FR2643664A1 - Method for exploiting underground water currents by boring - Google Patents

Abstract

Device making it possible to exploit underground water currents by special boring. It comprises a bore 1 into which is introduced the tube 2 made from plastic or metal material, outside which is arranged gravel 3, the tube being placed in a current zone 4. Gauze-screened slots 5 are made on this tube. A leaktight motorised pump 6 of the submerged-pump type is placed in the gauze-screening zone of the tube which is itself held by centring rings 7; a swelling wood plug 8 placed at the bottom of the tube prevents the passage of the gravel into the tube. The invention may be used to exploit underground water currents regardless of their size or their type.

Description

 The present invention relates to a method allowing the exploitation of underground water currents by particular drilling.

 In known devices of this kind, casings with bottom of strainer tubes and pumps are placed inside the tube, but they quickly clog up due to their elementary technique. In addition, these devices have the disadvantage that we have to dig deep to the water table to extract equivalent amounts of water.

 The device according to the invention makes it possible to avoid these drawbacks.

It is indeed possible to exploit water in regions which have or which do not have a water table on underground currents of one meter or more in height as in a water table of four meters in height.

 The device, object of the invention, comprises a borehole whose diameter varies according to the technical data and the operating result, carried out by a drill bit or by a blade tool or by a downhole hammer, after locating the current zones (hard part, clay or other).

 A plastic or metal tube, held by centering rings, is placed two meters or more below the water stream to make a decantation pocket under the water flow zone, the tube however not being able to be placed less than 0.50 centimeters from the bottom of the borehole.

 On this tube are made strainer slits, 2.5 mm minimum to avoid clogging by fines that carry batten. They are then positioned on this tube so that they reach the level of the water stream of the underground currents. A study of the size of the slits and the passage of water allows to arrive at the following result knowing that the passage of water is 1 liter per second per cm2, a slit 2.5 mm x 100 = 2.5 cm2. 1 liter x 2.5 cm2 = 2.5 1 and 2.5 1 / second x 3600 seconds = 9000 liters / hour or 9 m3 / hour. Slits on strainers made on four sides and 1.20 meters high allow 5 x 4 = 20 water passages, i.e. 9 m3 x 20: 180 m3 of water passage per hour, - knowing that 1/3 will be obstructed by graveling, the passage remains 135 m3 for a suction of 40 m3 / hour.

 Inside the tube are installed a compressed air flush and a tube cleaning system. A suction of waste and water by compressed air from the flush using a hose lowered to the bottom of the tube and a cleaning by tubes allows to evacuate the spoil.

 Draining gravel is then placed outside the tube between the drilling space and the outside diameter of the tube, replacing the sand and drilling waste to prevent clogging. Depending on the case, external water must be added to facilitate the functioning of the compressed air because the water level must be at least 2.5 meters from the blowing point for extraction by l air works.

 As soon as the gravel reaches the base of the tube from the outside, a special wooden swelling plug is pushed to the bottom of the tube using a string of rods.

 A sealed motor-driven pump, of the submerged pump type, is then placed at the level turned down from the current level to allow the pumping of the water, after pumping test for one hour, the flow rate is constant all year round.

 The appended drawing illustrates, by way of example, an embodiment of the device according to the present invention.

As shown, the device presents
Figure 1 which shows in longitudinal section the entire drilling device.

 Figure 2 which shows in longitudinal section a part of the drilling device.

 FIG. 3 which represents a finished section of the drilling device along the line AA shown in FIG. 1.

 The device shown in FIG. 1 comprises a borehole 1 into which a plastic or metal tube 2 is introduced, outside of which is gravel 3; the tube being placed in a current zone 4. Strainer slots 5, with a dimension of at least 2.5 millimeters are made on the plastic or metal tube. A sealed motor pump of the submerged pump type 6 is placed in the straining zone of the tube, which is itself maintained by centering rings 7 at a distance which cannot be less than 0.50 centimeters from the bottom of the borehole and finally a plug. made of swelling wood 8 placed at the bottom of the tube prevents gravel from passing through the interior of the tube.

 The device shown in FIG. 2 comprises a borehole 1 into which a plastic or metal tube 2 is introduced, outside of which is arranged draining gravel 3; the tube itself being placed in a current zone 4. 2.5 mm strainer slots are made on the tube; a waterproof motor-pump 6, of the submerged type, placed in the strainer zone allows the pumping of water.

 The device represented in FIG. 3 comprises the borehole 1 in which the plastic or metal tube 2 is placed, the draining gravel 3 disposed outside the tube between the drilling space and the outside diameter of the tube, and the centering rings 7 holding the tube in the center of the device.

 The device, object of the invention, can be used for the exploitation of underground currents, whatever their nature (rivers, underground streams}, and their size (knowing that it can reach at least ten centimeters wide, a height of two centimeters to several meters or tens of meters).

Claims (8)

 1) Device for exploiting underground water currents whatever their size; characterized by the fact that it includes a foragel  in which is placed a tube 2, surrounded by draining gravel 3, and comprising strainer slots 5; a compressed air flush and a motor pump 6 placed in the tube; centering rings 7-; and a swelling wooden plug 8.  2) Device according to claim l characterized in that the drilling is carried out by a drill bit, a blade tool or a downhole hammer.  3) Device according to claim 1 characterized in that the tube is made of plastic or metal.  4) Device according to claim 1 characterized in that the tube 2 comprises grilling slots 5 whose dimension is 2.5 millimeters minimum to avoid clogging by fines transported by water.  5) Device according to claim l characterized by the fa-it that the compressed air flush and the tube cleaning system allow the evacuation of waste.  6) Device according to claim 1 characterized in that the sealed motor pump 6 is located at the level of the current stream 4, and that it is a submerged sealed pump.  7) Device according to claim l characterized in that the tube 2 comprises centering rings 7 intended to hold the tube in the center of the device.  8) Device according to claim 1 characterized in that the swelling wooden plug 8 seals the end of the tube and prevents the clean gravel from rising.