OF A FLUID

DESCRIPTION

TECHNICAL FIELD

The present disclosure relates to a vortex device and a method for hydroacoustic treatment of a fluid, in particular a liquid, such as water. The vortex device according to the present disclosure is particularly useful in the field of enhanced oil recovery by replacement of oil with water, implemented as a secondary and/or tertiary oil recovery operations.

BACKGROUND

Replacing oil with water is one of known methods of enhanced oil recovery. This method is used when the displacement of oil takes place simultaneously with formation pressure maintenance. The waterflooding is employed after primary recovery operations are finished, and therefore it serves as secondary oil recovery method (EOR - Enhanced Oil Recovery).

Waterflooding employs water as a working agent, due to its accessibility and low cost. Water is injected into an underground oil formation, via an injection well, called a borewell, wherein it displaces oil from porous (capillary) media, i.e. a rock skeleton within with oil is deposited. Capillary forces cause capillary imbibition: water is soaked inside the rock capillaries and oil is displaced. An oil displacement bank is formed in front of a displacement front and undisplaced oil and water remain behind the displacement front.

For a water injection field, and in particular injection wells, potential problems associated with enhanced recovery techniques can include inefficient oil recovery due to a variable permeability in a subterranean formation and a difference in flow rates of fluid from the injection well into the subterranean oil formation. The residual oil saturation, i.e. the volume of the oil that is not recovered and remains in the oil formation, varies within a wide range from 0,05 to 0,90 fractions of a unit.

The residual oil saturation depends on various factors, such as a ratio of mobility of oil and water and a heterogeneity of filtration volumetric properties of the oil reservoir: porosity, permeability, etc. There are known from the prior art various waterflooding methods.

US2011042092 discloses a method and a system for propagating pressure pulses in a subterranean well. The system is provided with a vortex chamber having at least one inlet and an outlet. A vortex is created when the fluid composition spirals about the outlet, and resistance to the flow of the fluid composition alternately increases and decreases. The well can include a variable flow resistance system which propagates pressure pulses into a formation in response to the flow of a fluid composition from the formation. In this system, the multiple flow passages direct the fluid composition into two flow path selection devices.

US8555975 discloses an apparatus for inducing and impeding a rotational flow of a fluid. The apparatus consists of a fluid chamber (exit assembly) comprising two fluid inlets, each having longitudinal axis perpendicular to the longitudinal axis of the fluid chamber, wherein each inlet axis and fluid chamber axis are offset from one another. The fluid chamber comprises a peripheral ring region which is formed by two fluid directors. The inlets are implemented so as to cause the fluid to rotate in the outer ring region in opposite rotational directions. The inlets of the fluids can be tubular, rectangular, pyramidal, etc. The fluid directors are arranged to form an inner channel - between the fluid directors, forming a flow path between opposite points of the outer ring region. The fluid directors impede the flow of a fluid rotationally about the inner region of the fluid chamber. Further, the fluid directors maintain a rotational and non-rotational flow of fluid within the peripheral ring region of the fluid chamber. The outlet of the fluid chamber is formed in the middle of the inner channel. The apparatus provides regulation of the flow rate of a fluid between two or more zones of subterranean oil formation.

SUMMARY

The object of the invention is a vortex device for a hydroacoustic treatment of a fluid that flows through the vortex device. The device comprises an inlet section having a substantially cylindrical shape and an inlet section lumen of a first diameter, wherein the inlet section lumen is restricted by an inner wall; an outlet section having a substantially cylindrical shape and an outlet section lumen of a second diameter that is smaller than the first diameter; wherein the inlet section is coaxial with the outlet section and connected with the outlet section via a conical reducer. The inlet section comprises tangential inlets configured to introduce the fluid to the inlet section tangentially with respect to the inner wall, such as to generate a concurrent flow of the fluid upon entry to the inlet section. The vortex device further comprises a conical cover comprising: a base that covers the inlet section lumen; and a tapex that protrudes outside the vortex device; such that the conical cover is configured to direct the fluid from an outside of the vortex device to the inlets of the inlet section.

Preferably, the inlet section comprises three tangential inlets.

Preferably, the inlet section comprises four tangential inlets.

Preferably, the tangential inlets of the inlet section are arranged in a single plane in the inlet wall of the inlet section.

Preferably, the tangential inlets are spaced apart from one another by the same distance along a ring.

Preferably, the first diameter is equal to a half of the second diameter.

Preferably, the first diameter is larger than a half of the second diameter.

Preferably, the device further comprises a pipe in which the vortex device is assembled.

Preferably, the vortex device is assembled coaxially with respect to a longitudinal axis of the pipe.

Preferably, the vortex device constitutes a reducer of a lumen of the pipe.

Another object of the invention is use of the vortex device as described herein for hydroacoustically treating a liquid or a gas.

Preferably, the liquid is water.

Another object of the invention is a method for hydroacoustic treatment of a stream of a fluid by means of the vortex device as described herein, the method comprising the steps of: arranging the vortex device within the stream, with the tapex of the cover arranged upstream with respect to the direction of the flow of the stream; inputting the stream to the inlet section of the vortex device; collecting the treated fluid at an outlet of the outlet section of the vortex device.

Preferably, the fluid is water.

Preferably, the method further comprises using the treated fluid in enhanced oil recovery by waterflooding.

BRIEF DESCRIPTION OF DRAWINGS

The present disclosure is presented by means of example embodiments in the drawing, in which: Fig. 1 shows schematically, in a cross-sectional view, a principle of operation of a waterflooding plant;

Fig. 2 shows schematically a first embodiment of a vortex device in two cross- sectional views;

Fig. 3 shows schematically a second embodiment of a vortex device;

Fig. 4 shows schematically the vortex device provided with a cover, in a cross- sectional view;

Fig. 5 shows schematically the cover of the vortex device;

Figs. 6A and 6B show a model of the vortex device with and without a cover, respectively;

Fig. 7A and 7B show a model of the vortex device installed within a pipe/pipeline with and without a cover, respectively;

Fig. 8 shows schematically a cross-sectional view of the vortex device installed in a pipe/pipeline, indicating a direction of fluid flow;

Fig. 9A and 9B show graphs indicating fluid flow through the vortex device;

Fig. 10 shows schematically directions of fluid flow inside the vortex device;

Fig. 11 shows schematically water flow in capillary pores of an oil formation;

Fig. 12 shows spectra of amplitude-frequency of the vortex device;

Fig. 13shows schematically a cross-sectional view of a waterflooding plant with the vortex device mounted therein;

Fig. 14 shows a detailed embodiment of the vortex device with detailed dimensions.

DETAILED DESCRIPTION

The vortex device as presented herein may be used in enhanced oil recovery, such as waterflooding. Nonetheless, the vortex device is also suitable in the other applications, where there is a need for use of hydroacoustically treated fluids.

The vortex device according to the present disclosure, due to its structural features, can hydroacoustically treat fluids, during the flow of the fluid through the vortex device. The hydroacoustic treatment that is applied to the fluid by means of the vortex device includes the creation of vortexes and acoustic vibration within the fluid stream.

Example embodiments of the vortex device are shown in Figs. 2 - 7. The vortex device 20 has a flow-through construction, so that it can be installed inside a pipe/pipeline 10-such as a pipe reducer, enabling the whole volume of the fluid stream, transported within the pipe, to flow through the vortex device - as shown in Fig. 8. The arrows in Fig. 8 represent schematically direction of the fluid flow within the pipe with the vortex device 20 assembled therein.

Fig. 4 shows a longitudinal cross-section of the vortex device 20. The vortex device 20 comprises an inlet section 21 and an outlet section 23, each having a substantially cylindrical shape and arranged substantially coaxially with respect to each other.

The inlet section 21 has a diameter d1 which is greater than a diameter d2 of the outlet section 23.

The inlet section 21 and the outlet section 23 are connected via a concentric conical reducer 22. The inlet section 21 forms a vortex flow. Bevel gear 22 increases the speed of rotation of the fluid and it helps to maintain the strength and uniformity of the vortex. And the exhaust section 23 passes this stream to the pipeline

The inlet section 21 comprises at least two tangential inlets 211. In other words, each inlet 211 of the inlet section 21 is provided tangentially to a curved surface of an inner wall 212 of the inlet section 21. Thus, the longitudinal axis of each inlet 211 of the inlet section 21 and the longitudinal axis 30 of the vortex device are perpendicular to each other, whilst being offset from one another.

Therefore, the fluid flows into the inlet section 21 of the vortex device 20 at a tangent and begins to flow in a circular forward motion towards the outlet section 23. The outlet section 23 is provided with an axial outlet 231 , through which the fluid follows out of the vortex device 20. The motion of fluid within the vortex device 20 will be further discussed in details below.

Preferably, the inlet section 21 may be provided with three inlets (as shown in Fig. 3), or the inlet section 21 may be provided with four inlets 211 (as shown in Fig. 2A depicting cross-sectional view (A-A) of the vortex device of Fig. 2B).

The inlets 211 may be implemented in a single plane perpendicular to the longitudinal axis 30 of the vortex device 20, forming together a ring design (as shown in the single cross-sectional plane A-A on Fig. 2A). Preferably, the inlets 211 are spaced apart from each another by the same distance (as visible in Figs. 2A and 3).

The inlets 211 shall be arranged so as to introduce the fluid into the inlet section 21 in the same direction, which can be either clockwise or anticlockwise (but not both), as shown in Figs. 2A, 3 and 9B. Such arrangement enables to obtain substantially undisturbed circular motion of the fluid flow at its entrance into the inlet section 21 of the vortex device 20. Moreover, this provides appropriate operation of the vortex device 20, so as to obtain the creation of the vortexes and acoustic vibration within the fluid stream.

The vortex device 20 is further provided with a conical cover 213 (as shown in Figs. 4 and 5). The cover 213 has a form of a cone with a cone tapex 213a arranged outside the vortex device 20 and a cone base 213b arranged inside the vortex device 20. The cone base 213b forms a flat inner wall of the inlet section 21 substantially perpendicular to the longitudinal axis 30 of the vortex device 20 (as shown in Fig. 4). The longitudinal axis of the cover 213 and the longitudinal axis of 30 of the vortex device 20 are substantially coaxial.

The conical shape of the cover 213 provides desired characteristic of the flow of the fluid stream upon entry through the inlets 211 , and therefore upon entry to the inlet section 21 of the vortex device 20.

As shown in Fig. 8, the vortex device 20 is configured to be mounted in the pipe/pipeline 10 such as to arrange the cone tapex 213b upstream with respect to the direction of the fluid flow.

During the operation of the vortex device 20, the tapex 213a of the conical cover 213 smoothly splits the fluid stream and directs the fluid into the inlets 211 of the inlet section 21 of the vortex device 20. Therefore, the conical shape of the cover 213 prevents formation of locally increased drops in the pressure of the fluid stream, upon entry through the inlet section 21. Also, the direction of fluid flow is converted by the conical shape of the cover 213 from a coaxial direction to a substantially perpendicular direction (with respect to the pipeline 10), while maintaining particular properties of the fluid flow, such as the velocity of the fluid.

Therefore, the conical cover 213 converts the direction of fluid flow, in total, by 90°, without undesirable deceleration of the stream velocity and generation of undesired interruptions within the fluid flow.

Preferably, the tapex angle a of the conical cover is 45°. Such angle a provides most suitable conditions of the fluid flow upon entry into the inlet section 21 of the vortex device 20. Nonetheless, the tapex angle a may be different than 45° and still effect hydroacoustic treatment of the fluid, including vortex and acoustic vibrations of the treated fluid. The angle a may vary from 15 to 160°. In particular embodiments, smaller angles, from a = 45° are recommended, depending upon the field conditions, such as: inlet pressure of the injection pipeline, flow rate, diameter of the pipe/pipeline 10, residual strength, etc.

According the customized field conditions, it is recommended to keep the allowable angle range of a = 45° ± 20°.

Fig. 6 shows schematically the vortex device 20 with a cover 213, whereas Fig. 6B shows the vortex device without a cover. The same applies to Figs. 7A and 7B, which show the vortex device mounted in the pipe/pipeline 10.

The proper operation of the vortex device 20, installed in the pipe/pipeline 10, requires the presence of the cover 213- as shown in Figs. 6A and 7A. Figs. 6B and 7B are intended to show the through-flow interior of the vortex device.

The outer diameter of the vortex device should match the inner diameter of the pipe/pipeline, so as the whole volume of the fluid stream can be treated in the vortex device 20. Due to the upstream arrangement of the cover tapex 213a, the stream first strikes the conical cover 213 and it is distributed so as to reach the tangential inlets 211 of the inlet section 21. The conical shape of the cover 213 provides the equal distribution of the fluid into the inlets 211.

The inlets 211 constitute the flow connection of the pipe/pipeline 10 environment and the inlet section 21 of the vortex device 20, where the first vortexes are generated. The mutual arrangement of the inlets 211 and the conical cover 213 keeps the fluid stream“attached” to the walls of the vortex device 20 (at the cover 213 and at the inlets 211 ), thus avoiding local separations of the stream flow and creating a flow circulation effect.

Preferably, the diameter d1 of the inlet section 21 is slightly larger than half of the diameter d2 of the outlet section 23 or of the inner diameter of the pipe/pipeline.

The vortex device 20 can be installed directly in an existing pipe/pipeline, as schematically shown in Fig. 7A. Moreover, the vortex device 20, for convenience of the assembly, maybe have a form of a ready-to-use pipe fitting (as shown in Fig. 8) that can be fixed with the pipe/pipeline 10, by simply screwing it with the existing pipe/pipeline 10 elements.

Fig. 10 shows schematically directions of fluid flow inside the vortex device 20. This figure represents the schematic diagram of the fluid flow in the vortex device. For the simplicity and better understanding of the flow regime inside the vortex device, only the streamlines of the fluid flowing inside the vortex device are represented. Frequency (f) distributions due to the flow before the entry and after leaving the vortex chamber are also indicated in the Fig. 10. This frequency distributions are due to the primary vortex in the first half of the vortex device while breakdown of this primary vortex into two secondary vortices in the other half of the vortex device, as indicated by the circular arrows. This flow feature is attained due to the design of the vortex device according to the present disclosure.

Furthermore, the inlets 211 direct the fluid tangentially to the inner cylindrical wall 212 of the inlet section. This allows the fluid to acquire a circular motion at frequency f1.

Due to centrifugal forces in the axial region 30 of the vortex device 20, the pressure in the fluid stream drops, forming a counter-flow, which stimulates the precessional motion of the fluid inside the vortex device 20. The frequency of this motion is schematically marked as f2 - in Fig. 10. As a result of the above, two streams of the same rotational direction and opposite linear motions are formed. This causes the generation of a third frequency (f3) inside the outlet section 23 of the vortex device 20. The vortex flow thus created leaves the outlet section 23 via the axial outlet 231 and enters a stationary environment of the pipe/pipeline. This creates oscillations of frequency f4.

The frequency f1 is the main frequency of the system which has equal interval of oscillations while the other frequencies: f2, f3, f4 are based on the average number of the oscillations.

Therefore, when passing through the vortex device 20, some of water flow energy is converted into a vortex flux, while the remaining water energy is transformed into elastic vibrations within a certain frequency range, and varies at different rates of water injection.

The main energy in the water flow is the kinetic energy and somewhat pressure energy due to the inlet pressure. During the vortex generation, a part of the energy is transferred into two further forms i.e. vibration and momentum flux of the vortex. This transformation of energy is not standard as it strictly depends on the geometry and diameter of the pipe as well as on the rate of water flowing through the pipe and vortex device. A higher flow rate will have a higher velocity in a same pipeline which will directly affect the energy conversion in the system.

In other words, the fluid in the vortex device is subjected to dynamic and acoustic treatment. The exact dimensions of the vortex device, such as the diameters and length of the inlet section, inlets of the inlet section, outlet section and concentric reducer may have different values. They can be designed depending on the fluid flow rate and the fluid pressure in the pipe/pipeline in which the vortex device is to be mounted. The certain dimensions may be modelled by using a computer program (e.g. CFD), calculating the movement paths and velocity variations of the fluid, during the flow throughout the vortex device.

Examples of calculations are presented in graphs of Fig. 9A and 9B, wherein the fluid is water. The graphs show velocity variations of the water flow within the inlet section, the concentric reducer and the outer section of the vortex device as described above. The blank areas in the graphs of Fig. 9 represent walls of the vortex device, shown schematically below each graph - for better understanding of the geometry of the vortex device. The calculations results shown as graphs are made as default for the volumetric flow rate of the water of 100m ³ per day and operating pressure of the pipeline of 70 bars.

The vortex device according to the present disclosure is particularly suitable in the treatment of water. During the flow of water through the vortex device, it starts spinning dynamically and vibrating acoustically, wherein the acquired acoustic vibrations preferably is in the range of 1 to 45 kFIz.

These special properties of water are maintained by the water for a substantially long time period. Thus, such water can be used in various applications downstream the vortex device 20. The duration of time for which these special properties sustain in the water depends, among others, on the location of the vortex device assembly and the path of the water pipeline. In general, the properties are maintained for a longer time is the water pipeline has a vertically downward construction, in which the gravitational force acts strongly on the stream.

The total value of the energy of the water stream, i.e. the kinetic energy and the pressure energy of the water flow (i.e. its potential energy), after the treatment in the vortex device remains the same, as it was before the treatment. Nonetheless, when the water enters the inlets 211 of the inlet chamber, its area ratio decreases significantly, which results in an exponential increase in the velocity, which further creates the vortexes in the vortex device 20. The rise in the velocity is visible as an increase in the value of the kinetic energy of the water stream and a decrease in the pressure energy of the stream. Further, at the outlet of the vortex device, the pressure energy of the stream increases, whilst the velocity of the stream decreases. The total energy losses of the water stream, caused by its treatment in the vortex device, do not exceed 5%, and they are negligible as they do not affect the operation of the vortex device.

In particular, surprisingly, it was found that water treated in the vortex device can be used as a working agent in waterflooding. Experimental measurements confirmed that the water treated by the vortex device, when used in waterflooding as a working agent, provides an increase in oil extraction rate. Especially, the water after treatment in the vortex device demonstrates higher mobility, wherein introduced into the oil formation, which results in an increase of the oil extraction rate because such treated water is able to penetrate“more trapped” oil regions by overcoming capillary forces within tighter layers of the oil formation.

Consequently, no other water treatments or chemical additives may be necessary, or the need thereof is significantly reduced. Waterflooding using water treated by the vortex device is more environment-friendly since the treated water contains no chemical additives.

Fig. 1 shows schematically a cross-sectional view of the waterflooding procedure, and Fig. 13 shows an arrangement of the vortex device within the waterflooding plant.

Each water injection pipe 40 that supplies water into an injection wellbore 41 , is equipped with the vortex device 20 near the inlet of the injection wellbore 41. The vortex device 20 affects the viscosity of the water, as the water is swirled into a vortex and starts spinning dynamically and vibrating acoustically. The treated water is introduced into the injection wellbore 41 and propagates to the subterranean oil formation 42. The vortex parameters and acoustic frequencies acquired by the water cause the reduction of the size of the residuals present in the injected water, such as residual oil, sand, minerals and salts (natural water components).

Moreover, the properties acquired by the water in the vortex device affect the permeability of the rock skeleton of the subterranean oil formation 42 and prevent coagulation of colloid and dispersed oil systems of the subterranean oil formation 42.

Fig. 11 shows the water treated in the vortex device, reaching the porous rock skeleton of the subterranean oil formation 42. The water treated in the vortex device, has greater power to sweep the oil that is locked in capillaries of the rock skeleton, by disturbing the dynamic equilibrium on the water-oil interface. That results in moving the front of oil substitution with water, resulting in increased efficiency of oil recovery by 10 to 20%.

In the waterflooding plant, the vortex device can be installed either at the ground level or in the injection wellbore 41. Nonetheless, in the latter case, it is recommended to install the vortex device not deeper than halfway to the subterranean oil formation 42.

Fig. 12 is the amplitude-frequency spectra (in kHz) of vortex devices at different water discharge rates.

Preferably, the water temperature of the water treatment by using the vortex device is of 15 - 40°C, and more preferably 20°C.

The vortex device according to the present disclosure does not comprise moving parts, which could be prone to wear, providing low costs of its maintenance and limited failure tendency.

A detailed embodiment of the vortex device is shown in Fig. 14 that indicates particular dimensions of its components. This vortex device is designed for treatment of water at a volumetric flow rate of 100m ³ per day and operating pressure of the pipeline of 70 bars. The vortex device can be installed in the pipeline of the waterflooding plant at the ground level. The treated water can be injected into the borewell for enhanced oil recovery, resulting in increased efficiency of the oil recovery by 10%.

Although the invention is presented in the drawings and the description and in relation to its preferred embodiments, these embodiments do not restrict nor limit the presented invention. It is therefore evident that changes, which come within the meaning and range of equivalency of the essence of the invention, may be made. The presented embodiments are therefore to be considered in all aspects as illustrative and not restrictive. According to the abovementioned, the scope of the invention is not restricted to the presented embodiments but is indicated by the appended claims.