METHOD FOR UNBLOCKING A DEEP WELL PLUGGED BY AN ADSORBENT

Abstract

A method is proposed for making geological deep wells that are clogged unblocked and capable of absorbing fluid again by adding an acid from the group of carboxylic acids and vinylogous carboxylic acids.

Claims

1. A method for unblocking a deep well plugged by an adsorbent, which comprises introducing one or more carboxylic acids selected from the group consisting of a monocarboxylic acid, a dicarboxylic acid, a tricarboxylic acid, a vinylogous carboxylic acid, into the plugged deep well.

2. The method of claim 1, wherein the carboxylic acid is selected from the group consisting of ascorbic acid, citric acid and/or citric acid monohydrate.

3. The method of claim 1, wherein a part of brine located in the deep well is displaced from the deep well by the carboxylic acid.

4. The method of claim 1, wherein a probe is inserted into the deep well prior to the addition of the carboxylic acid, and wherein the carboxylic acid is delivered through the probe to the desired depth of the deep well.

5. The method of claim 1, wherein after the dissolution of the adsorbent, the carboxylic acid and the dissolved adsorbent are pumped out of the deep well.

6. The method of claim 1, wherein the carboxylic acid is pressurized in addition to the hydrostatic pressure prevailing in the deep well (11).

7. The method of claim 1, wherein the adsorbent is a lithium adsorption agent.

8. The method of claim 1, wherein the adsorbent is a manganese oxide type adsborbent.

9. A method for dissolving a lithium adsborbent and/or a manganese oxide type adsorbent comprising employing one or more of a carboxylic acid selected from the group consisting of a monocarboxylic acid, a dicarboxylic acid, a tricarboxylic acid and a vinylogous carboxylic acid.

Description

DRAWING

[0028] The single FIGURE shows a schematic representation of two deep wells for the extraction of lithium-bearing brine.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0029] In FIG. 1, plant 1 for the extraction of lithium ions from a lithium-containing brine or from lithium-containing deep water is shown in a highly simplified form and only as one block. An initial deep well 3, which is driven several thousand meters into subsurface 5 in some cases, is upstream of plant 1. At the bottom of deep well 3, subsurface 5 is usually porous or fissured and karstified. In many cases, cracks or fissures are purposefully introduced by deep-injecting a fluid under pressure into the deep well after first deep well 3 and/or second deep well 11 have been made. As a result, subsurface 5 cracks at the end of deep well 3 or 11 and forms the desired cracks and fissures (“hydraulic stimulation”). Such cracks and fissures are desirable, because they enable, or facilitate, the pumping of deep water (not shown in FIG. 1) from first deep well 3, but also the re-injection of the water in second deep well 11.

[0030] The deep water/brine in first deep well 3 is conveyed by first pump 7 and fed to plant 1. The invention is not limited to the aforementioned use of plant 1. There could also be additional or alternative geothermal utilization of the deep water or lithium-bearing brine conveyed by first deep well 3 in plant 1. After the deep water or brine is processed in plant 1, it is pumped by optional second pump 9 into second deep well 11.

[0031] Second deep well 11 is used to reintroduce into subsurface 5 the depleted deep water or brine. In many cases, the lengths of first deep well 3 and second deep well 11 are approximately the same.

[0032] In the case of second deep well 11, the subsurface at its lower end should also be as porous, fissured or karstified as possible, so that it can absorb the depleted brine.

[0033] If the subsurface does not naturally already have sufficient porosity or permeability and transmissibility, i.e., liquid absorption capacity, it can also be provided with cracks and fissures by hydraulic deep injection, in order to improve liquid absorption capacity. It is obvious that such fissures and cracks are relatively narrow, so that they can be plugged by solids, such as an adsorbent, which has entered second deep well 11, for example, due to a malfunction of plant 1. The liquid absorption capacity of the subsurface is then negatively reduced. This can either lead to an increased demand of electrical energy for pump 9 or even to the fact that the flow rate or the delivery capacity of pump 9 decreases so much due to the increased flow resistance in subsurface 5 that upstream plant 1 can no longer be operated economically or operated at all.

[0034] According to the invention, it is now provided that, in the event of such a blockage or plugging of the subsurface or of the deep well 11, a carboxylic acid, a di- or tricarboxylic acid, a vinylogous carboxylic acid or an acid from the group of the aforementioned acids or a mixture thereof is brought to the bottom of second deep well 11 or to a location of the deep well that is clogged by adsorbent. Surprisingly, it has been found that the specified acids dissolve adsorbents, in particular adsorption agents for lithium or manganese oxide type adsorbents, very well.

[0035] This makes it possible to dissolve an adsorbent that has become trapped in the cracks and fissures at the bottom of second deep well 11 or in deep well 11. This restores the porosity, fissurization and karst cavities of subsurface 5 at the bottom of second deep well 11, and also the continuity of deep well 11, or prevents a negative impairment of such properties and thus also of the absorption capacity for deep water or other fluids.

[0036] Another variation is to lower an (injection) probe (not shown) into deep well 11 until the end of the probe reaches the bottom of deep well 11 or the location of the clogging. Then, the probe delivers the acid into deep well 11 and can directly dissolve the adsorption agent present there without any distribution losses.

[0037] Usually, after the adsorbent has been dissolved, it is pumped out again through the probe together with the acid and disposed of.

[0038] Furthermore, by increasing the pressure on the acid or liquid located in second deep well 11, it is possible to force the acid into the “clogged” fissures and cracks in the subsurface, thereby accelerating the dissolution of the adsorption agent.