Associated petroleum gas: composition. Natural and associated petroleum gas

Oil and gas are the most important types of raw materials in the world. A special place in the oil and gas industry is associated petroleum gas. Previously, this resource was not used. But now the attitude to this valuable natural fossil has changed.

What is associated petroleum gas

This hydrocarbon gas, which is released from wells and from reservoir oil during its separation. It is a mixture of vaporous hydrocarbon and non-hydrocarbon constituents of natural origin.

Its quantity in oil can be different: from one cubic meter to several thousand in one ton.

According to the specifics of production, associated petroleum gas is considered a by-product of oil production. Hence its name comes. Due to the lack of the necessary infrastructure for gas gathering, transportation and processing, a large amount of this natural resource is lost. For this reason, most of the associated gas is simply burned in torches.

Gas composition

Associated petroleum gas consists of methane and heavier hydrocarbons - ethane, butane, propane, etc. The composition of gas in different oil fields may differ slightly. In some regions, the associated gas may contain non-hydrocarbon constituents - compounds of nitrogen, sulfur, oxygen.

Associated gas, which gushes after the opening of oil reservoirs, differs by a smaller number of heavy hydrocarbon gases. The "heavier" part of the gas is in the oil itself. Therefore, in the initial stages of development of oil fields, as a rule, a lot of associated gas with a large content of methane is produced. In the process of exploitation of deposits, these indicators are gradually decreasing, and most of the gas is made up of heavy components.

Natural and associated petroleum gas: what is the difference

Associated gas in comparison with natural gas contains less methane, but has a large number of its homologues, including pentane and hexane. Another important difference is the combination of structural components in different fields in which associated petroleum gas is extracted. The composition of APG can even vary in different periods on the same deposit. For comparison: the quantitative combination of natural gas components is always constant. Therefore APG can be used for different purposes, and natural gas is used only as an energy source.

Getting APG

The associated gas is obtained by separation from oil. For this, multi-stage separators with different pressures are used. Thus, in the first stage of separation, a pressure of 16 to 30 bar is created. At all subsequent stages, the pressure is gradually lowered. At the last stage of production, the parameter is reduced to 1.5-4 bar. The values of APG temperature and pressure are determined by the separation technology.

Gas, obtained at the first stage, immediately goes to the gas processing plant. Great difficulties arise when using gas with a pressure below 5 bar. Previously, such APG has always been burned in torches, but recently the policy of gas utilization has changed. The government began to develop incentive measures to reduce environmental pollution. Thus, at the state level in 2009, the APG flaring rate was established, which should not exceed 5% of the total associated gas production.

Application of APG in industry

Previously, APG was not used in any way and was immediately burned after production. Now scientists have examined the value of this natural resource and are looking for ways to use it effectively.

Associated petroleum gas, the composition of which is a mixture of propanes, butanes and heavier hydrocarbons, is a valuable raw material for the energy and chemical industries. APG has a calorific value. So, during combustion, it releases from 9 to 15 thousand kcal / cubic meter. In its original form it is not used. Cleaning is mandatory.

In the chemical industry of methane and ethane contained in the passing gas, plastics and rubber are produced. Heavier hydrocarbon components are used as raw materials for the production of high-octane fuel additives, aromatic hydrocarbons and liquefied hydrocarbon gases.

On the territory of Russia, more than 80% of the associated gas production falls on five oil and gas producing companies: Rosneft, Gazprom Neft, OAO LUKOIL Oil Company, TNK-BP Holding OJSC, Surgutneftegaz ". According to official data, the country annually extracts more than 50 billion cubic meters of APG, of which 26% goes for processing, 47% is used for industrial purposes, and the remaining 27% is burned in torches.

There are situations in which it is not always profitable to use associated petroleum gas. The use of this resource often depends on the size of the deposit. Thus, gas produced in small deposits is advisable to use to provide electricity to local consumers. In medium-sized fields, it is most economical to extract liquefied petroleum gas from a gas processing plant and sell it to chemical industry enterprises. The optimal option for large deposits is the production of electricity at a large power plant with subsequent sale.

Harm from APG combustion

Combustion of associated gas pollutes the environment. Around the torch is thermal destruction, which affects the soil in a radius of 10-25 meters and vegetation within 50-150 meters. During combustion, nitrogen oxides and carbon, sulfur dioxide and unburned hydrocarbons enter the atmosphere. Scientists estimated that as a result of APG combustion about 0.5 million tons of soot per year are emitted.

Also products of combustion of gas are very dangerous for human health. According to statistics, in the main oil refining region of Russia - the Tyumen region - the incidence of the population in many types of diseases is higher than the average indicators throughout the country. Especially often the inhabitants of the region suffer from pathology of respiratory organs. There is a growing trend in the number of neoplasms, diseases of the sense organs and the nervous system.

In addition, the products of combustion of APG cause pathologies that occur only after a while. These include the following:

• infertility;
• Miscarriage of pregnancy;
• Hereditary diseases;
• Weakening of immunity;
• Oncological diseases.

APG utilization technologies

The main problem of utilization of oil gas is a high concentration of heavy hydrocarbons. In the modern oil and gas industry, several efficient technologies are being used that make it possible to improve the quality of gas by removing heavy hydrocarbons:

1. Gas Fractional Separation.
2. Adsorption technology.
3. Low-temperature separation.
4. Membrane technology.

Ways of utilization of associated gas

There are many methods, but in practice only a few are used. The main way is utilization of APG by splitting into components. This process of processing makes it possible to obtain dry stripped gas, which, in fact, is the same natural gas, and a wide fraction of light hydrocarbons (NGL). This mixture can be used as a raw material for petrochemicals.

The separation of the petroleum gas takes place in installations for low-temperature absorption and condensation. After completion of the process, dry gas is transported through gas pipelines, and NGL is sent to refineries for further processing.

The second effective way of processing APG is the cycling process. This method involves injecting gas back into the formation to increase pressure. This solution allows to increase the volume of oil recovery from the reservoir.

In addition, associated petroleum gas can be used to generate electricity. This will allow oil companies to significantly save money, as there is no need to buy electricity from the outside.