Today, oil and gas have the greatest value among all minerals. It is they, despite the development of new technologies in the field of energy, that continue to be mined around the world and used to produce products necessary for human life. However, along with them there is the so-called associated petroleum gas, which has not found any use for quite a long time. But in the last few years, the attitude towards this type of mineral has changed radically. It began to be valued and used along with natural gas.

Associated petroleum gas (APG) is a mixture of various gaseous hydrocarbons that are dissolved in oil and are released during oil production and treatment. In addition, APG is also the name given to those gases that are released during thermal processing of oil, for example, cracking or hydrotreating. Such gases consist of saturated and unsaturated hydrocarbons, which include methane and ethylene.

It is worth noting that associated petroleum gas is contained in oil in different quantities. One ton of oil can contain either one cubic meter of APG or several thousand. Since associated petroleum gas is released only during the separation of oil, and it cannot be produced in any other way except together with oil, then, accordingly, it is a by-product of oil production.

The main place in the composition of APG is occupied by methane and heavier hydrocarbons, such as ethane, butane, propane and others. It is worth noting that different oil fields will contain, firstly, different volumes of associated petroleum gas, and, secondly, it will have different compositions. Thus, in some regions, non-hydrocarbon components (compounds of nitrogen, sulfur, oxygen) can be found in the composition of such gas. Also, the gas that comes out of the ground in the form of fountains after opening oil layers contains a reduced amount of heavy hydrocarbon gases. This is due to the fact that the part of the gas that appears to be “heavier” remains in the oil itself. In this regard, at the very beginning of the development of oil fields, APG, which contains a large amount of methane, is produced along with oil. However, with further development of the field, this indicator decreases and heavy hydrocarbons become the main components of the gas.

Utilization of associated petroleum gas

Until recently, this gas was not used in any way. Immediately after its production, associated petroleum gas was flared. This was mainly due to the fact that there was no necessary infrastructure for its collection, transportation and processing, as a result of which the bulk of APG was simply lost. Therefore, most of it was burned in torches. However, the combustion of associated petroleum gas had a number of negative consequences associated with the release into the atmosphere of a huge amount of pollutants, such as soot particles, carbon dioxide, sulfur dioxide and much more. The higher the concentration of these substances in the atmosphere, the less healthy people are, since they can cause diseases of the reproductive system of the human body, hereditary pathologies, cancer, etc.

Thus, until recently, much attention was paid to the utilization and processing of associated petroleum gas. Thus, there are several methods that have been used to utilize APG:

1. Processing of associated petroleum gas for energy purposes. This method allows the use of gas as fuel for industrial purposes. This processing method ultimately produces environmentally friendly gas with improved properties. In addition, this method of disposal is very beneficial for production, since it allows the enterprise to save its own funds. This technology has many advantages, one of which is environmental friendliness. Indeed, unlike simple APG combustion, in this case there is no combustion, and, therefore, the emission of harmful substances into the atmosphere is minimal. In addition, it is possible to remotely control the gas utilization process.
2. Application of APG in the petrochemical industry. Processing of such gas takes place with the appearance of dry gas, gasoline. The resulting products are used to satisfy household production needs. For example, such mixtures are integral participants in the production processes of many artificial petrochemical products, such as plastics, high-octane gasoline, and many polymers;
3. Enhanced oil recovery by injecting APG into the reservoir. This method causes the combination of APG with water, oil, and other rocks, resulting in a reaction that interacts with exchange and mutual dissolution. In this process, water is saturated with chemical elements, which, in turn, leads to a more intensive oil production process. However, despite the fact that this method, on the one hand, is useful, as it increases oil recovery, on the other hand, it causes irreparable damage to the equipment. This is due to the deposition of salts on the equipment during the use of this method. Therefore, if such a method makes sense to apply, then along with it many activities are carried out aimed at preserving living organisms;
4. Using "galzift". In other words, gas is pumped into the well. This method is distinguished by its cost-effectiveness, since in this case you only need to spend money on purchasing the appropriate equipment. The method is advisable to use for shallow wells in which large pressure drops are observed. In addition, “gas lift” is often used when installing rope systems.

Despite the variety of methods for processing associated petroleum gas, the most common is the separation of gas into components. Thanks to this method, it becomes possible to obtain dry purified gas, which is no worse than the natural gas familiar to everyone, as well as a wide fraction of light hydrocarbons. In this form, the mixture is suitable for use as a raw material for the petrochemical industry.

Use of associated petroleum gas

Today, associated petroleum gas is no less valuable mineral resource than oil and natural gas. It is extracted as a by-product of petroleum and is used as fuel, as well as for the production of various substances in the chemical industry. Petroleum gases are also an excellent source for producing propylene, butylenes, butadiene and other products involved in the production of materials such as plastics and rubbers. It is worth noting that in the process of multiple studies of associated petroleum gas, it was revealed that it is a very valuable raw material because it has certain properties. One of these properties is its high calorific value, since its combustion releases about 9-15 thousand kcal/cubic meter.

In addition, as mentioned earlier, associated gas, due to its methane and ethane content, is an excellent source material for the production of various substances used in the chemical industry, as well as for the production of fuel additives, aromatic hydrocarbons and liquefied hydrocarbon gases.

This resource is used depending on the size of the deposit. For example, the gas that is extracted from small deposits would be appropriate to use to provide electricity to local consumers. It is most rational to sell the extracted resource from medium-sized deposits to chemical industry enterprises. It is appropriate to use gas from large deposits to produce electricity at large power plants for further sale.

Thus, it is worth noting that associated natural gas is currently considered a very valuable mineral resource. Thanks to the development of technology and the invention of new ways to clean the atmosphere from industrial pollution, people have learned to extract and rationally use APG with minimal harm to the environment. At the same time, today APG is practically not recycled, but is used rationally.

Associated petroleum gas (APG), as the name suggests, is a by-product of oil production. Oil lies in the ground along with gas, and it is technically almost impossible to ensure the production of an exclusively liquid phase of hydrocarbons, leaving gas inside the formation.

At this stage, gas is perceived as an associated raw material, since world oil prices determine the greater value of the liquid phase. Unlike gas fields, where all production and technical characteristics of production are aimed at extracting exclusively the gaseous phase (with a slight admixture of gas condensate), oil fields are not equipped in such a way as to effectively carry out the process of production and utilization of associated gas.

Further in this chapter, the technical and economic aspects of APG production will be examined in more detail, and based on the conclusions obtained, the parameters for which an econometric model will be built will be selected.

General characteristics of associated petroleum gas

The description of the technical aspects of hydrocarbon production begins with a description of the conditions of their occurrence.

Oil itself is formed from the organic remains of dead organisms settling on the sea and river bottoms. Over time, water and silt protected the substance from decomposition, and as new layers accumulated, the pressure on the underlying strata increased, which, together with temperature and chemical conditions, caused the formation of oil and natural gas.

Oil and gas occur together. Under conditions of high pressure, these substances accumulate in the pores of the so-called parent rocks, and gradually, undergoing a process of continuous transformation, rise to the top by microcapillary forces. But as it goes up, a trap can form - when a denser layer covers the layer through which the hydrocarbon migrates, and thus accumulation occurs. At the moment when a sufficient amount of hydrocarbons has accumulated, the process of displacing initially salty water, heavier than oil, begins to occur. Next, the oil itself is separated from the lighter gas, but some of the dissolved gas remains in the liquid fraction. It is the separated water and gas that serve as tools for pushing oil outward, forming water or gas pressure regimes.

Based on the conditions, depth and contour of the location, the developer selects the number of wells to maximize production.

The main modern type of drilling used is rotary drilling. In this case, drilling is accompanied by a continuous rise of drill cuttings - formation fragments separated by a drill bit - outward. In this case, to improve drilling conditions, a drilling fluid is used, often consisting of a mixture of chemical reagents. [Gray Forest, 2001]

The composition of associated petroleum gas will vary from field to field - depending on the entire geological history of the formation of these deposits (source rock, physical and chemical conditions, etc.). On average, the proportion of methane content in such gas is 70% (for comparison, natural gas contains up to 99% of its volume in methane). A large number of impurities creates, on the one hand, difficulties for transporting gas through the gas transmission system (GTS), on the other hand, the presence of such extremely important components as ethane, propane, butane, isobutane, etc. makes associated gas an extremely desirable raw material for petrochemical production . The oil fields of Western Siberia are characterized by the following indicators of hydrocarbon content in associated gas [Popular Petrochemistry, 2011]:

• Methane 60-70%
• Ethane 5-13%
• · Propane 10-17%
• · Butane 8-9%

TU 0271-016-00148300-2005 “Associated petroleum gas subject to delivery to consumers” defines the following categories of APG (according to the content of C 3 ++ components, g/m 3):

• · “Skinny” - less than 100
• · “Medium” - 101-200
• · “Fat” - 201-350
• · Extra fatty - more than 351

The following figure [Filippov, 2011] indicates the main activities carried out with associated petroleum gas and the effects achieved by these activities.

Figure 1 - Main activities carried out with APG and the effects from them, source: http://www.avfinfo.ru/page/inzhiniring-002

During oil production and further step-by-step separation, the gas released has a different composition - the gas with a high content of methane fraction is released first, and at the next stages of separation gas is released with an increasingly higher content of hydrocarbons of a higher order. Factors influencing the release of associated gas are temperature and pressure.

A gas chromatograph is used to determine the content of associated gas. When determining the composition of associated gas, it is also important to pay attention to the presence of non-hydrocarbon components - for example, the presence of hydrogen sulfide in APG can negatively affect the possibility of gas transportation, since corrosion processes can occur in the pipeline.

Figure 2 - Scheme of oil preparation and APG accounting, source: Skolkovo Energy Center

Figure 2 schematically depicts the process of step-by-step oil refining with the release of associated gas. As can be seen from the figure, associated gas is mostly a by-product of the primary separation of hydrocarbons produced from an oil well. The problem of metering associated gas lies in the need to install automatic metering devices at several stages of separation, and subsequently deliveries for disposal (gas processing plants, boiler houses, etc.).

The main installations used at production sites [Filippov, 2009]:

• Booster pumping stations (BPS)
• Oil separation units (OSN)
• · Oil treatment units (OPN)
• · Central oil treatment points (CPPN)

The number of stages depends on the physical and chemical properties of the associated gas, in particular on factors such as gas content and gas ratio. Often, gas from the first stage of separation is used in furnaces to generate heat and preheat the entire mass of oil, in order to increase the gas yield at the subsequent stages of separation. For driving mechanisms, electricity is used, which is also generated in the field, or main power networks are used. Mainly used are gas piston power plants (GPPP), gas turbine (GTS) and diesel generator (DGS). Gas facilities operate on first-stage separation gas, while the diesel station operates on imported liquid fuel. The specific type of power generation is selected based on the needs and characteristics of each individual project. A gas turbine power plant in some cases can generate excess electricity to supply nearby oil production facilities, and in some cases the remainder can be sold on the wholesale electricity market. In cogeneration type of energy production, plants simultaneously produce heat and electricity.

Flare lines are a mandatory attribute of any field. Even if not used, they are needed to burn off excess gas in an emergency.

From the point of view of the economics of oil production, investment processes in the field of associated gas utilization are quite inertial, and are oriented primarily not on market conditions in the short term, but on the totality of all economic and institutional factors over a fairly long-term horizon.

The economic aspects of hydrocarbon production have their own specifics. Peculiarities of oil production are:

• Long-term nature of key investment decisions
• · Significant investment lags
• · Large initial investment
• · Irreversibility of initial investment
• Natural decline in production over time

In order to assess the effectiveness of any project, a common model for assessing the value of a business is the NPV assessment.

NPV (Net Present Value) - the assessment is based on the fact that all future estimated income of the company will be summed up and reduced to the present value of these incomes. The same amount of money today and tomorrow differs by the discount rate (i). This is due to the fact that in the time period t=0 the money we have has a certain value. While in the time period t=1 inflation will spread to these funds, there will be all sorts of risks and negative impacts. All this makes future money “cheaper” than current money.

The average life of an oil production project can be about 30 years, followed by a long cessation of production, sometimes stretching for decades, which is associated with the level of oil prices and the payback of operating costs. Moreover, oil production reaches its peak in the first five years of production, and then, due to the natural decline in production, it gradually fades.

In the early years, the company makes large initial investments. But production itself begins only a few years after the start of capital investments. Each company strives to minimize the investment lag in order to achieve payback on the project as soon as possible.

A typical project profitability graph is shown in Figure 3:

Figure 3 - NPV diagram for a typical oil production project

This figure shows the NPV of the project. The maximum negative value is the MCO (maximum cash outlay) indicator, which reflects how much investment the project requires. The intersection of the graph of the line of accumulated cash flows with the time axis in years is the payback time of the project. The rate of NPV accumulation is decreasing, due to both the decreasing production rate and the time discount rate.

In addition to capital investments, production requires operating costs every year. An increase in operating costs, which may include annual technical costs associated with environmental risks, reduces the NPV of the project and increases the payback period of the project.

Thus, additional expenses for accounting, collection and utilization of associated petroleum gas can be justified from a project point of view only if these expenses increase the NPV of the project. Otherwise, there will be a decrease in the attractiveness of the project and, as a result, either a decrease in the number of projects being implemented, or the volumes of oil and gas production within one project will be adjusted.

Conventionally, all associated gas utilization projects can be divided into three groups:

• 1. The recycling project itself is profitable (taking into account all economic and institutional factors), and companies will not need additional incentives for implementation.
• 2. The utilization project has a negative NPV, while the cumulative NPV from the entire oil production project is positive. It is this group that all incentive measures can be concentrated on. The general principle will be to create conditions (through incentives and penalties) that make it profitable for a company to undertake recycling projects rather than pay penalties. Moreover, so that the total costs of the project do not exceed the total NPV.
• 3. Recycling projects have a negative NPV, and if they are implemented, the overall oil production project for a given field also becomes unprofitable. In this case, incentive measures will either not lead to a reduction in emissions (the company will pay fines up to their cumulative cost equal to the project’s NPV), or the deposit will be mothballed and the license surrendered.

According to the Skolkovo Energy Center, the investment cycle in the implementation of APG utilization projects is more than 3 years.

Investments, according to the Ministry of Natural Resources, should amount to about 300 billion rubles by 2014 to achieve the target level. Based on the logic of administering projects of the second type, the rates of payments for pollution should be such that the potential cost of all payments would be above 300 billion rubles, and the opportunity cost would be equal to the total investment.

Associated petroleum gas

Associated petroleum gas (PNG) - a mixture of various gaseous hydrocarbons dissolved in oil; they are released during the extraction and distillation process (these are the so-called associated gases, mainly composed of propane and butane isomers). Petroleum gases also include petroleum cracking gases, consisting of saturated and unsaturated (ethylene, acetylene) hydrocarbons. Petroleum gases are used as fuel and to produce various chemicals. From petroleum gases, propylene, butylenes, butadiene, etc. are obtained through chemical processing, which are used in the production of plastics and rubbers.

Compound

Associated petroleum gas is a mixture of gases released from hydrocarbons of any phase state, consisting of methane, ethane, propane, butane and isobutane, containing high molecular weight liquids dissolved in it (from pentanes and higher in the homologous series) and impurities of various compositions and phase states.

Approximate composition of APG

Receipt

APG is a valuable hydrocarbon component released from mined, transported and processed hydrocarbon-containing minerals at all stages of the investment life cycle before the sale of finished products to the final consumer. Thus, the peculiarity of the origin of associated petroleum gas is that it is released at any stage from exploration and production to final sale, from oil, gas, (other sources are omitted) and in the process of their processing from any incomplete product state to any of the numerous final products.

A specific feature of APG is usually the low consumption of the resulting gas, from 100 to 5000 Nm³/hour. The content of hydrocarbons C3 + can vary in the range from 100 to 600 g/m³. At the same time, the composition and quantity of APG is not a constant value. Both seasonal and one-time fluctuations are possible (normal changes in values ​​are up to 15%).

The gas from the first separation stage is usually sent directly to the gas processing plant. Significant difficulties arise when trying to use gas with a pressure of less than 5 bar. Until recently, such gas in the vast majority of cases was simply flared, however, now, due to changes in state policy in the field of APG utilization and a number of other factors, the situation is changing significantly. In accordance with the Decree of the Government of Russia dated January 8, 2009 No. 7 “On measures to stimulate the reduction of atmospheric air pollution by products of combustion of associated petroleum gas in flares”, a target indicator for flaring of associated petroleum gas was established in the amount of no more than 5 percent of the volume of produced associated petroleum gas oil gas. At the moment, the volumes of extracted, utilized and flared APG cannot be estimated due to the lack of gas metering stations at many fields. But according to rough estimates, this is about 25 billion m³.

Disposal routes

The main ways of APG utilization are processing at gas processing plants, generating electricity, burning for own needs, injection back into the reservoir to enhance oil recovery (maintaining reservoir pressure), injection into production wells - the use of “gas lift”.

APG utilization technology

Gas flare in the West Siberian taiga in the early 1980s

The main problem in the utilization of associated gas is the high content of heavy hydrocarbons. Today, there are several technologies that improve the quality of APG by removing a significant portion of heavy hydrocarbons. One of them is the preparation of APG using membrane units. When using membranes, the methane number of the gas increases significantly, the lower heating value (LHV), heat equivalent and dew point temperature (both hydrocarbons and water) are reduced.

Membrane hydrocarbon units can significantly reduce the concentration of hydrogen sulfide and carbon dioxide in the gas flow, which allows them to be used to purify gas from acidic components.

Design

Gas flow distribution diagram in the membrane module

By its design, the hydrocarbon membrane is a cylindrical block with permeate, product gas outlets and an APG inlet. Inside the block is a tubular structure of selective material that allows only a certain type of molecule to pass through. The general flow diagram inside the cartridge is shown in the figure.

Operating principle

The installation configuration in each specific case is determined specifically, since the initial composition of APG can vary greatly.

Installation diagram in basic configuration:

Pressure scheme for APG preparation

Vacuum scheme for APG preparation

• Pre-separator for cleaning from coarse impurities, large droplets of moisture and oil,
• Receiver at the input,
• Compressor,
• Refrigerator for additional cooling of gas to a temperature of +10 to +20 °C,

• Fine filter for gas purification from oil and paraffin compounds,
• Hydrocarbon membrane block,
• instrumentation and automation,
• Control system, including flow analysis,
• Condensate recovery system (from separators),
• Permeate recovery system,
• Container delivery.

The container must be manufactured in accordance with fire and explosion safety requirements in the oil and gas industry.

There are two schemes for APG preparation: pressure and vacuum.

Unlike natural gas, associated petroleum gas contains, in addition to methane and ethane, a large proportion of propanes, butanes and vapors of heavier hydrocarbons. Many associated gases, depending on the field, also contain non-hydrocarbon components: hydrogen sulfide and mercaptans, carbon dioxide, nitrogen, helium and argon.

When oil reservoirs are opened, gas from the oil caps usually begins to gush out first. Subsequently, the main part of the produced associated gas consists of gases dissolved in oil. Gas from gas caps, or free gas, is “lighter” in composition (with a lower content of heavy hydrocarbon gases) in contrast to gas dissolved in oil. Thus, the initial stages of field development are usually characterized by large annual production volumes of associated petroleum gas with a larger proportion of methane in its composition. With long-term exploitation of the field, the production of associated petroleum gas is reduced, and a large share of the gas falls on heavy components.

Injection into the subsoil to increase reservoir pressure and, thereby, the efficiency of oil production. However, in Russia, unlike a number of foreign countries, this method, with rare exceptions, is not used, because it is a highly costly process.

Use locally to generate electricity for the needs of oil fields.

When significant and stable volumes of associated petroleum gas are released - use as fuel at large power plants, or for further processing.

The most effective way to utilize associated petroleum gas is its processing at gas processing plants to produce dry stripped gas (DSG), wide fraction of light hydrocarbons (NGL), liquefied gases (LPG) and stable gas gasoline (SGG).

A large consulting company in the fuel and energy sector, PFC Energy, in its study “Utilization of Associated Petroleum Gas in Russia,” noted that the optimal option for using APG depends on the size of the field. Thus, for small fields, the most attractive option is to generate electricity on a small scale for their own field needs and the needs of other local consumers.

For medium-sized fields, according to researchers, the most economically feasible option for associated petroleum gas utilization is the extraction of liquefied petroleum gas at a gas processing plant and the sale of liquefied petroleum gas (LPG) or petrochemical products and dry gas.

For large fields, the most attractive option is to generate electricity at a large power plant for subsequent wholesale sale to the power grid.

According to experts, solving the problem of associated gas utilization is not only an issue of ecology and resource conservation, it is also a potential national project worth 10-15 billion dollars. Only the utilization of APG volumes would make it possible to annually produce up to 5-6 million tons of liquid hydrocarbons, 3-4 billion cubic meters of ethane, 15-20 billion cubic meters of dry gas or 60-70 thousand GWh of electricity.

Russian President Dmitry Medvedev instructed the Russian government to take measures to end the practice of irrational use of associated gas by February 1, 2010.

At the present stage of development of the oil industry, producing companies have taken a course towards increasing the efficiency of utilization of associated gas, an inevitable companion of “black gold” in any field in the world. Operators are moving from simple and familiar gas flaring to the latest technologies for its use and processing. However, the utilization of petroleum gas is still unprofitable and labor-intensive.

What is associated gas

Associated petroleum gas (APG) is found in oil reservoirs. It is released when the reservoir pressure decreases to a level less than the oil saturation pressure. The gas factor - the concentration of gas in oil - depends on the depth of the deposits and ranges from five cubic meters in the upper layers to several thousand cubic meters per ton in the lower layers. APG is released during oil preparation and production. After opening the formation, the gas fountain first begins to flow from the “cap”. In addition, gaseous hydrocarbons are formed during thermal processing of raw materials, including hydrotreating, reforming and cracking.

The direct separation of petroleum gas from oil using separation is carried out in order to achieve the standard quality of “black gold”. This work is carried out using multi-stage separators. At the first stage of such a device, the pressure is up to 30 bar, at the last - up to 4 bar. In turn, the temperature and pressure of the resulting gas depends on the specific separation technology. At the same time, the gas output is variable and ranges from 100–5000 cubic meters per hour or 25–800 cubic meters per ton.

The composition of the gas may vary depending on the specific characteristics of the oil, the conditions of its formation and occurrence, as well as factors that may contribute to the degassing of the raw material. Wet gases are extracted to the surface along with light oil, and dry gases are extracted from heavy oil.

The value of the resulting product is directly proportional to the volume of hydrocarbons in its composition, the content of which fluctuates at the level of 100–600 grams per cubic meter of APG. The gas that is released from the “caps,” called free gas, contains fewer heavy hydrocarbon components than that dissolved directly in the oil. Due to these properties, the share of methane in APG at the initial stages of field development is higher than in later periods of block development. After the gas caps are depleted, the main part of the APG is replaced by gases dissolved in oil.

Classification of APG by qualitative composition:

1. Pure hydrocarbon (95–100% hydrocarbons).
2. Hydrocarbon with carbon dioxide (admixture of 4–20% CO 2).
3. Hydrocarbon with nitrogen (admixture 3–15% N 2).
4. Hydrocarbon-nitrogen (up to 50% N 2).

Petroleum gas differs from natural gas, which consists mainly of methane, in large quantities of butane, propane and ethane, and other saturated hydrocarbons. APG includes not only gas, but also vapor components, high-molecular liquids, starting with pentanes, as well as substances that are not hydrocarbons - mercaptans, hydrogen sulfide, argon, nitrogen, helium, carbon dioxide.

Danger to humans and nature

Due to the low pace of development of the infrastructure necessary for collecting, moving and processing petroleum gas and due to the lack of demand for it, all associated gas, without exception, was previously flared directly at oil production sites. Even now, it is not possible to estimate the volume of associated gas flared, since many fields do not have accounting systems.

According to average estimates, we are talking about tens of billions of cubic meters per year worldwide. In the 2000s, 6.2 billion cubic meters of APG were burned annually in Russia alone. A study of the development of the Priobskoye field in the Khanty-Mansi Autonomous Okrug allows us to conclude that such data were significantly underestimated, since about a billion cubic meters of APG are burned in this area alone per year.

It is estimated that as a result of gas combustion over Russian territory, about 100 million tons of carbon dioxide are generated annually. Such estimates were made based on the assumption of efficient gas utilization, although this is far from reality. In fact, due to incomplete combustion of gas, methane, which is considered a more active greenhouse gas than carbon dioxide, also enters the atmosphere. When gas is burned, nitrogen oxide and sulfur dioxide are also released. Such components in atmospheric air cause an increase in cases of diseases of the respiratory system, vision and gastrointestinal tract of people living in oil production regions.

About 500 thousand tons of active soot also enter the atmospheric air annually. Environmental experts believe that soot particles can be freely transported over long distances and deposited by ice or snow on the earth's surface, which leads to deterioration of the situation in oil field areas due to the fall of solid polluting particles.

In addition to the release of toxic components into the atmosphere, thermal pollution also occurs. Around the torch in which APG is burned, thermal destruction of the soil begins within a radius of up to 25 meters, vegetation suffers over a larger area - within a radius of up to 150 meters.

Before the entry into force of the Kyoto Protocol in 2004, which includes a requirement for the use of associated petroleum gas, the Russian state practically did not pay close attention to the problem of associated gas utilization. The situation has changed for the better since 2009, when a decree of the Russian government ordered that no more than 5% of the volume of associated petroleum gas be flared.

The flaring of associated petroleum gas abroad is strictly prosecuted by the authorities and is subject to significant fines. The financial penalties for incineration are such that it becomes economically unfeasible. In Russia, such effective measures have not yet been taken.

The Ministry of Natural Resources of the Russian Federation, for example, stated that 55 billion cubic meters of oil gas are produced annually in the country and only 26% of this volume is sent for processing, another 47% is used locally for the needs of the field and is written off, and the rest of the gas - 27% - is flared . Pronedra wrote earlier that 95 percent utilization of APG in Russia is expected only by 2035.

Transport problems

The low rate of reduction in gas combustion volumes is primarily due to the underdevelopment of technologies that would allow it to be effectively utilized. The composition of such a gas is unstable and includes impurities. Large costs are associated with the need to “shrink” APG, since it is characterized by a high level of moisture content, reaching 100%.

APG is saturated with heavy hydrocarbons, which significantly complicates the process of its transportation through pipeline systems. Potential gas consumers are usually located at considerable distances from oil fields. Laying pipelines to gas processing plants is associated with the high cost of implementing such projects. A kilometer of pipeline for pumping APG costs about $1.5 million.

South Priobskaya compressor station

Due to transportation costs, the cost of pumping 1 thousand cubic meters of gas costs $30. For comparison, the cost of producing the same amount of natural gas at Gazprom enterprises is a maximum of $7. With the cost of APG production up to 250 rubles and transportation - 400 rubles per 1 thousand cubic meters, the price for such gas on the market is set no higher than 500 rubles, which automatically makes any processing method unprofitable. Let us recall that Lukoil proposed establishing preferential taxation for APG production subject to advanced processing.

Significant operating costs are also associated with losses of associated gas along the way of its movement to processing points. It is not possible to calculate the scale of technological losses, since there is currently no established system for their instrumental accounting. The unprofitability of working with APG leads to the fact that industry companies actually include the cost of construction and operation of pipeline systems and compressor stations for gas transportation in the cost of oil.

Use of gas for field needs

As an alternative to inefficient combustion and costly processing, APG utilization technology can be used by injecting it together with working fluids back into the reservoir - into the “cap” - during oil production to restore the pressure of the deposits. In this way, an increase in the degree of reservoir recovery can be achieved.

Based on the results of the research, it turned out that using the method of injection into the reservoir, up to an additional 10 thousand tons of oil can be produced per year from one well. The possibility of introducing a technology for injecting associated gas into the reservoir along with water, which is called “water-gas stimulation,” is currently being studied. Unfortunately, the practice of pumping gas into reservoirs is used mainly abroad, and in Russia, due to its high costs, it has not yet gained popularity.

Oil field operators also use APG for power generation. The generated energy is used both for the needs of the field and for power supply to nearby areas. For operators engaged in the development of small fields, it is economically feasible to produce energy to meet their own needs and supply energy in small volumes to third-party consumers.

Shinginskaya gas turbine power plant operating on associated petroleum gas

If we are talking about producing oil gas in large blocks, then in this case the most attractive option is the production of energy at powerful power plants with further wholesale sales to the general energy system. In Russia, the construction of power plants using associated gas in fields is already used everywhere. The total volume of generation under the mentioned scheme approaches 1 billion kWh per year.

The effectiveness of APG for energy production is advisable provided that the generation is located close to the fields. The most effective option is the use of power plants with microturbines. A large number of installations of both piston and turbine types that operate on oil gas are already being produced. The exhaust fractions generated when APG is used in such systems can be used to supply heat to facilities.

At the same time, the presence of heavy group hydrocarbons in APG negatively affects the efficiency of using gas as fuel for energy generation, namely, it reduces the nominal productivity of stations and reduces the operating time of generating facilities between repairs. It should be noted that the unstable composition and contamination with impurities makes the use of APG for energy generation without preliminary drying and purification problematic.

APG purification and processing

All associated gas that oil companies do not flare or use for injection into reservoirs or to generate electricity is sent for processing. Before transportation to processing facilities, oil gas is purified. Freeing gas from mechanical impurities and water facilitates its transportation. In order to prevent the precipitation of liquefied fractions in the cavities of gas pipelines and to lighten the mixture as a whole, some of the heavy hydrocarbons are filtered out.

Removing sulfur elements makes it possible to prevent the corrosive effect of APG on the walls of pipelines, and the extraction of nitrogen and carbon dioxide makes it possible to reduce the volume of the mixture not used in processing. Cleaning is carried out using different technologies. After cooling and compression (compression under pressure) of the gas, it is separated or processed using gas dynamic methods. Such methods are inexpensive, but do not allow the extraction of carbon dioxide and sulfur components from APG.

Separation separators at an oil treatment plant

If sorption methods are used, hydrogen sulfide is not only partially removed, but also drying from water and wet hydrocarbon fractions is carried out. The disadvantage of sorption is the unsatisfactory adaptation of the technology to field conditions, which leads to the loss of up to a third of the APG volume. To remove moisture, the glycol drying method can be used, but only as an additional measure, since it does not extract anything else from the mixture except water. Another specialized method is desulfurization - as the name implies, used to remove sulfur components. Alkaline cleaning and amine washing methods are also used.

Adsorption dryer for drying associated gas

All of the above methods can now be considered obsolete. Over time, they will probably be replaced or combined with the newest and quite effective method - membrane purification. The principle is based on different rates of penetration of different APG components through membrane fibers. Until now, this method has not been used due to the fact that until the release of hollow fiber membranes on the market, its use was ineffective and did not have advantages over other gas treatment methods.

The principle of operation of the membrane installation

Purified gas, if not immediately sold to consumers in liquefied form for domestic and municipal needs, undergoes a separation procedure in two segments - to obtain fuel or raw materials for the petrochemical industry. After it arrives at the processing plant, APG is separated using low-temperature absorption and condensation into main fractions, some of which are ready-to-use products.

As a result of separation, mostly stripped gas is formed - methane with an admixture of ethane, and a wide fraction of light hydrocarbons (NGL). Stripped gas can be freely transported through pipeline systems and used as fuel, as well as serve as a raw material for the production of acetylene and hydrogen. In addition, gas processing produces automotive liquid propane-butane (i.e. gas motor fuel), aromatic hydrocarbons, narrow fractions and stable gas gasoline. NGLs are sent for further processing to petrochemical plants. There, plastics, rubber, fuel additives, and liquefied hydrocarbons are produced from these raw materials.

1 - gas injection into the reservoir; 2 - fuel for the power plant; 3 - combustion; 4 - deep cleaning; 5 - main gas pipeline; 6 - APG separation; 7 - NGLs; 8 - fuel; 9 - compressor station; 10 - APG transportation

Abroad, the latest method for producing liquid hydrocarbons from associated gas using Gas-to-liquids technology, which involves processing by chemical methods, is being rapidly introduced. In Russia, this technique is unlikely to find wide application, since it is tightly tied to environmental temperature conditions and can only be implemented in latitudes with a hot or temperate climate. In Russia, the predominant share of oil volume is produced in the northern regions, so in order to adopt the Gas-to-liquids method, you will have to carry out painstaking research work.

The industry is actively implementing the technology of cryogenic compression of APG using a single-flow cycle. The most powerful cooling systems are already capable of processing up to 3 billion cubic meters of associated gas per year. An effective solution is to install such complexes at distribution stations.

Associated petroleum gas, despite the low and sometimes zero profitability of its processing, is widely used in the fuel and energy complex and the petrochemical industry. Due to the combustion of APG, irreversible losses of a colossal amount of raw energy resources occur. Thus, almost 140 billion rubles are flared in Russia every year - the total cost of propane, butane and other components contained in associated gas.

Improving APG utilization technologies will allow Russia to produce an additional 6 million tons of liquid hydrocarbons, 4 billion cubic meters of ethane, up to 20 billion cubic meters of dry gas per year, as well as generate 70 thousand GW of electrical energy. Establishing work on the effective utilization of APG is not only a way to solve environmental problems and problems of saving energy resources, but also the basis for the establishment of an entire industry, the cost of which at the national level, according to the most conservative estimates, is estimated by experts at one and a half ten billion dollars.