US20170260856A1

US20170260856A1 - Device for sampling a pressurised fluid, equipped with means for increasing the volume of the sampling chamber

Info

Publication number: US20170260856A1
Application number: US15/529,296
Authority: US
Inventors: Jean-Paul CRABEIL; Thierry WALRAVE
Original assignee: Flodim Sarl
Current assignee: Flodim Sarl
Priority date: 2014-11-25
Filing date: 2015-11-05
Publication date: 2017-09-14
Also published as: WO2016083092A1; FR3028880B1; FR3028880A1; EP3224452A1

Abstract

A device for sampling a fluid, includes a sampling chamber including a first piston driven by the fluid, and an additional device configured to increase the volume of the sampling chamber. The sampling chamber serves as both a sampler and also as a container for the sampled fluid and it can also be used as a cell for the analysis of the fluid.

Description

The invention relates to the technical field of exploration and exploitation of underground environment, such as the operation of gas reservoirs (gas storage/withdrawal, exploitation of conventional or unconventional gas or hydrocarbons) and monitoring of these operations (contamination of operations on aquifers). The invention relates in particular to the field of monitoring of geological sites comprising oil or gas hydrocarbons.
In particular, the invention relates to fluid sampling devices, and more particularly to a device for sampling fluids under pressure in a well, a pipe, a tube, a duct, a reservoir or the like.
Fluids present in underground environments need to be sampled via wells to determine their composition, in order to characterize the geological reservoirs affected by these wells and their evolution over time during the industrial process of storage and/or production.
To implement these methods, it is therefore necessary to have a device for taking fluids under pressure in a well drilled through a geological formation. Such a device is called sampler or withdrawer.
FTS (Flow Through Sampler) samplers are known, making it possible to obtain fluid samples from a well drilled through a geological formation. Such a device consists of a sample chamber with a spring-loaded valve at each end. A locking mechanism connects the valves and keeps them open together. Above the chamber, there is a clock to program the closing time, and a triggering mechanism to release the valves. The lower end includes means for allowing the fluid to penetrate. At the top, there is a cable grip for attaching a cable.
U.S. Pat. No. 5,945,611 discloses a device for taking fluids under pressure in a pipe, a pipe, a duct or the like. The device comprises a plurality of pistons, a body having a common passage, in which said pistons are slidably mounted, a side inlet port and a side exit port located within said passage and communicating with the pipeline, said inlet and outlet ports located such that movement of the pistons may cover and uncover said inlet and outlet ports.
U.S. Pat. No. 5,896,926 discloses a device for in situ sampling underground aquifer fluids under static conditions without disturbing the surroundings but comprising a “packer” for isolating the sampling system with the zone located above it, and an in-situ pumping system located within said sampler to “suck” the fluid into the sampling chamber.
Also known from French patent application FR 2999224 (WO 2014/087061) is a sampling device comprising, on the one hand, a piston controlled by a spring bathing in an oil chamber for sampling the fluid and, on the other hand, a second piston for expelling the fluid during transfer. The device is held in the open or closed position by the compressed spring housed in the oil-filled chamber. The oil contained in the chamber of the spring makes it possible to damp the decompression effect and to carry out the sampling without jerk. The device allows the recovery of the sampled fluid thanks to the mechanical action of a solid piston through a manual valve. This device also has the advantage of being able to be lowered in the open position in the underground environment, in order to allow a complete filling of the sampling chamber.
In order to recover the sampled fluid and to transport the sample to be analyzed, these sampling devices require the use of means for extracting the fluid from the sampling chamber and for conditioning the fluid drawn in a dedicated container. These means are complex, may alter the collected fluid (leakage, pollution of the fluid . . . ) and require manipulations.
The invention relates to a device for sampling a fluid comprising a sampling chamber comprising a first piston driven by the fluid and additional means for increasing the volume of the sampling chamber so as to adjust the pressure in the Sampling chamber. Thus, the sampling chamber serves as a sampler but also as a container for the withdrawn fluid and may also serve as a cell for fluid analysis.
The invention relates to a device for sampling at least one pressurized fluid comprising at least one sampling chamber comprising an internal volume for receiving said fluid, said sampling chamber comprising a first piston adapted to be displaced by said fluid. Said sampling chamber comprises additional means for increasing the volume of the sampling chamber.
According to the invention, said sampling chamber is a transport container for said fluid.
According to one embodiment of the invention, said additional means for increasing the volume of said sampling chamber comprise a compensating piston serving as a stop for said first piston and means for adjusting the position of said compensation piston.
According to one feature of the invention, the means for adjusting the position of said compensation piston are hydraulic means.
According to one aspect of the invention, said compensating piston has a stroke representing between 0.1 and 20% of the volume of sampled fluid.
Advantageously, said sampling device comprises a lower chamber disposed below said sampling chamber and has in the lower part of said sampling chamber a fitting for removably fixing said sampling chamber and said lower chamber, said fitting comprising means for passing a fluid between said sampling chamber and said lower chamber.
Preferably, said compensation piston essentially slides within the fitting around an inner cylinder.
In addition, said sampling device may include a sampling actuation system for opening or closing said sampling chamber.
According to an alternative embodiment of the invention, said actuating system comprises motorization means opening and closing said sampling chamber and electronic or mechanical control means of said motorization means.
Advantageously, said electronic control means comprise a clock and/or communication means and/or at least one temperature sensor and/or at least one pressure sensor and/or at least one CCL sensor and/or at least one gamma ray sensor.
According to one feature of the invention, said sampling chamber is fixed in a removable manner, below said actuating system.
According to one aspect of the invention, said sampling chamber has an upper valve for allowing or inhibiting the passage of said fluid into said sampling chamber, said upper valve being arranged above the first piston.
Advantageously, said sampling device comprises from one to five sampling chambers, preferably from one to three sampling chambers. In addition, the invention relates to the use of a device according to the invention for producing a sample of a fluid in an underground formation. For this use, the following steps are carried out:

- a) said sampling device is lowered with said sampling chamber closed in said underground formation;
- b) withdrawing said fluid from said sampling chamber of the sampling device by opening said sampling chamber for a predetermined time;
- c) pulling said sampling device to the surface with said sampling chamber closed; and
- d) recovering said closed sample chamber containing said fluid as a sample of said fluid.

Advantageously, during the sampling step, the compensation piston is held in an upper position, and in the recovery step of the sampling chamber, the compensation piston is lowered in a lower position.
Preferably, said fluid is conveyed within the closed sampling chamber.
According to one aspect of the invention, it is carried out a further step of analyzing said fluid contained in said sampling chamber.
According to an alternate embodiment of the invention, before the analyzing step, it is carried out a further step of conditioning said sampling chamber substantially at the temperature and pressure conditions of said underground formation.
Advantageously, said sample is taken for the monitoring of a CO2 storage site, a site for exploring or exploiting conventional or non-conventional hydrocarbons, or a geothermal site.

Other characteristics and advantages of the device according to the invention will appear on reading the following description of non-limiting examples of embodiments, with reference to the accompanying drawings and described hereinafter.

FIG. 1 illustrates the sampling device according to the invention before the fluid is sampled.

FIG. 2 illustrates the sampling chamber and the lower chamber of the sampling device according to the invention before the fluid is sampled.

FIG. 3 illustrates the sampling chamber and the lower chamber of the sampling device according to the invention after the fluid has been sampled.

FIG. 4 illustrates the sampling chamber of the sampling device according to the invention after the fluid has been sampled.

FIG. 5 illustrates the sampling chamber of the sampling device according to the invention for the transport of the fluid.

FIG. 6 illustrates the intermediate connection of the sampling device according to the invention.

FIG. 7 illustrates the sampling chamber of the sampling device according to the invention equipped with covers for transporting the fluid.

The present invention relates to a device for sampling at least one pressurized fluid, also called a sampler.
The sampler according to the invention comprises at least one sampling chamber defining an internal volume for receiving the fluid to be sampled. During sampling, the sampling chamber is filled with the fluid to be sampled. Then, when the sampling is complete, i.e. during the ascent of the sampler to the surface, or during the transport of the fluid, the sampled fluid is contained within this sampling chamber. The sampler according to the invention further comprises additional means for increasing the volume of the sampling chamber so as to adjust the pressure in the sampling chamber. The additional means for increasing the volume of the sampling chamber make it possible to reduce the pressure in the sampling chamber (in the case of a compressible fluid) or to create a gas cap above the fluid (in the case of an incompressible fluid), in particular when the sampling chamber comprises the fluid to be sampled. These additional means make it possible to limit the risks associated with the transport of pressurized equipment; thus, it is no longer necessary to extract the sampled fluid for its analysis, which makes it possible to use the sampling chamber as a container for transporting the sampled fluid (sampled fluid transporting bottle).
In addition, the sampler may comprise the following means, alone or in combination:

- A system for actuating the sample, which opens and closes the sampler, so as to allow or prevent the introduction within the sampler of the fluid to be sampled from the outside environment. The actuating system is preferably located above the sampling chamber.
- A lower chamber, preferably located below the sampling chamber. The lower chamber communicates with the sampling chamber so as to allow fluid transfer between the sampling chamber and the lower chamber.
- Means for attaching a cable, the cable making it possible to lower and pull up the sampler in a well or a pipe, a tube, a conduit, a tank, etc.

The sampling chamber is formed by a cylindrical envelope in which a first piston moves. The first piston is displaced by the sampled fluid: the pressure of the sampled fluid causes the first piston to move down. The sampled fluid is therefore contained within in the cylindrical envelope between the upper part of the sampling chamber and the first piston.
According to one embodiment of the invention, the additional means for increasing the volume of the sampling chamber comprise a compensation piston and means for adjusting the position of the compensation piston. In a lower position of the first piston, i.e. at the end of the sampling and during the transport of the sampler, the first piston is in abutment against a compensating piston. The compensating piston is controlled by adjustment means so as to vary the pressure within the sampling chamber. The means for adjusting the position of the compensating piston position the compensating piston in the upper position during sampling and during pulling the sampler to the surface. The means for adjusting the position of the compensating piston position the compensation piston in the lower position for the transport of the sample. With the first piston abutting the compensating piston, and in view of the pressure of the fluid drawn in the sampling chamber, the lowering of the compensation piston causes the first piston to be lowered.
According to one embodiment of the invention, during the preparation prior to descent, a fluid, for example oil, is injected under the compensation piston until it protrudes, for example of approximately 15 mm, which makes it possible to create an (oil) buffer on which the first piston comes to rest when it is in abutment with the compensating piston. Once the tool has been brought up to the surface, this (oil) buffer is evacuated, allowing the sample to be transported to the laboratory at a pressure less than that of the sampling, or even zero (all depends on the quantity of dissolved gas recovered by the sampler. Thus, the internal volume containing the sampled fluid increases, which makes it possible to reduce the pressure in the sampling chamber (in the case of a compressible fluid) or to create a gas cap above the fluid (in the case of an incompressible fluid). Preferably, this layer of gas or gas cap has a small volume with respect to the volume of the sampling chamber. For this purpose, the stroke of the compensating piston may represent between 0.1% and 25% of the sampled volume, or even more, preferably between 0.1 and 20% of the sampled volume withdrawn. This adjustment of the pressure makes it possible to limit the risks associated with the transport of a pressurized equipment; it is therefore no longer necessary to extract the sampled fluid for its analysis, which makes it possible to use the sampling chamber as a transport container for the sampled fluid and as a PVT cell since it is possible to put the sample back to the underground conditions.
According to one embodiment of the invention, the position of the compensation piston may be regulated by hydraulic means; the piston is moved by injecting and withdrawing oil.
According to one embodiment of the invention, a system for actuating the sample allows the opening and closing of the sampler. The actuating system may be comprised in a cylindrical envelope. Preferably, this opening and this closure are achieved by a valve, called upper valve, located above the first piston. The upper valve is driven by the actuating system, when the sampler is in the desired position in the well for sampling. The actuating system comprises motorization means, in particular at least one electric motor capable of driving the upper valve. The actuating system further comprises means for controlling the motorization means. The control means control the motorization means when the sampler is in the desired position. The control means may be mechanical control means operated from the surface by a user. Alternatively, the control means may be electronic. The electronic control means may comprise means for real-time communication with means located at the surface so as to inform the user of the conditions within the well. According to a first alternate embodiment, the electronic control means may comprise an automatic clock, which will trigger the control of the motorization means at a predetermined instant. According to a second alternate embodiment, the control means and the information returned in real time can enable the specialist to trigger the sampling once the position of the sampler in the well has been determined. The control means may comprise one or more sensors to determine the position of the sampler in the well. The sensors integrated in the control means may comprise one or more temperature sensors, one or more pressure sensors, one or more CCL sensors (Casing Collar Locator, this type sensor allowing to determine the position of the casing joints in a well), one or more gamma ray sensors, etc. Alternatively, these two alternate embodiments may be associated, and an automatic clock mechanism may be coupled to different sensors. In order to withstand high temperature and high pressure conditions, the electronic control means may be integrated into a Dewar vase type heat shield which is a container designed to provide very good thermal insulation. This tube may be in the form of a double-layer glass or metal container. It may be regarded as two thin-walled containers intertwined with one another. The narrow space between these two containers is almost entirely devoid of air, and the near vacuum prevents conduction and convection of heat. In addition, the pressure sensor may be a Quatzdyne sensor or equivalent, which is a high-precision sensor and may withstand temperatures up to 200° C.
According to one embodiment of the invention, the sampling chamber is releasably secured, for example by a threaded connection, to the actuating system in order to be able to isolate the sampling chamber, to form a transport container.
According to one embodiment of the invention, the lower chamber is in communication with the sampling chamber. The lower chamber may be comprised in a cylindrical envelope. The outer diameter of the lower chamber may be substantially the same as the outer diameter of the sampling chamber, for example by a threaded connection. According to one embodiment of the invention, the lower chamber is in communication with the sampling chamber by means of a fitting, called intermediate fitting. The fitting allows the lower chamber and the sampling chamber to be fixed in a removable manner. Thus, the sampling chamber may be isolated from the lower chamber to form a transport container.
The fitting includes means for passing a fluid from the sampling chamber to the lower chamber. The fluid passing means prevent the passage of the fluid in the opposite direction from the lower chamber to the sampling chamber. The fluid passing means may comprise a lower cylinder, a nozzle screw, and a valve system. Advantageously, the lower chamber has a volume greater than the volume of the sampling chamber so as to enable complete transfer of the fluid initially contained in the sampling chamber to the lower chamber. Furthermore, the assembly may be constituted in such a way as to ensure a slow passage of the transfer fluid, which makes it possible to ensure that the PVT (pressure, volume, temperature) characteristics of the underground fluid are not changed.
The compensation piston is movable with respect to the fitting. Preferably, the compensation piston is movable essentially within the fitting, so that in a lower position the compensating piston does not protrude from the fitting whereas in the upper position the compensating piston protrudes with respect to the fitting. The height of the protrusion substantially corresponds to the stroke of the compensating piston.
FIG. 1 illustrates the sampling device prior to sampling the fluid, according to a non-limiting embodiment of the invention. The sampling device is substantially cylindrical in shape and comprises, from top to bottom, three compartments: a control compartment 20 comprising an actuating system, a sampling chamber 3 and a lower chamber 13.
The illustrated control compartment 20 comprises, in a non-limiting manner:

- an electric motor 19 for starting or stopping the sampling,
- a control axis 18 transmitting the movement of the electric motor 19,
- a lower tip 21 of the control compartment 20 closing the lower part of the control compartment 20,
- an engine cradle 22 for supporting the electric motor 19,
- an upper tip 23 of the control compartment 20 closing the upper part of the control compartment 20,
- a watertight passage 24, in particular for electric cables,
- a fitting 25 of the control compartment 20 with control means (not shown), for example electronic or mechanical control means, and
- a fitting 17 of the control compartment 20 with the sampling chamber 3, in order to detachably fix the control compartment 20 to the sampling chamber 3.

The illustrated sampling chamber 3 includes in a non-limiting manner:

- an upper valve 1 for opening or closing the sampling chamber, that is to say to enable or to prevent the filling of the sampling chamber 3; the upper valve 1 is driven by the actuating system, in particular by the motorization means 19; when the upper valve 1 is open, the fluid penetrates laterally through openings (oblong in the illustrated embodiment) provided in the body of the sampler (above the upper valve 1), passes through the upper valve 1 and penetrates in the sampling chamber 3,
- an upper tip 2 of the sampler closing the upper part of the sampling chamber 3 with the upper valve 1,
- a first piston 4, which is in an upper position before the fluid is sampled, is pressed onto upper tip 2 and therefore emptying the space between the first piston 4 and the upper tip 2;
- an intermediate fitting 9, located in the lower part of the sampling chamber and which makes it possible to fix in a removable manner the sampling chamber 3 to the lower chamber 13,
- a compensating piston 5, movable relative to the intermediate fitting 9, which is an upper position before the fluid is sampled, by means of a fluid (oil) located between the compensation piston 5 and the intermediate fitting 9, and
- a flap 10 fixed to the intermediate fitting 9 and which allows passage of the fluid from the sampling chamber 3 to the lower chamber 13.

The illustrated lower chamber 13 comprises, in a non-limiting manner:

- a lower tip 14 of the sampler closing the lower chamber 13,
- a closed bottom nose 15 which is fixed to the lower tip 14, which is at the lower end of the sampler, and has a substantially conical shape, and
- a lower valve 16 making it possible to empty the lower chamber 13.

Before the fluid is sampled (FIG. 1 and FIG. 2), the first piston 4 is pressed against the upper nozzle 2, the volume of the sampling chamber 3 between the first piston 4 and the intermediate fitting 9 comprises a filling fluid, such as oil, and the volume of the lower chamber 13 is empty or comprises air. In the pressed position of the first piston 4 to the upper tip 2, a substantially conical surface of the protruding piston 4 penetrates into a substantially conical hollow surface of the upper tip 2.
During the sampling of the fluid, the fluid enters the sampling chamber 3 by the upper valve 1. The sampled fluid exerts a force on the first piston 4 which moves down, and the sampled fluid begins to fill the volume of the sampling chamber 3 between the upper tip 2 and the first piston 4. The lowering of the first piston 4 causes a displacement of the filling fluid from the sampling chamber 3 to the lower chamber 13 through the intermediate fitting 9 and the flap 10.
Once the sampling is complete and the sampler has returned to the surface (FIG. 3 and FIG. 4), the first piston 4 is in abutment against the compensating piston 5 which is in the upper position. The sampling chamber 3 then only includes the sampled fluid. All the filling fluid is then in the lower chamber 13.
At the surface, the sample is prepared (FIG. 5) by keeping the sampling chamber 3 only, dismantling the control means 20 and the lower chamber 13. In order to allow the safe transport of the pressurized fluid, a gas pad is formed within the sampling chamber 3 by lowering the compensation piston 5, enabling an increase in the volume of the sampling chamber 3.
An example embodiment of the intermediate fitting 9 is illustrated in detail on FIG. 6. This intermediate fitting 9 may be composed of two valves 7 a and 7 b, equipped with a throttle 27, a drain valve 8, a compensation piston 5, an inner cylinder 6, a nozzle screw 26 and a flap 10, which is in turn composed of a body, a spring 28, a ball 12 and a calibration screw 11.
During the preparation prior to descent, a fluid, preferably oil, is injected under the compensating piston 5 until it protrudes, for example by about 15 mm, thereby creating a buffer (of oil) on which the first piston 4 comes to bear when the latter is in abutment against the compensation piston 5. This (oil) buffer, once the sampler has been drawn to the surface, is disposed of, allowing the sample to be transported to the laboratory at a pressure less than that of the sampling, or even zero (depending on the quantity of dissolved gas withdrawn by the sampler).
In one embodiment of the invention, the sampler may be prepared, as illustrated on FIG. 1 and FIG. 2, before any descent into a well, by carrying out the following steps:

- Step 1: vacuum is created above the first piston 4, for example by connecting the inlet of the upper valve 1 to a vacuum pump; in this way, the first piston 4 is pressed against the upper tip 2.
- Step 2: the compensation piston 5 is put in its upper position, by carrying out the following steps:
  - The drain screw 8 is unscrewed and then becomes a filling screw, and the drain screw 8 is replaced by a hose which dips into an oil container.
  - The valve 7 a is unscrewed, and replaced by a hose connected to the lower part of an oil container, and in an upper part of this container, a hose is connected to a pump capable of making vacuum or pressure.
  - Vacuum is first created in the intermediate fitting 9 and then the valve 7 b is opened, which sucks the oil through the filling hose and fills the volume under the compensation piston 5. Once this volume is filled, the valve 7 b is closed and the vacuum pump is stopped.
  - The compensation piston 5 is then pushed by injecting oil under pressure, for which purpose the valve 7 b is closed; the oil hose may then be disconnected and replaced by the drain screw 8, the pressure pump is connected to the oil container and the compensating piston 5 is moved out of the desired distance (e.g. 15 mm); the injection is then stopped, the oil hose is disconnected and the valve 7 a is screwed back. Air contained under the compensation piston 5 is then evacuated and an oil buffer is created under the compensating piston 5.
- Step 3: the volume of the sampling chamber 3 is filled with oil under the piston 4.
- Step 4: the whole intermediate connection 9 is screwed into the sampling chamber 3.
- Step 5: the lower chamber 13 is screwed onto the intermediate connection 9.
- Step 6: the lower tip 14 is screwed with its valve 16 on the lower part of the lower chamber 13.
- Step 7: vacuum is made in the lower chamber 13, for example by means of a vacuum pump connected to the lower valve 16.
- Step 8: the lower nose 15 is fixed to the lower tip 14 of the sampler.
- Step 9: the whole control compartment 20 is placed and fixed on the sampler via the fitting 17 of the control compartment 20 to the sampling chamber 3.

According to one embodiment of the invention and as illustrated on FIG. 3 (on which the control compartment is not shown), at the desired depth, the opening of the upper valve 1 is triggered via the Electric motor 19. The pressure exerted on the upper part of the piston 4 by the fluid to be sampled causes the piston 4 to move, whereby the oil contained under the piston 4 is transferred from the sampling chamber 3 to the lower chamber 13 via a nozzle created in the nozzle screw 26 and contained in the flap 10.
The function of the flap 10 equipped with its ball 12, slightly calibrated by the calibration screw 11 which presses the spring 28, is double: first, it prevents the transfer of oil by gravity when the sampler is lowered; secondly it opens to compensate for the expansion of the volume of oil created by the raising of the oil temperature during the descent.
When the piston 4 comes into abutment with the compensation piston 5, the latter compresses the small volume of oil injected before the descent, and, once the balance of the pressures has been established, stops movement of the piston 4.
After a predetermined time, the upper valve 1 is then closed via the electric motor 19 and the sampler may be drawn up.
According to one embodiment illustrated on FIG. 4, FIG. 5 and FIG. 7, in order to form the transport container for the sample, when the sampler is drawn to the surface, the cable head is first disconnected from the electronic compartment. Then, the electronic compartment of the control compartment is disassembled. Then, the sampling assembly (sampling chamber and lower chamber) from the is disconnected from the control head assembly.
According to an alternate embodiment, a verification of the sampled volume may be carried out after this disassembly. For example, verification may involve weighing the complete sampler prior to descent and after the ascent, the difference in weight indicating whether the sampler is full or not.
The pressure in the sampler chamber 3 of the sampler may represent a hazard. In order to limit the risks associated with the transport of pressurized equipment, it is possible to substantially reduce this pressure by creating a gas cap.
On the one hand, the gas cap is achieved by adjusting the position of the compensation piston 5, bringing it into its lower position. Since the compensation piston 5 is pushed by the first piston 4, the pressure in the oil chamber is equal, for example, to three times the pressure in the upper chamber of the sampler, in view of the ratio of the surfaces of the first piston 4 and the compensation piston 5.
On the other hand, the gas cap may be achieved by the temperature difference. Indeed, the final pressure contained in the sampler is influenced by the final temperature. This temperature has an influence on both the oil and the sampled liquid. Since the volume of the lower chamber 13 is greater than that of the sampling chamber 3, the oil contained in the lower chamber 13 represents no risk. Moreover, a sample taken at a high temperature (for example 200° C.) is no longer at this temperature once the sampler has been drawn to the surface; the final pressure of the fluid at the surface is therefore no longer the same as that of the bottom, which is safe.
According to one embodiment, in order to reduce the pressure inside the sampler, the following steps may be carried out:

- Step 1: the lower chamber 13 of the intermediate fitting 9 is unscrewed to check whether the oil transfer is complete or not (FIG. 4).
- Step 2: the drain screw 8 of the intermediate fitting 9 is disassembled and replaced by a drain hose connected to a drainage container.
- Step 3: the valve 7 b of the intermediate fitting 9 is unscrewed, the first piston 4 is then free to push back the compensation piston 5, which makes it possible to drain the volume of oil injected before the descent between the compensation piston 5 and the intermediate fitting 9 (FIG. 5).
- Step 4: the flap 10 is unscrewed from the intermediate fitting 9.
- Step 5: a lower cover 29 is screwed onto the intermediate fitting 9 to replace the lower chamber 13, as well as an upper protective cover 30 for protection of the upper valve 1 (FIG. 7). The sampler is then conditioned for its transport, in particular for shipment to an analysis laboratory.

In an alternate embodiment, the sampler comprises several sampling chambers. For example, the sampler may comprise two or three sampling chambers. According to one embodiment of the invention, several assemblies comprising an actuating system, an upper valve, a sampling chamber and a lower chamber are assembled one below the other. Such a sampler allows for several consecutive samplings to be achieved at different depths, without having to draw to the surface the sampler between the samplings.
The sampler according to the invention is particularly suitable for sampling fluids in deep wells, for example greater than 3000 m, under high pressure and high temperature conditions. The sampler according to the invention may be provided for sampling a fluid in pressures up to 650 bars and more and at temperatures close to 200° C. and higher.
The sampler according to the invention may be used in the field of monitoring a CO₂storage site, a geothermal site, a site for exploring or exploiting hydrocarbons, oils or gases, conventional or non-conventional, for example for a shale gas site.
The invention also relates to the use of a sampling device for producing a fluid sample in an underground environment, in which the following steps are carried out:

- a) The sampling device, with the sampling chamber 3 closed, is lowered into a well (or a pipe, a duct, a reservoir, etc.) of the underground environment, in particular by means of a cable fixed on the actuation system of the sampler;
- b) When the sampler is at the predetermined position (detected by mechanical or electronic means), the fluid is withdrawn into the sampling chamber 3 of the sampling device by opening the sampling chamber 3, for example by means of the actuation means which actuates the opening of the upper valve 1;
- c) Drawing the sampling device to the surface with the sampling chamber 3 closed, in particular by means of a cable; and
- d) collecting the sample chamber 3 containing the fluid as a transport container; for example, according to one embodiment of the invention, the sampling chamber 3 is separated from the drive system and from the lower chamber 13, and a gas cap is generated in the sampling chamber.

The collection of the sampling chamber as a transport container makes it possible to avoid any extraction and reconditioning of the sampled fluid, which may be a source of deterioration thereof: leakage, pollution . . . .
The gas cap is achieved by adjusting the position of the compensation piston. For example, the gas cap may be achieved by maintaining the compensation piston in the upper position during the steps of descent, sampling and ascent, and by lowering the compensation piston in the lower position during the recovery step.
The use of the device according to the invention may also comprise a step of analyzing the sampled fluid. The sampled fluid is transported, in the sampling chamber, from the sampling site to the analysis laboratory. Prior to this analysis step, it is possible to condition the sampling chamber substantially under the conditions of temperature and pressure of the underground environment. Thus, the sampling chamber of the sampler is used for sampling, as a transport container and as a PVT (pressure, volume, temperature) analysis cell.
In the description and in the drawings, the following reference signs are used:

- 1 upper valve
- 2 upper tip of sampler
- 3 sampling chamber
- 4 first piston
- 5 compensation piston
- 6 inner cylinder
- 7 a, valves
- 7 b
- 8 drain valve
- 9 intermediate fitting
- 10 flap
- 11 valve calibration screw
- 12 flap ball
- 13 lower chamber
- 14 lower tip of the sampler
- 15 bottom nose
- 16 lower valve
- 17 fitting sampler/control compartment
- 18 control axis
- 19 electric motor
- 20 control compartment
- 21 lower tip of control compartment
- 22 engine cradle
- 23 upper tip of the control compartment
- 24 watertight passage
- 25 fitting control compartment/electronic control means
- 26 nozzle screw
- 27 throttle valve
- 28 valve spring
- 29 upper transport cover
- 30 lower transport cover

Claims

1. A device for sampling at least one pressurized fluid, comprising at least one sampling chamber including an inner volume for receiving said fluid, said sampling chamber comprising a first piston capable of being displaced by said fluid, wherein the sampling chamber comprises an additional device configured to increase the volume of the sampling chamber.

2. The device according to claim 1, wherein said sampling chamber is a container for transporting said fluid.

3. The device according to claim 1, wherein said additional device configured to increase the volume of said sampling chamber comprises a compensation piston serving as a stop for said first piston and a system configured to adjust a position of said compensation piston.

4. The device according to claim 3, wherein the a system configured to adjust the position of said compensation piston is a hydraulic system.

5. The device according to claim 3, wherein said compensation piston has a stroke representing between 0.1 and 20% of the volume of the sampled fluid.

6. The device according to claim 1, further comprising a lower chamber located below said sampling chamber, and, in a lower part of said sampling chamber, a fitting for releasably securing said sampling chamber to said lower chamber, said fitting having a system configured to pass fluid between said sampling chamber and said lower chamber.

7. The device according to claim 6, wherein said additional device configured to increase the volume of said sampling chamber comprises a compensation piston serving as a stop for said first piston and a system configured to adjust a position of said compensation piston, and wherein the compensation piston slides within said fitting around an inner cylinder.

8. The device according to claim 1, wherein said sampling device comprises a sampling actuation system for opening or closing said sampling chamber.

9. The device according to claim 8, wherein said actuating system comprises a motor opening and closing said sampling chamber and an electronic or mechanical control system of said motor.

10. The device according to claim 9, wherein said electronic control system comprises at least one of the following: a clock, communication system, a temperature sensor, a pressure sensor, a CCL sensor, a gamma ray sensor.

11. The device according to claim 8, wherein said sampling chamber is fixed in a removable manner, below the actuating system.

12. The device according to claim 1, wherein said sampling chamber comprises an upper valve for allowing or preventing the passage of fluid in said sampling chamber, said upper valve being disposed above the first piston.

13. The device according to claim 1, wherein said sampling device comprises one to five sampling chambers.

14. A method a for producing a sample of a fluid in an underground environment with a device according to claim 1, the method comprising:

a) lowering the sampling device in said underground environment with the sampling chamber closed;

b) sampling fluid within the sampling chamber of the sampling device by opening the sampling chamber for a predetermined time;

c) drawing the sampling device to the surface with said sampling chamber closed;

d) recovering the closed sampling chamber.

15. The method according to claim 14, wherein, said sampling chamber comprises a compensation piston serving as a stop for said first piston and a system configured to adjust the position of said compensation piston, the compensation piston is held, during fluid sampling, in an upper position, and the sampling chamber is, in the recovering step, displaced in a lower position by the compensation piston.

16. The method according to claim 14, wherein the fluid is conveyed while being in the closed sampling chamber.

17. The method according claim 14, further including a step of analyzing the fluid contained in the sampling chamber.

18. The method according to claim 17, further including, before the analysis step, a step of conditioning said sampling chamber at the temperature and pressure conditions of the underground environment.

19. The method according to claim 14, wherein the sample is taken for monitoring a CO₂storage site, a site for exploring or exploiting conventional or unconventional hydrocarbons, or a geothermal site.