What is the "warehouse" of oil and gas?

There are many oil and gas depots in the developed oil and gas fields, which are "warehouses" specially used for temporarily storing crude oil. It mainly receives crude oil transported by oil pump stations in oil fields. It is stored in oil tanks of oil depots and then transported by pipeline tankers.

The primary task of oil depot is to store oil (gas).

In order to ensure the normal production of crude oil in oil fields, and considering the unbalanced transportation situation, crude oil produced by thousands of oil wells is continuously input into the oil depot and temporarily stored through various oil pump stations every day. The oil storage capacity of the oil depot is determined according to the output of oil wells in the oil depot control area. An oil depot has several oil tank areas, and each oil tank area has several oil tanks. Each oil tank can store thousands to tens of thousands or even hundreds of thousands of cubic meters of crude oil.

There are many kinds of oil tanks, including cylindrical, spherical, square and water drop. According to the position, there are vertical tanks and horizontal tanks; According to the structure, there are arch tanks, cone-top tanks, torque-free tanks and floating-top tanks; There are various crude oil tanks, light oil tanks and gas tanks according to their uses (Figure 46). Some gas tanks can also change shape. For example, there is a gas tank with several floors in Shanghai, and its top is sometimes high and sometimes low. During the day, the gas consumption is large, and the gas in the tank is pressed down by the weight of the tank top and pressed into the underground pipe network densely distributed in the urban area for users to use. At night, when the consumption is reduced, the gas in the fuel tank will push the top of the fuel tank higher. Although the top of the tank weighs tens of tons, the gas pressure formed by the tank is still very small, even only 1% of atmospheric pressure due to its large diameter.

Don't look at those huge oil and gas tanks standing there so majestically. In fact, it is also very fragile. 1956, a tornado blew an empty oil tank of more than 1000 cubic meters in Shanghai into the air, reaching a place more than 100 meters away, and the oil tank was smashed. Experienced oil workers know that oil tanks under construction are most afraid of wind, especially oil tanks without roofs, which will be deformed when the wind blows.

The disadvantage of surface oil tanks of various sizes is that they occupy a lot of land and are unsafe. Especially during the war, it is extremely vulnerable to enemy attacks, and a bomb can destroy the entire oil depot. Crude oil and refined oil are difficult to put out once they catch fire. Even if they flow into the river, they will burn and drift along the river. In order to prevent this from happening, underground oil depots appeared.

Fig. 46 Various oil tanks

Underground oil depots can be divided into natural oil depots and artificial oil depots. In suitable places such as ravines, dig horizontal tunnels, go deep into mountainous areas, make one or several big holes in them, and then build oil storage tanks in these artificial caves. In addition to this kind of oil tank placed in caves, there is also a kind of oil tank built directly by underground space. For example, some salt rocks or gypsum mines are well sealed, and they can be used as natural oil depots after being processed and sealed. There are also underground caves as natural oil depots, but the sealing work of such caves is more complicated. Once completed, the temperature difference in the cave is very small, which can greatly reduce the loss of petroleum products.

Some holes are too deep to be used as oil depots, so natural gas can be stored. The volume of this natural cave can reach millions or even tens of millions of cubic meters. What a huge natural oil and gas reservoir! Moreover, there is no doubt that this underground oil and gas storage is the best way to store oil during the war. At present, many countries are vigorously looking for and building such underground oil and gas reservoirs.

In order to ensure the safety of the fuel tank, when storing oil in the fuel tank, a certain space must be reserved for the fuel tank to "breathe", that is, a breathing valve is installed at the top of the fuel tank to control the air in and out. Breathing valve is an indispensable part of fuel tank, just like human nostrils. In the process of loading and unloading oil, the breathing valve can automatically adjust the discharge or entry of air in the oil tank, which is called "big breathing". Under normal circumstances, the amount of oil in the fuel tank will expand or compress due to the rise and fall of the outside temperature during the day and night, so the air will enter and exit through the breathing valve with the change of the amount of oil. People call this phenomenon "small breathing". The "breathing" of the fuel tank can fill the fuel tank in time, and when the oil is low, it can be supplemented with air; When there is too much oil, the air will run out. In this way, the top of the tank can be prevented from being damaged due to too large or too small pressure in the tank, and the safety of the oil tank can be ensured.

The second task of the oil depot is to load oil.

The so-called oil loading means loading the crude oil stored in Snoely into a tanker of a train or a car, and then transporting it abroad. The methods of loading oil can be roughly divided into "loading" and "loading".

The so-called "loading oil" means loading oil from the entrance at the upper part of the tanker (Figure 47). Usually, there are two methods. The first one is the trestle type oil loading with "small crane pipe", which acts like a faucet with a certain height and can rotate freely. The oiler stands on the trestle to operate the hanging pipe and observe the loading of the oil tank. When a tanker enters the special railway line, it can aim at the loading position to load oil, and can be loaded into multiple oil tanks at the same time. After loading, the tanker leaves the oil depot (Figure 48).

Fig. 47 is a schematic diagram

Fig. 48 schematic diagram of loading oil in small crane pipe

The second "big hanging pipe" oil loading method. The "big crane pipe" is like a big nozzle for refueling locomotives in a railway station, but it can automatically lift and move left and right, and can refuel multiple oil tanks at the same time (Figure 49).

Fig. 49 Oil loading of crane pipeline

When the tanker enters the proper position of the oil depot, the oil loading pipeline is connected with the oil unloading port at the bottom of the tanker through the oil loading arm and quick connector, and then the oil can be loaded. At present, in many oil depots in China, this kind of oil loading equipment has realized automatic control, greatly reducing the labor intensity of workers and raising the oil loading level to a new height.