Transportation of heavy crude oil

Transportation of heavy crude oil


At the beginning of explaining the transfer of heavy crude oil and natural bitumen, it should be said that according to the United States Energy Institute, the International Energy Agency (IEA) and the World Energy Association, the demand for energy increases annually with the increase in the world’s population. Global demand for crude oil has increased from 60 million barrels per day to 84 million barrels per day over the past 20 years.

In the past, due to the high costs of extraction, transportation, refining and low price in the market, the production of heavy crude oil and natural bitumen was considered uneconomical. On the other hand, the reduction of medium and light oil resources along with the increasing demand of energy in the world has become an incentive to extract and exploit these hydrocarbon resources. In Canada, about 700,000 barrels per day of synthetic oil are produced from heavy crude oil and oil sands and transported through pipelines to refineries in Canada and the United States.
Extraction and processing of heavy crude oil and natural bitumen due to their high viscosity (in other words, resistance to flow) in reservoir conditions, which reduces their mobility, and also high ratios of carbon to hydrogen, hard and it’s hard. However, with the increase in the price of crude oil, the reduction of medium and light crude oil reserves and the abundance of unconventional crude oil (i.e. heavy oil and oil sands or natural bitumen), the extraction and exploitation of these resources have been taken into consideration.

However, using the resources of heavy crude oil and natural bitumen in terms of technology in all stages, including extraction and production from the tank to transfer and refining in the refinery, is associated with many problems. Due to the high density and viscosity of heavy crude oil and natural bitumen (viscosity greater than cP 1000) and very low displacement capability at tank temperature, their transportation through pipelines will usually be a challenge.

It will be very difficult to transfer and refine these compounds due to the presence of asphaltene deposits, heavy metals, sulfur and salt using conventional refining methods and without improving their initial quality in order to reach the usual characteristics of light crude oil.
The high viscosity of 10 cP to 6 and the low API level of heavy oils (in the case of heavy oil less than 20 and for extra heavy oil less than 10) result from the high amount of asphaltene and the low relative contribution of compounds with low molecular weight. Heavy and extra heavy crude oil may contain large amounts of sulfur, salt and metals such as nickel and vanadium. The transfer of these compounds through the pipeline is accompanied by problems such as the instability of asphaltenes, paraffin precipitation and high viscosity, which cause multiphase flow, clogging of pipes, high pressure drop and interruption in the production path. Nevertheless, this category of petroleum materials has attracted growing attention from the oil industry. The current trend in increasing the exploitation of heavy crude oil and natural bitumen has been due to the reduction of medium and light crude oil reserves, limited supply and increase in the price of crude oil.
Currently, Canada and Venezuela are the main countries that use heavy crude oil reserves. 95% of the heavy crude oil produced in Canada and Venezuela is transported through pipelines. The reason for this is that the pipeline is low-cost, environmentally friendly and the most effective tool for transporting crude oil from the production field to the refinery.
The main recovery methods, such as the primary recovery method, which depends on the natural energy available in the reservoir to send the crude oil out of the well, are insufficient for the extraction of heavy crude oil and natural bitumen, which is due to the extremely high viscosity and resistance of the fluid to flow. is Therefore, after the primary and secondary recycling methods are used to produce and extract the remaining oil, additional extraction methods are used by applying thermal energy or injecting a fluid. The extraction methods are generally thermal methods, using solvents (light hydrocarbons, gas, carbon dioxide, nitrogen, etc.), chemical (injection of surfactants, alkaline compounds, polymeric materials, etc.) and biological methods. Viscosity division of heavy crude oil and natural bitumen, unlike other non-thermal methods where the process of viscosity reduction will be quite slow and dependent on the amount of diffusion and dispersion of liquids, will quickly decrease by several times.
In the meantime, the most common thermal method of increasing harvest, which is used in the oil industry,
1 – Steam sealing, steam intensification cycle
2- (CSS), steam injection with gravity separation
3- (SAGD), combustion in place
4- (ISC), the method of injecting air and making fire (THAI).

In all these cases, the goal is to increase the mobility of heavy crude oil and bitumen by reducing the viscosity in order to improve recovery or production, and then to improve the conditions of transportation through the pipeline. The existing desire to exploit the sources of heavy crude oil and natural bitumen in the oil industry has led to the development of various methods and technologies for the transfer of these compounds.
The important thing about heavy crude oil is the high share of compounds with high molecular weight, including asphaltenes. In this regard, problems may occur due to the instability of asphaltene, such as the formation of asphaltene precipitation as a result of reducing the pressure to below the starting pressure of asphaltene precipitation during the transportation of heavy crude oil. Also, clogging in the pipe wall may also occur as a result of asphaltene precipitation. which reduces the cross-sectional area of the pipe for the passage of oil fluid and while reducing the intensity of the flow, it causes an increase in pressure drop and the creation of multiphase flow.
There are various methods to improve and facilitate the transportation of heavy oil through the pipeline, including preheating the oil along with heating the pipeline, mixing and diluting the oil using light hydrocarbons, and forming heavy oil emulsion. In water, he pointed out the improvement of the relative quality and the creation of an annular flow in the center of the pipe.

In this article, an attempt has been made to examine the various technologies available for the transfer of heavy crude oil in terms of the advantages and disadvantages of each method, with the aim of conducting additional research and experiments in order to reach a practical solution to improve the economic transfer of oil. To be used heavily.

Transportation of heavy crude oil

In order to transport heavy crude oil optimally and economically, it is necessary to minimize the required power of the pump to pump oil in a long way by reducing the pressure drop of the pipeline. However, due to the high viscosity of these compounds in reservoir conditions compared to normal light crude oil, the use of conventional pipelines to transport heavy crude oil and natural bitumen to the refinery is not suitable, and the viscosity of these compounds must be reduced first. . As shown in the figure, in general, the methods used to improve the transportation of heavy oil and natural bitumen through the pipeline can be divided into three categories:

Figure 1. Classification of different methods of improving the transportation of heavy oil and natural bitumen using pipelines

A- Viscosity reduction (for example, preheating heavy crude oil and natural bitumen and then heating the pipeline, mixing and diluting with the help of light hydrocarbon compounds or solvents, creating an emulsion of oil in water and reducing the pour point of oil by means of a reducing agent Pouring point (PPD)
B- Reducing friction (for example, pipeline lubrication using a central flow of reducing additives
friction giver)
C- Upgrading and converting in place

Heavy oil and the production of a synthetic oil with improved viscosity and API grade and with the lowest amount of asphaltene, sulfur and heavy metals.

Methods of reducing viscosity


Dilution of heavy crude oil in order to reduce viscosity is one of the tools to improve the transmission through the pipeline, which has been used as a common method since the 1930s in the oil industry. Diluting fluid always has a lower viscosity than heavy crude oil and natural bitumen. It is well known that the lower the viscosity of the diluting fluid, the more the viscosity of the resulting mixture will decrease. The main diluents used are natural gas condensate, naphtha, white oil and lighter crude oil. However, the use of organic solvents such as alcohol, methyl tert-butyl ether, tert-amyl methyl ether has also been investigated. The use of these organic solvents was considered based on their use as an improver of the octane number of gasoline. A mixture of hydrocarbons and organic solvents that have a polar group in their molecular structure have shown positive effects in reducing the viscosity of heavy crude oil at a fixed dilution rate. By using dilution, it is possible to transfer large amounts of heavy crude oil. . The mixture resulting from mixing heavy crude oil and agent
The thinner has a lower viscosity, and as a result, it is easily transported by the pump at a lower cost.
The dilution of heavy crude oil in order to improve its transfer process through the pipeline requires two sets of pipelines, one for the oil and the other for transferring the recycled diluent to the beginning of the transfer path.
Of course, it is clear that the use of diluent to improve the conditions of heavy crude oil transportation will be economical only if the dilution agent is relatively cheap and easily available.
The amount of diluent required for heavy crude oil or in other words the proportion of diluent in the final mixture varies from 0 to 20%, while in the case of natural bitumen, this amount is in the range of 25 to 50%.
Light condensate of natural gas (C5 + composition) is a mixture of liquid hydrocarbons with low density and viscosity, which is obtained as a by-product in the processing of natural gas. This condensate, which is recovered from natural gas, is used as a dilution agent for heavy crude oil. And natural bitumen has been used in the oil fields of Canada and Venezuela with the aim of improving the conditions of transporting these heavy compounds through the pipeline.

Although it is significantly reduced by mixing heavy crude oil and natural bitumen with viscous gas condensate, the precipitation, separation and accumulation of asphaltene will cause instability during transportation and storage. The reason for this is that the asphaltene in crude oil Heavy is insoluble in alkanes such as normal pentane and heptanes, and the condensate is known as a light oil rich in paraffin. Also, asphaltene particles tend to interact with each other and accumulate.

The viscosity of the mixture obtained from oil and condensate depends on factors such as the characteristics of heavy crude oil or bitumen, the characteristics of condensate, the degree of dilution, the ratio of heavy oil to condensate, and also the operating temperature.

The limitations that can exist in the use of condensate are:


Its availability, which depends on the demand for natural gas, due to the growing production of heavy crude oil and natural bitumen, the production of condensate is not sufficient to meet the existing need for use as a diluent. Also, most of its components are not good solvents for asphaltene, and as a result, sedimentation may increase. The instability of condensate during storage is also one of its limitations.
In this context, the use of light crude oil has also been investigated, but compared to condensate, it has a lesser effect in reducing the viscosity of heavy crude oil and natural bitumen. The compatibility of light oil, in addition to its availability, in the face of the reduction of normal light crude oil reserves, its application and use as a diluting compound for heavy crude oil is limited. Based on the studies, light hydrocarbons such as kerosene are also effective in improving the conditions of transporting heavy crude oil and natural bitumen through the pipeline. Lederer presented an empirical relationship similar to the classical Arrhenius relationship to estimate the viscosity of the mixture resulting from the mixing of heavy crude oil and diluents. Based on this, the viscosity of the mixture will be calculated.

In this regard, Vo and Vd are respectively the volume fraction of heavy crude oil and diluent, µo and µd are the viscosity of heavy crude oil or bitumen and diluent respectively. α is also an experimental constant whose value varies between 0 and 1. Shu proposed an empirical formula to determine the constant α for the mixture obtained by mixing heavy crude oil or bitumen with light hydrocarbon diluents. The desired relationship depends on the viscosity ratio of oil to diluent (light hydrocarbons) and their density.

Most of the light hydrocarbons used to dilute heavy crude oil and bitumen are expensive and not readily available in large quantities. For this reason, it will be necessary to recover the diluents and return them for reuse. However, the separation of diluents from oil requires the installation and use of additional pipelines, which, of course, leads to an increase in operating costs. In addition, in order to easily and conveniently transport heavy crude oil and bitumen through pipelines, the viscosity of diluted or mixed oil should be less than 0.2 s.Pa. Another diluent that is commonly used is an oil cut. It is called Nafta. Naphtha has a high API grade and shows good compatibility with asphaltenes. Gatto suggested that a mixture of naphtha and an organic solvent could reduce the amount of diluent needed. In the figure, the decreasing trend of the relative viscosity of heavy crude oil diluted by a mixture of naphtha and an organic solvent is well observed. The reason for this can be the increase in polarity or hydrogen bonding of solvents and the ability of polar solvents to affect the asphaltene compounds of heavy crude oil. In this set of tests, the crude oil sample is mixed with 15 percent by weight of diluent and then its viscosity is measured. The viscosity of the crude oil sample at the beginning and before adding naphtha as an equivalent diluent
s.Pa 440 is reported.


Another method that is usually used to reduce the viscosity of heavy crude oil and bitumen and to improve the absorption flow.
They are used

تاثیر-دما-بر-کاهش-گرانروی-نفت-خام Effect of temperature on viscosity

Use of temperature effect. Heating the pipeline causes a rapid drop in viscosity and a decrease in the oil’s resistance to flow. The effect of temperature on the viscosity of several heavy crude oil samples is shown in Fig. As can be seen, heating can be used as a tool to reduce the viscosity of heavy petroleum compounds. As the temperature increases, the viscosity of heavy oils decreases several times. In this method, heavy crude oil is preheated and then the pipeline is heated to improve the flow.

The effect of a mixture of naphtha and different organic solvents on the viscosity of a heavy crude oil sample at 20°C. The numbers represent the volume fraction of the solvent used in the mixture of naphtha and solvent.

Effect of temperature on viscosity reduction of different crude oil samples


However, heating with the aim of increasing the temperature of the fluid will require a large amount of energy and cost.
Also, internal corrosion of pipelines increases at higher temperatures. Heating the pipeline may cause changes in the rheological properties of crude oil, which can cause flow instability. In addition to the heat loss that occurs along the pipeline and due to low oil flow, a large number of heating stations are required, which increases costs. Of course, in most cases, the pipeline is insulated to maintain high temperature and reduce heat loss to the surrounding environment.

Also, sudden expansion and contraction along the pipeline can cause problems. As a result, all these cases increase the operating costs of the heating method along with the pumping systems for a long distance between the oil field and the storage place or the final refinery.

This method is not suitable and cannot be used in the case of crude oil transportation through undersea pipelines. It should be noted that the cooling effect of water and land around the pipeline makes this method more efficient.

Emulsion of heavy crude oil in water


Emulsion of crude oil in water is present in oil tanks, inside the well, during drilling and during transportation. This method is one of the newest tools for transferring heavy crude oil through the pipeline in the form of oil-in-water (W/O) emulsion, water-in-oil (O/W) or double emulsion such as oil-in-water-in-oil (O/O) W/O) and water in oil in water (W/O/W) with a particle size of about microns. The creation of oil-in-water emulsion has been proposed as an alternative method to improve the transportation of heavy crude oil through pipelines.

In this method, heavy crude oil is emulsified in water and is stabilized with the help of surfactants. With the help of surfactants, oil is dispersed in water in the form of droplets, and a stable emulsion of oil in water with lower viscosity is produced. The methods used to create oil droplets include the use of tools such as high-speed stirrers, stirring with a stator rotor, colloidal mill, high-pressure homogenizer devices, creating emulsions with the help of membranes and ultrasonic waves.

A layer of surface active materials placed in the water-oil interface prevents the growth of droplets and the creation of phase separation and the formation of separate oil and water phases from each other. A single layer of surface active material is located on the common surface of the oil-in-water emulsion in such a way that its polar part (hydrophilic head) is in contact with water and its end and non-polar part (hydrophobic part) is in contact with oil.

This is the feature of the surface active substance layer that stabilizes the oil-water contact surface and controls the behavior of the emulsion. Heavy crude oil is a complex mixture of thousands of different compounds. Meanwhile, asphaltenes act as natural emulsifiers. Other surface active compounds in crude oil include naphthenic acids, resins, perphyrins, etc.

The presence of these compounds increases the complexity of crude oil emulsion. The transfer of heavy crude oil using emulsion technology includes three stages: creating an oil/water emulsion, transferring the formed emulsion, and separating the oil phase from the water phase. Of course, the recovery and separation of crude oil requires breaking the emulsion of oil in water.

In the separation stage, methods such as thermal demulsification, electrical demulsification, chemical demulsification, pH change, solvent addition and membrane demulsification can be used. The use of surfactants and water with the aim of creating a stable oil-in-water emulsion with heavy crude oil in order to improve its transfer using a pipeline has been the subject of various researches and numerous patents.

The rheology of the created emulsion is an important condition in improving the transmission through the pipeline. Emulsion rheology mainly depends on the volume of distributed oil and droplet size distribution. Droplet size distribution also depends on the type of surfactants, mixing energy and pressure. Surface active materials that are usually used are non-ionic compounds such as Triton 114-X, which, based on their ability, have various capabilities such as stability against the accompanying water salinity, cheapness, easy separation of the emulsion caused by them, and no formation of organic compounds. They have unfavorable properties that change the properties of oil. However, heavy crude oil emulsions have Newtonian force both at high shear stresses and show shear thinning behavior at low shear stresses. The flow characteristics of the created emulsion will depend on the characteristics of the hydrophilic polar part and the hydrophobic non-polar end of the used surfactants.
There are various basic challenges related to the application of this technology in order to transfer heavy crude oil, among which the following can be mentioned: cost and choice of surfactant; The ability of the surfactant to maintain the stability of the emulsion during transportation through the pipeline; Ease of separation of surfactants from crude oil at the end point, especially considering that the density of heavy oil is close to the density of water; The various characteristics of the formed emulsion, such as rheological and stable characteristics, which depend on various parameters such as particle size distribution, temperature, salinity and pH of water, components in heavy crude oil, energy spent for mixing and oil/water volume ratio.

It should be mentioned that the presence of natural hydrophilic particles and compounds such as clay and silica in crude oil can cause emulsion instability.
Various studies have been conducted in relation to the rheological properties of emulsions. According to one of the latest works in this field, various factors including temperature, salt concentration, oil volume fraction and the number of stirrer revolutions can affect the rheology of crude oil emulsion. Various mechanisms through which it is possible.

امولسیون-نفت-و-قیر-طبیعی Oil and natural bitumen emulsion

Instability in oil-in-water emulsion means:

1- Oswald’s evolutionary process

2- Sedimentation or creaming due to the difference in density and the continuity of the drops. But the necessity and reduction of tension is to use a surfactant to make the emulsion stable against interfacial cuts.
Sometimes, the oil-in-water emulsion system may contain solid particles and gas, which will increase the complexity of the process.

3- In general, the smaller the droplet size, about 10 micrometers or less, the better the stability of the emulsion. The behavior of the emulsion obtained from heavy crude oil in water is complicated due to the interaction between the various components in the system and many other factors that were mentioned. This method of transferring heavy crude oil in the emulsion process
It was developed by the Venezuelan Oil Company (PDVSA) in the 1980s. More details of this process have been provided by various individuals and research groups.

Lowering the pour point


Heavy crude oil is described as a colloidal suspension containing soluble asphaltenes and a liquid phase of maltenes. The interconnection and deposition of asphaltene macromolecules in oil is due to its viscosity and high density, and it creates a great resistance against the flow inside the pipeline.
Therefore, reducing this effect through the use of drop point reducers can improve the properties
be a flow of oil. The pour point of oil is the lowest temperature at which the fluid flow stops and properties
It loses its flow.

For example, it is very difficult to transport waxy crude oil through a pipeline in cold weather. The reason for this is that the decrease in temperature causes the growth of crystals that prevent the flow of oil molecules. The crystallization process depends on weather, structure and composition of oil, temperature and pressure during transfer. There have been various methods to minimize wax and asphaltene precipitation agents, and among them, the use of polymer inhibitors has been considered as an alternative.

The addition of co-polymers such as polyacrylate, polymethacrylate, methacrylate, etc. prevents precipitation and stabilizes the transmission. Based on the viscosity measurement data, Makado found that at a temperature lower than the starting temperature of the wax crystals, the copolymer will have a great effect in reducing the viscosity. In order to prevent the formation of wax crystals that can cause pipeline clogging, pour point reducing agents are used, which contain an alkyl group with a long chain length and soluble in oil and a semi-polar molecular structure. The long chain alkyl group penetrates into the wax crystal and the polar part is placed on the surface of the wax and reduces the size of the wax crystal.

In most cases, the compounds that reduce the pour point have very polar functional groups.

Friction reduction methods


The high viscosity of crude oil causes many problems in its production, refining and transportation through wells and pipelines. The drag force, wall friction and pressure drop in the pipeline are much higher in the case of heavy crude oil compared to conventional light oil. Drag is the result of the stresses created in the wall by the fluid and causes a drop in fluid pressure. This factor causes the transportation of oil through the pipeline to long distances with problems.

Accordingly, drag reduction is a lubrication method based on core-annular flow to reduce pressure drop in heavy oil transportation through pipelines.
The most common method of reducing friction in order to improve the conditions of transporting heavy oil through the pipeline includes the addition of drag reducing substances and the creation of core-annular flow. Both methods reduce flow drag by changing the velocity field, for example, by reducing turbulent disturbances near the pipeline wall region. However, in most of the studies conducted on the reduction of drag, viscosity reduction through physical or chemical methods has been discussed, but according to Newton’s law of viscosity, flow drag is dependent on fluid viscosity and velocity profile.

Additives to reduce drag


The pressure drop that occurs during the transportation of heavy crude oil through the pipeline is more important in long distances and its effect will be more severe. In this case, the use of drag reducing additives is proposed as an option to reduce the negative effects of pressure drop. In the transportation of crude oil through the pipeline, the flow is often in turbulent conditions. Also, the high frictional loss caused by high viscosity causes the loss of a large part of the energy used to transport crude oil. High drag in turbulent flow is caused by the radial transfer of flow momentum by small fluid vortices. Polymer drag reduction technology was presented in the past decades. Based on the observations made, adding polymer material (methyl methacrylate) to the pipeline containing the turbulent flow of monochlorobenzene has reduced the drag by 30 to 40 percent. Accordingly, drag reducing additives help to reduce friction near the walls of the pipeline and in the turbulent flow in the center of the fluid flow.

Drag reducing additives are divided into three categories:


1- Polymers 2- Fibers 3- Surfactants.


The main role of these additives is to reduce the growth of turbulent flow vortices by absorbing the energy released from breaking and collapsing the laminar flow layers. Also, these additives help to reduce the friction near the pipeline walls and inside the central core and the turbulent flow, which will result in higher flow rates at a constant pumping pressure. According to the mentioned contents, the solubility of the drag reducing additive in heavy crude oil will be an important and main factor in choosing the appropriate additive.
Also, a suitable additive should be resistant and stable against decomposition, chemical agents and heat.
In connection with the common problems related to the use of these additives, we can mention the tendency of these compounds to separate from the main phase during storage, the problems related to the dissolution of these materials in heavy crude oil, and the problem of shear destruction during dissolution. Also, determining the amount of additive needed to keep the pressure drop constant is one of the difficulties of this method.

گرانروی-قیر-طبیعی-ونفت Viscosity of natural bitumen

Creation of core-ring current


The high viscosity of bitumen and heavy oil causes a large pressure drop during transportation through the pipeline, and for this reason, pumping crude oil in single-phase flow conditions is associated with many difficulties. One of the other ways to reduce pressure drop caused by friction in pipelines in order to facilitate the transfer of bitumen and heavy crude oil is the development of core-annular flow. The main idea of this method is to surround the core and central part of the heavy crude oil while it is flowing in the pipeline by a thin film of water or solvent near the pipe wall, which acts as a lubricant and causes the pump pressure to be approximately Maintain the pressure required to pump water or solvent. In this case, water or solvent flows like a ring and heavy crude oil forms the core of the flow.

In this method, the required water or solvent is between 10 and 30% of the oil flow. In these conditions, the pressure drop along the length
The pipeline is weakly dependent on the viscosity of heavy oil and will be more dependent on the viscosity of water. Also, in the conditions where heavy oil flows in the center of the pipe and water near the surface of the pipe wall, the pressure drop is reduced by 90% compared to the condition without water lubrication. The pipelines are visible.

In this flow regime, the solvent flows on the surface of the pipe wall and lubricates the heavy oil that flows in the core. In this case, the flow of heavy oil in the core is almost a pipe flow. However, in the case of the two-phase flow of water and oil in the pipeline, different flow regimes may be observed depending on the characteristics of the oil such as density, surface tension, flow rate and intensity of fluid injection flow.

Although by using this method it is possible to reduce the pressure drop of the flow to the level of the pressure drop of the water transfer, but reaching the complete core-annular flow happens rarely and only for fluids whose density is close to each other. When the density difference between oil and water is high, the Archimedes force causes the radial movement of the oil core.

This effect causes the transfer of the core to the upper wall of the pipeline. In addition, the stability of the flow system is still under investigation.
The flow speed and capillary instability caused by surface tension causes the core to break. But increasing the speed improves the stability of the kernel.

In-situ quality improvement method


The increase in the exploration of huge sources of heavy oil and bitumen with the aim of meeting global demands and environmental concerns has led to the participation and accompaniment of in-situ quality improvement methods along with increasing oil recovery. It will be possible to upgrade the oil in situ when using heat recovery methods such as ISC, SAGD, CSS and the new THAI method and the catalytic process of improving the quality of the in situ. These processes are based on reducing the viscosity of heavy crude oil through heat in order to improve the flow from the reservoir to the production well. Quality improvement is done by separating and thermal decomposition of heavy molecules into smaller molecules. In-situ thermal fracture reaction reduces the viscosity of heavy oil and bitumen, and as a result improves flow and production. However, among all these processes, the THAI process combines a catalytic upgrading process with an oil recovery method.



In order to increase the extraction of heavy oil and bitumen, it is necessary to develop technologies to transfer these compounds through pipelines. In this article, different methods and technologies for the transfer of heavy and extra heavy crude oil from exploration and production areas to the place of processing and refining were examined.
Fully practical technologies along with new methods for transferring heavy crude oil have been formed mainly on the basis of reducing the viscosity of crude oil, reducing the drag force in the pipeline and improving the relative quality of crude oil to synthetic oil. Each of the three categories mentioned in the field of viscosity reduction and pressure drop methods with the aim of facilitating the transfer of heavy crude oil through the pipeline along with the advantages and disadvantages of each one were stated.

According to the study, improvement of the operation method, reliability, cost, dimensions and size of the equipment, repairability
And the maintenance, infrastructure and required resources, the type of crude oil and changes in the quality of crude oil can be considered as important and effective factors in this field.

With the increase in the production of heavy and extra heavy crude oil in different regions of the world, more innovation in technology and research and development will be needed in order to achieve a suitable solution for transporting heavy crude oil. In fact, the existing answers as well as the future solutions should include things such as the structure and physical and chemical properties of the produced oils, the logical transfer between the production well and the place of export or refining, the existing infrastructure and operational issues, the transfer distance, The quality of crude oil for export or refining, operating and maintenance costs, environmental issues. In the meantime, it will be cost-effective to transfer crude oil by viscosity reduction method in operational areas where sufficient quantities of lighter oils, condensates or water are available and the necessary infrastructure for mixing is available.

Of course, in this connection, the examination and determination of the characteristics of diluted crude oil should also be considered in order to achieve an economic and suitable solution. Research and development related to surfactants, flow improvers, drag reducing compounds, catalysts and other valuable additives are among the research fields in the transfer of heavy oil compounds.

In addition to conducting basic research and with the aim of creating confidence in the audience and users of new technologies, the development of crude oil transfer methods should be based on the results obtained from pilot tests and semi-industrial units.

By examining the development process of different methods, it is expected that in the near future, the path of crude oil transfer technologies will be directed from outside well methods to inside well methods, and in other words, oil-water emulsion can be formed in the tank or crude oil The inside of the tank will be upgraded and find more suitable conditions for transfer.

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