Stable gas condensate

A hydrocarbon liquid consisting of heavy hydrocarbons C 5+, in which no more than 2-3% of the mass is dissolved. propane-butane fraction. Two groups (I and II) of stable condensate have been established depending on the content of impurities - water, mechanical impurities, chloride salts.

In accordance with the OST 51.65 - 80 standard, stable condensate is defined as a mixture of methane, naphthenic and aromatic hydrocarbons that meets the requirements for a number of physicochemical parameters. The main indicator - saturated vapor pressure - at plus 38º C should be 66650 Pa (500 mm Hg). Thus, the vapor pressure of a stable condensate must be such that, at normal atmospheric pressure, it can be stored in a liquid state up to a temperature of the order of plus 60°C.

Properties of the transported fluid

The properties of oil that characterize the possibility of transportation through a pipeline or transportation in tanker tanks depend on its composition. The properties of oil are determined by the quantitative ratio between paraffin, naphthenic, aromatic hydrocarbons and other components. These properties must be taken into account at all stages of handling oil (and oil products):

· during commodity accounting operations;

· during pumping or transportation;

· when processed and used as fuel.

Density. Density usually varies from 650 to 920 kg/m3. The concept of relative density is also used, which is determined by the ratio of the density of liquid hydrocarbons to the density of water at 20°C. Accurate determination of the density of liquid hydrocarbons is of great commercial importance, since the volumes of the tanks used are well known, and this allows for more accurate determination of the commercial weight of the pumped product.

A general property of the densities of liquid hydrocarbons is that they decrease with increasing temperature (1 oil barrel = 42 gallons = 0.158988 m 3 = 159 l).

From the following graph it follows (see Fig. 2.) that for the considered oils, with an increase in temperature by 100 degrees. Celsius, their density decreases by 120-150 kg/m 3, i.e. by 15-18%.

Rice. 2.

The volumetric compression coefficient is a value that characterizes the change in the relative volume of a liquid when the pressure changes by one unit. The characteristic values ​​of this coefficient for oil and condensate are in the range (5-15).10 - 4 1/MPa, i.e. these products have low compressibility.

Such large values ​​of the volumetric compression ratio of oil and liquid hydrocarbons are responsible for strong hydraulic shocks in pipelines that occur when unsteadiness occurs during the movement of the transported product.

The general pattern is that the volumetric compression ratio decreases as the density of the liquid increases.

The coefficient of volumetric expansion is a value characterizing the relative change in the volume of a liquid when the temperature changes by 1º C.

Liquefied hydrocarbon gases have a particularly high coefficient of volumetric expansion among liquid hydrocarbons. At the same temperature increase, propane (butane) expands 16.1 (11.2) times more than water, and 3.2 (2.2) times more than a petroleum product such as kerosene.

As the temperature rises, LPG expands and creates dangerous stresses in the metal, which can lead to destruction of the tanks. This should be taken into account when filling the latter, maintaining the volume of the vapor phase required for safe operation, i.e. it is necessary to provide a steam “cushion”. For tanks where the design temperature rise of the stored product does not exceed 40° C, the degree of filling is taken to be 0.85; with a larger design temperature difference, the degree of filling is taken to be even less.

The overwhelming majority of liquid hydrocarbons pumped in main pipelines under transportation conditions belong to the so-called. Newtonian fluids, the main property of which is the ability to move even when a minimum shear stress is applied to them.

By ensuring the pumping of a liquid hydrocarbon mixture in a single-phase state and maintaining its “Newtonian” properties, not only minimal energy losses for its transportation are ensured, but also stable conditions for its pumping.

To do this, when transporting liquid hydrocarbon mixtures, the necessary thermobaric parameters are maintained, and the liquid mixtures themselves, if necessary, are appropriately processed in order to achieve the properties necessary for pipeline transportation.

Viscosity. The choice of pumping technology, energy consumption for transporting liquid hydrocarbons, etc., depend on the viscosity of the transported product. A special feature of viscosity as a physical property of a liquid is a very wide range of its values ​​for different hydrocarbon liquid systems, as well as its strong dependence on the transportation temperature. A general property of the viscosity of liquid hydrocarbons is that it decreases with increasing temperature.

In the international system of SI units, dynamic (molecular, shear) viscosity is measured in poise (centipoise, cP) or in mPa. c: the viscosity of liquid hydrocarbons varies over a wide range - from 0.5 to 250 mPa. With.

Pour point- this is the temperature at which the oil (petroleum product) in the test tube does not change its level when the test tube is tilted 45° for 1 minute. The transition of oil from liquid to solid occurs gradually, over a certain temperature range. From the standpoint of physicochemical mechanics of petroleum dispersed systems, the pour point of oil is defined as the transition from a freely dispersed sol to a bound dispersed state (gel).

The temperature of oil (liquid hydrocarbon product) pumped through an underwater pipeline depends (except for the temperature at the entrance to the pipeline) depends on the temperature of the bottom layer of sea water in the case when the pipeline is laid on the seabed without burial, or on the temperature of the soil in the case when the pipeline located in an underwater trench.

The temperature of the pumped liquid determines the viscosity value and its other rheological characteristics and thus affects the pumping mode; it determines the possibility of oil (liquid hydrocarbon product) solidification if its temperature reaches the pour point value.

Since the temperature of the transported product usually decreases as it moves through the pipeline, this can lead to a noticeable increase in its viscosity and coefficient of hydraulic resistance and, as a consequence, to an increase in hydraulic friction losses as long as the temperature of the product drops. Sometimes, this can lead to a complete stop of the pipeline.

If the oil being transported is a waxy or highly waxy (non-Newtonian for transport conditions) environment, such loading fluctuations complicate the operation of pipelines, especially in the case of offshore fields and subsea pipelines. Transport of products with low productivity leads to the formation of stagnant zones and the accumulation of paraffin deposits (sometimes, even when using paraffin deposit inhibitors) with a gradual increase in pressure drop in the pipeline.

The main reason for the formation of paraffin deposits is the temperature factor - its decrease during transportation, and the distribution of paraffin deposits in the pipeline is determined by the characteristics of its thermal regime.

On short offshore pipelines, most often field pipelines, a technology is sometimes used based on the use of associated heating of the product, which occurs due to heating of the pipe walls.

Thorio writes:

TaxHelp writes:

I'm bringing up an old topic. The Supreme Arbitration Court is now deciding whether one of TNK's subsidiaries produced oil or condensate (this affects taxes). Of course, no one in court will bother with the analysis of c7. The decision will be made in a month and a half at best. If you have a Facebook account, you can watch the video of the court hearing.

The biggest problem with TNCs, IMHO, is accounting: they did everything under oil.

But the position of the tax inspectorate is striking. In a nutshell, they mixed the extracted oil and condensate and sent the mixture to a product preparation facility. The question for the inspection is whether gas condensate was prepared at product preparation facilities? The answer is “no”.

The tax authorities are having a blast! I just collapsed with laughter listening to the taxman’s speech. To the question “Did gas condensate arrive at the treatment reception points?” he replied “Only HYDROCARBON RAW MATERIALS arrived at the reception points, but gas condensate was not allowed in!”.... (Thorio, this struck me too)))

Such illiteracy, stupidity and stupidity just turn out the lights.

The taxman’s “important” argument is that the output products were assessed according to GOST for commercial oil, which means that only oil was produced, but there was no condensate! "There was no boy, there was no!!" “It doesn’t matter that there are gas deposits on the balance sheet and condensate is being extracted from them! Hydrocarbon raw materials came in, and the output was OIL, which means you pay grandma, capitalist-exploiter!!”

Insanity is for the insane. Yes, there is nothing but oil, and there shouldn’t be. Both condensate and oil are a single substance, varying in properties. And that is why there is no GOST for condensate, but there is a GOST for COMMERCIAL oil.

The state is again stepping on its rake, which, unfortunately, knocks not only on the heads of government agencies, showing all their incompetence, but also on the heads of subsoil users.

Is it really so difficult to rewrite several laws, and if it is so important to keep records of production (and this is really important because it affects the wear and tear of equipment, etc.), then keep records not according to the type of phase state of the formation fluid in the formation (the railway worker doesn’t give a damn “what the subsoil user has in the reservoir - liquid oil or reservoir gas from which condensate falls out), and according to the characteristics of the commercial product after preparation and before shipping by rail or Transneft pipe - density, content of sulfur-containing substances, paraffins, fractional distillation, etc. - these are the characteristics that are important for transport workers, and are specified in GOST for commercial oil!

Please, then, any tax officer come with your certified thermometer and measure the density and check. Check the laboratories that issued the analysis document.

The only trouble is that it won’t be interesting anymore. Fish bite better in muddy water! You look at it in court and it’ll “ride” - the judges are not geologists, it’s difficult for them to figure out what is condensate and what is “unstable condensate”, they can also believe that butane, as a separate component of a multi-component system, can be separately developed from a deposit (!) (laughing to no magician). And the proceeds to the budget from an “unscrupulous” entrepreneur is a bonus!

The state has made a mess in this matter, and the tax authority, as a representative of this state, says “I will punish you in full for this mess.”

Free circus!

It's all sad. What a charade...this is the state....

P.S. Looks like I know which region the legs grow from. The smartest tax office is there

It’s also a pity that the subsoil user does not always, in my opinion, clearly outline the situation. Although I’m not a lawyer, I think I can explain to a lawyer the difference between condensate and oil. I already have experience))

It would be a good tradition to invite not only lawyers but also high-level specialists and experts to the court. And let them speak from the side of the court, explaining to the judges the essence of the issue. Then it will be more difficult for some authorities to explain themselves in court.

Also, it should be very profitable for subsoil user companies to take the initiative to change legislation in matters where there is a mess. There is no one else to do this. It will cost less than constant tax collection. Rosneft definitely won’t do this, the penalty for them is transferring money from one pocket to another. The institutions don’t give a damn about such problems, and even those who still survived are in ruins. This remains only for private companies.

Liquid mixtures of hydrocarbons (all of which have different molecular structures and boil at high temperatures), which are released as a by-product in gas condensate, gas and oil fields, are collectively called gas condensates. Their composition and quantity depend on the location and conditions of extraction, and therefore vary widely. However, they can be divided into two types:

• stable gas condensate in the form of gasoline and kerosene fractions (and sometimes higher molecular weight liquid components of oil),
• an unstable product, which, in addition to hydrocarbons C5 and higher, includes gaseous hydrocarbons in the form of a methane-butane fraction.

Condensate can come from three types of wells where it is produced:

1. Crude oil (it comes in the form of associated gas, which can lie underground separately from crude oil (in layers) or be dissolved in it).
2. Dry natural gas (features a low content of hydrocarbons dissolved in it, condensate yield is low).
3. Wet natural gas (produced from gas condensate fields and is characterized by a high content of gasoline condensate).

The amount of liquid components in natural gases varies from 0.000010 to 0.000700 m³ per 1 m³ of gas. For example, the yield of stable gas condensate at various fields:

• Vuktylskoye (Komi Republic) - 352.7 g/m³;
• Urengoyskoye (Western Siberia) - 264 g/m³;
• Gazlinskoye (Central Asia) - 17 g/m³;
• Shebelinskoe (Ukraine) - 12 g/m³.

Natural gas condensate is a multicomponent mixture of various liquid hydrocarbons with low density, in which gaseous components are present. It condenses from the raw gas during a temperature drop at (below the dew point of the produced hydrocarbons). It is often called simply "condensate" or "gas gasoline".

Schemes for separating condensate from natural gas or oil are varied and depend on the field and purpose of the products. As a rule, at a technological installation built next to a gas or gas condensate field, the extracted gas is prepared for transportation: water is separated, purified to a certain extent from sulfur compounds, hydrocarbons C1 and C2 are transported to the consumer, a small fraction of them (of the extracted) is pumped into the formations for maintaining pressure. The separated fraction (after removing C3 components from it, but with a small content of them) is the gas condensate that is sent as a feed stream to oil refineries or petrochemical synthesis plants. Transportation is carried out by pipeline or liquid transport.

Gas condensate is not used as a raw material for the production of gasoline with a low octane number, to increase which anti-knock additives are used. In addition, the product is characterized by a high cloud point and pour point, which is why it is used to produce summer fuel. Gas condensate is used less frequently as gas condensate, since additional dewaxing is required. This direction uses less than a third of the extracted condensates.

The most interesting technological solution is the use of a product such as a wide fraction of light hydrocarbons for petrochemical synthesis. With its receipt, the processing of gas condensate begins. Deeper processes continue in pyrolysis plants, where NGLs are used as feedstock to produce important monomers such as ethylene, propylene and many other related products. Then the ethylene is sent to polymerization units, from which various grades of polyethylene are produced. The result is polypropylene. The butylene-butadiene fraction is used to make rubber. Hydrocarbons C6 and higher are the raw material for the production of petrochemical synthesis (benzene is obtained), and only the C5 fraction, which is the raw material for obtaining valuable products, is not yet used effectively.

The term "stable condensate"

Stable condensate is a liquid mixture of hydrocarbons with the formula C15 H12 and higher, which have more than three or four carbon atoms in the molecule. The number of carbon atoms depends on the specification. Stable condensate is a liquid that is colorless or slightly colored, the relative density is from 0.72 to 0.78. This is a flammable product that is classified as a hazardous substance due to its toxicological properties. When combined with air, condensate vapors form an explosive mixture.

A stable condensate is obtained from the product, which releases natural gas. There is such a thing as unstable gas condensate, which is obtained by condensation under conditions of decreasing pressure or temperature of natural gas. To transport gas condensate for processing using bulk transport, it is necessary to remove volatile fractions from it by rectification or keeping it for a certain time under conditions of atmospheric pressure and elevated temperature. It is after removing the volatile fractions that a stable gas condensate is obtained. The degree of removal of volatile fractions is checked and determined from the specifications for vapor pressure according to Reid for various containers (tanks, storage facilities). Thus, according to recommendations developed by the American Petroleum Institute, for market raw materials this indicator at a temperature of 15 degrees Celsius should not exceed 69 kPa. This indicator value is associated with excess pressure in vertical storage facilities. A higher Reid vapor pressure value is possible, but this will lead to evaporation of the raw material during storage from the breathing valves that are supplied to all tanks.

In nature, gas condensate in most cases is in a gaseous state as a composition of slightly lighter hydrocarbon gases. If pressure or temperature drops below a certain value, the so-called critical value, the process of reverse condensation begins. Reverse condensation stops the process of extracting condensate outside, which is explained by the higher permeability of rocks to gas than to liquid hydrocarbons. But at the same time, the condensate accumulated in the rocks worsens their gas permeability. To avoid reverse condensation and condensate loss during this process, the internal pressure and permeability to gas and liquid hydrocarbons are increased in the formation. There is a cycling process, which consists of injecting partially stripped gas into the formation in order to maintain in-situ pressure above the maximum pressure at which any of the phases of the multicomponent system will be in a state of equilibrium.

Stable gas condensate is used to produce motor fuels, as well as in the chemical industry.

Stable condensate comes in two types – dark and light. It depends on such factors: where it was extracted from, from what depth the extraction took place. It is because of the difference in these factors that the color changes depending on the content of impurities - from brown to light yellow.

Considering that stable condensate is a rather dangerous product, safety requirements must be strictly observed when interacting with it. Thus, workers carrying out its collection and drainage must wear personal protective equipment. All equipment for stable condensate must be tested for leaks. For small fires, foam fire extinguishers and sand are used to extinguish. In case of larger fires, mechanical or chemical foam, as well as water, are used.

Companies whose news contains stable condensate:

Reservoir products from a number of fields, along with gaseous components, also contain pentane and heavier hydrocarbons (C 5+). According to the static reporting form 34 TP, C 5+ hydrocarbons are usually called gas condensate. In practice, the term stable condensate is also used. This product, along with C5+ hydrocarbon, also contains propane, butane and other compounds. Stable condensates meet the requirements of GOST 51.60-80.

Some condensates have a pronounced methane character (Markovskoye), while others are dominated by naphthenic hydrocarbons (Ustye-Chesalskoye, Bovanenkovskoye). Some condensates contain significant amounts of aromatic hydrocarbons. For example, in the condensates of the Mitrofanovskoye, Nekrasovskoye, Kulbeshkakskoye, Ust-Labinskoye fields, their amount is 46-63%.

Stable condensate from the same field can have different characteristics. This depends, on the one hand, on the decrease in the reservoir pressure of the field, on the other, on the operating mode of the installations where heavy hydrocarbons are separated from gas. Thus, a decrease in the isotherm at LTS units increases the degree of condensation of hydrocarbons gs, C 6, which in turn leads to an increase in the content of light fractions in the condensate. The influence of separation temperature on the fractional composition of condensate is especially significant when its content in the reservoir gas is insignificant and the content of high-boiling fractions is high.

The physicochemical characteristics of condensates determine their commercial properties.

To assess the possibility of obtaining certain brands of motor fuels from condensates, their unified technological classification was established according to the industry standard OST 51.56-79. According to this classification, condensates are analyzed according to the following indicators: saturated vapor pressure, sulfur content, fractional composition, content of aromatic hydrocarbons and paraffins, pour point.

I - sulfur-free and low-sulfur with a mass fraction of total sulfur not exceeding 0.05%. These condensates do not require purification from sulfur compounds;

II - sulfurous with a total sulfur content from 0.05 to 0.8%. The need to purify condensates of this class and its distillate fractions in each specific case is decided depending on the initial requirements;

III - high-sulfur with a total sulfur content above 0.80%. The inclusion of a unit for removing sulfur compounds in the processing schemes for these condensates is mandatory.

Based on the mass fraction of aromatic hydrocarbons in gas condensates, they are divided into three types: A 1, A 2 and A 3 . Types A 1, A 2 and A 3 include condensates containing more than 20, 15-20 and less than 15% aromatic hydrocarbons, respectively.

H 1 - highly paraffinic, in the fraction of which with a boiling point of 200-320°C the content of complexing agents is at least 25% (wt.). From these condensates, liquids, n-alkanes and jet and diesel fuels can be obtained using a dewaxing process;

H 2 - paraffinic, the 200-320°C fraction contains 18-25% (wt.) complexing agents;

H 3 - low-paraffin, the content of complexing agents in the 200-320 °C fraction is 12-18% (wt);

H 4 - wax-free, the content of complexing agents in the diesel fraction is less than 12% (wt.).

According to the fractional composition, condensates are divided into three groups - F 1 F 2 and F 3:

F 1 - condensates of a lightweight fractional composition containing gasoline fractions of at least 80% (wt.), boiling no higher than 250 ° C;

F 2 - condensates of intermediate fractional composition, boiling away within the temperature range of 250-320 ° C;

F 3 - condensates boiling above 320°C.

Thus, a technological characteristic code is established for gas condensate, which is used to determine the appropriate direction for its processing. For example, the condensate of the Shatlyk field is designated by the code IA 3 N 1 F 3. The characters included in it are decrypted as follows:

I - class: the total sulfur content in the condensate is no more than 0.05% (wt); A 3 - type of condensate: content of aromatic hydrocarbons less than 15% (wt); H 1 - type: highly paraffinic condensate, in the 200-320 ° C fraction the content of complexing agents is above 25% (wt); F 3 - end boiling point above 320 °C.

Where ,gi- mass content of sulfur compounds in stable condensate, %; M i is the molar mass of sulfur compounds; T- the number of sulfur atoms in the substance.