Oil and gas pipeline transportation came about with the development of the oil industry. As early as October 1865, the United States built the world's first oil pipeline. The pipeline is 50mm in diameter and about 10km long. 1886 the United States also built the world's first long-distance gas pipeline. The pipeline runs from Kane, Pennsylvania to Buffalo, New York, with a length of 140km and a diameter of 200mm.
China constructed the first crude oil pipeline from the Karamay oilfield in Xinjiang to the Dushanzi oil refinery in 1958. The pipeline is 147km long with a diameter of 150mm. 1963 saw the construction of the first natural gas pipeline. The pipeline runs from Jiulongpo in Ba County, Chongqing to Banan District, with a total length of 84.14km and a pipe diameter of 400mm, referred to as the Bayu Line.In 1976, China built the Gera refined oil transportation pipeline. The pipeline starts from Golmud in Qinghai Province and ends at Lhasa in Tibet, located on the Tibetan Plateau, the roof of the world, and is the highest altitude oil pipeline, with a total length of 1,080km, and a pipe diameter of 150mm. since then, with the development of oil and gas fields in Daqing, Shengli, North China, Central China, Sichuan, etc., it has built a crude oil pipeline network through the Northeast, North and East China, the Sichuan-Yuzhou natural gas ring network, the Zhongwu, Shaanxi-Beijing, Shibing-ning-land natural gas pipelines, and the West-East gas pipeline, and the West-East gas pipeline. Sichuan and Chongqing natural gas ring network, Zhongwu, Shaanxi-Beijing, Shibining-Lan natural gas pipelines, and the West-to-East natural gas pipeline system. By 2013, the total length of completed oil and gas pipelines in China had exceeded 10×104km, initially forming a pattern of oil and gas pipeline network spanning across the east and west, north and south, covering the whole country and connecting to overseas.
One, the composition of oil and gas pipelines
There are many types of oil and gas pipelines, categorized in different ways. For example, according to the length and mode of operation can be divided into oil and gas transportation pipeline within the oil field pipeline and long-distance oil and gas transportation pipeline. According to the different types of medium being transported, the oil and gas transportation pipeline can be divided into crude oil transportation pipeline, refined oil transportation pipeline, natural gas transportation pipeline, oil and gas mixing pipeline and so on. According to the different locations of the pipeline, the oil and gas pipeline can be divided into onshore pipeline and submarine pipeline. The following mainly introduces the composition of long-distance oil pipeline and long-distance gas pipeline.
1. Long-distance oil pipeline composition
Long-distance oil pipeline by the station, line and auxiliary facilities and other parts of the composition, as shown in Figure 7-21.
Figure 7-21 Composition of long-distance oil pipeline
1-well field; 2-transfer station; 3-transmission pipeline from well field; 4-main facilities of the first station; 5-dispatch center; 6 -Tubing cleaner issuing area; 7 -Auxiliary facilities such as boiler room of the first station; 8 -Microwave communication tower; 9 -Line valve room; 10 -Dormitory; 11 -Intermediate station; 12, 13, 14 -Crossing railroads, river works; 15 -End station; 16 -Refinery; 17 -Loading trestle; 18 -Loading port
The main function of the oil transmission station is to pressurize and heat the oil. According to the different locations, the oil transmission station can be divided into the first station, intermediate station and end station. Pipeline starting point of the oil transfer station is called the first station, its task is to receive the oil field collection and transmission joint station, refinery production workshop or port tanker oil, etc., after measurement, pressurization, heating (for heating the transmission pipeline) into the next station. The first station generally has more oil storage equipment, pressurization, heating equipment and perfect metering facilities.
Oil in the process of transportation along the pipeline, due to friction, heat dissipation, terrain changes and other reasons, its pressure and temperature will continue to fall. When the pressure and temperature drop to a certain level, in order to make the oil continue to move forward, it is necessary to set up an intermediate oil transfer station to pressurize and warm up the oil. Separately pressurized oil transfer station is called intermediate pumping station; separately warmed oil transfer station is called intermediate heating station; both pressurized and warmed oil transfer station is called heat pumping station. According to the different functions, the intermediate station is usually equipped with pressurization, heating facilities, certain oil storage facilities, pipe cleaner sending and receiving facilities. Intermediate station should be equipped with a cross-station process.
The end station is located at the end of the pipeline oil transmission station (depot), its role is to receive pipeline oil, oil storage or transfer to the user. The end station is generally equipped with more oil storage equipment, more accurate metering facilities, oil transfer facilities and pipe cleaner sending and receiving facilities.
Long-distance pipeline line part includes the pipeline itself, along the valve room, through the rivers, valleys and other obstacles through (cross) crossing structures. Auxiliary facilities include communication, monitoring, cathodic protection, pipe cleaner sending and receiving and living facilities for staff along the line.
2. Composition of long-distance gas pipeline
Long-distance gas pipeline composition and long-distance oil pipeline is similar, also includes the first station, intermediate station, end station, trunk pipeline and auxiliary facilities and other parts, as shown in Figure 7-22.
The main function of the first station of the gas pipeline is to receive the incoming gas from the natural gas treatment plant, separate it (drying, dust removal), regulate the pressure and metering, and then send it to the trunk line. Unlike oil transmission, the pressure of gas extraction wells is relatively high, and natural gas extraction, processing, transmission of all aspects of the closed, in order to fully utilize the pressure of the gas wells, usually, the first station of the long-distance gas pipeline most of the pressurization equipment is not set up, and can rely on the residual pressure of the gas wells to the next station, such as Shaanxi and Beijing lines, the first booster station is located in the pipeline from the starting point of the 100km.
Figure 7-22 Composition of long-distance gas pipeline
Based on different functions, the intermediate station of the gas pipeline can be divided into receiving station, distribution station and gas pressure station. The function of the receiving station is to receive the gas from the branch line or gas source along the line; the function of the distribution station is to supply the gas to the branch line or users along the line; the function of the gas pressure station is to pressurize the gas.
The function of the end station of the gas pipeline is to receive the gas from the pipeline, separate it, regulate the pressure, measure it and send it to the gas distribution station of the users. If the end station directly to the city gas pipeline network, the end station can also be called the city gate station. In the conditions of the region, the end station should be built underground gas storage, in order to adjust the imbalance of gas supply.
Two, the characteristics of oil pipeline and operation control
(A) the characteristics of oil pipeline
1. hydraulic characteristics
Oil in the pipeline in the process of flow, the pressure can gradually reduce, often referred to as pressure drop. Pressure drop mainly includes along the course of the pressure drop (customarily referred to as pipeline friction), local pressure drop and differential pressure drop.
(1) along the course of the pressure drop: mainly oil flow through the straight pipe section, due to oil and pipe wall, oil and oil friction between the consumption of pressure energy. It can be calculated by Darcy's formula:
In the formula hL - pipeline along the resistance loss, m;
λ - along the friction resistance coefficient, dimensionless, related to the fluid flow;
g -- acceleration of gravity, m/s2;
v -- speed of movement of oil, m/s;
d -- inner diameter of the pipe, m;
L - the calculated length of the pipeline, m.
(2) local pressure drop: it refers to the pressure energy consumed when the oil flows through various fittings or valves. Long-distance oil pipeline pressure energy loss is mainly along the resistance loss, local resistance loss is relatively small, generally not calculated separately, but according to the different terrain along the pipeline undulation, take the trunk length of 1% to 2% as an additional length of local friction resistance loss along the line, combined in the pipeline along the friction resistance loss of the length of the calculation of the calculation of the length of the pipeline together. Usually, in the terrain is relatively flat lot, take the additional length of the local pressure drop along the length of the calculation of pressure drop of 1%; in the terrain undulation is relatively large lot to take 2%; other lots can be between 1% and 2% of the value.
(3) differential pressure drop: refers to the pipeline along the topographic changes caused by the transported oil in the pipeline moving water pressure rise or fall. Differential pressure drop in a certain pipe section is only related to the end of the pipe section and the beginning of the altitude, and the middle of the pipe section has nothing to do with terrain changes. The differential pressure drop in a pipe section is equal to the difference in elevation between the end and beginning of the calculated section.
Oil in the pipeline transportation process, the pressure energy consumed by the pumping unit to provide. For this reason, the pipeline should be set up along the line of a certain oil transfer pumping station to meet the oil flow flow consumed by the pressure energy. Arrangement of pumping stations, usually the first according to the working parameters of the pipeline, the longitudinal section of the pipeline drawing hydraulic slope drop line, initially determine the possible layout of the pumping station location, and then comprehensively consider the pipeline towards the humanities, geology, the environment, transportation, life and other conditions of the station site to make appropriate adjustments.
2. Thermal properties
Transportation of "three high" oil is a common method of heating transmission, the purpose of which is to increase the temperature of the oil, to avoid solidification of the oil flow in the pipeline; to reduce the oil in the paraffin wax, colloid and other precipitation and condensation in the wall of the pipeline; to reduce the viscosity of the oil, reducing the pressure drop in the pipeline.
Oil flow in the pipeline during the flow of temperature drop with the volume, ambient temperature, heat dissipation conditions, oil temperature and many other factors related to the heating of oil pipeline oil flow temperature along the line of the law of change can be used to calculate the Schulhoff temperature drop formula, that is:
In the formula G - pipeline quality of the volume of transmission, kg / s;
K -- oil flow through the pipe wall to the pipe laying the surrounding environment of the heat transfer coefficient, W / (m2 - ℃);
l -- temperature calculation point from the outlet of the heating station distance, m;
t0 -- temperature of the medium around the pipe, ℃;
tc -- temperature of the oil at the outlet of the heating station, ℃;
tl -- temperature of the oil at l from the outlet, ℃.
C - the specific heat capacity of the oil at the average conveying temperature, J/(kg-°C),
D - the calculated diameter of the pipeline (for the pipeline without thermal insulation, take the diameter of the steel pipe; for the pipeline with thermal insulation layer, take the thermal insulation layer The average value of the inner and outer diameters), m.
In fact, the supply and demand of heat energy and pressure energy for heating oil pipelines are interrelated and mutually affect each other. Increase the supply of thermal energy, the transport temperature rises, the viscosity of the oil is reduced, the pipeline frictional resistance is reduced. Increase the supply of pressure energy, on the one hand, the transmission volume increases, the temperature drop becomes slower; on the other hand, at a higher pressure, it can be transported to a lower temperature fluid. In this interconnection and influence of the two kinds of energy, heat energy is the dominant role. Therefore, the heating of the pipeline should be considered in its thermal characteristics and hydraulic characteristics, according to the thermal characteristics of the entire line of calculation of the number of heating stations required, according to the hydraulic characteristics of the entire line of determination of the number of pumping stations required, and then in the longitudinal section of the pipeline on the heating station, pumping station layout and calibration and adjustment.
(B) oil pipeline operation control
1. Operation parameter adjustment and control
In the process of oil pipeline operation, due to the influence of many factors, its operating conditions will change to a certain extent. Therefore, in the actual operation of the pipeline, sometimes need to regulate and control the parameters.
Regulation is generally used as the object of delivery, control is generally used as the object of the pumping station inlet and outlet pressure.
Transportation of many methods of adjustment, commonly used to change the speed of the pump, turning the pump impeller, demolition of multi-stage centrifugal pump impeller level, the size of the pump to match the size of the import and export throttling and so on.
The purpose of pressure regulation is to ensure the stability of the pipeline operation process, the object of its regulation is the inlet and outlet pressure of the oil station. The common measures of pressure regulation is to change the speed of the oil transfer pump unit, throttling and reflux.
2. Oil pipeline water strike and its control
Oil pipeline system during normal operation, its flow pattern is stable. However, in the actual production process, it is necessary to start and stop the pump, the opening and closing of the valve, process switching and other operations. These operations will make the pipeline fluid flow rate of the sudden change, thus causing a sudden change in the pressure inside the pipe, this phenomenon is called water strike.
Water strike hazard is mainly reflected in two aspects: one is overpressure hazard, may make the pipeline system pressure exceeds the pressure capacity of the pipeline pipeline damage; the second is the decompression damage, may make the pipeline system pressure is lower than the normal working pressure, resulting in the pipeline destabilization and deformation. Of course, the pressure wave generated by the water strike may also propagate upstream or downstream, which may have some influence on the characteristics of the pumping station upstream or downstream. Therefore, effective measures should be taken to control the hazards of water strike, commonly used methods are pressure relief protection, automatic adjustment of the control valve, automatic shutdown of the pumping unit and other protective measures.
Pressure relief protection is possible in the pipeline overpressure position, the installation of a special pressure relief valve, in the event of a water strike overpressure, open the pressure relief valve from the pipeline to release a certain amount of liquid, so that the pressure in the pipeline down to avoid water hazards.
Automatic adjustment of the regulating valve protection is based on changes in pipeline operating pressure automatically adjust the valve opening to meet the requirements of the protection of pipeline systems. Control valve automatic adjustment protection is mostly used in conjunction with other protective measures.
Automatic shutdown of the pumping unit is in the pumping station suction pressure is too low, the outgoing pressure is too high, through the automatic control system to shut down one or more pumps, in order to reduce the pumping station's energy output, reduce the pumping station's conveying capacity, so that the outgoing pressure drops, the incoming pressure rises. This method is mainly used for tandem pump unit pump station protection.
Three, the sequence of oil delivery
Oil sequence delivery refers to a pipeline, according to a certain batch and order, continuous delivery of different types of oil. As a result of frequent changes in the transmission of oil varieties, so in the alternation of two kinds of oil, in contact with the interface will produce a section of mixed oil. Mixed oil produced by two main factors: one is due to the cross-section of the pipeline, the liquid flow along the radial flow velocity distribution is not uniform, so that the back of the oil in a wedge shape into the front of the oil; the second is due to the turbulence of the pipeline liquid diffusion effect.
(I) detection of oil mixing
In order to guide the operation and management of the sequential transmission pipeline, it is necessary to detect the oil mixing in the process of alternation of the two oil products. At present, the commonly used methods to detect the concentration of mixed oil are density method, ultrasonic method, marking method.
Density method is the use of mixed oil density and the density of each component oil, concentration of the principle of linear superposition between the detection. This method is installed along the pipeline can automatically and continuously measure the density of oil detection instrument, through continuous detection of changes in the density of mixed oil, detection of changes in the concentration of mixed oil.
Ultrasonic method is based on the characteristics of sound waves in different densities of oil in the propagation speed of different detection. At room temperature, the greater the density of the oil, the faster the propagation speed of sound waves in the oil. Mixed oil concentration of ultrasonic method is based on this principle, in the pipeline along the installation of ultrasonic detection instrumentation, through continuous measurement of sound waves through the pipeline time, to determine the density of the oil flow in the pipe, so as to detect the concentration of mixed oil.
Marking method detection is the first fluorescent materials, chemical inert gases and other substances with the function of marking dissolved in organic solvents similar to the nature of the transported oil, made of marking solution. When used, in the pipeline at the beginning of the initial contact area of the two oil products to add a small amount of marking solution, the marking solution with the oil flow together, and along the axial diffusion, in the pipeline along the detection of the concentration distribution of marking substances in the oil flow, you can determine the oil mixing section and oil mixing interface.
(B) measures to reduce the amount of oil mixing
In the sequence of oil delivery, we always want to minimize the amount of oil mixing, there are many measures to control the amount of oil mixing, first of all, we can use advanced and reasonable technical and technological measures to reduce the amount of oil mixing (for example, to simplify the process, increase the amount of alternating oil delivery, the use of airtight conveying process, etc.); second is to take some specialized measures to Reduce the amount of mixed oil, such as mechanical isolation method and liquid isolation method.
Mechanical isolation method is to put certain mechanical facilities in the middle of the two kinds of oil, the two kinds of oil isolation, in order to reduce the mixing of oil. Commonly used isolation facilities are rubber isolation ball and leather bowl-shaped isolator.
Liquid isolation method is in the two alternating oil between the injection of isolation fluid, in order to reduce the amount of mixed oil. Commonly used as isolation fluid substances are: and two kinds of oil properties close to the third oil, two kinds of oil mixture, water or oil gel, other compounds of the gel, etc., of which the gel isolation fluid has better application characteristics.
(C) mixed oil treatment method
There are two main methods of dealing with mixed oil: one is to ensure that under the premise of the oil quality standard requirements, mixed oil in batches into the pure oil sales or downgrade use. Such as in the sequence of gasoline and diesel fuel delivery, the gasoline concentration of high mixed oil section received in the gasoline mixed oil storage tanks, diesel fuel concentration of high mixed oil section received in the diesel fuel mixed oil storage tanks, the two kinds of mixed oil mixed into gasoline and diesel fuel, respectively, in small batches of pure oil sales. This method is applicable to the lesser degree of oil mixing and the end point of the two oil products are sold in larger quantities. Secondly, the blended oil will be transferred to the refinery nearby for processing. This method is applicable to the heavier degree of oil mixing, or the end point of the mixed oil products in the pure oil sales volume is small.
Four, gas pipeline and city gas transmission and distribution
Gas pipeline is the only means of transporting large quantities of natural gas on land. One of the methods of transporting natural gas by sea is to reduce the natural gas to -160 ℃ to become liquefied natural gas, and then loaded on board the ship transportation, transported to the destination and then warmed by the liquid state into a gaseous state, to restore the performance of natural gas. Another method of natural gas transportation in the sea is still laying submarine gas pipelines. The natural gas produced from the North Sea oil fields in the Atlantic Ocean is transported to the UK and mainland Europe by a 1000km subsea pipeline.
The main components of natural gas are methane, ethane, propane, butane and other hydrocarbons, with small amounts of hydrogen sulfide, carbon dioxide and water vapor, and sometimes liquids such as condensate and water in the wells. Hydrogen sulfide and carbon dioxide, among others, must be removed at a treatment site before entering the pipeline.
Natural gas pipeline has the following characteristics: First, the gas pipeline is a continuous closed pressure delivery system, unlike the oil pipeline system, sometimes the oil into the atmospheric tanks; Second, the natural gas pipeline is more directly for the user services, direct supply of households or factories; Third, the natural gas density is small, the static head of influence is less than the oil pipeline, the design of the difference between the height of less than 200m static head of negligible, almost unaffected by the slope, the gas pipeline is not affected by the gradient, the gas pipeline is not affected by the gradient of the gas pipeline. Gas pipeline is almost unaffected by the slope; Fourth, natural gas is compressible, so there is no sudden stoppage of transmission generated by the water problem; Fifth, natural gas pipeline than oil pipeline to pay more attention to safety; Sixth, natural gas pipeline and city gas pipeline is different from natural gas from gas wells to start the transmission of pressure than the city of high gas, natural gas pipeline into the city after the terminus of the city pipeline to depressurize to the city pipeline pressure to the city of gas supply.
A complete city gas distribution system mainly consists of the following parts:
(1) gas distribution station. The gas distribution station is the starting point and general hub of the city gas distribution system, whose task is to accept the incoming gas from the trunk line pipeline, and then carry out the necessary treatment such as dust removal and odorizing, and then input it into the gas distribution network according to the user's demand after metering and pressure regulating for the user's use.
(2) Gas storage station. The task of the gas storage station is to store natural gas, which is used to balance the imbalance of urban gas consumption. The main equipment in its station is a variety of different types of gas storage tanks. In practice, gas distribution stations and gas storage stations are usually built together and are collectively called storage and distribution stations.
(3) Pressure regulating station. Pressure regulating station is set up in the city gas distribution pipeline network system of different pressure levels between the pipeline, or set up in some specialized users, there are aboveground and underground. The main equipment in the station is the regulator, whose task is to regulate the pressure of natural gas in the pipeline network according to the requirements of users to meet the needs of users.
(4) Gas distribution pipeline network. Gas distribution pipeline network is a pipeline system that transports and distributes natural gas to users. According to the shape can be divided into dendritic gas distribution pipeline network and ring gas distribution pipeline network. The former applies to small cities or enterprises within the gas supply, which is characterized by each gas point of the gas may only come from a direction; ring gas distribution network can be supplied from multiple directions, local failure, will not cause all gas supply interruption, high reliability, but the investment is larger.