 meters. Recently, oil and gas production has touched 3000 meters of water. Especially the improvement and innovation of drilling, floating production system and submarine technology have greatly reduced the capital expenditure and operating expenditure of deepwater oil and gas exploration and development. Since 1998, the average capital expenditure of deepwater oil and gas exploration and development has shown a downward trend, and the capital expenditure per barrel of oil has dropped from $6/barrel before 10 to less than $4/barrel now. The comprehensive cost of deep-water oil and gas exploration and development projects is getting closer to that of shallow-water projects. The development cycle of deepwater oil and gas projects (from discovery to oil and gas production) is getting shorter and shorter. The oil and gas fields discovered at the end of 1990s usually put into production in 5-6 years, while it took at least 8 years before 10. With the continuous improvement of deepwater infrastructure, the development cycle may be further shortened.
The exploration and development of deep-sea oil is an important frontier of petroleum industry and a high-risk industry. Although great progress has been made in the development of deep-sea oil in the North Sea, the Gulf of Mexico, Brazil and West Africa, the price is extremely high. Compared with continental shelf and onshore exploration drilling operations, deepwater operations have high construction risks, high technical requirements and very expensive costs, so the capital risks are also extremely high.
The most direct risk of deep-sea oil and gas resources exploration is huge construction risk. The offshore platform has complex structure, huge volume, high cost and high technology content, especially compared with the land structure, its marine environment is very complicated and harsh. Wind, waves, ocean currents, sea ice and tides always act on the platform structure and are also threatened by earthquakes and tsunamis. Under this environmental condition, adverse factors such as environmental corrosion, marine organism attachment, foundation mud erosion, foundation dynamic softening structural material aging, component defects, mechanical damage, fatigue and damage accumulation will all lead to the attenuation of platform structural components and the overall resistance, which will affect the safety and durability of the structure.
Deep-water oil and gas exploration and development is risky and rewarding. Although the total reserves of shallow water oil and gas fields are still dominant, they are mainly related to the proportion of some super-large oil fields in the Middle East. However, the average reserve scale and average daily output of deepwater oil and gas fields are obviously higher than those of shallow water oil and gas fields. Therefore, although the exploration and development cost of deep-water oilfield is obviously higher than that of shallow-water oilfield, the cost per unit reserve is not very high because of its high reserves and output, which attracts many oil companies to "treasure hunt" in the deep sea.
With the continuous development of offshore oil and gas development, offshore oil engineering technology is changing with each passing day. In the development of deepwater oil and gas fields, traditional jacket platforms and gravity platforms are gradually replaced by deepwater floating platforms and underwater production systems, and the design and construction technologies of various deepwater platforms are also constantly improving. At present, there are more than 2,300 sets of underwater production facilities and 204 deep-water platforms in the world. The maximum working water depth of TLP has reached1.434m, SPAR is 2073m, FPSO is1.900m, and the multifunctional semi-submersible platform has reached1.928m..
At the same time, deepwater drilling equipment and pipe laying technology have also developed rapidly. There are 14 in-service drilling facilities in the world that can drill in 3000m water depth, and the fifth and sixth generation deepwater semi-submersible drilling platforms and drilling ships are under construction. The working water depth of the 6th generation deepwater drilling ship will reach 3658m, and the drilling depth can reach11000m. The lifting capacity of the deep-water lifting pipe-laying ship reaches10.4 million tons, the underwater welding depth is 400 meters, the underwater maintenance depth is 2000 meters, and the deep-water pipe-laying length reaches10.2 million kilometers.
With the rapid development of seismic technology in the world, a large number of advanced computers have been put into use. At present, visualization and virtual reality technology have been initially realized: Landmark Company has developed 3D volume interpretation software and 3D animation software such as 3DVI and Voxcube; Geoquest developed GeoViz 3D interpretation software for human-computer interaction. Paradigm company developed VoxelGeo；; DGI developed EarthVision；; The photo company developed 3Dviz 3D visualization software.
In terms of virtual reality, ARCO and Norsk Hydro developed and established an immersive virtual reality system, Texaco developed and established a virtual reality viewing hall, Alternate Realities Co., Ltd. developed and established a VisionDome, SGI Company of the United States established a special demonstration hall, IBM Company developed and established a virtual reality system that can be used to reproduce the simulated reality of 4D seismic reservoirs, and Geoquest Company of Schlumberger and others are developing virtual reality systems.
In terms of seismic attribute acquisition, the international community has gone from direct oil and gas detection and bright spots in the 1960s to instantaneous attribute or complex trace analysis in the 1970s, multi-attribute analysis in the 1980s and multi-dimensional attribute analysis (such as dip angle, azimuth angle and coherence) in the 1990s. At present, there are more than 70 seismic attributes about time, amplitude, frequency, absorption and attenuation obtained from seismic data, including kinematic and dynamic attributes, geometric attributes and physical attributes.
The focus of foreign geophysical research: the most representative of foreign petroleum geophysical exploration is offshore seismic exploration technology. On the one hand, the Gulf of Mexico and the North Sea have typical exploration complexity; On the other hand, the United States, Britain and other countries have developed science and technology and rich talents, and the level of geophysical theory and technology basically represents the international status quo. The exploration targets in the Gulf of Mexico and the North Sea are mainly salt domes and their surrounding strata, fractured reservoirs and the distribution of remaining oil in old oil fields, and they mainly face four theoretical and technical problems: (1) seismic wave propagation theory and forward modeling in complex media; (2) Seismic imaging of salt dome structure; (3) improvement of signal-to-noise ratio and extraction of weak signals; (4) Identification of complex reservoirs and oil and gas. Around these three aspects, foreign geophysical theory and technology have developed rapidly.