RU2788491C1 - Oil dehydration and desalination method - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to the oil industry, in particular to methods for dehydrating and desalting oil, and can be used in the complex preparation of oil in field conditions and at oil refineries. A method for dehydrating and desalting oil is proposed, which includes mixing dehydrated oil and fresh water in a mixer in a turbulent mode, directing the mixture to a coalescent to coarsen water droplets, and their subsequent separation in settling equipment. The process of mixing dehydrated oil and fresh water in the mixer is carried out at a speed of movement of the water-oil emulsion of 0.4-0.6 m/s. In this case, the processing time is 10-20 s, and the speed of the water-oil emulsion in the coalescent is maintained in the range of 0.02-0.06 m/s at a processing time of 125-200 s.

EFFECT: proposed method allows to effectively carry out the process of dehydration and desalting of oil by intensive mixing of fresh water and dehydrated oil in short periods of time.

1 cl, 5 tbl

Description

The invention relates to the oil industry, in particular, to methods of dehydration and desalting of oil and can be used in the complex preparation of oil in field conditions and at oil refineries.

A known method of dehydration and desalting of oil (patent RU No. 2074231, IPC C10G 33/00, B01D 17/04, publ. 27.02.1997) in oil fields and refineries. Oil is subjected to hydrodynamic perturbation by passing it through channels made of hydrophobic material, separating it by portions of water into layers alternating along the channels by periodically adding a portion of water to the initial section of the channels, and then settling.

The known method is complex in hardware design and is not effective enough for oil desalting. Low efficiency, in terms of oil desalting, is due to the fact that there is no effective mixing of fresh water and oil, which is necessary for the desalting process. It is assumed that the emulsified dispersed aqueous phase is “carried out” from the volume of the oil emulsion to the “emulsion-water” phase interface under the influence of the resulting circulation currents in the emulsion when moving along vertical hydrophobic channels of alternating layers “water-emulsion”. In addition, a large amount of fresh (tap) water is required to ensure the formation of alternating water-emulsion layers. And the further joint transport of such a quantity of liquid to the settling tanks does not exclude the re-emulsification of water in oil.

Also known is a method for dehydrating oil (patent RU No. 2439314, IPC E21B 43/34, B01D 17/04, publ. the content of oil products is not more than 1% at a temperature of 5-50 ° C, dispersion is carried out in an oil pipeline with a laminar oil emulsion flow at the site of the oil pipeline after the point of supply of a water-oil-soluble demulsifier, when dispersed, water in a volume of 2-15% of the volume of oil being prepared is sent to the oil emulsion at an angle of 45 ± 5 ° to the direction of the pipeline axis through holes with a diameter of 5-15 mm, the rest is directed under the wastewater layer.

The known method involves the implementation of the dehydration process in a laminar mode of movement in the pipeline, which, despite the presence of a dispersing device, is unfavorable for the processes of dispersing fresh water and further coalescence of emulsified water droplets, while there is no device for coarsening water droplets.

The closest is the method of dehydration and desalination of oil (Urazov I.I., Gubaidulin F.R., Sudykin S.N., Mukhametgaleev R.R. / Development and implementation of intensifying devices for the preparation of high-viscosity oil in PJSC Tatneft / Exposition Oil Gaz. - 2016. - No. 7. - P. -36-38), including the mixing of dehydrated oil and fresh water in the mixer in a turbulent mode with a speed of the water-oil emulsion of at least 0.5 m/s, the direction of the mixture into the coalescent at a speed movement of water-oil emulsion 0.05 m/s to enlarge water droplets and subsequent separation in settling equipment.

The disadvantage is the difficulty of maintaining a strictly defined speed of the emulsion in the mixer and coalescent, which is associated with the uneven flow of dehydrated oil, thereby requiring additional control. Also, no information is provided on the required processing time of the water-oil emulsion in the mixer and coalescent.

The technical problem is the effective implementation of dehydration and desalting of oil by intensive mixing of fresh water and dehydrated oil in short periods of time.

Technical problems are solved by the method of dehydration and desalting of oil, including mixing of dehydrated oil and fresh water in a mixer in a turbulent mode, directing the mixture into a coalescent to coarsen water droplets and their subsequent separation in settling equipment.

What is new is that the process of mixing dehydrated oil and fresh water in the mixer is carried out at a speed of movement of the water-oil emulsion of 0.4-0.6 m/s, while the processing time is 10-20 seconds, and the speed of movement of the water-oil emulsion in the coalescer is maintained at interval 0.02-0.06 m/s with a processing time of 125-200 sec.

The method of dehydration and desalting of oil is carried out as follows.

Well production after separation of associated petroleum gas is sent to the stage of formation water separation. The separated reservoir water is sent to treatment facilities and further for injection into the reservoir pressure maintenance system. Pre-dehydrated oil from the stage of preliminary water discharge through the oil heating unit is sent to the hot dehydration stage. After deep dehydration, the oil is sent to the desalination stage, where before the desalination stage after the fresh water supply point, a block of intensifying devices is located - a mixer and a coalescent.

In the mixer, effective dispersion of fresh flushing water in oil is carried out, in the coalescer, water droplets collide with each other, merge and enlarge. Further, in the dehydrator of the desalting stage, under the action of gravitational forces, water rapidly settles into the lower part of the apparatus. Thus, the process of separating water from oil is accelerated and the time required for settling the oil emulsion in the dehydrator is reduced.

The mixer is a pipe device of the estimated diameter and length, filled with nozzles (for example, Pall rings) fixed in the flange connection of the mixer, to prevent the nozzles from being carried away by the liquid flow, partitions made of expanded metal or metal mesh are used.

Dry oil and fresh water are mixed in a volume of 1-10% of the volume of oil being prepared in a mixer in a turbulent mode. The water-oil emulsion moves in the mixer at a speed of 0.4-0.6 m/s, while the processing time is 10-20 seconds. The flow regime of the liquid flow through the mixer pipeline is turbulent, i.e. the flow in which the liquid moves while mixing, there is an effective mixing of fresh water with dehydrated oil.

Next, the flow of water-oil emulsion enters the coalescent. The coalescent is a pipe device of the estimated diameter and length, filled with nozzles (for example, Pall rings). When the water-oil emulsion moves in the coalescent, finely dispersed water drops collide with each other on the surface of the Pall rings, they merge and enlarge. The speed of movement of the water-oil emulsion in the coalescent is 0.02-0.06 m/s, and the processing time is 125-200 seconds. Further, water is separated from oil in the dehydrator of the desalination stage.

Table 1 shows the results of dehydration and desalting of carboxylic oil using a block of intensifying devices - a mixer and a coalescent, depending on the change in the volume of fresh water supply in the range of 1-10%.

Table 1 Name of indicator Indicator value 1. Volume of fresh water, % 1 2 3 five 10 2. Mass concentration of chloride salts
after the dehydrator of the desalination stage, mg/l 252 118 86 64 42 3. Mass fraction of water in oil after
dehydrator of the desalination stage, % 0.11 0.19 0.25 0.33 0.45

Table 1 shows that when fresh water is supplied in a volume of 1 to 10% before the block of intensifying devices, the mass concentration of chloride salts after the dehydrator of the desalination stage is from 42 to 252 mg/l, the mass fraction of water in oil is from 0.11 to 0 .45%.

Table 2 shows the results of dehydration and desalting of carboxylic oil, depending on the change in the speed of the water-oil emulsion in the mixer. The results are presented with a volume of fresh water - 3%.

table 2 Name of indicator Indicator value 1. Volume of fresh water, % 3 2. The speed of movement of the emulsion in the mixer, m/s 0.3 0.4 0.5 0.6 3. Mass concentration of chloride salts
after the dehydrator of the desalination stage, mg/l 109 96 95 99 4. Mass fraction of water in oil after
dehydrator of the desalination stage, % 0.31 0.3 0.32 0.34

Table 2 shows that when changing the speed of the water-oil emulsion in the mixer in the range from 0.3 to 0.6 m/s, the mass concentration of chloride salts after the dehydrator of the desalting stage is from 95 to 109 mg/l, the mass fraction of water in oil is from 0.3 to 0.34%. At the same time, the optimal range of the speed of movement of the water-oil emulsion in the mixer is the interval of 0.4-0.6 m/s, which provides a mass concentration of chloride salts of not more than 100 mg/l, which, in accordance with GOST R 51858-2002, meets the requirements of the 1st quality group commercial oil.

Table 3 shows the results of dehydration and desalting of carboxylic oil depending on the change in the processing time of the water-oil emulsion in the mixer. The results are presented at the speed of movement of the water-oil emulsion in the mixer - 0.5 m/s and the volume of fresh water - 3%.

Table 3 Name of indicator Indicator value 1. Volume of fresh water, % 3 2. The speed of movement of the emulsion in the mixer, m/s 0.5 3. Processing time of the emulsion in the mixer, sec five 10 15 20 4. Mass concentration of chloride salts
after the dehydrator of the desalination stage, mg/l 108 95 94 93 5. Mass fraction of water in oil after
dehydrator of the desalination stage, % 0.36 0.32 0.32 0.31

From table 3 it can be seen that when the processing time of the water-oil emulsion in the mixer is changed from 5 to 20 seconds, the mass concentration of chloride salts after the dehydrator of the desalination stage is from 93 to 108 mg/l, the mass fraction of water in oil is from 0.31 to 0.36 %. At the same time, the optimal time range for processing the water-oil emulsion in the mixer is the interval of 10-20 seconds, which provides a mass concentration of chloride salts of not more than 100 mg/l.

Table 4 shows the results of dehydration and desalting of carboxylic oil depending on the change in the speed of the water-oil emulsion in the coalescent. The results are presented with a volume of fresh water - 3%.

Table 4 Name of indicator Indicator value 1. Volume of fresh water, % 3 2. The speed of the emulsion in the coalescent, m/s 0.01 0.02 0.04 0.06 3. Mass concentration of chloride salts
after the dehydrator of the desalination stage, mg/l 96 96 99 one hundred 4. Mass fraction of water in oil after
dehydrator of the desalination stage, % 0.29 0.29 0.3 0.3

When changing the speed of the water-oil emulsion in the coalescent from 0.01 to 0.06 m/s, the mass concentration of chloride salts after the dehydrator of the desalting stage is from 96 to 100 mg/l (see Table 4), the mass fraction of water in oil is from 0 .29 to 0.3%. In this case, the optimal range of the speed of movement of the water-oil emulsion in the coalescent is the interval of 0.02-0.06 m/s, because reducing the speed to 0.01 m/s does not affect the quality of the treated oil.

Table 5 shows the results of dehydration and desalting of carboxylic oil depending on the change in the processing time of the water-oil emulsion in the coalescent. The results are presented at the speed of movement of the water-oil emulsion in the coalescent - 0.04 m/s and the volume of fresh water - 3%.

When changing the processing time of the water-oil emulsion in the coalescer from 50 to 200 sec (see Table 5), the mass concentration of chloride salts after the dehydrator of the desalting stage is from 94 to 107 mg/l, the mass fraction of water in oil is from 0.28 to 0.34 %. At the same time, the optimal range of processing time for the oil-water emulsion in the coalescent is the interval of 125-200 seconds, which provides a mass concentration of chloride salts of not more than 100 mg/l.

Table 5 Name of indicator Indicator value 1. Volume of fresh water, % 3 2. The speed of the emulsion in the coalescent, m/s 0.5 3. Processing time of the emulsion in the coalescent, sec 50 125 150 200 4. Mass concentration of chloride salts
after the dehydrator of the desalination stage, mg/l 107 99 98 94 5. Mass fraction of water in oil after
dehydrator of the desalination stage, % 0.34 0.3 0.3 0.28

Thus, the proposed method allows you to effectively carry out the process of dehydration and desalting of oil by intensive mixing of fresh water and dehydrated oil in short periods of time.

Claims (1)

A method for dehydrating and desalting oil, including mixing dehydrated oil and fresh water in a mixer in a turbulent mode, directing the mixture into a coalescent to coarsen water droplets and their subsequent separation in settling equipment, characterized in that the process of mixing dehydrated oil and fresh water in a mixer is carried out with the speed of movement of the water-oil emulsion is 0.4–0.6 m/s, while the processing time is 10–20 s, and the speed of movement of the water-oil emulsion in the coalescer is maintained in the range of 0.02–0.06 m/s with a processing time of 125– 200 s.