FR2467179A1 - DEVICE FOR THE PREPARATION BY ELECTRIC TREATMENT OF WATER USED IN PARTICULAR IN DRILLING SLUDGE - Google Patents

Abstract

A device for preparation of dilution liquid for drilling muds comprising a casing (1) having an inlet and an outlet for the dilution liquid and provided with coaxially mounted hollow electrodes (4, 5) connected to a direct current source (6) and separated from each other by a diaphragm (7). The electrodes (4, 5) are shaped as truncated cones whereas a tube (8) is mounted inside the inner electrode (4) along its geometrical axis (a), one of the ends of that tube being smootly connected with the end of the inner electrode (4), by a rounded angle on the side of its smaller base, and with the other end - with the outlet for the dilution liquid provided in the casing (1).

Description

 The present invention relates to techniques for drilling wells and, more particularly, to a device intended for the preparation of water for diluting or mixing drilling mud.

 The present invention can be used in the petroleum and natural gas industry for the preparation and treatment of drilling muds.

The invention can also be used in particular in water circuits for heating and cooling, in the chemical industry, in civil engineering for intensification of the dispersion and dissolution processes.

 The efficient drilling of wells at minimum cost and at high speed depends to a large extent on the quality of the drilling mud itself depending on the quality of the raw materials and their preparation methods. The qualities of a drilling mud and the duration of its preparation depend to a large extent on the qualities of the mixing or mixing fluid which is, in most cases, industrial water.

 Industrial water contains different ions in solution, the most common of which are: chlorides, sulfates, bicarbonates of sodium, potassium, calcium, magnesium as well as various impurities such as organic compounds, iron salts, aluminum, copper, etc., etc.

The mineralization of industrial waters is generally between a few tenths of a percent and a few units of a percent, sometimes much more, while their electrical conductivity can for example be between 10 1 and 10 3 ohm 1. cl 1.

Dissolved substances present in industrial water and other impurities reduce its ability to disperse clays, exert a harmful influence on their behavior, lower the thermostability and resistance to salt pollution of drilling muds, deteriorate their parameters of use ( viscosity, water release factor), reduce the rate of dissolution in the slat of reagents regulating the characteristics and parameters of drilling muds.

 It is possible to reduce the harmful influence on a drilling mud of dissolved substances and impurities contained in water or even to entirely eliminate this influence if the water is purified from said substances and impurities and if pass the salts in the form of bases. It is possible to carry out this purification by treatment of the mixing fluid in an electric field created by a direct current.

Electric water treatment devices are already known comprising electrodes separated by permeable partitions (cf. "Applied electrochemistry" published under the supervision of AL Rotinian, Editions "Khimiya",
Leningrad, 1974, p. 392, in Russian).

On the other hand, a device is contacted (cf. Author's certificate NO 407 844, issued in the USSR) which comprises a current source joined to electrodes executed in the form of hollow cylinders and arranged coaxially with one another. These electrodes are separated by a diaphragm and are placed in a body or a capacity which comprises tubes or pipes for the inlet and outlet of the liquid to be treated and the treated liquid respectively.

A relatively low intensity of the electrochemical reactions is observed in the known devices.
The space between the electrodes. In the event of a laminar flow of the liquid to be treated in the space provided between the electrodes, the different layers of liquid are treated in an irregular manner since the movement of the ions in said devices only occurs under the effect of 'a potential difference, so that the speed of electrochemical reactions is as low as possible. The direction of passage of the liquid from the vicinity of one electrode to the vicinity of the other is substantially that of normal to the surface of the diaphragm which separates them. For this reason, in the presence of solid particles, in particular clay particles, said particles quickly clog the pores and cells of the diaphragm and the operating reliability of the devices is thereby compromised.

Since the electrodes have a cylindrical shape, the contact surface of the liquid with the electrodes and the speed of flow of the liquid along the electrodes remains invariable, which increases the energy consumption.

 In the event of a laminar flow of the liquid, the insoluble deposits which separate from the treated liquid are deposited on the electrodes, which leads to increased energy costs, less reliability of operation of the device and poor quality of the treatment.

 It has therefore been proposed to create a device for preparing the fluid for diluting, diluting or mixing drilling mud in which the electrical treatment electrodes have a structure and a shape making it possible to increase the intensity of the electrochemical reactions while improving the quality of the treatment, lowering energy costs and increasing reliability during operation.

The device according to the invention comprises a capacity or a body, having an inlet and a outlet intended for the mixing fluid, in which electrodes are arranged coaxially, connected to a source of direct current, separated by a diaphragm, executed in the form of cssne trunks, the enclosure of the interior electrode comprising along its geometric axis a pipe or pipe of which one of the ends is joined without discontinuities at the end of the interior electrode on the side of its smallest base and the other end of which is joined at the start of the treated fluid.

 According to a variant of the invention, ribs are formed on the external wall of the internal electrode, along the said electrode, following at least one helical spiral.

 The installation of the ribs in the interelectrode space makes it possible to give the flow of liquid during treatment a turbulent circulation regime which intensifies the electrochemical reactions.

According to another variant of the invention, the external electrode has a large number of orifices over its entire length or height and the diaphragm adheres to the internal surface of the external electrode. This arrangement of the electrode and the diaphragm makes it possible to increase the treatment area of the interior electrode and to further increase the operating reliability of the diaphragm. The outer electrode can be joined by its end of the smallest section with a capacity intended to collect the slags or deposits via an insulating joint.

 The capacity intended to collect the schlamms makes it possible to separate them without losing fluid.

The device for preparing a drilling mud mixing fluid according to the present invention, while being of a relatively simple design, makes it possible to substantially intensify the treatment process while reducing energy consumption and improving reliability of the device.

 The invention will be better understood and other objects, details and advantages thereof will appear better in the light of the explanatory description which follows of an embodiment given solely by way of nonlimiting example, with references to single nonlimiting drawing attached in which there is shown schematically a device intended for the preparation of a g chage fluid according to the invention, seen in cross section.

 The device of the invention comprises a body or capacity 1 having an inlet 2 of fluid to be treated and an outlet 3 of the treated fluid. In the body 1 are arranged two hollow electrodes 4 and 5 nested one inside the other, providing an interelectrode space. The electrodes 4 and 5 are connected to a direct current source 6 and are separated by a diaphragm 7. The diaphragm 7 separates the treatment zones from the electrodes 4 and 5 and ensures minimal penetration of the fluid in the action zone from electrode 4 to the action area of electrode 5.

 The electrodes 4 and 5 are executed, for example, in the form of truncated cones with circular bases of the same orientation; the interior electrode 4 constitutes a hollow body traversed along its geometric axis "a" by a tube or a pipe 8, one of the ends of which is joined without discontinuity at the end of the electrode 4 which has the smallest section and the other end of which is joined to the fluid outlet pipe 3.

 Deflectors or ribs 9 are fixed on the outer wall of the interior electrode 4, distributed over its height or length and following at least one helical spiral. These ribs 9 arranged in the interelectrode space intensify the electrochemical reactions by creating within the liquid in flow of turbulent regimes.

 The execution of the electrodes 4 and 5 in the form of truncated cones and the arrangement inside the interior electrode 4 of a pipe 8 ensures a distribution of the flow velocities of the fluid resulting from its rotation or "twisting" and an increase in velocities by decreasing the rays of the liquid veins along the cones thanks to which the solid inclusions and the insoluble sediments of salts separate from the fluid to pass into a capacity 13 while the purified, treated fuid, leaves at the opposite, by the pipe 8. The outer electrode 5 over its entire length or height is pierced with a large number of through orifices 10 allowing the passage of the fluid in an enclosure It surrounding the electrode 5. At its inner surface comes adhere or press the diaphragm 7, which can be made of a suitable porous material, in particular electrically insulating. The ribs 9 can, according to an alternative embodiment, serve to maintain the diaphragm 7 at a suitable distance from the electrodes 4 and 5. Thanks to such an execution of the electrode 5 and of the diaphragm 7 the treatment zone in the electric field of the inner electrode is increased and the operating reliability of the diaphragm 7 is improved.

 The outer electrode 5 by its end of smaller section is joined, by means of a dielectric seal 12, to the envelope of the capacitor 13 intended to collect the schlamms.

 The capacity 13 intended to collect the schlamms is for example a pipe arranged vertically in the appended figure in which flaps 14 and 15 are installed which are controlled by a servomechanism 16. To purge the liquid and the sediments from the enclosure 11 we use a lower pipe 17 while to purge the gases an upper pipe 18 is used.

The device operates in the following manner after having injected into the electrodes 4 and 5, connected (in the example considered) to the positive pole and to the negative pole respectively, a voltage from the current source 6, we begin to pump at through the pipe 2 the fluid to be treated so that it enters the enclosure 22 located above the electrode 4. Then the fluid arrives in the interelectrode space between the electrode 4 and the diaphragm 7.

Thanks to the ribs 9, the fluid is driven in a rotational movement when it descends in this interelectrode space and its speed is accelerated because the radii of the sections of the cones decrease. It follows that its angular speed increases.

Since the pressure in the space between the electrode 4 and the diaphragm 7 is higher than the pressure behind the diaphragm 7, the fluid passes through the diaphragm 7 and penetrates to the electrode 5 by closing the electrical circuit.

In the area of the negative electrode t there are electrochemical transformations of the salts which are found in water in the form of Me-R compounds (Me representing a metal, R being a negative ion, for example: Na-Cl,
Na = Me, Cl = R) into Me-OH type compounds, hydroxides. The negative ions under 1 t action of the potential gradient on the surface of electrode 4 and the concentration gradient of OH ions leaving this surface pass into the zone of electrode 5 where they form acids entering into reaction with the hydrogen ions which are released on the surface of this electrode.

 If it is a question of treating the fluid in the zone of the positive electrode, the polarities of the electrodes 4 and 5 are exchanged, for example by means of a not shown polarity switch.

The circulation of the fluid in the region of the ribs 9 occurs in several directions: rotary (circular) circulation around the common geometric axis "a" of the electrodes 4 and 5, rotary movement in a plane perpendicular to the ribs 9 and downward movement. In addition, the fluid follows these trajectories at variable and different speeds because of the reduction in the radii of the sections of the cones. Thus favorable conditions for treatment are created: separation of the solid particles towards the periphery of a spiral element, active displacement of the ions towards the electrodes, uniform treatment along the entire cross-section of the flow. Ultimately the speed of electrochemical transformations increases.

 The acceleration of the flow during the treatment and the reduction of the contact surface with the electrodes due to their conical shape contribute to a more rational use of electrical energy. The centrifugal separation of the solid particles in a spiral or conical helix does not lead to clogging of the alveoli, cells or pores of the diaphragm 7 since the particles move tangentially to it. The rotational movement having a reduced value in a plane perpendicular to the ribs 9 is opposed to an intimate adhesion of the particles against the diaphragm 7 while the circular rotation of fluid around the axis Waw retains the particles by centrifugal forces. periphery of the spiral vein. At the exit of the interelectrode space, the solid inclusions and the insoluble deposits of the salts remain in the capacity 13 intended for the collection of deposits or schlamms while the fluid treated electrically and purified by centrifugal action of the type hydrocyclone rises and leaves via pipes 8 and 3. After a certain filling of the capacity 13 with deposits, the components 14 and 15 are rotated in turn by 900C for example and the deposits are rejected at the discharge. The acid products of the reactions which form in the area of the positive electrode are discharged through the pipe 17. Said products can be used for regulating the parameters of the drilling mud during its purification. The gases which are released in the electrode zones are evacuated into the atmosphere by the pipe 18. The treatment of the mixing fluid in the zone of the negative electrode makes it possible to obtain the required value of the pH of the drilling mud and to avoid its treatment with certain chemical reagents.

 The device according to the invention makes it possible to intensify and improve the treatment by displacement of the layers of liquid in several directions, to increase the reliability of the separation of the solid inclusions and the insoluble deposits of the treated fluid, to raise the indices economical by a more rational use of electrical energy with acceleration of the circulation of the liquid and reduction of its contact surface with the electrode as the treatment progresses.

Claims (4)

RESELL ICAT IONS  1. Device for the preparation of dilution, dilution or mixing fluid for drilling mud comprising a body, having an inlet and an outlet for this mixing fluid, in which electrodes connected to a direct current source are arranged coaxially and separated by a diaphragm characterized in that the electrodes are executed in the form of trunks of cones and that in the enclosure of the interior electrode along its geometrical axis is installed a pipe of which one of the ends is joined without discontinuity at the end of the interior electrode on the side of its smallest section and at the other end is joined at the start of the mixing fluid. 2. Device according to claim 1 c a r a c t é r i s in that on the outer wall of the inner electrode, along said electrode, are fixed ribs following at least one spiral. 3. Device according to one of claims 1 and 2 characterized in that the outer electrode, over its entire length, is pierced with a large number of through holes while the diaphragm is pressed on its inner surface .  4. Device according to one of claims 1 to 3 character ized in that the external electrode is joined by its end of smaller section by means of a dielectric seal to a capacity intended to collect the schlamms or deposits.