Salute! The breakthroughs in oil extraction technology have made the country more and more confident.

How many steps are there to extract oil? Find it, drill a well, and then extract it.

As a liquid mineral, the exploration and development of oil is a typical exploration and production integrated model. Therefore, drilling is the core work throughout the entire oil and gas development process, and the level of its technology directly determines the level of oil and gas development.

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The exploitation of oil resources is not an easy task. Unlike solid mineral deposits, oil and gas reservoirs are often buried deep below the surface and require certain mining equipment to assist. In addition, liquid minerals are mobile, and unreasonable mining will lead to a reduction in recovery rate.

So how did humans successfully extract such a valuable resource as oil? What attempts have Chinese scientists made?

Initial exploration: Does China really have no oil?

In the early days when the technical conditions were relatively poor, the discovery of oil, like other minerals, depended on natural outcrops. As the "Book of Han·Geography" states: "Dingyang, Gaonu, there is Wei water, which is flammable." Gaonu, roughly located in Yanchang County, Shaanxi Province today, became the first oil well on land in China. In 1935, the Chinese Workers' and Peasants' Red Army took over the Yanchang Oil Plant, and the oil products it developed strongly supported the War of Resistance Against Japan and the War of Liberation.

In 1938, with the approval of the Central Committee of the Communist Party of China, two drilling rigs and their equipment from Yanchang Oilfield were transferred to Yumen, and the first oil well was drilled at Yumen Laojun Temple, marking the beginning of the development of China's first modern oilfield and the cradle of China's petroleum industry - Yumen Oilfield. It can be regarded as an important "meritorious oil mine" in China .

Laojunmiao Oil Mine in Yumen Oilfield. Image source: China Government website

With the Second Industrial Revolution, the invention of the internal combustion engine promoted the development of the oil extraction industry and the production of the petrochemical industry. The original oil and gas resources were far from meeting the needs of the rapidly developing production and life. As a result, countries began to pay more attention to oil extraction.

After Japan launched the war of aggression against China, it conducted extensive mineral surveys and plunder in China's Northeast region. The scope of oil and gas exploration covered an area from Hailar in North Xing'an Province to Rehe Province. It even developed a 2,000-meter rotary drilling rig powered by a steam engine and drilled a 1,000-meter-deep exploratory well on the edge of the Daqing Oilfield.

Even so, there is still a gap between the reservoir depth of 1,357 and 1,382 meters of the first oil well in Daqing Oilfield, Songji No. 3 Well.

At that time, the "marine oil generation theory" dominated the field of oil extraction. In 1922, Blackweld, a geology professor at Stanford University in the United States, pointed out in a paper titled "Oil Resources in China and Siberia": "China has no Mesozoic or Cenozoic sediments; most of the Paleozoic sediments do not generate oil; therefore, China will never produce a large amount of oil."

This is how my country was labeled as an oil-poor country.

There is oil, but it is still a bit difficult to get it out

In 1939, Chinese experts discovered the Laojunmiao Oilfield in Yumen, Gansu Province in a continental basin, which shook the dominance of this theory . This marked the beginning of the theory of continental oil generation in China. The subsequent development of the Daqing Oilfield and its petroleum geology research ultimately laid a solid foundation for the theory of continental oil generation.

The main engine of the Beu-40 drilling rig used by the 1205 drilling team in 1960. Image source: Daqing Oilfield History Exhibition Hall

In contrast, Japan was constrained by the oil exploration idea of ​​"marine oil generation theory", and even though it introduced geophysical exploration technology from the United States, it still mainly used exploration technology based on electrical methods. That is, it was necessary to first discover oil outcrops and then conduct geological structure surveys, which resulted in low exploration efficiency.

After a full thirty years in Northeast China, Japan only obtained exploration results for viscous, high-sulfur heavy oil, and the flow rate was very small. With Japan's refining technology at the time, it was difficult to use this oil to refine the gasoline needed by the army. It was necessary to import new technology and equipment from the United States. By the time it was successfully produced, the war was over.

Faced with the dilemma of insufficient supply of oil resources, Japan could only seek other ways to break through technology. In order to solve the problem of insufficient oil supply, Japan had to spend a huge amount of money to carry out the project of liquefying coal into artificial oil, and to carry out the production of primary liquefied light oil and secondary hydrogenation liquefied oil. However, due to the limitation of conditions, the oil output was not high, and several artificial oil factories were built. In the end, due to the lack of funds and equipment in the later stage, they were all unsuccessful. All these reasons were due to the backward drilling equipment.

Oil drill pipe and drill bit. Copyright image. Reprinting and using may cause copyright disputes.

The pure liquefied oil, in terms of both quantity and quality, could not meet Japan's oil demand. The lack of oil forced Japan to abandon its plan to continue looking for oil in Northeast China, leaving only some small core drilling rigs. Japan also completely gave up its oil exploration work in Northeast China and turned its attention to Sakhalin Island in the north and Indochina Peninsula and Malay Archipelago in the south.

With the elimination of the Northward Advancement Faction from the decision-making level and the defeat of Britain and France on the European battlefield, Japan realized that the opportunity to seize the rich resources in Southeast Asia to solve the problem of extreme oil shortage had come . Sumatra and Darakan in Indonesia, important production areas for companies such as the East India Company, would be within easy reach.

Japan's first step in the southern invasion was Hanoi, followed by a military alliance with Germany and Italy, which also caused strong reactions from the United States, Britain and other countries. In 1940, the US State Department issued a statement of moral embargo against Japan, imposing an embargo on aviation gasoline with an octane number of more than 87. Britain and the Netherlands followed suit. Britain cut off the supply of oil from Borneo to Japan; the United States persuaded the Dutch East India Company to suspend the shipment of oil to Yokohama and Nagasaki.

This measure, which was tantamount to declaring war on Japan economically, did not serve to contain Japan. Instead, it prompted Japan to take risks and formulate and complete the plan to attack Pearl Harbor , and ultimately forced the United States to abandon its neutrality and join the Allied camp, which became the fuse for the outbreak of the Pacific War.

Of course, this is just one of the manifestations of the necessity and urgency of oil and gas exploration and development. Even if the energy consumption structure has changed, as long as the demand for oil and gas consumption remains, the exploration and development work will continue.

What are the difficulties in oil exploration and production?

As the exploration progresses, the cost of development work increases. As almost all large and medium-sized basins suitable for the development of oil and gas reservoirs in the land area have been explored, the focus of oil and gas exploration has shifted from medium and shallow layers to deep and ultra-deep layers.

This trend is particularly evident in my country. On the one hand, my country's oil and gas consumption and external dependence have been increasing, and on the other hand, my country's geological conditions for shallow oil and gas reservoirs are indeed not good. On the contrary, a number of large oil and gas fields have been discovered in the central and western basins, such as Tahe, Puguang, Anyue, Jingbian, Shunbei, etc., indicating that the characteristics of my country's proven deep and ultra-deep carbonate oil and gas reservoirs are very different from those in the world, showing broad exploration prospects.

Xinjiang Oilfield. Copyrighted images from the photo library. Reproduction and use may lead to copyright disputes.

China's oil and gas exploration is more urgent to make breakthroughs in deep and ultra-deep layers. As a result, the pressure has shifted from new reservoir formation theories to drilling equipment.

Early oil drilling equipment used impact drilling, the principle of which is to use a large iron cone to repeatedly lift and impact, breaking the bottom like a large chisel to work.

This method was first used in southwest my country to drill small-diameter wells for extracting salt. It has a drilling capacity of several hundred meters and can drill salt wells as deep as one kilometer. It has a history of more than 1,000 years.

Rotary drilling, which only appeared in the early 20th century, mainly relies on rotation and pressure to operate like an electric drill, which has increased the working efficiency of the drilling rig several times and also increased the drilling limit several times, with the deepest reaching over 10,000 meters.

Drilling rigs at night. Copyrighted images from the photo library. Reproduction and use may cause copyright disputes.

For solid mineral production, conventional hydraulic rotary drills with a drilling capacity of several thousand meters are quite sufficient.

Because the drilling capacity has surpassed our underground tunnel mining capacity for solid minerals, but for oil and gas, which require integrated exploration and mining, its capacity is still insufficient, because the difficulties in the development of oil and gas resources are reflected in two aspects.

Mining of solid mineral coal. Copyright image. Reproduction may cause copyright disputes.

On the one hand, it is difficult to explore . There are three reasons for this. First, deep drilling is necessary. No matter how perfect the theory is or how rich and detailed the ground geophysical survey is, deep drilling verification is ultimately required. Second, as the depth of exploration increases, exploration funds are burning faster. Just like building a building, as the floors increase, both the foundation and the structure need to be fully redundantly designed and constructed. Third, exploration is constantly adjusted as the degree of exploration increases. Drilling work is carried out in a high temperature, high pressure, and high salt environment, and the exploration risk and difficulty continue to increase.

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In challenging wells, pore pressures, fracture gradients, and complex geometries combine to create a narrow operating window. In practice, it is like embroidering in deep formations. Whether it is the inability to feedback effective drilling parameters, weak sidecutting capabilities, difficult drill bit steering, or even a narrow range of drilling operating capabilities, it will lead to costly and time-consuming events.

On the other hand, it is difficult to extract . Among the reservoir-forming elements of oil and gas, the reservoir cover is still in a flat state in the stratum as a whole. Just like the soft-boiled egg you eat, what we want to obtain is the soft part (oil and gas), but its microstructure is not that simple, it is more like a sponge with countless water-proof interlayers. If you want to extract oil and gas, you must drill into the right position, and then the pressure of the stratum will directly squeeze out the water (oil and gas) in the sponge.

But the problem is that the existence of the aquiclude (caprock) means that you are powerless even though there is only one layer of separation. So what we want to do most is to connect as many reservoirs as possible, of course, we can also choose to interrupt the caprock (fracking method).

This is the dilemma we encounter in mining. First, it is difficult for us to clearly and accurately study the fine-scale geological structure deep underground by geophysical exploration alone. Second, even if we obtain the fine structure, we need to have sufficiently flexible drilling technology to directly reach our expected layer.

Keep looking for oil! There are always more solutions than problems

In order to successfully extract oil, people have found the most direct solution, which is horizontal wells. Horizontal wells can produce more oil and gas than vertical wells because they are parallel to the formation. The permeability of tight formations is very low, and it is difficult for oil and gas to migrate to the wellbore. Through hydraulic fracturing and proppant pounds, the permeability is increased, and the increase in lateral length increases the exposed area of ​​the oil and gas reservoir in a single well, which can achieve economic development of tight oil and gas formations. Since 2010, horizontal wells have become the main production method for shale gas and tight oil.

In addition, the middle and late stages of oilfield development are particularly difficult, which has greatly promoted the further development of drilling guidance technology. After years of water injection development, most of the oil wells in old oilfields have entered the high water content stage. After the underground oil layer is flooded, only a thin layer of oil floats on the water surface, commonly known as "floating on water". At this time, horizontal well drilling technology can come in handy. It can greatly increase the possibility of hitting this layer of oil skin with the bull's eye, which is also a major driving force for the development of drilling guidance technology.

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Simple drilling guidance technology is far from enough. During the drilling process, due to the single geological target detection method and the difficulty in controlling the wellbore trajectory, it is difficult to track the target oil layer in a timely and accurate manner, resulting in a low reserve drilling rate and the inability to efficiently develop complex oil and gas reservoirs.

When the formation types and trends of oil fields are complex and the reservoir location is uncertain, the potential development direction turns to thin and poor layers and oil sand bodies, which puts forward requirements for logging while drilling technology.

The current mainstream technology is far from being satisfied with simple drilling guidance. It will also be equipped with complex geophysical survey equipment to develop into a set of mature logging while drilling equipment. It uses mathematical analysis methods to link seismic attributes with logging curves and establishes a pre-drilling geological guidance model for intelligent drilling. With the help of statistical models, samples can be automatically discovered, reservoir conditions can be automatically predicted, wellbore trajectories can be accurately controlled, and the drilling rate can be improved.

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Oil and gas resource drilling has intelligent navigation

Recently, the domestically developed intelligent drill guide developed by my country has made important progress in the actual drilling application of the TP259-2H production well in the western Tarim Basin, and obtained high-yield industrial oil and gas flow. This application progress proves that my country has entered the high-end field of ultra-deep oil and gas exploration and development technology, mastered key core technologies, and achieved the core technology development of the entire industry chain such as drilling, logging, logging, oil testing, and geophysical detection.

At the same time, the advent of this domestically-produced "oil heavy weapon" has achieved breakthroughs in technology and equipment, and the equipment has been independently developed, which has strongly supported the verification and innovation of oil and gas exploration theories that are compatible with my country's geological accumulation background.

Intelligent drilling guide while drilling azimuth electromagnetic wave, resistivity imaging logging tool into the well photo. Image source: Chinese Academy of Sciences

In my country's upstream business practice, ultra-deep basins have high temperatures, high pressures, high oil and gas maturity, and near-source accumulation, which are more conducive to the generation of natural gas and light oil, with abundant resources and low exploration levels. Major strategic breakthroughs in oil and gas discoveries are basically concentrated in deep and ultra-deep layers, such as the increase in reserves and production in the piedmont of the Tarim Basin, the Sichuan Basin, the southern edge of the Junggar Basin, and the Qaidam Basin.

In addition, there are still a large number of old wells in China that have been shut down after long-term water injection and multiple measures have failed. Using "intelligent drilling" to take coring at a fixed point and orientation in the oil layer and extract the remaining oil is the only way to stabilize and increase production in old oil fields in the future and improve resource utilization . It has become a powerful means of low-cost potential tapping of low-permeability reservoirs. It has a very broad promotion space in tapping the remaining oil potential in old oil fields, which will further enhance the strategic guarantee capability of China's own oil fields.

Conclusion

How many steps are there to extract oil? If you look at this question again now, you will find that we have taken one step after another and are still taking steps today.

For my country, from being labeled as "absolutely without oil resources" by various countries in the beginning to now being able to easily extract oil with "intelligent drilling", the efforts and sweat put into repeated experiments are immeasurable.

It is precisely because of the efforts of scientists and miners that the strategic resource of oil has been firmly protected, and has provided tremendous confidence for the country's economic, social development and national defense security.

Planning and production

Produced by Science Popularization China

Author: Jing Bo, Geological Engineer

Producer丨China Science Expo

Editors: Lin Lin, Jin Yufen (Intern)