RU2792303C1 - Mobile plant for water purification from hydrogen sulfide for injection into reservoir, method for its implementation and pressure aeration device - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is intended to implement the technology of water purification from hydrogen sulphide before supplying it to the reservoir pressure maintenance system (PMS) for subsequent injection into the reservoir of the oil field. Mobile installation for water purification from hydrogen sulphide is a monoblock, including pressure vessel operating under pressure (VUP), and the mass-transfer column device integrated with it (MCU). VUP and MCU are located perpendicular to each other. The MCU is equipped with regular countercurrent nozzles with vertical contact grids and is a vertical cylindrical vessel equipped with an elliptical bottom in the upper part, in which a fitting for the outlet of gas enriched with hydrogen sulphide, a fitting for a pressure sensor and a fitting for a temperature sensor are located. In the upper part of the VUP there is a pressure aeration device, which includes a pipeline placed horizontally along the entire length of the vessel with a fitting for gas supply. Vertical distribution manifolds are connected to the pipeline at an equal distance from each other, perpendicular to which horizontal ramps are attached, extending in different directions from the attachment point. Filter cartridges are attached to horizontal ramps via pipe fittings. Bottom of the VUP is configured with a purified water outlet suitable for feeding into the PMS system.

EFFECT: reduction of concentration of hydrogen sulphide in neutralized water H₂S with minimal capital costs.

4 cl, 2 dwg

Description

The present invention relates to the oil and gas industry and is intended to implement the technology of water purification from hydrogen sulfide before supplying it to the reservoir pressure maintenance system (RPM) for subsequent injection into the reservoir of the oil field.

At the early stage of field development, the most economically feasible is the use of mobile oil treatment units (MFTP), consisting of separate technological blocks of complete factory readiness, combined into a single complex and not requiring the arrangement of traditional stationary structures. In the process of early oil production, it becomes necessary to stabilize the reservoir pressure. The most common is the hydrodynamic method of enhanced oil recovery - injection of water into the reservoir, therefore, before the construction of a stationary block cluster pumping station (BKNS), a mobile BKNS (MBKNS) is promptly connected to the MUPS. For injection, produced formation water is used, which is separated in the process of separation from the oil-water fluid at the MUPF, and process water from water wells (hereinafter referred to as H ₂ S water), contaminated with hydrogen sulfide. The composition of hydrogen sulfide dissolved in water includes molecules of gaseous H ₂ S, hydrosulfide ions HS ^- and sulfides S ^{2 -} therefore, before being fed into the reservoir pressure maintenance system and injected into the reservoir, contaminated water must be cleaned of hydrogen sulfide. According to clause 1.9. OST 39-225-88 in the water injected into the productive reservoirs of oil reservoirs, hydrogen sulfide should be absent.

To purify water from hydrogen sulfide and sulfur compounds in field conditions, the method of water treatment with chemical reagents-neutralizers is most often used. Another purification method is the use of specially developed methods for saturating water with oxygen (or air) in the presence of an aqueous solution of an oxidation catalyst based on compounds of iron, copper and other variable metals, while the catalyst and oxygen (or air) are fed directly into the water stream with sulfur compounds . As a result of the reaction, sulfur compounds are converted into elemental sulfur, which is subsequently removed from the water by settling, flotation, filtration or centrifugation.

These purification methods have a number of significant disadvantages: high cost of reagents; a large specific consumption of neutralizers requires an impressive size of the reagent facilities; the complexity and duration of the technological process of cleaning; when storing and using reagents, special safety measures are required; difficulties with the disposal of generated waste; negative impact on the environment due to emissions of hydrogen sulfide into the atmosphere.

At low values of the hydrogen index of treated water (pH) under field conditions, the most effective is the use of aeration methods of removal - stripping of hydrogen sulfide. The advantages of the aeration method are safety and low cost compared to other cleaning methods.

A known method of water purification from sulfides and hydrogen sulfide by stripping hydrogen sulfide from pre-acidified water (up to pH 4.3÷5). Stripping can be carried out in an aeration basin, cooling tower, or any type of degasser. During aeration, along with the desorption of hydrogen sulfide, the oxidation of a part of it to colloidal sulfur is also possible. After such stripping, the residual concentration of hydrogen sulfide is 0.3 ÷ 0.5 mg/l, therefore it is recommended to oxidize the residual hydrogen sulfide by chlorination, and mix the treated water with a coagulant at a dose of 20 ÷ 30 mg/l (for example, Al ₂ (SO ₄ ) ₃ or FeCl ₃ ) to bind colloidal sulfur into flakes and direct to granular filters. After filters, water after re-chlorination is recommended to be alkalized in order to reduce its corrosive activity (V.A. Klyachko, I.E. Apeltsin. Purification of natural waters. - M.: Stroyizdat, 1971. - p. 475-479).

The disadvantages of this purification method include the need to use various reagents (acid, coagulant, chlorine and alkali) and a complex reagent economy. In addition, the environment is polluted with toxic hydrogen sulfide, which is blown into the atmosphere.

Known technology for the purification of formation water from hydrogen sulfide in a vertical column (hereinafter referred to as the reactor) by catalytic neutralization on a heterogeneous catalyst (LOCOS PW process; https://ahmadullins.com/publiclist/plastovye-vody/metody-ochistki). This process is implemented according to the following scheme. Produced water from oil production units is accumulated and settled in a buffer tank. Formation water is pumped from the buffer tank through the filter to the heat exchanger, where it is heated to 60-80°C and flows through the switchgear to the bottom of the reactor. Before entering the reactor, air at a pressure of 0.8 MPa is supplied to the formation water supply pipeline by a compressor. Air and formation water pass from the bottom upwards in cocurrent flow through the KSM catalyst densely loaded with one layer along the height of the reactor, on the surface of which the toxic, corrosive hydrosulfides contained in the formation water are oxidized by air oxygen into inert, odorless hydrosulfate and sodium thiosulfate. The mixture of exhaust air and neutralized formation water is discharged from the top of the reactor into a degassing tank. Exhaust air from the top of the degasser is directed to the candle through the droplet separator. Neutralized formation water from the degasser tank is sent further for injection into the formation.

The disadvantages of this technology for the treatment of formation waters from hydrogen sulfide include the following points:

- the reaction proceeds with direct-flow movement from bottom to top of air and formation water through the catalyst;

- the reaction of catalytic oxidation of hydrogen sulfide with molecular oxygen proceeds in a reactor on a heterogeneous catalyst. Material costs are required for the purchase of a catalyst, its special dense loading and periodic regeneration;

- a necessary condition for the course of the oxidation reaction is to maintain a pressure in the column of at least 0.5 MPa, which requires equipping with control devices and safety equipment from exceeding the design pressure;

- for carrying out the catalytic process, in addition to the column, additional equipment is required: a heat exchanger for heating water; a compressor for forcing air into the reactor; degassing capacity, - additional material costs for acquisition and maintenance;

- in addition to additional costs for auxiliary equipment, funds will be required for construction and installation work to equip the production site of the entire formation water desulfurization unit, as well as the construction of monolithic stationary foundations for the reactor (taking into account the height of the vertically standing column) and under the compressor (taking into account the anchoring of the unit ).

Known equipment for the implementation of absorption and desorption processes, the removal of dissolved gases from solutions and most effectively when stripping mercury from solutions and wastewater to the required sanitary standards and improves the efficiency of the column by eliminating the formation of stagnant zones around the periphery of the disks. (Patent SU1681923A1 IPC B01D 45/08, B01D 53/18, Published 10/07/1991). The equipment is a vertically oriented column and consists of a body divided into sections by solid partitions, perforated gratings with filter elements made in the form of porous disks pressed against the grating by clamping devices, overflow pipes, branch pipes. Porous discs have a diameter that exceeds the diameter of the lattice holes by one or two disc thicknesses. Due to the fact that the disks are pressed against the surface of the grate and there is a gap between the surface of the disks and the grate, part of the gas passes parallel to the surface of the grate and mixes the liquid between the holes, eliminating the formation of stagnant zones there and improving mass transfer. The initial liquid enters the upper section through the branch pipe and flows from section to section through the overflow pipes, and then exits the apparatus through the branch pipe. Gas is supplied in separate streams to each section through nozzles. It enters the space between the partition and the grate, passes through the filter elements and is evenly distributed over the cross section, intensively mixing the liquid. After contact with the liquid, the gas exits through the nozzles into a common manifold. Due to the design features of the perforated grate, which consists in the fact that the filter elements are made in the form of porous discs with a rough surface, uniform intensive mixing of the liquid is ensured on the entire surface of the grate, and stagnant zones are excluded.

The disadvantages of the analogue include the imperfection of the design of the division of the column into separate sealed sections and pipe systems of the overflow-treated liquid. The durability of the structure is not ensured due to the large number of clamping devices for fastening the filtering porous elements to the perforated grid, which will lead to process shutdowns, an increase in downtime and an increase in operating costs.

Known horizontal steel cylindrical tank (https://asuneft.ru/dobycha/gorizontalnyj-stalnoj-tsilindricheskij-rezervuar-opisanie-yomkosti-dlya-hraneniya-nefteproduktov.html?) for storing petroleum products. Horizontal steel ground tanks - cylindrical tanks made of steel or polymeric materials, designed to store liquids at enterprises or storage facilities and are located on the surface of the earth, on prepared sites.

Known gas-liquid separator (Patent 2766135, E21B 43/34 (2006.01), B01D 19/00 (2006.01), Published 08.02.2022) fluid separation. The gas-liquid separator consists of a housing having an inlet with at least one horizontal perforated branch pipe inside the housing with at least two outlets, at least one upper one - for selection of light fractions, at least one lower one - for selection of heavy fractions - liquids. Known gas-liquid separator allows you to effectively separate the gas-liquid medium into gas and liquid without additional adjustable elements and control units, which makes its design reliable and autonomous.

A disadvantage of the known devices is the inability to use them to clean water from hydrogen sulfide for injection into the reservoir.

The purpose of the claimed invention is to create a quickly erected device that provides effective purification of process water from water wells - H ₂ S water from hydrogen sulfide by associated petroleum gas prepared at MUPN for supplying purified water to the RPM system.

The technical result of the invention is to reduce the concentration of hydrogen sulfide in the neutralized water H ₂ S with minimal capital costs.

This goal is achieved by the claimed mobile installation for water purification from hydrogen sulfide, which is a monoblock, including a pressure vessel (SVD) and an integrated mass transfer column apparatus (MCA), together with a support and fastening system, forming a spatial structure in the dimensions of a standard 40-foot container and vertical mass transfer column apparatus (MCA).

SVD and ICA are located perpendicular to each other. The MCA is equipped with regular counterflow nozzles with vertical contact grids and is a vertical cylindrical vessel equipped with an elliptical bottom in the upper part, in which there are: a fitting for removing gas enriched with hydrogen sulfide after the blowing process; fitting for pressure sensor and fitting for temperature sensor.

In the upper part of the MCA, a fitting is welded for introducing H ₂ S water for purification, under which the input and irrigation units are installed, and sections with a regular AVR packing are installed along the entire inner perimeter and at the entire height of the column (Patent RU2461406C2 MPKB01D3 / 28, Publ.20.09. 2012 "Mass transfer contact device for the interaction of liquid and gas"). The main structural elements of the ATS regular packing sections are vertical gratings sandwiched between zigzag-shaped partitions.

A horizontally directed perforated pipe is mounted in the lower part of the MCA, connected to a fitting welded on the shell of the MCA, through which associated petroleum gas, previously prepared at a mobile oil treatment unit (MUPN), is supplied countercurrently to the treated water H ₂ S.

In the lower part of the MCA, it is equipped with a hardware flange for connecting the MCA to the SVD.

A cylindrical adapter post (strictly vertically upwards) is equipped on the SVD shell, the hole size of which is equal to the inner diameter of the MCA to ensure through unhindered flow of the treated H ₂ S water from the MCA into the SVD cavity. On the cylindrical adapter post above the hole at the interface between the vertically standing mass-exchange column apparatus and the horizontal vessel, a mating hardware flange is welded. The connection of two vessels is carried out by means of hardware flanges.

In the upper part of the SVD there is a pressure aeration device, which includes a pipeline placed horizontally along the entire length of the vessel with a fitting for gas supply. Vertical distribution manifolds are connected to the pipeline at an equal distance from each other, perpendicular to which horizontal ramps are attached, extending in different directions from the attachment point. Filter cartridges are attached to horizontal ramps by means of nozzles.

At the bottom of the SVD there is a fitting for the outlet of purified water suitable for supply to the RPM system.

The combination of two technological devices into one monoblock gives advantages in the form of a two-stage purification technology: the first stage is the desorption of hydrogen sulfide in an MCA with countercurrent regular packings with vertical contact grids; the second stage - post-treatment water H ₂ S pressure aeration in SVD.

The inventive mobile installation for water purification from hydrogen sulfide is illustrated by the drawings of figure 1, figure 2, where:

1 - pressure vessel (SVD);

2 - mass transfer column apparatus (MCA);

3 - fitting B2 for gas outlet;

4 - fitting for pressure sensor;

5 - fitting for temperature sensor;

6 - fitting A1 for introducing water for treatment;

7 - hardware flange;

8 - transition post;

9 - perforated pipe;

10 - fitting B1 for supplying gas to the column for exhaust;

11 - input and irrigation nodes;

12 - sections of the regular ATS packing;

13 - fitting B3 for supplying gas to the SVD for aeration

14 - gas supply pipeline;

15 - vertical distribution manifold;

16 - fitting A2 for the output of purified water.

17 - horizontal ramp;

18 - branch pipe

19 - filter cartridge.

The mobile plant for water purification from hydrogen sulfide must be sealed against the environment. Tightness class 5 according to OST 26.260-14-2001.

To ensure unloading of the junction of two vessels of the SVD and SVD, and to keep the SVD from the effects of wind load, a vertical truss (not shown in the diagram) is rigidly fixed to the frame of the horizontal SVD, inside which the SVD is located.

Mobile installation of water purification from hydrogen sulfide operates as follows.

Process water from water wells - water H ₂ S, with hydrogen sulfide dissolved in it at a concentration of 300 ÷ 350 mg / l, through the inlet fitting A1 (6), is fed into the MCA (2), which is a cylindrical vessel with a shell diameter of 1000 mm, for the upper section of the ATS mass-transfer nozzle equipped with an irrigation system (11), which makes it possible to evenly distribute H ₂ S water over the entire section of the MCA. ATS nozzle sections (12) are installed along the entire inner perimeter and at the entire height of the SSC. The water pressure at the column inlet is 0.04 MPa. Water flows down through the openings of the contact vertical grid, and sequentially, at each stage, it is sprayed along the zigzag partition with gas coming from the perforated pipe (9) in the lower part of the MCA with a pressure of 0.2 MPa. In this case, a droplet flow is formed, which forms the film motion. Irrigation is supplied to the ATS along the normal to the surface. Drops effectively penetrate into the liquid film, which achieves the maximum possible degree of perturbation of the film flow and the highest efficiency of the mass transfer process. Apparatuses with AVR class nozzles combine valve, jet and ejection modes of phase interaction, with effective implementation of mass transfer at extremely high irrigation rates. As a result of the desorption process, the concentration of hydrogen sulfide at the outlet of the column is reduced to 50 mg/l.

From the MCA (2) through the opening of the transition rack (8), the treated water flows freely into the SVD (1) with a capacity of 40 m ³ , together with the support and fastening system, forming a spatial structure in the dimensions of a standard 40-foot container. Water with a hydrogen sulfide concentration of 50 mg/l that has entered the cavity of the SVD begins to be affected by the pressure aeration process. Through the gas supply pipeline (14), gas at a pressure of 0.2 MPa, passing through vertical distribution manifolds (15), through horizontal ramps (17) and pipes (18) is fed into the filter cartridges (19), and, passing through their porous shell, forms a fine gas cloud of droplets with a diameter of 0.5 ÷ 1.5 mm, which fills the entire water space in the lower part of the SVD with an area of 1200x6000 mm and, rising up, reacts with dissolved hydrogen sulfide. As a result of aeration with gas, the concentration of hydrogen sulfide in water H ₂ S drops to 20÷30 mg/l.

Filter cartridges are rigid cylinders with a 20 mm thick filtering septum, and are made of a porous material based on physically crosslinked low-pressure polyethylene powder. The specified porosity of the cartridges (40-55%) provides atomization (dispersion) of the incoming gas with bubbles within 0.5÷1.5 mm. Under the action of hydrodynamic pressure, the gas filter cartridge is not deformed, the filter pores do not expand over time, and the dispersion of gas bubbles remains constant. For complete saturation of the treated water with dispersed gas, the calculated water level is maintained above the filter cartridges.

The treated water is discharged from the mobile unit through a branch pipe with a fitting A2 (16). Further, H ₂ S water with a minimum residual content of hydrogen sulfide is sent to a mobile neutralization unit for final purification with highly effective reagents with a high reaction rate and large absorption capacity.

The concentration of H ₂ S at the outlet of water after each stage of purification (column MCA, vessel SVD) is controlled by in-line hydrogen sulfide analyzers. Analyzer data is transmitted to the operator's workstation. In addition, the degree of purification is controlled by the results of laboratory analyzes of samples carried out according to the established schedule (2 times a day).

Purified process water from water wells after stripping and final neutralization of hydrogen sulfide is supplied to the MBKNS manifold block, where it is mixed with formation water from a mobile oil treatment unit. The combined flow enters the inlet of the MBKNS pumps for injection into the reservoir through the reservoir pressure maintenance system.

The claimed mobile plant for water purification from hydrogen sulfide provides a tenfold reduction in the concentration of hydrogen sulfide in the process water of water wells from 300 ÷ 350 mg / l to 20 ÷ 30 mg / l, due to the use of a two-stage technology for stripping hydrogen sulfide from water with associated petroleum gas in a mass transfer column apparatus with regular ATS nozzles and a pressure vessel combined into a single monoblock.

In addition, due to the closed system of the aeration process in a sealed monoblock, the risk of hydrogen sulfide entering the environment is eliminated.

The proposed technical solution allows at an early stage of field development to quickly put into operation a mobile BKNS and, having organized timely injection of water, stabilize reservoir pressure and ensure an increase in the rate of production of early oil.

In addition to the economic and technological efficiency of cleaning, the claimed mobile unit provides the following advantages:

- efficiency of commissioning, due to the non-foundation installation of the MCA;

- optimization of the technological scheme: there is no need for communications of two separate technological devices (MCA and SVD);

- optimization of the reagent facilities of the water treatment plant;

- multiple reduction of operating costs for water treatment;

- reducing the risks of exposure to hazardous production factors on the environment (emissions of hydrogen sulfide into the atmosphere).

The claimed invention meets the criterion of "novelty" due to the fact that the totality of the claimed features does not exist in the objects of the known level of technology (public information, knowledge, information).

The claimed invention is industrially applicable, since it is carried out industrially, mounted on a mobile OTU of a newly developed field of one of the oil companies, and the distinctive features of the device made it possible to obtain the desired technical result.

Claims (4)

1. Mobile unit for water purification from hydrogen sulfide for injection into the reservoir, which is a monoblock, which includes two mutually perpendicularly placed vessels: a horizontal high-pressure vessel with a pressure aeration device located in it and a vertical mass-transfer column apparatus integrated with it, equipped with regular nozzles with vertical contact grids. 2. Mobile plant for water purification from hydrogen sulfide for injection into the reservoir according to claim 1, including a vertical mass-transfer column apparatus equipped with regular nozzles with vertical contact grids, which is equipped with an elliptical bottom in the upper part, in which a fitting is located for outputting gas enriched with hydrogen sulfide, after the blowing process; fitting for pressure sensor, fitting for temperature sensor; fitting for the input of process water from water wells, under which input and irrigation units are installed; in the lower part, a horizontally directed perforated pipe is mounted, connected to a fitting, through which associated petroleum gas, previously prepared at a mobile oil treatment unit, is supplied countercurrently to the treated water; in addition, the lower part of the mass transfer column apparatus is provided with a hardware flange for connecting the mass transfer column apparatus with a pressure vessel. 3. Mobile plant for water purification from hydrogen sulfide for injection into the reservoir according to claim 1, in which on the shell of a horizontal vessel operating under pressure, a cylindrical adapter post is equipped, the hole size of which is equal to the inner diameter of the mass transfer column apparatus to ensure through unhindered flow of the treated process being cleaned water from water wells, for this, on a cylindrical transition rack above the hole at the junction of a vertically standing mass-exchange column apparatus and a horizontal pressure vessel, a response hardware flange is welded; in the lower part of the SVD, a fitting is equipped for discharging purified water, suitable for supplying to the reservoir pressure maintenance system for subsequent injection into the reservoir of the oil field, while the horizontal vessel contains a pressure aeration device, including a horizontal pipeline with a fitting for gas supply, to which at an equal distance vertical distribution manifolds are welded from each other, perpendicularly to which horizontal ramps are attached, extending in different directions from the attachment point, in turn, filter cartridges are attached to the horizontal ramps by means of nozzles. 4. The method of water purification from hydrogen sulfide for injection into the reservoir, including a two-stage purification process, the first stage is the desorption of hydrogen sulfide in a vertical mass transfer column apparatus with countercurrent regular nozzles with vertical contact grids; the second stage is post-treatment of water by pressure aeration in a horizontal vessel operating under pressure, while post-treatment by pressure aeration is carried out by dispersing desulfurized gas through a pressure aeration device.

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