Method for providing an underground barrier for a water reservoir

Abstract

The invention relates to a method for providing an underground barrier for a water flow. The method includes the steps of drilling in soil a number of parallel vertical holes; inserting pipe strings into the drilled holes, where each pipe string has a pipe string wall with a plurality of openings arranged distributed along the length of the pipe string; introducing injector means in each of the pipe strings; positioning the injector means at a plurality of discrete depths in the respective pipe string and aligned at each depth with at least one of the openings in the pipe string wall; and injecting at each discrete depth a sealing compound, such as sodium silicate, through the at least one aligned opening into the soil.

Claims

1. A method for providing an underground barrier for a water flow, which method comprises the steps of: drilling in soil a number of parallel vertical holes; inserting pipe strings into the drilled holes, wherein each pipe string has a pipe string wall with a plurality of openings arranged distributed along the length of the pipe string; introducing an injector in each of the pipe strings; positioning the injector at a plurality of discrete depths in the respective pipe string and aligned at each depth with at least one of the openings in the pipe string wall; injecting at each discrete depth a sealing compound through the at least one aligned opening into the soil; before injecting the sealing compound blocking the pipe string passage above and below the at least one aligned opening; and pumping the sealing compound in the space between the blockages and the pipe string wall, such that sealing compound is pumped through the at least one aligned opening and is injected into the soil; wherein the plurality of openings in the pipe string are provided with unidirectional passages, which prevent inflow into the pipe string.

2. The method according to claim 1, wherein the unidirectional passages are provided by flexible sleeves arranged around the pipe string wall.

3. The method according to claim 1, wherein the sealing compound is injected into the soil in substantial radial direction.

4. The method according to claim 1, wherein the pitch in longitudinal direction of the pipe string between the plurality of openings is between 25 cm and 150 cm.

5. The method according to claim 4, wherein the pitch in the longitudinal direction of the pipe string between the plurality of openings is 80 cm.

6. The method according to claim 1, wherein the number of parallel vertical holes are drilled using a sonic drilling method.

7. The method according to claim 1, wherein the sealing compound is sodium silicate.

8. An underground reservoir comprising: a geological formation with at least one porous geological layer along which water flows; and an underground barrier arranged downstream of the water flow, which underground barrier is provided with the method according to claim 1 and wherein the underground barrier extends from a depth above the porous geological layer to a depth below the porous geological layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features of the invention will be elucidated in conjunction with the accompanying drawings.

(2) FIGS. 1A-1C show the different steps of an embodiment of the invention.

(3) FIG. 2 shows a detail of the injection means.

(4) FIG. 3 shows an embodiment of an underground reservoir according to the invention.

(5) FIG. 4 shows a pipe string with openings covered by flexible sleeves.

(6) FIG. 5 is a cross section of the pipe string in FIG. 4.

DESCRIPTION OF THE INVENTION

(7) FIG. 1A shows soil with a number geological layers 1, 2, 3. According to an embodiment of the method according to the invention vertical holes 4 are drilled into the soil 1, 2, 3. As shown in FIG. 1B pipe strings 5 are then inserted into the vertical holes 4. Then the injectors are let down into each pipe string 5 and positioned at discrete heights to inject clouds of sealing compound 6 into the geological layers 1, 2, 3 to provide a watertight underground barrier.

(8) FIG. 2 shows a detailed view of the step of injecting sealing compound 6 into the geological layers 1, 2, 3. The pipe string 5 is provided with a plurality of openings 7.

(9) Injector 8 is let down through the pipe string 5 to a discrete height. Then the passage of the pipe string 5 is blocked by inflatable or expandable blocking means 9, which are called packer in the field, above and below an opening 7 in the pipe string wall.

(10) The blocking means 9 and the pipe string wall define a space 10 in which sealing compound 6 is pumped, which is then injected through the openings 7 into the geological layers 1, 2, 3.

(11) FIGS. 4 and 5 show the pipe string 5. The plurality of openings 7 in the pipe string 5 are provided with unidirectional passages, which prevent inflow into the pipe string 5. The unidirectional passages are provided by flexible sleeves 10 arranged around the pipe string 5 wall. When sealant is injected, the pressure will push the flexible sleeve 10 away from the wall of the pipe string 5, such that the sealant can flow from inside of the pipe string 5 through the openings 6 to the outside.

(12) FIG. 3 shows a geological formation 11 with a number of geological layers 1, 2, 3. A number of vertical holes 4 is drilled into the soil, as explained above with reference to FIGS. 1A-1C and a sealing compound, such as sodium silicate, is injected into the geological layers 1, 2, 3 to provide an underground barrier.

(13) The geological layer 2 is a porous layer and guides a flow of water W. Due to the underground barrier, this flow of water W is buffered in the underground reservoir formed by the porous geological layer 2 and the underground barrier of sealing compound 6.