Apparatus and process for separating and treating produced water

Abstract

An apparatus for separating and treating produced water comprises a gas-liquid mixture (GLM) separating unit having GLM feed and discharge pipes and a water purification unit having a stack of plates and a device for discharging separated oil and pipes for discharging water and mechanical impurities. The GLM separating unit and the water purification unit are configured conjointly in the form of a horizontal tank containing coalescer stacks and having a vertical trap mounted on its upper surface, said trap being in the form of a dome with an open central pipe connected to the GLM feed pipe for introducing a GLM into the central pipe. The dome is equipped with a common pipe for discharging partially dehydrated GLM, discharged via the central pipe, and oil, discharged via the annulus of the dome. The technical result consists in simplifying the process for separating and treating produced water by creating a trap in a single apparatus that combines the functions of separating a gas-liquid mixture and treating and purifying water, including the removal of mechanical impurities.

Description

[0001] INSTALLATION AND METHOD FOR SEPARATING AND PREPARING PRODUCED WATER

[0002] The group of inventions relates to equipment and technologies for the separation and subsequent preparation of produced formation water in an oil, gas and water collection system.

[0003] The closest to the proposed installation for separation and preparation of produced water is the installation for preparation of produced formation water (RF Patent No. 2596259, B01D19 / 00, issue 10.08).2016), including a pipeline for feeding the produced gas-liquid mixture (GLM) to a GLM separation unit, a pipeline for removing GLM from the GLM separation unit, a water preparation unit equipped with a stack of parallel plates as a filter for cleaning from mechanical impurities, a water discharge pipeline, wherein the GLM separation unit is a pipe water separator or an emulsion phase separation unit or a pipe settling tank-separator, the water preparation unit is a horizontal pipe closed at the ends, a pipeline for introducing oil-containing water into it, coming from the separation unit, the stack of parallel plates is connected to a cap for collecting mechanical impurities through an opening at the bottom of the horizontal pipe, and a cap for collecting released gas and oil is installed after the stack of parallel plates, in the upper part of the horizontal pipe, a pipeline for removing released gas and oil from the cap for collecting them in the separation unit.

[0004] The disadvantage of the prototype plant is its lack of efficiency due to the complexity associated with the need to use separate units: a gas-liquid separation unit and a water preparation unit; moreover, the parallel plate pack in the water preparation unit is installed only as a filter for cleaning out mechanical impurities.

[0005] The prototype of the claimed method for separating and preparing produced water is a method implemented by a unit for separating and preparing produced water (RU Patent No. 2596259, B01D19 / 00, issued on 10 August 2016), which includes feeding the produced gas-liquid mixture (GLM) into the GLM separation unit, removing the GLM from the GLM separation unit, preparing water coming from the separation unit in a unit equipped with a pack of parallel plates as a filter for cleaning from mechanical impurities, removing water from the preparation unit, wherein the GLM separation unit is a pipe water separator or an emulsion phase separation unit or a pipe settling tank-separator, the water preparation unit is a horizontal pipe closed at the ends with a cap for collecting the released gas and oil, which are removed to the unit separations.

[0006] The disadvantage of the prototype method is its lack of efficiency due to the complexity associated with the need to use separate units: a gas-liquid separation unit and a water preparation unit; moreover, the parallel plate pack in the water preparation unit is installed only as a filter for cleaning from mechanical impurities.

[0007] A cylindrical horizontal oil and gas settling tank is known (RU Patent No. 103801, B01D17 / 00, published April 27, 2011), from which water is discharged through a water outlet nozzle into a hydraulic seal to improve the quality of the water in terms of its oil content. The height of the water overflow point in the hydraulic seal is matched to the water level in the cylindrical horizontal settling tank and is set below the oil overflow point by an amount determined by the quality requirements for the water discharged from the settling tank.

[0008] The disadvantage of this water seal, which is not included in the design of the settling tank according to Russian Patent No. 103801 and does not improve the efficiency of the settling tank itself, is its lack of multifunctionality.

[0009] The closest to the claimed hydraulic seal device in terms of the set of essential features is the hydraulic seal device in a separation unit (RF Patent No. 2236887, BO1D19 / 00, issued September 27, 2004) for separating oil and gas in a well production gathering and preparation system. The separation unit contains a vertical hydrocyclone apparatus with pipelines for supplying a gas-liquid mixture (GLM), removing gas and liquid, a concentric drip-eliminating chamber and a gas-equalizing branch pipe. The vertical hydrocyclone apparatus is installed in a horizontal tank, its lower end rests at the points of connection with the cylindrical shell of the tank, the lower end of the drip-eliminating chamber is located at the same level as the lower end of the hydrocyclone apparatus, the gas outlet pipeline is installed with its lower end at a level corresponding to the upper generatrix of the tank.In this case, the gas outlet pipeline is central in the vertical hydrocyclone apparatus, and the gas-liquid mixture is supplied to the vertical hydrocyclone apparatus tangentially into the annular space (illustration to Russian patent No. 2236887).

[0010] According to the description of the Russian Federation patent No. 2236887: the placement of the lower end of the hydrocyclone apparatus resting at the points of connection with the cylindrical shell of the process tank and the placement of the lower end of the drip-elimination chamber at the same level with the lower end of the hydrocyclone apparatus makes it possible to increase the level of the water seal, which, in turn, prevents the passage of gas into the liquid and vice versa, the passage of liquid into the gas line;

[0011] - installation of the gas outlet pipeline with its lower end at a level corresponding to the upper generatrix of the process tank leads to the prevention of gas breakthrough from the inlet cavity of the vertical hydrocyclone apparatus into the gas cavity of the process tank.

[0012] Thus, the hydraulic seal device according to Russian patent No. 2236887 (a prototype of the hydraulic seal device) is part of a separation unit with a vertical hydrocyclone apparatus and serves, accordingly, for the effective separation of the gas-liquid mixture by the separation unit itself. Namely: the gas-liquid mixture is fed into the separation unit through the annular space of the hydraulic seal, vertically installed on the upper generatrix of the horizontal process tank, and its central pipe serves as a gas outlet. The device serves to prevent gas breakthrough from its annular space (from the inlet cavity of the vertical hydrocyclone apparatus, where the gas-liquid mixture is fed) into the gas cavity of the horizontal process tank, since the gas-liquid mixture, which is denser relative to the gas, is located under the lower end of the gas outlet pipe.

[0013] A disadvantage of the prototype hydraulic seal device (RU Patent No. 2236887), included in the design of the separation unit, is its insufficient efficiency due to the lack of multifunctionality. The tasks to be solved and the expected technical result consist of the development of an efficient unit and method for the separation and preparation of produced water with a simplification due to the organization of the hydraulic seal in a single apparatus combining all the functions of the prototype - separation of GLM, preparation and purification of water, including purification from mechanical impurities; in addition, the multifunctional hydraulic seal device proposed for the implementation of the unit serves to receive and separate GLM with the separation of water and the separate discharge of partially dehydrated GLM and oil, increasing the efficiency of separation and preparation of produced water by the proposed unit.

[0014] The stated problem is solved in that the proposed unit for separation and preparation of produced water, including a gas-liquid mixture (GLM) separation unit with GLM supply and discharge pipelines and a water purification unit with a plate pack and a device for removing separated oil and pipelines for removing water and mechanical impurities, is distinguished by the fact that the GLM separation unit and the water purification unit are made integrally in the form of a horizontal process tank (HPT) with coalescer packs with a vertical hydraulic seal installed on the upper generatrix of the GTU, performing the following functions: receiving GLM at the unit, a GLM separation unit and water separation and the function of a device for separate removal of partially dehydrated GLM and oil; the unit contains a common pipeline for removing partially dehydrated GLM and oil.

[0015] The installation contains a cap with a central pipe as a water seal for receiving the gas-liquid mixture, separating the gas-liquid mixture and separating water and removing partially dehydrated gas-liquid mixture, and with the possibility of removing oil through the annular space of the cap.

[0016] The stated problem is also solved by the fact that the proposed method for separating and preparing produced water, including separation of the gas-liquid mixture (GLM) and purification of water using a plate pack with the removal of separated oil, water and mechanical impurities, is distinguished by the fact that the supply of GLM and the separation of GLM with the separation of water from it are carried out in a vertical hydraulic seal installed on the upper generatrix of the horizontal process tank (HPT), and the purification of the separated water is carried out by packs of coalescers installed in the HPT, whereby partially dehydrated GLM and oil are removed separately through the vertical hydraulic seal, after which they are transported through a common discharge pipeline.

[0017] The dehydrated gas-liquid mixture and oil are discharged separately through a cap with a central pipe discharging the dehydrated gas-liquid mixture, and, correspondingly, the oil is discharged through the annular space of the cap. The stated problem is also solved by the fact that the proposed hydraulic seal device for the separation and treatment of produced water, installed vertically on the upper generatrix of the horizontal process tank (HPT), used for the introduction of the gas-liquid mixture, having an open central pipe for discharge, is distinguished by the fact that it is a cap with a central pipe for the introduction of the gas-liquid mixture, the separation of water and the discharge of partially dehydrated gas-liquid mixture, and an annular space of the cap for the discharge of oil.

[0018] The claimed objects are illustrated in Figure 1, where:

[0019] 1 - horizontal technological tank (HTU)

[0020] 2 - Coalescer packs

[0021] 3 - cap

[0022] 4 - central pipe

[0023] 5 - gas supply pipeline

[0024] 6 - common pipeline for the removal of partially dehydrated gas-liquid mixture and oil

[0025] 7 - water drainage pipeline

[0026] 8 - pipeline for removing mechanical impurities

[0027] 9 - gas-liquid separation zone

[0028] 10 - water calming zone with residual oil and mechanical impurities

[0029] 11 - zone of mechanical impurities

[0030] 12 - purified water zone

[0031] 13, 14 - partitions.

[0032] The multifunctional hydraulic seal device is vertically installed on the upper generatrix of the horizontal process tank (HPT) 1 and is a cap 3 with a central pipe 4 that performs the following functions: receiving the gas-liquid mixture, separating the gas-liquid mixture with separation of water and removing partially dehydrated gas-liquid mixture; the annular space of the cap 3 between the pipe 4 and the cap 3 serves to remove oil; the partially dehydrated gas-liquid mixture and oil, separately removed by means of this hydraulic seal device, are then removed together through a common pipeline 6. The hydraulic seal itself is formed by the said water, separated during the separation of the supplied gas-liquid mixture in the pipe 4.

[0033] The installation, designed for separation and preparation of produced formation water in the system for collecting water-cut products from wells of oil and gas fields located at stages 3 and 4 of development, equipped with a vertical hydraulic seal, is a sealed vessel operating under the pressure of the well product collection system in a pressure / flow mode.

[0034] The operation of the installation with a vertical hydraulic seal, implementing the claimed method of separating and preparing produced formation water, is carried out as follows.

[0035] The gas liquid mixture (GLM) continuously enters the GLM separation zone 9 under the pressure of the well production collection system through pipeline 5 in a vertical hydraulic seal, namely in a vertical pipe 4 open on both sides of the cap 3. In the GLM separation zone 9, the speed of the GLM flow decreases and calms down, and freely separable water is separated from it, with the formation of, accordingly, partially dehydrated GLM.

[0036] Partially dehydrated gas-liquid mixture is directed under pressure through pipe 4 of the vertical hydraulic seal to the upper part of cap 3 of the vertical hydraulic seal, from where it is continuously discharged through common pipeline 6 into the collection system.

[0037] The separated water from the gas-liquid mixture separation zone 9 is lowered into the water calming zone 10 of the horizontal process tank (HPT) 1. In order to prevent the downward movement of the oil and gas phases of the supplied gas-liquid mixture, the lower end of the pipe 4 is lowered into the layer of separated water below the lower edge of the cap 3 by 20-25% of the diameter of the horizontal part of the HPT 1, thus forming the hydraulic seal itself.

[0038] The separated water with residual oil content and mechanical impurities from pipe 4 of cap 3 enters the stilling zone 10 of horizontal process tank (HPT) 1, where due to a significant decrease in flow velocity, further gravitational separation of water and oil occurs. Droplets of oil float and, due to the difference in density, rise through the annular space between cap 3 and pipe 4 of the vertical hydraulic seal to the upper part of cap 3, where they mix with partially dehydrated gas-liquid mixture from the gas-liquid mixture separation zone 9, and are continuously discharged from the vertical hydraulic seal - a cap with a central pipe - together through a common pipeline 6 for removing partially dehydrated gas-liquid mixture and oil.

[0039] Thus, by separating the descending flow of separated water and the ascending flow of captured oil by the proposed vertical hydraulic seal, namely: the device of a cap 3 with an open central pipe 4, conditions are created to prevent their re-mixing.

[0040] Baffles 13 in GTU 1 serve to calm and direct the flow of purified water containing residual oil and mechanical impurities. Baffles 14 in GTU 1 create additional conditions for retaining mechanical impurities in zone 10.

[0041] Water from the calming zone 10 passes through a stack of coalescers 2. In coalescers 2, the oil droplets are enlarged, then float to the surface and are continuously removed from the apparatus through the annular space of the vertical hydraulic seal between cap 3 and pipe 4. Simultaneously, residual mechanical impurities are separated and settled in coalescers 2, where they settle in sections of zone 11 directly below coalescers 2. The precipitated mechanical impurities from all sections of zone 11 are periodically (as they accumulate) removed from the apparatus through pipeline 8. Purified water enters zone 12, from where its balance amount is continuously removed from the apparatus through pipeline 7.

[0042] Plate coalescers 2 can be used, for example, according to Russian patent No. 2618857, published May 11, 2017.

[0043] The claimed objects are thus linked by a single inventive concept: in particular, the operations of separating the gas-liquid mixture with the separation of water, which forms the hydraulic seal itself, and the separate discharge of partially dehydrated gas-liquid mixture and oil from the vertical hydraulic seal device are ensured by the claimed set of features of the unit for separating and preparing produced water. The claimed unit and method for separating and preparing produced water are effective when simplified by organizing the hydraulic seal in a single apparatus, combining all the functions of the prototype - separation of the gas-liquid mixture, preparation and purification of water, including purification from mechanical impurities; in addition, the multifunctional hydraulic seal device proposed for implementation of the unit serves to receive and separate the gas-liquid mixture with the separation of water and the separate discharge of partially dehydrated gas-liquid mixture and oil, increasing the efficiency of separating and preparing produced water by the proposed unit.

Claims

CLAUSES OF THE INVENTION 1. An installation for separating and preparing produced water, including a gas-liquid mixture (GLM) separation unit with GLM supply and discharge pipelines and a water purification unit with a plate pack and a device for removing separated oil and pipelines for removing water and mechanical impurities, characterized in that the GLM separation unit and the water purification unit are made as one in the form of a horizontal process tank (HPT) with coalescer packs with a vertical hydraulic seal installed on the upper generatrix of the GTU, which is a cap with an open central pipe connected to a GLM supply pipeline for introducing GLM into the central pipe, the cap is equipped with a common pipeline for removing partially dehydrated GLM, removed through the central pipe, and oil, removed through the annular space of the cap.

2. The installation according to paragraph 1, characterized in that the water separated in the central pipe from the supplied gas-liquid mixture is a medium that forms a water seal.

3. A method for separating and preparing produced water, including separating a gas-liquid mixture (GLM) and purifying the water using a plate pack with the removal of separated oil, water and mechanical impurities, characterized in that the supply of GLM and the separation of GLM with the separation of water from it are carried out in a vertical hydraulic seal installed on the upper generatrix of a horizontal process tank (HPT), and the purification of the separated water is carried out using coalescer packs installed in the HPT, wherein the partially dehydrated GLM and oil are removed separately through the vertical hydraulic seal, after which they are transported through a common discharge pipeline.

4. The method according to paragraph 3, characterized in that the dehydrated gas-liquid mixture and oil are discharged separately through a cap with a central pipe that discharges the dehydrated gas-liquid mixture and, accordingly, discharges oil through the annular space of the cap.

5. A hydraulic seal device for installing the separation and preparation of produced water, vertically installed on the upper generatrix of a horizontal process tank (HPT), used for introducing gas and liquid mixtures through a gas and liquid mixture supply pipeline, having an open central pipe for discharge and an annular space, characterized in that it is a cap with a central pipe connected to a gas-liquid mixture supply pipeline for introducing gas-liquid mixture into the central pipe; the cap is equipped with a common pipeline for removing partially dehydrated gas-liquid mixture, removed through the central pipe, and oil, removed through the annular space of the cap.

6. The device according to paragraph 5, characterized in that the water separated in the central pipe from the supplied gas-liquid mixture is a medium that forms a water seal.

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