EP0562301B1 - Configuration method for water wells - Google Patents

Abstract

With the method, surrounding areas at liquid-extracting or liquid-feeding points in well boreholes are flushed clear and are thus freed from mud in order to prolong the operating period of a well system. <IMAGE>

Description

The invention relates to a method for designing well areas to promote the effectiveness of the well.

Such a method is known from US-A-4,254,831.

Wells of all kinds have a limited lifespan because over time they build up due to sediments that are carried along or because they become blocked in the liquid entry areas. Since well bores are predominantly drilled with a relatively large diameter in order to be able to accommodate the well pipe, including a gravel filter layer surrounding it, well production is relatively expensive and the short life of such wells is a noticeable disadvantage. The clogging of the well pipe is initially delayed by the surrounding gravel filter layer. However, it has been found that the addition of sediment to the gravel filter layer increases progresses, the more the flow rate of the liquid into the well pipe decreases due to the increasing flow resistance.

The invention has for its object to design well bores so that their operating time is increased significantly.

• a) Bilden eines ersten Bohrloches bis in einen durch Voruntersuchungen als relativ gut flüssigkeitsführend erkannten Bodenbereich;
• b) Bilden von mindestens einem zweiten Bohrloch nahe des ersten Bohrloches bis in den gleichen Bodenbereich;
• c) Lockern und mindestens teilweises Ausspülen von Bestandteilen des die Bohrlöcher in dem erreichten Bodenbereich umgebenden Bodenmaterials durch Einpressen und/oder Absaugen von Flüssigkeit in bzw. aus mindestens einem der beiden Bohrlöcher;
• d) gegebenenfalls Tiefertreiben der Bohrlöcher bis in mindestens einen zweiten, als relativ gut flüssigkeitsführend erkannten Bodenbereich und Wiederholung des Verfahrensschrittes c);
• e) spätestens nach Entfernen der Bohrwerkzeuge Einbringen eines Brunnenrohres in mindestens eines der gebildeten Bohrlöcher dergestalt, daß durchlässige Brunnenrohrbereiche auf die Höhe der freigespülten Bohrlochumgebungsbereiche zu liegen kommen.

According to the invention, the object is achieved by the following successive, in part also known, process steps:

• a) Forming a first borehole into a soil region identified by preliminary investigations as being relatively good at carrying liquid;
• b) forming at least one second borehole near the first borehole into the same bottom area;
• c) loosening and at least partially flushing out constituents of the soil material surrounding the boreholes in the soil region reached by injecting and / or sucking off liquid into or from at least one of the two boreholes;
• d) if necessary, driving the boreholes deep into at least a second soil region, which is recognized as having a relatively good liquid carrying capacity, and repeating process step c);
• e) at the latest after removing the drilling tools, inserting a well pipe into at least one of the boreholes formed in such a way that permeable well pipe regions come to lie at the level of the flushed borehole surroundings.

The method according to the invention ensures that a high flow velocity of the liquid flowing into the well pipe results in the suction area of a well. The braking caused by a conventional gravel lining of different densities does not apply. This significantly reduces silting of the well pipe environment compared to conventional wells.

With a method of the invention, depending on the structure of the water-bearing soil layers determined, a more or less large-scale horizontal desludging can also be achieved in different soil layers that are spaced apart in the vertical direction. As a result, the application of this method is particularly suitable for well systems for cleaning contaminated soil areas and groundwater on the spot, where a liquid flow is forced in the soil between well pipe mandrel areas that are vertically spaced apart.

In particular, large, flushed-out floor areas can advantageously and subsequently be at least partially refilled with pourable, flushable fillers, the size and material properties of which may depend on the purpose of the well in question. In the case of cleaning wells, but also drinking water wells, bodies made of ceramic material with a large surface area can be selected as fillers, which are suitable for the adsorption of gases and dissolved substances and / or for the nesting of microorganisms. However, commercially available filter bodies can also be flushed in as fillers.

The important process step of rinsing out regions of the liquid-bearing soil layers can be promoted by drilling several additional bores around the first borehole at a distance that still allows rinsing out, and later using the central first borehole as a well bore. A rinsing-out distance is to be understood as the distance to be selected in which, by pressing into the outer borehole in the region of the central borehole serving as a reflux borehole, the fluid flow is so strong that the pressure difference creates between the boreholes Connecting channels are created and ultimately a flushing out of soil material is achieved around the central borehole. During a rinsing process, a drill pipe used to inject liquid or to discharge the pressure fluid and the dissolved solids can be continuously moved forward.

Preliminary tests have shown that when the method according to the invention is used, in many cases afterwards the usual sheathing of the well pipe with a gravel filter layer can be dispensed with. It is practically possible to create a natural well without a flow obstruction through filters at the entry or removal point. This means that well bores with a much smaller diameter and accordingly can be drilled cheaper. Where you do not want to do without an outer gravel filter sheathing of a well pipe, with the method used, the hole selected as the well bore can only be flushed out after at least one surrounding area has been flushed out and before the well pipe has been inserted be drilled out to a larger diameter. The subsequent graveling of the well bore is then carried out according to the central arrangement of the well pipe in the well bore.

A well system is explained in more detail below with the aid of the attached schematic drawing, which has been designed using the method according to the invention.

Fig. 1

eine Draufsicht auf die Bohrlöcher der Brunnenanlage;

Fig. 2

einen Vertikalschnitt durch die Brunnenanlage entlang der Linie II-II in Fig. 1;

In detail show:

Fig. 1

a plan view of the boreholes of the well system;

Fig. 2

a vertical section through the fountain along the line II-II in Fig. 1;

1 and 2, a central borehole and, at a short distance from it, two additional boreholes 11 and 12 are driven into the ground 13 on both sides. For this purpose, drill pipes 14, 15 and 16 can be used, which are screwed or driven into the ground and with which the method can be carried out after the drill core has been removed. Drill pipes can later also function as well pipes. The drill core provides information about the nature of the various perforated soil layers, which are designated by letters AF in FIG. 2. In The boreholes 10 to 12 formed can, however, also be introduced after removal of the drill cores from the boreholes 14-16, measuring probes (not shown), with which the groundwater permeability of the individual soil layers AF can be determined, for example, using groundwater measurement samples.

The well system chosen as an example is of interest to two layers of soil that are at a vertical distance from one another and are relatively well permeable to water. These are the soil layers C and F, which are mainly sediment layers consisting of sand and gravel.

The first step is to gradually drill hole 10. As soon as the removed core shows that a first well-permeable groundwater layer, here layer C, has been reached, the other two holes 11 and 12 are also drilled to the same height . If it turns out that the bottom layer C is also struck by these holes and that it is not just a small sand and gravel lens, the rinsing of the bottom layer C in the area of the holes drilled begins. Water is pressed under high pressure into the middle drill pipe 14, as indicated in FIG. 2 by the downward arrow 17. At the same time, groundwater is extracted from the two other drill pipes 15 and 16 together with the sand and gravel material loosened by the pressurized water 17 pressed into the central bore 10, as indicated by the two upward arrows 18 and 19. In this process step, it is possible, in particular at the beginning, to switch between the three drill pipes 14 to 16 with the pressure water inlet, thereby loosening the sediment material is facilitated. The drill pipe introducing pressurized water can be moved forwards over the height of the bottom layer C during the pressurized water entry. Finally, this rinsing creates a more or less homogeneous cavity 20, the limitation of which is indicated in FIG. 1 and FIG. 2 by a dash-dotted or solid line 21.

Subsequently, the central bore 10 is driven further with the central drill pipe 14 until the second, well water-bearing bottom layer F is reached. After continuing the two other boreholes 11 and 12 also up to the bottom layer F, the rinsing process described above is repeated there and a second, more or less homogeneous cavity 22 with the boundary line 23 is created.

In the illustrated embodiment, the two cavities 20 and 22 formed are then filled with granular ceramic material with a large pore surface, which is flushed into the cavities with water. The ceramic grains 24 can be populated with soil-cleaning microorganisms.

1, two additional bores 51 and 52 are indicated with dash-dotted lines, with the aid of which larger cavities which are more concentric with the central bore 10 can be flushed out during the implementation of the method, the delimitation of which is indicated by a dash-dotted line 53. In the case of well systems for the extraction of drinking water, as a rule only a single well water-bearing soil layer is drilled, in which the rinsing and - depending on the nature of the soil - a subsequent support and filter filling is then carried out. A subsequent drilling of the hole selected for water production can then generally be omitted, which considerably reduces the cost of drilling the well. The diameter of the well pipe used depends on the drill pipe diameter.

Claims (6)

1. Process for configuring well areas to promote the well efficacy, characterized by the following sequential process steps:

   a) forming a first borehole (10) down to a soil area (C) recognized by tests as relatively highly liquid-bearing;

   b) forming at least one second borehole (11, 12) in the vicinity of the first borehole (10) down to the same soil area (C);

   c) loosening and at least partially flushing out constituents of the soil material surrounding the boreholes (10-12) in the soil area (C) reached by injecting and/or sucking out liquid into or out of at least one of the boreholes (10-12);

   d) if appropriate, driving the boreholes (10-12) deeper down to at least a second soil area (F) recognized as relatively highly liquid-bearing and repeating the process step c);

   e) at the latest after removing the drilling tools (14-16) introducing a well tube into at least one of the resulting boreholes (10-12) in such a manner that permeable well tube areas come to be situated at the height of the borehole surrounding areas (20, 22) which have been flushed free.
2. Process according to Claim 1, characterized in that the borehole surrounding areas (20, 22) which have been flushed free are at least partially filled with pourable packings which can be flushed in.
3. Process according to Claim 2, characterized in that the packings are grains (24) made of ceramic material and having a high surface area for the adsorption of gases and dissolved substances and/or for colonization by microorganisms.
4. Process according to Claim 2, characterized in that the packings flushed in are commercial filter bodies.
5. Process according to one of Claims 1 to 4, characterized in that a plurality of additional bores (51, 52) are accommodated around the first borehole (10) at a distance still permitting flushing out and the central first bore (10) is later used as a well bore.
6. Process according to one of Claims 1 to 5, characterized in that, during a flushing out operation, a bore tube (14-16) used to feed or remove the pressurized liquid is continuously advanced.

Images