RU2277116C1 - Oil desalting process - Google Patents

Abstract

FIELD: crude oil treatment.

SUBSTANCE: oil emulsion is preliminarily separated from drainage water and, after addition of demulsifier, oil desalting process is carried out by washing moving emulsion under dispersing conditions with a washing fluid in at least two steps. Volume of washing fluid added in the first desalting step is larger than that in the second step by a factor of 2.0-2.5. Washing fluid is notably 3-10% aqueous sodium nitrate solution, which is preheated before addition to at least 45°C in both desalting steps. In the first step, oil is subjected to hot settling preferably for 2 h and, in the second step, 3 h. Demulsifier utilized is based on oil-soluble surfactants added in amounts 25 to 55 g/t.

EFFECT: reduced consumption of demulsifier at higher degree of desalting, in particular for oils with high level of chlorides.

7 cl, 2 ex

Description

The invention relates to the oil industry, in particular to processes for the desalination of oil during its preparation in the oil fields.

It is known that the high content of water and chloride salts in oil during its processing causes severe corrosion of technological equipment, an increase in energy consumption and a decrease in the overhaul distance of plants. Therefore, the question of the exclusion of these adverse factors, i.e. dehydration and desalination of oils (especially heavy viscous oils) is very important in oil refining.

A known method of separating oil emulsions, including for the purpose of desalination, by washing them with a washing liquid in the form of an aqueous solution of a complex of inorganic salts obtained by desalting natural waters treated with an alcohol solution of alkali metal silicate (1).

However, this known method is energy-intensive with high labor costs due to the need to obtain a special (and therefore scarce) complex of salts used to prepare the wash liquid. This leads to an increase in the cost of the oil preparation process, and is not always feasible in the field.

There is also known a method of dehydration and desalting of oil, by a two-stage oil treatment with washing liquid, according to which the oil is heated to 30-40 ° C, introducing into it at the first stage of the washing liquid, which is a solution of diethanolamide acid decanexadecane fraction in a concentration of 0.1-0 , 5 wt.%, Followed by hot sludge at a temperature of 60-70 ° C and oil separation, and in the second stage, the concentration of a solution of diethanolamide of acid decanexadecane fraction of 0.05-0.1 wt.% At a sediment temperature of 50-60 ° C ( 2).

The disadvantage of this method is its complexity due to additional operations and a deficiency of the reagent, and additional acidification of the flushing fluid leads to corrosion of the oilfield equipment.

Closest to the proposed invention in technical essence is a method of desalting oil, according to which a preliminary separation from the oil emulsion of drainage water is carried out, a demulsifier is introduced into the oil in an amount of 75 g / t and the subsequent process of desalination of oil is carried out by washing it in the intensive dispersion mode with washing liquid, which is an aqueous solution of sodium nitrate or ammonium nitrate, followed by hot sludge for 3 hours at a temperature of + 55 ° C and separation pouring water at the same time (3).

The disadvantage of this method is the lack of effectiveness of desalination, especially heavy oil with a high content of chloride salts, with mineralization of associated water more than 120 g / dm ³ , which leads to increased corrosion of equipment, high consumption of reagents and the production of oil that does not meet the requirements of commodity.

The technical problem solved by the invention is to increase the degree of desalination, including heavy oils with a high content of chlorides, and at the same time reduce the consumption of demulsifier.

An additional technical result is the expansion of the range of available, non-corrosive and inexpensive chemicals for the preparation of washing liquids used for desalting.

The specified technical result is achieved by the proposed method of oil desalination, including preliminary separation of drainage water from the oil emulsion, introducing a demulsifier into the oil and the subsequent process of oil desalination by washing it in the dispersion mode with a washing liquid containing an aqueous solution of inorganic sodium salt of nitric acid, followed by hot sludge and separation of the water released in this process is new, that the process of desalination is carried out along the course of oil at least two stages, while the desalination process is carried out with heated oil, and the volume of washing liquid introduced into the oil at the first stage of desalination is 2.0-2.5 times larger than the volume of washing liquid at the second stage of desalination, moreover, as the specified washing liquid use an aqueous solution of sodium nitrite.

The concentration of sodium nitrite in the washing liquid is 3-10 wt.%.

At both stages of desalination, the pH of the washing liquid is at least 9.

The washing liquid at both stages of desalination is heated to a temperature not lower than + 45 ° C before it is fed to the oil.

Hot sludge oil in the first stage of desalination is preferably 2 hours, and in the second stage 3 hours.

In the proposed method, a demulsifier in an amount of 25-55 g / t is introduced into the oil, and a demulsifier based on oil-soluble surfactants of the Kemeliks or Separol type or a mixture thereof is used as a demulsifier.

The task posed by the creation of the invention is solved by the following.

Thanks to the desalination process in two stages with certain modes and reagents on each of them, an increase in the degree of purification of oil, including heavy, from salts, and giving it the quality of marketable oil is provided.

The feasibility of using sodium nitrite in the form of an alkaline solution with a pH of at least 9 is due to the fact that in acidic and neutral environments, nitrites wash out salts in oil with low efficiency, and in an alkaline medium at pH above 9-10 with a fairly high efficiency.

The multi-stage desalination process with washing the heated oil with hot washing liquid at each stage has a positive effect on the level of salts in the crude oil, especially if the ratio of washing liquid at I: II stages is related as 2.0-2.5: 1. Washing in the proposed method is carried out in the intensive dispersion mode followed by hot sludge, preferably at the first stage - 2 hours, at the second stage - 3 hours.

When implementing the proposed method, the following operations are carried out in the following sequence:

- oil emulsion is fed to a preliminary discharge unit, on which a preliminary discharge of drainage water is performed;

- in the separated oil serves demulsifier in the amount of 25-55 mg / DM ³ ;

- further, through a process pump, oil is passed through a heat exchanger, where it is heated to a temperature of 70-80 ° C;

- the heated oil enters the first degree of desalination, while the washing liquid is introduced into the oil through the dispersant, preheated to a temperature of at least 45-50 ° C and representing an aqueous solution of sodium nitrite with a concentration of 3-10 wt.%;

- then the mixture enters the sumps, for example, type OG-200, where it is stratified into oil and water;

- separated water is sent through a drainage line to a preliminary discharge tank (RPS),

- and the remaining oil is diverted to the second stage of desalination, where a washing liquid — an aqueous solution of sodium nitrite with a concentration of 3–10 wt%, is fed into the oil stream through the second dispersant;

- then the resulting mixture enters the sumps of the second stage, where it settles;

- the separated water is then sent to the RPS, and the oil is sent to the tank of salable oil;

- the ratio of the volume of washing liquid in the first stage of desalination is 2.0-2.5 times greater than the volume of washing liquid in the second stage.

The proposed method was tested in laboratory and field conditions using crude oil obtained at the installation of primary oil treatment (UPPN) "Nozhovka" Perm region, and is illustrated by the following examples.

Example 1 (laboratory).

Desalination was carried out in two stages. At stage I, oil (after preliminary dehydration at the UPPN, with a density of 918 kg / m ³ , salt content of 11510 mg / l, and water cut of 4.7%) is filled with 100 ml bottles and heated to a temperature of + 75 ° С. The demulsifier “Kemelix 3437x” is introduced in a dosage of 55 g / t of oil. An aqueous solution of sodium nitrite of 5% concentration is heated to a temperature of + 50 ° C and injected in an amount of 7 ml into hot oil. At the same time, the bottle is shaken vigorously for 5 minutes and placed on sedimentation at a temperature of + 80 ° C for 2 hours. The settled water is taken.

At the second stage, an aqueous solution of sodium nitrite of 5% concentration in a volume of 3 ml heated to a temperature of + 50 ° C is added to the remaining oil, and at the same time it is intensively mixed for 5 minutes. The sedimentation is carried out for 3 hours at a temperature of + 80 ° C. The selection of oil for analysis on the content of chloride salts is made from the upper layer. Determination of the content of chloride salts in oil is carried out according to GOST 21534-76. The results showed that the salt content in the separated oil is 56 mg / l, which corresponds to the indicators of marketable oil of the first quality group according to GOST R 51858-2002.

Example 2 (commercial).

The proposed method was tested in the field. The oil emulsion was desalted with the following characteristics: density - 1031-1059 kg / m ³ , water cut - 54-67%, initial salt content of 102300-126600 mg / l and volume, ≈ 4370 t / day. The specified oil emulsion is fed into a preliminary discharge tank, on which a preliminary discharge of drainage water is made to a residual content of 1.6-4.9%. The separated oil is supplied with the Kemelix 3437x demulsifier in an amount of 25-55 g / t oil. Then, through a process pump, oil is passed through a heat exchanger, where it is heated to a temperature of 70-80 ° C. Heated oil enters the first degree of desalination, while a washing liquid is introduced into the oil stream through a dispersant brand RGD (adjustable hydrodynamic dispersant), preheated to a temperature of at least 45-50 ° C and representing an aqueous solution of sodium nitrite with a concentration of 3-10 wt. .%;

- then the mixture enters the sumps, for example, type OG-200, where it settles for 2 hours and is stratified into oil and water;

- the separated water is sent to the RPS along the drainage line;

- and the remaining oil is diverted to the second stage of desalination, where a washing liquid — an aqueous solution of sodium nitrite with a concentration of 3–10 wt%, is fed into the oil stream through the second dispersant;

- then the resulting mixture enters the sumps of the second stage, where it settles for 3 hours;

- the separated water is then sent to the RPS, and the oil is sent to the tank of salable oil;

- the ratio of the volume of washing liquid in the first stage of desalination is 2.0-2.5 times greater than the volume of washing liquid in the second stage;

- after conducting these tests, it was possible to obtain a stable value of the concentration of chloride salts in commercial oil of less than 100 mg / l, which corresponds to the parameter of commercial oil.

The results obtained during the tests are shown in the table. The data presented in the table show that the proposed method of desalination has the following advantages over the known:

- provides effective desalination of heavy oils with a high initial salt content in them;

- allows you to get marketable oil of the first quality group with the characteristics dictated by the new stricter GOST R 51858-2002;

- allows to reduce the demulsifier consumption by 1.5-3 times in comparison with the prototype;

- expands the range of reagents used for the preparation of washing liquid.

INFORMATION SOURCES

1. Auth. testimonial. USSR No. 1168585, Cl. C 10 G 33/04, 1983

2. Auth. testimonial. USSR No. 883153, Cl. C 10 G 33/04, 1980

3. RF patent No. 1666520, Cl. C 10 G 33/04, 1989

Table
The results of the desalination of oil by the proposed and known prototype methods №№ The list of operations and modes of the method Oil quality Demulsifier consumption during desalination, g / t Oil heating temperature, ° С Dispersion Supply of flushing fluid at the first stage, l / t of oil Flushing fluid supply at the second stage, l / t oil The temperature of the washing fluid, ° C The concentration of NaNO ₂ in the wash. liquid, wt.% The ratio of the volumes of flushing fluid at I and II steps Number of salts, g / l For the proposed method one 35 60 + 69 46 fifty 7 1.5: 1 119 2 55 70 + 72 36 60 5 2: 1 89 3 40 80 + 88 35 fifty 3 2.5: 1 67 four 25 80 + 80 40 40 7 2: 1 84 5 55 70 + 60 60 fifty 10 1: 1 147 6 fifty 70 + 81 40 fifty 7 pH = 5-6 2: 1 219 For the known prototype method 7 75 55 + 115 0 55 10 NaNO ₃ 1-0 203 8 75 55 + 79 38 fifty 10 NaNO ₃ 2: 1 142 Note: 1) In experiments 1.3, the initial oil (after preliminary water discharge) had a density of 917 kg / m ³ , with a salt content of 3490 mg / l and a water cut of 1.95%. In experiments 2.4-8, the initial oil (after preliminary discharge of water) had a density of 918 kg / m ³ , with a salt content of 4720 mg / l and a water cut of 2.7%.
2) In experiments 1,3,5–8, the Kemelix 3437x demulsifier was used, in experiment 2, Separol-FLEK ML-3594, and in experiment 4, their mixture in a mass ratio of 70:30, respectively.
3) In experiments 1-5, 7.8, the pH of the medium was 9-10.

Claims (7)

1. A method of desalting oil, including preliminary separation of drainage water from the oil emulsion, introducing a demulsifier into the oil and the subsequent process of oil desalination by washing it in the dispersion mode with a washing liquid, which is an aqueous solution of an inorganic sodium salt of nitric acid, followed by hot sludge and separation of the released while water, characterized in that the desalination process is carried out along the course of the oil in at least two stages, while the process of desalination pouring is carried out with heated oil, and the volume of washing liquid introduced into the oil at the first desalination stage is 2.0-2.5 times larger than the volume of washing liquid at the second desalination stage, and an aqueous solution of sodium nitrite is used as the indicated washing liquid. 2. The method according to claim 1, characterized in that the concentration of sodium nitrite in the washing liquid is 3-10 wt.%. 3. The method according to claim 1, characterized in that at both stages of desalination, the pH of the washing liquid is at least 9. 4. The method according to claim 1, characterized in that the flushing fluid at both stages of desalination is heated to a temperature not lower than + 45 ° C before being fed into the oil. 5. The method according to claim 1, characterized in that the hot sludge oil in the first stage of desalination is preferably 2 hours, and in the second stage 3 hours 6. The method according to claim 1, characterized in that a demulsifier is introduced into the oil in an amount of 25-55 g / t. 7. The method according to claim 1 or 7, characterized in that as a demulsifier use a demulsifier based on oil-soluble surfactants of the type "Kemelix", or "Separol", or a mixture thereof.