RU2789772C1 - Method for decolmating filters and well pre-filter zone - Google Patents

Abstract

FIELD: geotechnology.

SUBSTANCE: invention relates to the field of geotechnology, and in particular to methods for restoring the injectivity of technological wells in the extraction of minerals by downhole underground leaching in infiltration-type deposits. The method for decolmatation of the near-filter zone of wells includes chemical treatment with ammonium bifluoride and sulfuric acid, forcing a column of liquid in the well with a process solution, and keeping the solutions in the near-filter zone of the well. Ammonium bifluoride is used in crystalline form, and delivery to the filter zone is carried out by filling it through the wellhead. The mixing of the reagents in the near-filter zone is carried out by bubbling at a pressure of the gas-air mixture above atmospheric, but below the liquid column in the well. The exposure of the solution in the well is not more than 10 hours. Wells are preferably injection. Bubbling is carried out with a gaseous oxidizer for 1 hour. Air oxygen is used as a gaseous oxidizer.

EFFECT: increasing the efficiency of mining operations by increasing the turnaround time and well operability.

5 cl, 2 dwg

Description

Technical field

The invention relates to the field of geotechnology, and in particular to methods for restoring the injectivity of technological wells in the extraction of minerals by downhole underground leaching in infiltration-type deposits.

Prior Art

Known methods of filter decolmatization by mechanical removal of clay cakes or with the help of acids, alkalis, etc., i.e. chemical methods (see V.M. Gavrilko, B.C. Alekseev. Filters of boreholes. Ed. 2 revised and supplemented. M. Nedra, 1976 p. 307-338).

The main disadvantages of these methods are the low degree of filter cleaning and the short period between overhauls.

The closest (prototype) to the claimed is a method of decolmatization of the near-filter zone of wells, including pumping into the well a solution of ammonium bifluoride and sulfuric acid, a concentration of 40 g/l, forcing a liquid column in the well with a process solution, keeping the solutions in the well, mainly in the pumping out at least 24 hours, with the content of sulfuric acid and ammonium bifluoride in a mass ratio of 1: 2.1-6.4 (patent of the Republic of Kazakhstan No. 32339. METHOD OF DECLAMATION OF FILTERS AND WELL PRE-FILTER ZONE / Nietbaev M.A. and others. publ. 16.02.2016 .).

The main disadvantage of the known method is the dilution of the ammonium bifluoride solution by formation fluid and the duration of exposure of the solutions in the treated well.

The proposed technical solution is aimed at creating a highly efficient method for decolmatation of filters and the filter zone by reducing the exposure time of the mixture of solutions in the filter zone and increasing the overhaul cycle of wells.

Disclosure of invention

The technical result achieved by using a new method for decolmatation of the near-filter zone of wells consists in effective treatment with a mixture of bifluoride and sulfuric acid, where the bifluoride is delivered to the filter zone in crystalline form and dissolved directly in the filter zone by bubbling, which improves the quality of decolmatation and reduces the cost of well treatment .

The essential feature "ammonium bifluoride is supplied to the filter zone in crystalline form" is distinctive for this technical solution, which allows to avoid the loss of the reagent, because the solution is prepared directly in the filter zone, which increases the efficiency of processing colmatants in the filter zone (Dzhakupov D.A. “Improving the efficiency of various schemes of borehole underground leaching in the development of complex hydrogenous deposits.” PhD dissertation. Almaty, 2019, p. 81-85).

The distinctive essential feature "the mixing of reagents in the near-filter zone is carried out by bubbling at a pressure of the gas-air mixture above atmospheric, but below the liquid column in the well" is at the same time new, because this sign was not found in the open press by the authors. The preparation of solutions using bubbling and a gas-air mixture is widely known, but this process is usually carried out on the surface in special containers, after which the solutions are sent to their destination (wells, pipelines, etc.). At the same time, the efficiency of the reagent impact on the object decreases due to its dilution along the delivery path in the volume of the well liquid column. In the proposed solution, bubbling is carried out directly in the filter zone, where ammonium bifluoride is dissolved and mixed with a sulfuric acid solution while simultaneously delivering the resulting mixture to the filter zone. The boundary indicators of the force of the gas-air flow predetermine the minimum pressure for bubbling and mixing of the reagents, as well as the upper pressure level of the gas-air mixture at which active mixing is still possible. Exceeding the upper pressure level (more than the pressure of the liquid column in the well) will result in the release of the liquid column from the well, which is not the purpose of bubbling.

The distinctive essential feature "solution exposure in the well is no more than 10 hours" determines sufficient time to react with bridging agents in the near-filter zone. First of all, chemical reagents come into contact with bridging agents, spending all their energy on their dissolution. And this process occurs in the first hours of contact. In practice, the following happens - after the chemical treatment of the well during repair and restoration work (RVR), the well is left for 24-48 hours of exposure with reagents, and not because this is the period of the most effective effect on bridging agents, but it’s just more convenient - in a day - two in this is daytime, otherwise you will have to come to the well at night or in the morning, which is not entirely consistent with the work schedules of the RVR teams. The most active dissolution of colmatants occurs during the first 10 hours of exposure - Fig. 1, and then the dissolution slows down sharply and is carried out in the mode of a sluggish process, affecting not only the remains of bridging agents, but also the minerals that compose the formation in the area of the near-filter zone of the well, which is an undesirable factor that increases the mineralization of technological solutions. The significance of this feature is expressed in the reduction of treatment time and, consequently, the early commissioning of the well, which allows obtaining an additional product.

The distinctive essential feature “wells are preferably injection wells” reflects the specifics of the lithofacies and mineralogical and geochemical composition of ore-bearing strata of paleovalley-type deposits in the Vitim uranium ore region. Decomposition of clayey rocks and minerals (kaolinite, montmorillonite, calcite, magnesite, siderite, etc.) with sulfuric acid solution leads to chemical clogging of filters and the near-filter zone of technological wells. The process occurs in duration from several days to tens of years (Geotechnology of uranium (Russian experience). I.D. Akimova, A.S. Babkin, A.G. Ivanov et al. KDU, M. 2017, p. 150). Injection wells at production sites undergo clogging for 14-20 days and their injectivity drops from 2.5-3.0 m ³ /hour to 0.2-0.3 m ³ /hour. Therefore, the priority of treatment of injection wells is a priority.

The distinctive essential feature "bubbling is carried out with a gaseous oxidizer for 1 hour" determines the temporary sufficiency of mixing the reagents in the filter zone with the gas-air mixture supplied by the compressor through a hose with a diameter of 32 mm. As experience shows, the supply of air for an hour allows you to completely dissolve the crystals of ammonium bifluoride and mix the reagents (ammonium bifluoride and sulfuric acid solution 50 g/l according to the reaction 2NH4HF2+H2SO4=(NH4)2SO4+4HF). Air supply for more than 1 hour will entail unjustified costs, including diesel fuel.

The distinctive essential feature "air oxygen is used as a gaseous oxidizer" makes it possible to get by with the most economical gaseous oxidizer to achieve the goal - dissolution and mixing of the reagents.

The combination of the above distinctive essential features of the proposed technical solution allows you to increase the turnaround cycle of technological wells up to 72 days and achieve the stated goal in full.

Implementation of the invention

The following is information confirming the implementation of the proposed invention and shows its effectiveness in relation to known technical solutions.

On the diagram - Fig. 2 shows an example of the proposed method.

Ammonium bifluoride (3) in crystalline form 25 kg is poured into the technological well (1) through a funnel (2), which enters the filter zone (4), then sulfuric acid solution (6) is fed through the hose (5) into the filter zone (4) , with a concentration of 50 g/l in an amount equal to the liquid column of the well. So with an inner diameter of the well of 0.124 m and a liquid column height of 70 m, the volume of the sulfuric acid solution will be: 3.14 × 0.062 ² × 70 = 0.8 m ³ . Then, the reagents are bubbling through the hose (5) in the filter zone (4) of the well, supplying air (7) from a compressor, for example, XRVS 336 from Atlas Copco for 1 hour. The pressure of the gas-air mixture is set no more than the pressure of the liquid column in the well. For example, the groundwater level (8) in the well is at a depth of 130 m, with a well depth of 200 m. Accordingly, the liquid column is 70 m, while the pressure when air is supplied to the filter zone (4) of the well (1) will be 6 atmospheres . After holding the solution for 10 hours, airlift pumping of the well through the hose (5) is carried out with the removal of mechanical and chemical colmatans from the filter zone (4).

The efficiency of using the claimed invention lies in reducing the processing time of technological wells during RWR and increasing the extracted metal. So, for example, with a well flow rate of 6 m ³ / h and a content of 90 mg/l of metal in the productive solution and a reduction in the time of well standing under reagent treatment from 24 hours to 10 hours, we get that 7.5 kg of metal will be produced in 14 hours from one well additionally. And there are about 250-300 pumping wells in similar fields. Accordingly, this will amount to 1.8 - 2.2 tons of metal, which in monetary terms will be at least 7.5-9.0 million rubles.

Claims (5)

1. The method of decolmatation of the filter zone of wells, including chemical treatment with ammonium bifluoride and sulfuric acid, forcing the liquid column in the well with a process solution and keeping the solutions in the filter zone of the well, characterized in that ammonium bifluoride is used in crystalline form, and delivery to the filter zone is carried out by backfilling it through the head of the well, while the mixing of the reagents in the near-filter zone is carried out by bubbling at a pressure of the gas-air mixture above atmospheric, but below the liquid column in the well. 2. The method according to p. 1, characterized in that the exposure of the solution in the well is no more than 10 hours. 3. The method according to p. 1, characterized in that the wells are preferably injection. 4. The method according to p. 1, characterized in that sparging is carried out with a gaseous oxidizer for 1 hour. 5. The method according to p. 4, characterized in that air oxygen is used as a gaseous oxidizer.

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