CZ25775U1 - Sampling device for sampling samples of underground water, which are not susceptible to chemical influence from low-profile boreholes in rocks of low permeability - Google Patents

Description

Technical field

The sampling equipment enabling the acquisition of chemically unaffected groundwater samples from boreholes with a narrow profile and / or low yield is usable in boreholes where the groundwater level is found in the depths of tens of meters to 300 m.

- hydrogeology

- Ecology

- remediation

- waste disposal

- storage of raw materials.

Background Art

Groundwater sampling from exploration wells is an important part of projects related to the search for and assessment of the quality of available groundwater reserves, the removal of environmental burdens, the design and construction of underground repositories and storage facilities of various types. Based on the results of sampling, it is decided on the further progress of work and their financial costs, it is very important to take high-quality samples representing the real composition of groundwater in the rock environment, including the content of possible contaminants.

In the past, various types of sampling devices for various purposes have been designed to provide representative water samples that are not chemically altered when taken from a water source.

Basic types of sampling (sampling) devices and their properties are described in the Czech technical standard ČSN ISO 5667-18, Water quality - Sampling - Part 18: Guidelines for sampling of groundwater at contaminated sites. The selection of a suitable sampling device depends and varies according to the particular situation (demand for sample volume, sampling depth, contaminants, multiphase sample, etc.).

A relatively problematic area of water sampling is the sampling of deep boreholes with low groundwater levels, small diameter boreholes or boreholes whose yield is low.

Sampling equipment for the above purposes must meet the following requirements:

- possibility of sampling without atmosphere

- Possibility of sampling from a specific depth level, including multi-level sampling

- taking a representative sample of groundwater

- possibility of sampling from deep boreholes (even several hundred meters)

- Collection from narrow-profile boreholes (bore diameter 76 mm or less)

- boreholes with low flow rates and low yield.

Commonly used basic types of collection devices include the following:

Depth samplers are used to collect one defined sample volume. These include open samplers - simple samplers (bottles, pails) and sealed samplers allowing sampling from the desired depth in the borehole. With a closed sampler, it is possible to remove groundwater from a particular depth level, even from large depths and without air access, but in most cases it is not representative of the sample. In the water column in the borehole the groundwater is mixed from various depths, to oxygenate the groundwater and subsequently change its composition - a sample taken from a free borehole without pumping therefore does not correspond to the composition of groundwater in the surrounding rock environment. It is not possible to take samples of water from individual trays with this sampler. Significant differences in the physicochemical parameters contained in the samples taken by the depth sampler and pumping from the borehole delimited by the packers at the same depth are given by Laaksoharju et al. (1991).

Suction (surface) pumps are pumps located on the surface above the water level. These include centrifugal, piston, screw and peristaltic pumps. A big disadvantage of these pumps is that the height difference between the suction elements and the groundwater level in the borehole cannot be higher than 7 to 8 m and changes in groundwater chemistry are due to cavitation on the moving pump elements. Thus, the suction pumps have a relatively large technical limitation on shallow boreholes with groundwater close to the ground and are not suitable for determining a number of indicators, especially volatile substances.

Discharge pumps are located in a well below groundwater. These include:

Piston (inertial) pumps - based on the non-return valve principle - by means of a non-return valve located at the lower end of the sampling tube (water), the water is conveyed to the surface by a progressive oscillating movement of the tube in the well up and down. The efficiency of this type of pumps allows their use at depths up to 60 m.

The submersible pumps - most often the centrifugal and spindle pumps are widely available. Their limitation is usually a relatively large diameter and low head, the discharge height for submersible pumps ranges from 50 to 95 m.

In particular, limiting the discharge pumps is their size while maintaining sufficient discharge power. The limiting factor is also the need for a sufficient volume of sampled water in the well to run the pump.

Gas pumps utilize the energy of compressed gas (air) to yield a water sample to the earth's surface.

The air-lift is based on the principle of blowing compressed gas (usually air) into the borehole. The air pressure and the consequent reduction in the specific gravity (water density) of the water-gas mixture provide a discharge force to transport groundwater to the surface. During the mixing of gas with water there is a chemical violation of the natural state of water, for the vast majority of applications this method of collection is completely unsuitable.

The bladder pump is composed of a cylindrical vessel equipped with a flexible membrane. The propellant is pressurized gas, which is periodically injected into one part of the cylinder, expanding the membrane, and squeezing the sampled water through a check valve into the outlet line. Pumping speed can be changed by changing the pulse frequency using a three-way valve with a timer. This type of pump is suitable due to its small sampling device diameter and multi-level sampling. Another advantage is the separation of propellant from the sampled water itself by means of a membrane. Commercially produced gas diaphragm pumps can be used for sampling at depths up to 150 m.

The double-valve pump operates on a similar principle of compressed gas pulses that push the sampled medium into the outlet pipe. However, in the sampling chamber, there is no gas separating membrane from the sampled water, the chamber is separated from the sampled environment and from the outlet pipe by check valves and is periodically impregnated with propellant gas. The disadvantage of this system is the gasification and subsequent change in the chemical composition of the sampled water. This can be partially reduced by minimizing the interface between gas and pumped water. The advantage of this type of pump is a very small diameter (from 10 mm). For conventional pumps of this type, the maximum working height is up to 150 m.

General information on the suitability of basic types of samplers and sampling pumps is given in Table 5 of ISO 5667-18. Only underground closed samplers, gas diaphragm pumps and conditionally submersible pumps are suitable for groundwater abstraction for all types of indicators. While sampling with a sealed sampler does not change the composition of the groundwater, but as mentioned above, the sample in most cases does not represent the actual composition of groundwater in the rock environment.

-2 CZ 25775 Ul

Referenced literature:

Laaksohaiju, M., Ahonen, L., Blomqvist, R. (1991): Light-weight double packer equipment for water sampling and hydraulic measurements in deep drill holes. Geologian tutkimuskeskus Report YST-74. Espoo.

ISO 5667-18 (757051) Water quality - Sampling - Part 18: Guidelines for the sampling of groundwater at contaminated sites.

Sampling work in remediation geology. MoE Bulletin. Prague: Ministry of the Environment, 2007. Vol. 2. ISSN: 0862-9013.

The essence of the technical solution

Newly designed sampling equipment is by its technical nature included in the category of gas pumps. The principle of sampling is the closest to a gas diaphragm pump, but it is completely different from it by a design solution. The new sampling equipment is superior to the diaphragm gas pump due to, among other things, the higher structural strength and reliability of the materials used, which allows the sampling of water with a discharge height of more than 150 meters while maintaining the compact dimensions of the sampling device.

The designed offtake facility allows groundwater to be withdrawn from narrow-profile boreholes with a minimum diameter of 3.8 cm and / or boreholes whose yield is low and / or wells where the groundwater level is less than 150 meters and cannot be sampled with conventional sampling equipment. The described sampling device is not limited to narrow-profile boreholes, but can also be operated in boreholes with a wider drilling profile.

The basic principle of the sampler functionality is a hydraulic piston driven by compressed air. By cyclically vertically moving the piston within the body of the collection device, the water sample is drawn into the sample chamber, and the subsequent peristaltic movement of the piston is forced through the one-way valve through the transport tube to the earth's surface. The hydraulic piston inside the sampling device in the sampling cycle, where the piston decreases and the water sample is drawn into the sampling chamber, uses potential gravitational energy and thus actively contributes to obtaining a sample in the rock environment in places of low yield. When extruding a sample onto the Earth's surface, a one-way valve system is used to prevent the return of the already sampled sample to the output sample tube back to the collection device.

The sampling device is designed so that the water sample does not come into contact with air in any part of the sampling process and its chemical composition is not affected.

Only chemically inert materials: stainless steel DIN 1.4301, polyamide (PA), polyethylene (PE) and teflon (PTFE) are used for the construction of the body of the collection device and auxiliary components. No mechanically moving parts of the collection device are lubricated with organic or inorganic lubricants, which excludes secondary contamination of the water sample taken. The desired lubricity of the device components, in particular the internal surface of the sampling chamber and the piston, is achieved by high precision mechanical machining.

The body of the collection device consists of a steel cylinder with a diameter of typically 30 mm and a length of 600 mm. It is hollow in the middle and forms a sampling chamber (tube) with a wall thickness of 1.5 mm. At both ends of the collection device body, a solid, preferably steel, head with functional bore is connected to the sampling chamber. A steel hydraulic piston is slidably mounted in the central hollow part of the device, i.e. the body whose inner part serves as the sampling chamber. This piston is equipped with two PTFE guide rings for precise and smooth running at both ends and a PTFE sealing ring is located closer to the top. The surface of the piston and the inner part of the sampling chamber are polished to a high gloss for smooth piston operation and hydraulic tightness. In the lower part of the sampling device under the piston, the lower head is provided with one 5 mm wide bore - a channel that is terminated at the outlet outside of the device by a quick-coupling with a 6 mm diameter PA hose. Push-in quick-coupling fitting connected by a classical thread-3 CZ 25775 Union fitting. The drilling at the bottom of the sampling device opens below the hydraulic piston, is used to supply compressed air and moves to the upper position when compressed air pressure is applied. The quick coupler is located in the lower head in a recess - a cut-out cut at an angle of 20 ° from the body axis of the device so that it does not extend beyond the basic silhouette of the body of the collection device. In this way, it is well protected against damage when handling the collection device in a narrow well. Its slanted position makes it easy to connect and run the compressed air tubing outside the body of the collection device.

The upper head of the take-off device has two interconnected functional bores. The first bore serves to drain the sample extruded from the sample chamber above the hydraulic piston into the output sample tube. The opening of this bore is in the middle of the upper side of the upper head of the take-off device and is provided with a push-in one-way valve connected by a classic threaded fitting. The second bore is formed in a recess on the side of the upper head of the take-off device and serves to enter the sampled water into the sampling chamber above the piston. The outlet is provided with a one-way valve, which is located in the recess of the lower head of the collecting device similarly as a quick-action coupling on the lower head. The inlet one-way valve is turned downwards, which facilitates the flow of the water sample into the sample chamber and prevents solid particles released by abrasion from the well wall. Push-in push-in valves used on the top head prevent backflow of the sampled water during cyclic operation of the hydraulic piston.

On the outside of the sampling device body, two notches are grinded on the sides at the top and bottom of the head region to facilitate attachment of the otherwise smooth cylinder of the sampling device to the handling support rope or rod.

It is not always necessary to place the sampling device in the borehole at the required depth of collection, but only to a depth of about 20 meters below the piezometric height of the groundwater level in the sampled tray (collector, crack system). Only feed the supply tube to the required sampling depth. (Example: the sample tray is at a depth of 200 m below the ground surface, the piezometric level of a given tray is at 120 m below the ground surface. The supply sample tube is placed at a depth of 200 m, but the collection device can be placed at a depth of 140 m.) . This approach facilitates the pumping of the sample and saves the amount of compressed air consumed, as it is not necessary to displace the sample from the sampled depth, but from a lesser depth.

In addition to the sampling equipment itself, the supporting components and the sampling procedure are important for the water sampling itself. Pressure-resistant PA tubes are used for compressed air and sampled liquids to withstand a working pressure of at least 2.5 MPa. These hoses are normally supplied in rolls of 100 meters and can be adjusted using push-in couplings if necessary. A preferred solution has been found to be a 6 mm diameter tubing, which has a sufficiently low resistance to liquid flow but at the same time has a small volume. The compressed air source is a pressurized cylinder of 20 to 23 MPa or a high pressure compressor of 30 MPa. The inlet pressure of the compressed air to the sampling device is controlled by a pressure reducing valve depending on the sampling depth. A pressure of 1 bar is required for every 10 meters of the height of the extruded water column. For automatic application of pressure pulses at sampling, a pressure timer is preferably used, a device controlling the opening and closing of the crossover valve on the pressure bottle, or in the case of a compressor, a pressure timer controls its triggering. 2 intervals of different lengths can be set on the pressure timer. The first sets the length of application of the pressure impulse to the sampling device. With increasing depth of location of the sampling device in the borehole or increasing the number of offtake devices connected to one pressure source, it is necessary to extend the pressure interval appropriately to successfully displace the water sample on the earth's surface. The second pressure timer interval is idle. In the resting part of the sampling cycle, the pressure under the hydraulic piston in the sampling chamber is released and the piston drops to the lower position by its weight. A sample of water flows into the released area above the hydraulic piston. The length of the resting interval is controlled by the yield of the water source. The less abundant the sampled section of the rock, the longer the resting interval must be set to allow the sample to flow into the sample chamber. The length of both intervals is set experimentally based on the actual power of the sampling device.

-4CZ 25775 Ul

Due to the variability of the rock environment and the collectors, the length of individual intervals cannot be predicted in advance and fine-tuned during sampling.

The sampler itself embedded in the borehole is able to take a mixed groundwater sample. However, the demand for groundwater from individual depth horizons in the borehole is more frequent. In this case, the sampling device is placed between a pair of packers that isolates the selected horizon in the well. This arrangement allows for the collection of groundwater from individual collectors or fracture systems. To speed up sampling of multiple collectors in one borehole, it is possible to equip the borehole with a multi-hop system, and it is possible to sample several trays at once using multiple sampling devices. With a borehole diameter of 76 mm, it is possible in practice to collect up to 4 insulated trays simultaneously. The installation of a borehole with a multi-hop system with multiple sampling devices is technically and time-consuming and is therefore mostly used for long-term monitoring of groundwater in a borehole.

The method of sampling groundwater using a sampling device consists of several successive steps:

1) Attaching one or more collection devices to a desired position on a steel wire rope or a multi-link system rod using steel screw terminals.

2) Connect the input and output sample tubes to one-way valves at the top of the sampling device. The sampling input tube must be of such length that it reaches the desired sampling depth when the sampling device is embedded.

3) Attach the pressure hose to the push-in fitting on the bottom of the sampling device.

4) Embedding of the assembled sampling equipment including any demarcating packers to the required depth in the well.

5) Assembly and connection of the pressure source including the timer to the pressure hose leading to the sampling device. Pressure pulse power control depending on the depth of embedding of the sampling device in the borehole.

6) Setting the expected initial values of the pressure timer.

7) Start sampling by starting the pressure timer.

8) Adjustment of pressure timer interval values for optimum operation of the sampling device.

Basic terms and abbreviations used:

PA - polyamide

PE - polyethylene

PTFE - teflon packer - a device used to isolate a selected borehole section.

The rubber component of the packer is expanded by inflating and sealing the well borehole at a given location after embedding the packer in the borehole. By using multiple packers, more sections can be defined in the borehole. The use of multiple packers is referred to as a multi-pack system.

The sampling facility was successfully tested at 2 sites for in-situ groundwater sampling. It was a site of Melechov near Ledeč nad Sázavou, where sampling from the borehole in granite rock was tested. The second tested site was Stráž pod Ralskem, where the collection of Cenomanian sediments - sandstones - took place. The tests were successful in both cases and thanks to the above-described sampling device, the required groundwater sample was obtained from a depth of about 140 meters below the Earth's surface. In the case of the locality Stráž pod Ralskem, a unique sample of water was removed without breakage, making it possible to compare the rate of chemical influence during collection by conventional techniques used in the remediation of this site.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: Drawing of the sampling equipment for the collection of chemically unaffected groundwater samples from narrow-profile wells.

Figure 2: Diagram of the sampling device application at the borehole site.

- 5 CZ 25775 Ul

Examples of technical solutions

Example 1

The apparatus for collecting chemically unaffected groundwater samples from narrow-profile boreholes consists of the following components (Figure 1): two one-way socket valves 1, 2 for connecting the sample outlet tube 111 and the inlet sampling tube 112. At the top of the collection device 20 at the top 32 is a bore 3 is provided which connects the mouths of the valves 1, 2 to the sampling chamber 5. A notch 4 is ground on the outer surface of the upper head 32, by means of which the collection device can be securely attached to the carrying rope or rod. A similar notch 11 with the same functionality is located on the outer surface of the lower head 33 of the collection device. Inside the sampling chamber 5 a steel hydraulic piston 8 is inserted, which is provided with two guide rings 6, 9 and one Teflon sealing ring 7 for smooth operation. The hydraulic piston 8 is free to move in the sampling chamber 5 but is impermeable. A bore 10 is provided in the lower portion of the take-up device 20 in the lower head 33, which connects the sample chamber 5 to the socket 12 at a point below the hydraulic piston 8. A pressure hose 113 is connected to the socket connector 12, which is connected via a pressure timer 16 to the bottle. 18 with compressed air (Figure 2).

Figure 2 illustrates other necessary support components which are not necessarily part of the collection device itself, but are primarily used to handle and position the collection device 20 in the borehole and to perform the sampling method of the present invention. Figure 2 shows a sampling pattern from a borehole section defined by a pair of packers 21, 23. An electric wire rope reel 13 is used to lower the equipment into the borehole. It is seated on a stand equipped with a measuring wheel 14 to determine the depth of embedding. The packs 21, 23 are pumped in the borehole through the packer tubing 19 by means of a water pump 15. The packers 21, 23 defining the borehole section to be sampled are connected by a stainless steel tube 22. This is perforated in its central part and a groundwater sample is drawn in at this point. The tube 22 is connected to the inlet sampling tube 112 above the packer 21, which opens to the collection device 20. From the collection device 20, the groundwater sample is extruded through the outlet sampling tube 111 to the collection vessel 17. The sampling device 20 of this example is located outside the collection point. defined by packers 21, 23.

Example 2

The apparatus of Example 1, wherein the valve 2 is connected to the top head 32 in a recess 321 that is formed in the lower head 33 such that the valve 2 faces the lower head 33 and does not optically extend over the body edge 31. The push-in connector 12 is connected to the bottom Head 33 in recess 331, which is formed in lower head 33 so that clutch 12 is directed toward upper head 33 and does not optically extend over edge of body 31. Valve 2 and clutch 12 form an angle of 20 degrees to the longitudinal axis of body 31.

Example 3

The method of sampling using the collection device 20 of Example 1, wherein the collection device is located at a location defined by the packers 21, 23.

Industrial usability of technical solution

Future economic growth cannot do without the possibility of using underground rock structures and underground spaces to a greater extent and unconventionally. Today, a shallow part of the rock environment is used for the location of waste dumps of different character and deeper parts for the construction of underground gas storage facilities. In the future, the rock environment will be used to store not only food, archival materials and industrial stocks, but also to store excess energy, store CO ₂ emissions, build deep repositories of spent nuclear fuel and other very hazardous waste. For this purpose, it is necessary to determine the spatial and temporal changes of che-6C 25775 Ulmic composition of groundwater and gases caused by the influence of the rock environment by human activity.

Thanks to the above described sampling device, it is possible to take undisturbed representative samples of groundwater from narrow-profile exploration wells, even from large depths. The sampling equipment can be used for occasional water sampling and monitoring in the field of remediation geology, construction, water resources retrieval and hydrogeological and geological research and exploration work aimed at locating suitable sites for various types of storage.

Claims (10)

PROTECTION REQUIREMENTS An apparatus for collecting chemically unaffected groundwater samples from narrow-profile wells in low permeability rocks, characterized in that it consists of a hollow body (31), the upper end of which is provided with a head (32) with a bore (3) connecting it a valve orifice (1, 2) with a sampling chamber (5) forming the interior of the body (31), wherein a notch (4) is formed on the outer surface of the headhead (32) for attaching the device to the carrying rope or rod; provided with a lower head (33) with a bore (10) connecting the push-in fitting (12) to the sampling chamber (5), a notch (11) being formed on the outer surface of the lower head (33) furthermore, a steel hydraulic piston (8) provided with two guide rings (6, 9) and one Teflon ring (7) for leakage-free operation inside the sampling chamber (5) of the hydraulic piston (8), a pressure hose (113) is connected to the push-in connector (113) for connecting the device to the source (18) of the compressed air and to the one-way push-in valve. The inlet sampling tube (112) is connected to the one-way push-in valve (2) for taking the sample material from the tube (22) located at the collection point defined by the packers (21, 23). Device according to claim 1, characterized in that the valve (2) is connected to the head (32) in a recess (321) which is formed in the lower head (33) so that the valve (2) faces the lower head (33) and does not extend optically beyond the edge of the body (31). Device according to claim 1, characterized in that the coupling (12) is connected to the lower head (33) in a recess (331) which is formed in the lower head (33) so that the coupling (12) points towards the head (33) and does not extend optically beyond the edge of the body (31). Device according to claims 1 to 3, characterized in that the valve (2) and / or the coupling (12) make an angle of 20 degrees with the longitudinal axis of the body (31). Device according to claim 1, characterized in that the surface of the body (31) and the piston (8) is smoothed by mechanical treatment to increase the sliding action and avoid the need for the use of organic or inorganic lubricants. Device according to claim 1, characterized in that the device consists exclusively of chemically inert materials such as stainless steel DIN 1.4301, polyamide (PA), polyethylene (PE) and teflon (PTFE). Device according to claim 1, characterized in that the body (31) is formed by a steel cylinder having a diameter of 30 mm, a length of 600 mm and a wall thickness of 1.5 mm. -7 CZ 25775 Ul Device according to claim 1, characterized in that the tubes (111, 112 and 113) are made of polyamide, have a diameter of 6 mm and withstand a working pressure of up to 2.5 MPa. Apparatus according to claim 1, characterized in that the source (18) of the compressed air is a cylinder at a pressure of 20 to 23 MPa or a high-pressure compressor at a pressure of 30 MPa. The apparatus of claim 1, wherein the apparatus includes a pressure timer (16) for automatically applying pressure pulses when sampling.