RU2318987C2 - Well yield recovery method and device - Google Patents

Abstract

FIELD: water supply systems, particularly to clean well screens of plugging particles and substances, for instance for water intake wells.

SUBSTANCE: method involves arranging electrode of conducting material inside well; passing current through electrode, well wall and well screen so that well wall and screen are used as anode, electrode is used as cathode. Sign-alternating electric current pulses are applied to cathode and anode for mud removal from screen walls. Constant current is simultaneously supplied to move cations present in well fluid, to cathode and fluid pH reduction in screen zone.

EFFECT: increased efficiency of screen pore cleaning, decreased material consumption and costs, prevention of well screen damage.

5 cl, 1 dwg, 1 ex

Description

FIELD OF THE INVENTION

The invention relates to the field of water supply and drainage, and more particularly to cleaning the holes of the well filters from particles and substances clogging them and restoring the productivity of wells, in particular water wells.

State of the art

Typically, in a water intake or salt well, a mechanical filter is installed to clean the withdrawn water or saline from large rock particles. Mesh filters are most commonly used for this. However, during the operation of the well, the holes in the grid gradually overgrow and become clogged with precipitating substances and particles of water-bearing rock dissolved in water (mudding). As a result, well productivity may drop to a critical level and there is a need to clean the filter, for which a number of different methods are proposed, including, for example, mechanical, chemical and pneumatic cleaning. As is well known to specialists, all these processes are associated with problems such as inefficiency of cleaning, complexity, laboriousness and high cost of the corresponding process, damage to the filter and pipes of the well, problems associated with ecology and safety.

In particular, there is a known method of reconstructing wells that have reduced their productivity due to clogging of the filter openings with salts of substances dissolved in water and particles of water-bearing rock, by mechanical action (swabbing, evacuation, etc.) described in the book by V. M. Gavrilko, Alekseev B.C. Drill hole filters. - M., "Nedra", 1976, - p. 344.

There is also a known method of processing chemicals, in particular hydrochloric acid, described in the book of Vorontsov V.I., Shaber GB Intensification of the operation of drainage devices during the drainage of mineral deposits. - M., "Nedra", 1975, - 204 p. This method is expensive, requires special acid-resistant equipment, is unsafe and can lead to destruction of the well material.

A filter for biological wastewater treatment is also known from copyright certificate No. 685632, having a frame and a filter sheath and electrodes in the form of a mesh, an anode and a cathode of dissimilar materials, placed on it, and the filter sheath is placed between the electrodes. Under the influence of electrochemical reactions, the active space is saturated with copper ions, which prevent the development of biological colmatation. The disadvantage of this method is to prevent only biological colmatization and the inability to completely decolmatize the filter. Given that minerals create the main problem with mudding in wells, this method cannot be applied for well restoration.

From the copyright certificate No. 850818 (the closest analogue of the invention), a device and method for restoring well productivity are known. According to this method, an electrode of electrically conductive material is placed inside the well and an electric current from the connected power source is passed through the indicated electrode, the wall of the well and the well filter to ensure that the filter is cleaned of colmatant by moving ions between the electrode and the well filter. In the method and device proposed in the closest analogue, the current supply is not regulated. The supply of currents, including any value, allows side effects (heating, etc.), which does not contribute to the efficiency of the electrochemical processes, and this, in turn, does not contribute to the effectiveness of a full recovery of well productivity.

Disclosure of invention

Accordingly, the objective of the invention is the provision of a method and device for almost complete restoration of well productivity without the above-mentioned disadvantages of the prior art.

To solve this problem, a method for restoring well productivity is proposed, in which the well wall and the filter are used as the anode and the electrode is used as the cathode. To clean the filter, alternating electric current pulses are fed to them to separate the colmatant from the filter walls and, at the same time, direct current to transfer cations contained in the well solution to the cathode and to lower the pH of the medium in the filter zone.

The precipitate formed during the cleaning process can be removed by subsequent pumping of the well.

The electrode in the method according to the invention can be placed in a casing of a semipermeable material.

The implementation of the method is achieved by the device according to the invention, in which the power source is connected to the well wall and the filter. The power source is a direct current source and a pulse generator and is a means of supplying simultaneously alternating pulses of electric current and direct electric current.

In the course of the research, it was unexpectedly found that the use of the above method and device leads to the dissolution of the mud and its transfer to the sediment (suspension), which, as mentioned above, is easily removed from the well by its subsequent pumping. The mechanism of such a removal of colmatant is not fully established. It is assumed that the main role here is played by the change in pH in the filter zone, but other processes also seem to be of no small importance. Clarification of the characteristics of alternating and constant currents allows the achievement of an effect independent of the fact of the supply of currents, including any value that leads to the presence of side effects (heating, hydrogen formation, etc.). The use (supply) of weak currents ensures the effectiveness of electrochemical processes. When a positive amplitude is applied to the filter and the borehole wall, the pH of the medium changes to form an acidic medium near the filter wall and an alkaline one at the central electrode. Under the influence of an acidic environment, precipitates, which are metal oxides, mainly iron, dissolve. Under the influence of the potential difference, metal ions transfer to the negative central electrode. In the subsequent half-period, when a negative amplitude is supplied to the filter and the borehole wall, the reverse reaction does not occur. And in the subsequent positive amplitude of the alternating current supplied to the filter and the borehole wall, the transfer of metal ions will be enhanced by increasing the potential difference. The above effect can be enhanced in the above embodiment, when the electrode is placed in a casing of a semi-permeable material (permeable to ions, but not to water molecules), by preventing the mixing of acidic and semi-acidic media due to diffusion processes.

As a result of using the proposed method and device, the aforementioned problem is solved and effective cleaning of the well filter pores from deposits, in particular chemical (mineral) mud, is achieved, with relatively small material and labor costs and without the risk of damage to the well filter.

Brief Description of the Drawings

The drawing schematically shows the well and described as an example, a variant of the device for implementing the method according to the invention.

The implementation of the invention

The drawing schematically shows a well 1 having a wall 2 and a filter 3. These elements can have one of the structures well known to those skilled in the art and therefore are not described in detail here (in particular, wall 2 is usually a pipe wall, and the filter is made in the form of a perforated tubular body with net wrapped around it).

The zoned area adjacent to the filter is indicated by dashed lines under reference number 4. The colmatant can also accumulate in the well pit 5.

A device for implementing the inventive method comprises an elongated central electrode 6 and a power source 7 (means for supplying an alternating and, at the same time, constant electric current), which is a constant current source and a pulse generator. The power source 7 is connected to the wall 2 of the well and the electrode 6. In this case, the wall 2 and the filter 3 of the well are the anode, and the electrode 6 is the cathode.

In the presented embodiment, when implementing the method, the electrode 6 is placed passing through the central region of the well (along the axis of the well) and through the filter 2 so that it is located inside the filter. Then, alternating electric current pulses with a frequency of 50 to 100 hertz are generated with a superimposed component, which is applied to the wall 2 of the well and the electrode 6 through a power source 7.

In the process of passing an alternating electric current through the electrode-water (solution) -colmatant system, due to the flow of cations and anions contained in the water (solution), the colmatant dissolves and separates from the filter walls and distributes it throughout the filter, and under the influence of a constant component occurs additional transfer of cations to the central electrode and an additional pH shift in the anode zone (i.e., in the colmated zone 4) towards its lowering, which leads to an even greater effect of dissolution of matanta. This also contributes to the placement of the Central electrode in a tubular casing of a semipermeable material (not shown), for example, known materials that are impermeable to solution, but permeable to ions.

A precipitate (ferroferryhydrosol) formed during filter cleaning from colmatant can be removed from the well by pumping it.

Example

A well with a depth of 245 m, drilled in 2003 on the Cenomanian-Albian aquifer, represented by fine-grained sand. The design debit of the well is 10 m ³ / h. The mesh filter 15 m long is a brass mesh placed on a perforated tubular frame. After putting into operation, the well was not exploited. In 2004, when trying to take water from the well, it turned out that the filter was sealed with chemical colmatant. To clean the filter, decolmatization was carried out by applying an electric current in accordance with the invention with the following parameters:

- alternating current: frequency 100 Hz, voltage 40 V, current strength 0.6 A;

- direct current: voltage 60 V, current 0.7 A.

Processing was carried out 72 hours.

When pumping the well, the debit of the well was 9.5 m ³ / h.

Claims (5)

1. A method of restoring well productivity, in which an electrode of electrically conductive material is placed inside the well and an electric current is passed through the indicated electrode, the wall of the well and the well filter to ensure that the filter is cleaned of the mud, characterized in that the well wall and the filter serve as the anode, and the electrode is cathode, alternating pulses of electric current are fed to them to separate the colmatant from the walls of the filter and at the same time a direct current to transfer cations contained in the well solution ny, to the cathode and a shift in the pH of the medium in the direction of lowering in the filter zone. 2. The method according to claim 1, characterized in that the electrode is placed in a casing of semipermeable material. 3. The method according to claim 1 or 2, characterized in that the precipitate formed during the cleaning process is removed from the well by means of its subsequent pumping. 4. A device for restoring the productivity of a well equipped with a filter, comprising an electrode placed inside the well from an electrically conductive material and a connected power source for supplying electric current through the well filter and the electrode and ion movement between the electrode and the well filter, characterized in that the power source is connected to at the same time, it represents a direct current source and a pulse generator and is a means of supplying at the same time sign ennyh pulses of electric current, the wall of the well and the filter is the anode and electrode - cathode. 5. The device according to claim 4, characterized in that it comprises a casing of semipermeable material, placed around the electrode.