Abstract:
This invention concerns a module for extracting samples in gas phase of compounds present in an underground working liquid, the extractor module including a receptacle for the liquid, associated with a device for stirring the liquid, a liquid inlet duct, a liquid evacuation duct, an auxiliary gas admission duct, and an outlet duct for delivering auxiliary gas and gas extracted from the liquid. The auxiliary gas admission duct and the evacuation duct include a common segment, for preventing the auxiliary gas from passing is provided in the evacuation duct downstream from the common segment in the liquid-passing direction.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a module for extracting samples in gas phase of compounds present in an underground working liquid. The invention also relates to an installation for analyzing gas samples and including such an extractor module. 
     U.S. Pat. No. 5,090,256 provides for an installation of this kind, in which the extractor module receives a drilling liquid from a pump fed from a head for taking liquid samples. The extractor module stirs the liquid to release the gases that are to be found therein. The released gases are collected from the extractor module for subsequent analysis in a device located downstream. 
     That extractor module presents the drawback of being capable of extracting only part of the gases contained in the liquid, and in particular it does not enable heavy hydrocarbons of C5 to C8 order to be extracted. 
     French patent document FR-A-2 799 790 provides a receptacle for extracting gas from liquid fed by a pump and evacuated by a delivery line. A pipe connects the receptacle to means for analyzing and measuring the extracted gas, and an inlet for a gas, air or inert gas, admits gas into the receptacle in order to adjust the gas entry flow rate. 
     That receptacle for extracting gas, and the installation in which it is provided, also present a certain number of drawbacks. 
     In practice, the gas inlet often becomes clogged, contrary to the looked-for effect. 
     It is necessary to cause a large volume of liquid to flow through the receptacle in order to extract a quantity of gas that is sufficient for analysis. 
     Finally, the large volume of liquid in the receptacle requires heater means to deliver a large amount of heat, consequently consuming a large amount of energy, whereas little electrical energy is available in the vicinity of the extractor module. 
     The invention seeks to obtain an extractor module and an installation including the extractor module that mitigate the drawbacks of the prior art. 
     SUMMARY OF THE INVENTION 
     To this end, a first aspect of the invention provides an extractor module for extracting gas samples of compounds present in an underground working liquid, the extractor module comprising: 
     a receptacle for said liquid, associated with means for stirring the liquid in the receptacle in order to extract the compounds in the gas phase from the liquid, and 
     connected to the receptacle when it is operating to extract gas: 
     at least one liquid inlet duct for admitting liquid into the receptacle; 
     at least one liquid evacuation duct for evacuating liquid from the receptacle; 
     at least one auxiliary gas admission duct for admitting auxiliary gas into the receptacle; and 
     at least one outlet duct for delivering auxiliary gas and gas extracted from the liquid, for connection to gas reception. 
     The module is characterized in that the auxiliary gas admission duct and the liquid evacuation duct include at least one common segment for passing the liquid and the auxiliary gas. Means for preventing the auxiliary gas from passing is provided in the liquid evacuation duct downstream from the common segment in the liquid-passing direction. 
     By means of the invention, the efficiency with which gas is extracted from the volume of liquid contained in the receptacle is increased, both in terms of quantity and in terms of quality. It thus becomes possible to extract gaseous or liquid hydrocarbon compounds from the liquid in the range methane to octane, including aromatic compounds such as benzene-toluene-ethylbenzene-xylenes (BTEX) together with other gases such as hydrogen sulfide. 
     The inventors have also discovered that there could exist a dead volume of gas extracted from the liquid that stagnates in the receptacle, only a small quantity of which could be taken for sending to the means for analyzing the extracted gases. By means of the invention, this dead volume in the receptacle is decreased and the auxiliary gas is given a large area of contact with the liquid, thus encouraging the extraction of gas. The increase in extraction efficiency makes it possible to dimension the extractor module in a manner that is much more suitable for the quantity of gas needed for analysis purposes, thus making it possible to reduce the dimensions of the extractor module for a given volume of analyzed gas. In addition, there is no longer any need to supply so much heat for heating the liquid since a smaller volume of liquid is to be heated. The extractor module and the installation are thus made more efficient and less expensive. 
     In an embodiment of the invention that serves to reduce the extent to which the materials contained in the liquid clog and settle in the auxiliary gas admission duct, the common segment communicates with the receptacle via a fluid-passing window for passing the auxiliary gas and the liquid, and having, in its bottom portion, at least one edge lying substantially in a plane. Naturally, this fluid-passing window can be provided in any liquid evacuation duct and is independent of other characteristics. 
     In an embodiment of the invention that is simple to implement, provision is made for the window to have a profile that is rectangular. 
     In order to prevent the auxiliary gas admission duct from being dirtied by the liquid, provision is made in an embodiment of the invention for the auxiliary gas admission duct to open out into the liquid evacuation duct at a portion thereof that is situated so as to be substantially sheltered from splashes of liquid coming from the receptacle. 
     In an embodiment of the invention, adapted to rotary stirring of the liquid, the stirring means comprises a rotary stirrer and the auxiliary gas admission duct opens out into the liquid evacuation duct at a portion situated further upstream than downstream in the direction of rotation of the rotary stirrer. 
     In an embodiment of the invention, the auxiliary gas admission duct opens out into the liquid evacuation duct in a portion lying at a distance from the receptacle. 
     In an embodiment of the invention that facilitates liquid flow in the receptacle, the liquid evacuation duct slopes downwards relative to the receptacle. 
     An embodiment of the invention makes provision for the auxiliary gas admission duct to present both a segment for coupling to the liquid evacuation duct and an auxiliary gas feed segment connected to the coupling segment and bent relative thereto in a direction having a component parallel to the direction in which the liquid evacuation duct extends in the vicinity of the coupling segment, and for the coupling segment to open out into the liquid evacuation duct via a section that is larger than the section of the feed segment, thus enabling any splashes of liquid to be trapped away from the gas feed segment. 
     In an embodiment of the invention, the auxiliary gas feed segment in the vicinity of the coupling segment is directed to feed the auxiliary gas in the same direction as the direction in which liquid is evacuated in the liquid evacuation duct. 
     In an embodiment of the invention that enables an extractor module to be obtained that is compact, the auxiliary gas admission duct forms a top extension of a bottom rectilinear segment of the duct forming the liquid evacuation duct, the auxiliary gas admission duct and the liquid evacuation duct being adjacent to the receptacle and opening out into it through a common fluid-passing window, a liquid deflector being provided above the fluid-passing window in the auxiliary gas admission duct. 
     In order to make the extractor module more compact, the receptacle, the auxiliary gas admission duct, the liquid evacuation duct, and the liquid inlet duct are constituted by a single piece. 
     An embodiment of the invention that is simple to implement makes provision for the means for preventing the auxiliary gas from passing into the liquid evacuation duct downstream from the common segment in the liquid-passing direction to comprise a siphon in the liquid evacuation duct. 
     In order to ensure that the siphon is compact, in an embodiment of the invention, it is made beneath the portion of the liquid evacuation duct that is coupled to the receptacle. 
     In order to make it possible where necessary to clean, inspect, or observe a portion of the liquid evacuation duct, provision is made in an embodiment of the invention for the liquid evacuation duct to include a passage leading to the outside above the level of the siphon and downstream therefrom in the liquid-passing direction. 
     An embodiment of the invention that makes it easier to collect the extracted gases and to deliver them to the gas receiving means, provision is made for the receptacle to comprise a body surmounted by a removable collar with the gas outlet duct being provided thereon. Naturally, this characteristic can be provided in any module for extracting gas samples of compounds present in an underground working liquid, and is independent of other characteristics. 
     In order to cause the liquid or the water to drop back into the receptacle, an embodiment of the invention makes provision for the gas outlet duct to open out into the bottom portion of the collar in contact with the inside of the body of the receptacle, making an angle that is inclined towards the inside of the body of the receptacle. Naturally, this characteristic can be provided in any module for extracting gas samples of compounds present in an underground working liquid, and is independent of other characteristics. 
     An embodiment of the invention makes provision for the gas outlet duct to comprise a first segment for coupling to the collar and which is extended beside the gas outlet by a segment of a section that is smaller than the smallest section of the coupling segment, so as to reduce the risk of underground working liquid passing to the analyzer module and detect the clogging of the outlet duct. Naturally, this characteristic can be provided in any module for extracting gas samples of compounds present in an underground working liquid and is independent of other characteristics. 
     In a second aspect; the invention provides an installation for analyzing gas samples, the installation including an extractor module as described above, in which the liquid inlet duct is connected to a module for taking underground working liquid and in which the gas outlet duct is coupled to an analyzer module for analyzing gas samples. 
     An embodiment of the invention requiring little expense makes provision for the auxiliary gas admission duct to communication with the atmosphere, and the gas-sample analyzer module includes gas suction means. 
     Another embodiment of the invention, enabling the extracted gas to be urged towards the gas outlet duct, makes provision for the auxiliary gas admission duct to be connected to a source of compressed auxiliary gas. 
     For more effective heating of the liquid contained in the receptacle, an embodiment of the invention that can be provided in any installation for analyzing gas samples and independent of other characteristics makes provision for a liquid heater module which is interposed, outside the extractor module, in the liquid circuit between the liquid taking module and the extractor module. 
     In order to reduce the risks of water reaching the gas sample analyzer module, provision is made in an embodiment of the invention that can be provided in any gas sample installation and that is independent of other characteristics, for the gas outlet duct to be connected to the gas-sample analyzer module via a water-trapping module. 
     An embodiment of the invention makes provision for the collar to be connected in a leaktight manner to the body of the receptacle via a support plate of the extractor module, which plate includes a passage between the inside of the body of the receptacle and the inside of the collar. 
     In an embodiment of the invention, the water-trapping module is provided with means for maintaining its temperature at a predetermined value. 
     An embodiment of the invention makes provision for the analyzer module to be connected to the water-trapping module via a gas duct comprising a first segment for coupling to the water-trapping module, extended beside the gas outlet by a second segment of an inside section smaller than the inside section of the coupling first segment. By means of this embodiment, the risk of the underground working liquid passing to the analyzer module and the risk of the gas outlet duct becoming blocked are reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood after reading the following description made with reference to the accompanying drawings, given purely as non-limiting examples, and in which: 
         FIG. 1  is a diagram of an installation for analyzing samples of gas in accordance with the invention; 
         FIG. 2  is a diagrammatic vertical section of a first embodiment of the extractor module in accordance with the invention; 
         FIG. 3  is a diagrammatic plan view of the  FIG. 2  extractor module; 
         FIG. 4  is a diagram of an inside portion of the extractor module of  FIGS. 2 and 3 , including a fluid-passing window; 
         FIG. 5  is a diagrammatic vertical section showing a second embodiment of the extractor module in accordance with the invention; 
         FIG. 6  is a diagrammatic vertical section showing a third embodiment of the extractor module in accordance with the invention; 
         FIG. 7  is a diagrammatic vertical section showing a fourth embodiment of the extractor module in accordance with the invention; and 
         FIG. 8  is a diagrammatic vertical section of a collar forming part of the extractor module in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is described below with reference to an installation for taking liquid that has come to the surface while drilling an oil well, thus constituting an underground working liquid, also referred to as an underground working fluid. Liquid in the form of mud is sent to the bottom of the well and is then raised by pumping, as is known to the person skilled in the art. The liquid that comes up to the surface is charged with gas and other substances present in the well, and that need to be extracted from the liquid that has come up to the surface in order to obtain information about the layers of ground through which the borehole passes, their composition, their richness, and their hydrocarbon content, and also about their drilling conditions. Naturally, the underground working liquid could equally well be any other liquid, such as, for example, water or oil raised from underground. 
     The extraction installation of the invention comprises a module for taking liquid from the borehole, e.g. comprising a motor-driven pump unit (not shown) enabling the liquid that comes from the well to be sucked in via a liquid-sampling head  2  or strainer which is pushed into the well, and a hose  3  for connection to the sample-taking module  1 . The sample-taking module  1  sends the liquid that has been taken from the well via an outlet hose  4  to the inlet  5  of a liquid heater module  6 . The sample-taking module  1  is constituted by a frame carrying a motor and gearbox unit with two outlets driving firstly a peristaltic pump for taking the liquid from the well via the hose  3  and the head  2  at a rate lying in the range 0.15 liters per minute (λ/min) to 0.5 λ/min and delivering it to the hose  4 , and secondly a Bowden cable connected to the strainer  2  and driving a rotary scraper of the strainer, so as to prevent it from becoming clogged, as is described in U.S. Pat. No. 5,090,256. 
     By way of example, the liquid heater module  6  includes a heating resistance element (not shown) that is powered electrically. The inlet  5  for liquid entering the module  6  is located in the bottom thereof, while the outlet  7  for liquid leaving the module  6  is in the top thereof. By way of example, the power rating of the module  6  may lie in the range 1 kilowatt (kW) to 3 kW, thus enabling the liquid that goes from its inlet  5  to the outlet  7  to be raised to a selected temperature lying in the range 25° C. to 120° C., for example, and typically lying in the range 60° C. to 90° C. The working volume of the module  6  lies, for example, in the range 0.5 liters (λ) to 2.5 λ. The outlet  7  for liquid leaving the module  6  is connected via a hose  8  to the inlet duct  9  for liquid entering the gas-sample extractor module  10  of the invention. The heater module  6  is separate from the extractor module  10 . The module  10  has a gas outlet duct  11  connected via a gas outlet hose  12  to an inlet access  13  of a gas-sample analyzer module  14 . 
     In  FIG. 2 , the extractor module  10  of the invention comprises a receptacle  16 , for example a receptacle having a body in the form of a circular cylinder about an axis  15  of symmetry. Naturally, any other geometrical shape for the body of the receptacle  16  could be provided. In the description below, the axis of symmetry  15  of the receptacle  16  is assumed to be vertical. The liquid inlet duct  9  opens out into the receptacle  16  in the bottom portion thereof, for example and as shown, into the bottom of the cylindrical side surface  17  of the receptacle  16 . In embodiments that are not shown, the liquid inlet duct  9  opens out into the bottom  18  of the receptacle  16 . A washer  20  is supported by the upper portion  19  of receptacle  16 . The washer  20  has a circular recess to receive an O-ring gasket  22 . The washer also has a through-hole  23  to allow a fastener (not shown) to secure the washer  20  to a receptacle support plate  24 . Upper portion  19  of the receptacle  16  is held to face the support plate  24  in a leaktight manner by the O-ring  22 . 
     Beside the plate  24  of the support, at a distance from the edge  19 , there is provided a removable collar  25  held by any suitable means against the plate  24 , and in leaktight manner, by a sealing O-ring  26 . The collar  25  has a top surface  27  on which there is fixed an electric motor  28  whose central rotor  29  passes through central recesses  30 ,  31  allowing gas to pass through and provided respectively within the collar  25  and the support plate  24 . The gas outlet duct  11  communicates with the recess  30  within the collar  25 . The shaft  29  is connected inside the receptacle  16  to a rotary stirrer  32 , e.g. formed by a rod extending the shaft  29  and having one or more blades  33  fixed thereto and dipping into the receptacle  16 . The shaft  29  and the stirrer rod extend along the axis  15  of the receptacle  16 , for example, and the blades  33  are radial relative to the axis  15 , for example, and there are four of them, or two as shown. One or more liquid deflectors  34 , e.g. provided in the form of vertical plates, are fixed inside the side wall  17  above the level of the blades  33  so as to create turbulence inside the receptacle  16  due to the liquid therein rotating. A washer  35  is fixed inside the side surface  17  close to the edge  19  to protect the top of the receptacle  16  against splashes of liquid due to the stirring. A protective washer  36  is also fixed to the shaft  29  slightly beneath the washer  35 , the protective washer  36  having an outside diameter that is smaller than the inside diameter of the washer  35  so as to enable the shaft  29  to be inserted in the receptacle  16 . Naturally, the protective washer  36  could equally well be situated at the same level as or above the washer  35 . 
     An external duct  37  for evacuating liquid from the receptacle  16  is fixed to the side surface  17  of the receptacle  16  via a connection portion  38  between them. The connection portion  38  defines a portion  39  of the side surface  17  in which there is provided a fluid-passing window  40  for passing liquid and gas. The window  40  is provided above the blades  33  of the stirrer  32  and the deflectors  34 , and beneath the inside washer  35 . The fluid-passing window  40  has a bottom edge  41  and a top edge  42 . The bottom edge  41  is at a distance from the connection portion  38 . 
     As shown in  FIG. 4 , the bottom edge  41  lies in a plane perpendicular to the axis of symmetry  15  of the cylindrical side surface  17  of the receptacle  16 , as does the top edge  42 . By way of example, the window is rectangular. In embodiments that are not shown, the bottom edge  41  and/or the top edge  42  are contained in part only in such a plane. The stirrer  32  is controlled in such a manner as to cause the liquid to rise above the bottom edge  41  so that the liquid passes into the duct  37 . The plane portion of the bottom edge  41 , or the entire bottom edge when it occupies a plane as shown, ensures to a large extent that the window  40  does not become blocked by the liquid. By way of example, the window  40  may have a through section of area lying in the range 1 square centimeter (cm 2 ) to 6 cm 2 . 
     The external liquid extraction duct  37  has a rectilinear segment  43  for extracting liquid from the receptacle  16 , connected firstly to the connection portion  38  and secondly to a vertical segment  44  for coupling and downward extension. The liquid outlet segment  43  slopes downwards, e.g. at an angle lying in the range 25° to 45° relative to the axis  15 . The extension segment  44  is downwardly connected to an S-shaped segment  45  having two bends, with an upward first bend  45  and a downward second bend  46 . The bottom portion  47  of the downward second bend  46  is at a level that is higher than the top portion  48  of the upward first bend  45 , thus implementing a siphon for the liquid. The bottom portion  47  of the second bend is also below the liquid outlet segment  43 . The downward second bend  46  is connected at its bottom end to a segment  49  for evacuating liquid externally, e.g. by gravity into a waste vessel or the like (not shown). Thus, when liquid fills the upward first bend  45  from the top portion  48  of said first bend  45 , gas coming from the extension segment  44  is prevented from passing towards the downward second bend  46 , and any gas coming from the liquid evacuation segment  49  is prevented from passing towards the extension segment  44 . The segments  43 ,  44 , and  49 , and the bends  45  and  46  may be circularly cylindrical, for example. Naturally, any other means could be provided for making the segments connected to the extension segment  44  gastight. 
     A duct  50  for introducing an auxiliary gas is connected to the liquid outlet segment  43  of the receptacle  16  between the extension segment  44  and the connection portion  38  of the receptacle  16 . The auxiliary gas may be air, or any inert gas, such as nitrogen, for example. 
     The dimensions of the extractor module  10  can be as follows, for example. The liquid outlet segment  43  has a diameter lying in the range 15 millimeters (mm) to 55 mm and a length lying in the range 50 mm to 150 mm. The volume of the receptacle  16  lies in the range 40 cubic centimeters (cm 3 ) to 300 cm 3 , and the liquid reaches the liquid inlet duct  9  at a rate lying in the range 0.15 λ/min to 0.5 λ/min. The speed of rotation of the stirrer lies in the range 1500 revolutions per minute (rpm) to 3500 rpm. By way of example, the auxiliary gas admission duct  50  has a diameter lying in the range 2 mm to 6 mm, and is at a distance lying in the range 40 mm to 140 mm from the connection portion  38 , and possesses an angle of inclination lying in the range 30° to 50° relative to the axis  15  of the receptacle  16 , for example. 
     When the stirrer  32  is put into operation, the liquid introduced via the inlet duct  9  is stirred in the receptacle  16  and sent into the liquid evacuation duct  37  by passing through the window  40 . The liquid sent into the liquid evacuation duct  37  moves down the liquid outlet segment  43 , and then along the extension segment  44 , the first bend  45 , and once its level exceeds the bottom portion  47  of the second bend  46 , it moves down the liquid evacuation segment  49 . Because of the stirring of the liquid in the receptacle  16 , gas is extracted from the liquid. The auxiliary gas introduced via the introduction duct  50  is prevented from leaving the extension segment  44  because of the gas seal means provided downstream therefrom, so it is sent into the liquid outlet segment  43 , through the window  40 , into the receptacle  16  and through the washer  35 , the recess  31 , and the recess  30  so as to leave via the outlet duct  11 . Thus, the auxiliary gas serves to entrain the gas or gases extracted from the liquid. In  FIG. 2 , a duct for admitting auxiliary gas into the receptacle  16  is formed by the auxiliary gas introduction duct  50  and by the portion of the liquid outlet segment  43  that lies between the outlet of the auxiliary gas introduction duct  50  into the liquid outlet duct  43  and the connection portion  38 . There exists a common segment  51  constituted in  FIG. 2  by the portion of the liquid outlet segment  43  that extends between the connection portion  38  and the outlet of the auxiliary gas introduction duct  50  into the liquid outlet duct  43 , which has liquid flowing through it in one direction and auxiliary gas in the opposite direction, thereby likewise encouraging the extraction of gas from the liquid. Thus, the auxiliary gas flow circuit and the liquid flow circuit present a common segment outside the receptacle  16 . The auxiliary gas introduction duct  50  is coupled to a source of compressed auxiliary gas for allowing the gas extracted from the liquid to be transferred towards the gas outlet duct  11 . In a variant, the auxiliary gas introduction duct  50  is connected to the atmosphere and the gas-sample analyzer module  14  has a pump or other means for sucking in auxiliary gas together with the gas extracted from the liquid. 
     In  FIGS. 2 and 3 , the auxiliary gas introduction  50  opens out into the liquid outlet segment  43  in the bottom portion thereof, close to the connection segment  44 . In  FIG. 3 , it can be seen that the auxiliary gas introduction duct  50  opens out into the liquid outlet segment  43  at a portion thereof that is situated further upstream than downstream in the direction  52  of rotation of the blades  33  of the stirrer  32 . The auxiliary gas introduction duct  50  has a segment  53  for coupling to the liquid outlet segment  43  and an auxiliary gas feed segment  54  coupled to said segment  53 . The segment  54  is bent relative to the segment  53  to extend parallel to the direction in which the liquid outlet duct  43  extends and to extend upwards, so that the auxiliary gas penetrates into the feed segment  54  in the same direction as the direction in which liquid flows in the liquid outlet segment  43 . The section  55  allowing the auxiliary gas to pass from the coupling segment  53  is greater than that of the feed segment  54 . This disposition shelters the segment  54  from any splashing by the liquid present in the liquid outlet segment  43  to the right-hand side of the chain-dotted line  43   a  which represents the limiting trajectory for such splashing. 
     In  FIGS. 5 ,  6 , and  7 , the stirrer  32 , the rotor  29 , and the portions situated above the receptacle  16  are not shown for reasons of clarity. Naturally these portions should be present in the same manner to enable the extractor module to operate. The description below relates to those portions which differ for  FIGS. 1 to 4 . 
     In the embodiment shown in  FIG. 5 , the liquid outlet segment  43  is substantially horizontal and opens out fully firstly into the side surface  17  of the receptacle  16  and secondly into the coupling segment  44 . The auxiliary gas introduction duct  50  opens out into the liquid outlet segment  43  in a top portion thereof between the coupling segment  44  and the portion  38  for connection to the receptacle  16 . The fluid-passing window  40  is formed by the connection portion  38 , for example. 
     In the embodiment shown in  FIG. 6 , a duct  37   a  is adjacent to the side surface  17  of the receptacle  16 , is vertical, and communicates with the inside of the receptacle  16  via the fluid-passing window  40 . The portion of duct  37   a  situated beneath the top edge  42  of the window  40  forms the liquid outlet segment  43  of the receptacle  16  and the coupling segment  44 , while the portion of duct  37   a  situated above the bottom edge  41  of the window  40  forms the auxiliary gas admission and introduction duct  50 . A deflector  56  is provided in the duct  37   a  above and close to the top edge  42  of the window  40  so as to deflect downwards any splashes of liquid coming from the receptacle  16 . The common segment between the liquid outlet duct and the auxiliary gas admission duct  50  is formed by the portion of the duct  37   a  that is adjacent to the fluid-passing window  40 . 
     In the embodiment shown in  FIG. 7 , the auxiliary gas introduction duct  50 , the liquid outlet segment  43 , the coupling segment  44 , and the receptacle  16  are analogous to the embodiments shown in  FIGS. 2 to 4 . The first bend  45  comprises a rectilinear segment  57  forming the top portion  48  of the upward first bend  45  and coupled firstly at right angles to the coupling segment  44  and secondly at right angles to an upward liquid outlet segment  58  having a vertical wall  59  fixed to the segment  57  at a distance from the coupling segment  44 . The top edge  60  of the wall  59  forms the bottom portion  47  of the second bend  46 . A wall  61  is connected to the wall  59  to form the liquid evacuation segment  49 , a liquid outlet window  62  being provided in the bottom portion  63  coupling the wall  61  to the wall  59 . The first bend  45  and the second bend  46  as formed in this way, the wall  59 , and the wall  61  all lie beneath the liquid outlet segment  43 , a portion of the wall  61  being vertically in alignment with a generator line of the connection portion  38  of the side surface  17  of the receptacle  16 . The wall  61  joins the coupling segment  44  via a peripheral wall  64  surrounding the wall  59  and having a top edge  64   a  that is higher than the edge  60 . The top edge  64   b  of the wall  61  is at a distance from the bottom  18  of the receptacle  16  and at a distance from the liquid outlet segment  43 , thereby defining a passage  64   c  leading to the outside, making it possible, where necessary, to insert a cleaning tool. In addition, this embodiment makes it possible to obtain an extractor module having a structure that is compact and in a single piece. 
     In  FIG. 8 , the gas outlet duct  11  passes through the side wall  65  of the collar  25  and is extended outwards as a segment  66  coupled to the collar  25  and slopes upwards at a determined angle  66   a . The coupling segment  66  is circularly cylindrical, for example, having a diameter lying in the range 2 mm to 10 mm. The coupling segment  66  is connected at its end remote from the collar  25  to a segment  67  of inside cross-section that is smaller than that of the coupling segment  66 . A hose  68  of inside cross-section greater than that of the segment  67  is coupled to, and for example surrounds, the free end of the segment  67 , and plunges into a receptacle  69  for trapping the water contained in the incoming gas. The gases leave the water-trapping receptacle  69  via the gas outlet duct  12  which is connected to the gas-analyzer module  14 . The gas duct  12  has a first segment  70  coupled to the water-trapping module  69 , the segment  70  being extended towards the gas outlet by a second segment  71  of inside section smaller than that of the coupling segment  70 , and in turn coupled to the analyzer module  14  via a third segment  72  of the gas duct, of section greater than that of the segment  71 . 
     The invention thus makes it possible, with good efficiency, to extract the gas contained in the liquid that is introduced into the extractor module, making it particularly suitable for use in continuous analysis of gas brought to the surface while drilling a borehole.