Fluid thermodynamic characterisation device including a stacked ring seal, and method for assembling same

Abstract

The invention relates to a device for thermodynamic characterisation of a fluid, comprising a seal (31) for sealing a piston, the seal (31) comprising a stack of rings (71-75). The invention also relates to a method for mounting such a seal (31).

Description

[0001] Title: Description

[0002] THERMODYNAMIC FLUID CHARACTERIZATION DEVICE COMPRISING A SEAL

[0003] STACKED RINGS AND METHOD FOR ASSEMBLING SAME

[0004] Technical field

[0005] The invention relates to the field of thermodynamic characterization of a fluid, such as oil sampled during exploration or exploitation drilling.

[0006] State of the prior art

[0007] Conventional equipment for thermodynamic fluid analysis has a volume and mass that does not allow its transport to the sampling site, making it necessary to send samples to remote analysis laboratories.

[0008] Attempts have been made to miniaturize this equipment so that in situ analyses can be carried out.

[0009] In this context, a compact device has been proposed, described in document FR3001546A1, equipped with a compression chamber designed to receive a volume of fluid to be analyzed not exceeding 1 cm 3 This device includes a piston to modify the volume of the chamber. The piston is sealed by an annular seal.

[0010] Given the volume of the chamber and the pressure of the fluid in the chamber, which can reach 1000 bars, the seal undergoes deformations which can lead to measurement errors.

[0011] Statement of the invention

[0012] The invention aims to remedy the drawbacks of known thermodynamic characterization devices, in particular the drawbacks mentioned above.

[0013] For this purpose, the subject of the invention is a device for thermodynamic characterization of a fluid, comprising a body, a piston, a seal and a chamber intended to receive the fluid, the body forming a housing in which the piston is mounted to slide along a longitudinal direction so as to be able to modify the volume of the chamber, the seal extending radially between the piston and the body. According to the invention, the seal comprises a plurality of rings stacked along the longitudinal direction.

[0014] Such a seal improves the piston's tightness.

[0015] The stacking of rings makes it possible in particular to give the joint a rigidity and compactness capable of reducing its deformation when the device is used.

[0016] The invention thus makes it possible to reduce measurement errors, in particular when the device, also called a thermodynamic characterization “cell”, is sized to allow its transport, which assumes a chamber of relatively small volume and a relatively high fluid pressure in the chamber, typically up to 1000 bars.

[0017] The device can be implemented to characterize many types of fluid, including but not limited to hydrocarbons such as oil or gas.

[0018] In one embodiment, at least one of the rings includes a groove, or groove, configured to receive a portion of another of said rings.

[0019] Preferably, the groove extends circumferentially around the longitudinal direction.

[0020] In one embodiment, among the ring(s) that include a groove, one or more of these rings each have a V-shaped section.

[0021] Several materials can be used to make the rings.

[0022] It is preferred that one or more of said rings comprise a polymeric material, preferably comprising.

[0023] The polymer material of one or more rings may include fillers, which may be different from one ring to another.

[0024] By way of non-limiting example, one or more of said rings may comprise a material such as polyketone, e.g., polyetheretherketone, or polytetrafluoroethylene. In one embodiment, the rings comprise a first type of rings and a second type of rings stacked in an alternating manner.

[0025] Rings of the first type may comprise polytetrafluoroethylene loaded with glass fiber.

[0026] Rings of the second type may comprise graphite-filled polytetrafluoroethylene.

[0027] Of course, the seal can include, alternatively or additionally, rings made from other materials.

[0028] In one embodiment, the body comprises a shoulder configured to come opposite a first longitudinal end of the seal so as to prevent movement of the seal in a first direction along the longitudinal direction.

[0029] The device may comprise a retaining member configured to come opposite a second longitudinal end of the seal so as to prevent movement of the seal in a second direction along the longitudinal direction.

[0030] In one embodiment, the retaining member comprises a flange defining a retaining surface facing said second longitudinal end of the seal.

[0031] In one embodiment, the retaining member comprises a shim having peelable layers stacked along the longitudinal direction.

[0032] The shim preferably extends longitudinally between the second longitudinal end of the gasket and the retaining surface of the flange.

[0033] In one embodiment, the retaining member comprises a ring extending longitudinally between the shim and the second longitudinal end of the seal.

[0034] The ring is preferably made of bronze.

[0035] The invention also relates to a method of assembling, or mounting, such a device.

[0036] The method preferably comprises inserting the seal into the housing of the body. In one assembly embodiment provided for a retaining member comprising a shim as described above, the method comprises removing one or more of said layers of the shim so that the seal and the shim inserted into the housing define a longitudinal dimension equal to a reference dimension.

[0037] Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows.

[0038] Brief description of the drawings

[0039] The following detailed description refers to the attached drawings in which:

[0040] Fig. 1 is a partial longitudinal sectional view of a thermodynamic characterization device according to the invention, along a sectional plane passing through a translation axis of a piston of the device;

[0041] Fig. 2 is an enlargement of a portion of the device of Fig. 1, centered on the piston, the cut parts being shown without hatching to facilitate visualization of the references;

[0042] Fig. 3 is a half-sectional view of a seal of the piston of the device of Fig. 1, according to a sectional plane passing through the translation axis of the piston, the seal comprising several rings stacked along this axis, the cut parts being shown without hatching;

[0043] Fig. 4 is a half-sectional view of one of the rings of the seal of Fig. 3, along a cutting plane passing through the axis of translation of the piston, the cut ring being shown without hatching.

[0044] Detailed description of embodiments

[0045] Figure 1 shows a device 1 according to the invention, intended for the thermodynamic characterization of a fluid.

[0046] The device 1 comprises a fixed structure and a mobile structure, relative to the fixed structure, in a longitudinal direction D1. The direction DI defines a first direction SI of movement of the mobile structure, going from the top to the bottom of figure 1, and a second direction S2 going from the bottom to the top of figure 1.

[0047] In this non-limiting example, the fixed structure comprises different parts 3-6 assembled to each other in the manner illustrated in FIG. 1, the mobile structure comprising a piston 7 and a tie rod 8 secured to each other in longitudinal translation, that is to say in the direction D1.

[0048] With reference to Figure 2, which shows an enlargement of a part of these fixed and mobile structures, centered on the piston 7, the part 3 of the fixed structure, also called “body”, comprises an opening which passes through it from one side to the other in the direction Dl, so as to extend around an axis Al.

[0049] The opening of the body 3 comprises a bore 11 of axis Al and diameter XI which extends over a longitudinal portion of dimension X2, as well as a bore 12 of axis Al and diameter X3 which extends over a longitudinal portion of dimension X4.

[0050] In this non-limiting example, the dimensions XI, X2, X3 and X4 are respectively equal to 28 mm, 28 mm, 25 mm and 4.55 mm.

[0051] The diameter X3 of the bore 12 being less than the diameter XI of the bore 11, the body 3 forms a shoulder 13 defining an annular bearing surface which extends in a plane perpendicular to the direction Dl.

[0052] In this example, the opening of the body 3 comprises a counterbore 14 through which the bore 11 opens at a first longitudinal end of the body 3, also called the “upper end”. The counterbore 14 forms a shoulder 15 which defines an annular bearing surface extending in a plane perpendicular to the direction D1.

[0053] The opening of the body 3 also comprises a counterbore 17 through which the bore 12 opens at a second longitudinal end of the body 3, also called the “lower end”. The counterbore 17 forms a shoulder 18 which defines an annular bearing surface extending in a plane perpendicular to the direction D1.

[0054] The part 4 of the fixed structure, also called a “porthole” because it is configured to allow viewing of the interior of the chamber 41, is housed in the counterbore 17 of the body 3, so that a surface 21 of the porthole 4 rests on the annular surface formed by the shoulder 18.

[0055] The porthole 4 thus closes the opening of the body 3 at its lower end.

[0056] The piston 7 is received in a housing of the fixed structure here formed by the bores 11 and 12 and by the counterbore 14 of the body 3.

[0057] An annular seal 31 is arranged in the bore 11 so as to extend radially between the piston 7 and the surface of the body 3 which forms this bore 11. The structure of the seal 31 is described further below with reference to FIGS. 3 and 4.

[0058] Concerning the piston 7, this comprises a surface 32 arranged opposite the surface 21 of the porthole 4 (see figure 2).

[0059] In this example, a sensor 33 is housed in the piston 7 so as to have a surface 34 which is flush with the surface 32 of the piston 7. In a non-limiting manner, the sensor 33 is equipped with instruments including a strain gauge (not shown) and a platinum resistance probe (not shown) intended to measure the pressure and temperature of the fluid in the chamber 41.

[0060] These instruments are connected to a signal conditioning module (not shown) by cables (not shown) which pass through orifices 36 and 37 made respectively in the piston 7 and the tie rod 8.

[0061] The device 1 thus forms an annular chamber 41 which is delimited radially by the surface of the body 3 forming the bore 12. Longitudinally, the chamber 41 is delimited on the one hand by the surface 21 of the porthole 4 and, on the other hand, by the surface 32 of the piston 7 and the surface 34 of the sensor 33, the surfaces 21, 32 and 34 being in this example perpendicular to the direction D1.

[0062] The piston 7 is mounted to slide in the direction Dl, and consequently in the axis Al along which it extends.

[0063] Figures 1 and 2 show the piston 7 in a first position, in which the chamber 41 has a volume having a first value. A movement of the piston 7 towards the porthole 4, to a second position (not shown), makes it possible to reduce the volume of the chamber 41 to a second value lower than the first value.

[0064] In this non-limiting example, the volume of the chamber is of the order of 1.5 cm 3 when the piston 7 is in the first position and is substantially zero when the piston 7 is in the second position, the stroke of the piston 7 between the first and second positions being 3 mm.

[0065] Chamber 41 thus forms a compression chamber capable of containing a fluid under pressure.

[0066] In the example of Figure 1, the piston 7 is controlled using an actuation system comprising an electric motor equipped with an encoder (not shown).

[0067] The actuation system comprises a transmission mechanism configured to transform a rotary movement of a motor shaft (not shown) into a translation of the piston 7 along D1.

[0068] In this non-limiting example, the transmission mechanism comprises a screw 52 configured to be driven in translation along an axis A2, parallel to the axis A1, under the action of a nut 53. The drive shaft drives a screw (not shown), which cooperates with a wheel (not shown) secured to the nut 53, so as to form a gear of the wheel and worm type.

[0069] The screw 52 cooperates with the nut 53 which is integral with the part 6 of the fixed structure, so that a rotation of the nut 53 around the axis A2 causes a translation of this screw 52 along D1.

[0070] The transmission mechanism comprises in this example a lever arm 55 having a pivoting surface bearing on an axis 56 secured to the tie rod 8. The axis 56 defines an axis of rotation perpendicular to the direction D1 and passing through the translation axis A1. The lever arm 55 is thus connected to the tie rod 8 according to a pivot connection. In the example of FIG. 1, the pivoting of the lever arm 55 on the fixed structure is ensured by a connecting rod 57 arranged between one end of the lever arm 55 and the part 5, also called a “support”. Such a connecting rod 57 makes it possible to improve the distribution of loads during the movement of the piston 7. In a variant not shown, the lever arm 55 can be connected to the screw 52, ​​to the tie rod 8 or to the piston 7, as well as to the fixed structure of the device 1 according to any conventional technique not using such a connecting rod 57.

[0071] More generally, the transmission to the piston 7 of the translational movement of the screw 52 by the lever arm 55 makes it possible to multiply the force transmitted to the piston 7 and in particular to reduce the size of the engine.

[0072] The device 1 further comprises a play-compensating spring 61 formed by a stack of conical washers which are configured to exert a tensile force on the tie rod 8, and consequently on the piston 7, in the direction S2 of the direction D1.

[0073] Thus, when the piston 7 is moved in the direction SI under the action of the lever arm 55, the movable structure compresses the spring 61 which is dimensioned to maintain a load on this movable structure and on the lever arm 55, in order to prevent a play present in the transmission mechanism from causing measurement errors.

[0074] The device 1 also comprises circuits and valves, not shown, provided on the one hand to introduce a fluid sample into the chamber 41 for the purpose of analysis, for example, and, on the other hand, to evacuate the fluid from the chamber 41, in particular at the end of the analysis.

[0075] In a manner known per se, the device 1 comprises other organs, not shown, including, but not limited to:

[0076] - a system for heating the fluid contained in chamber 41, and / or

[0077] - a high-definition camera to study phase changes and / or sedimentations of the fluid contained in chamber 41, and / or

[0078] - a system for stirring the fluid contained in the chamber 41, for example by vibrations, and / or

[0079] - a system for cooling the fluid contained in chamber 41, and / or

[0080] - a gasometer connected to the chamber 41 in order to carry out additional tests. In general, the device 1 makes it possible to carry out thermodynamic analyses of a fluid such as a hydrocarbon oil, in particular by analyzing the phase behavior during a reduction in the volume of the chamber 41 under the action of a movement of the piston 7.

[0081] Such analyses can be carried out directly on the oil drilling site, for example, given the size and mass of the device 1 which facilitate its transport. In this example, the device 1 has a size of less than 0.1 m 3 and a total mass of around fifteen kg.

[0082] The invention relates more specifically to the sealing of the piston 7 and in particular to the structure of the seal 31 as well as to its assembly.

[0083] The following description refers to Figure 3 which shows the seal 31 in the free state, before assembly.

[0084] The seal 31 comprises a plurality of rings 71-75, i.e. parts each extending circumferentially around an axis which corresponds to the axis A1 when the seal 31 is mounted in the device 1.

[0085] The rings 71-75 are stacked along this axis and therefore along the direction DI to which it is parallel, so as to have a longitudinal dimension X5, or height, relatively large compared to the width X6 of the ring 71 of the seal 31.

[0086] In this non-limiting example, the seal 31 in the free state has a height X5 equal to 21.45 mm and a width X6 of 3 mm.

[0087] The rings 71 and 73 form respective longitudinal ends of the seal 31 by defining surfaces 81 and 82, respectively, which are perpendicular to the direction D1. The height X5 of the seal 31 corresponds to the distance along DI between the surfaces 81 and 82.

[0088] With reference to the section plane of Figure 3 which passes through the axis A1, the ring 71 has a generally rectangular section defining a radially external surface 83, a radially internal surface 84, said surface 81 which forms a longitudinally lower surface and a longitudinally upper surface 85. The surface 85 has a concavity defining a V-shaped annular groove (see Figure 3). More precisely, taking as reference a plane passing through the surface 81, the ring 71 has a longitudinal dimension which is maximum (cf. X7) radially at the surfaces 83 and 84, which is minimum (cf. X8) in a median radial position located equidistant from the surfaces 83 and 84, and which decreases monotonically from each of these surfaces 83 and 84 towards said median position. The groove formed by the surface 85 thus has a bottom located radially at the median position.

[0089] With reference to the ring 74 shown separately in Figure 4, this ring has a generally V-shaped section, defining a radially outer surface 91, a radially inner surface 92, a longitudinally lower surface 93 and a longitudinally upper surface 94.

[0090] The surfaces 91 and 92 are slightly inclined relative to the direction DI so as to present between them a width which is maximum (cf. Xll) at the level of the junction of these surfaces with the surface 94 and which is minimum (cf. X12) at the level of the junction of these surfaces with the surface 93.

[0091] The surface 94 of the ring 74 has a concavity having the same geometry as the surface 85 of the ring 71. Thus, the surface 94 of the ring 74 defines a V-shaped annular groove (see FIG. 4). Taking as reference a plane perpendicular to DI passing through the coordinate of the surface 93 longitudinally furthest from the bottom of the groove formed by the surface 94, the longitudinal dimension of the ring 74 is maximum (see X13) at the junction of the surfaces 91 and 92 with the surface 94, it is minimum (see X14) in a median position located equidistant from the surfaces 91 and 92, and it decreases monotonically from each of said junctions towards said median position. The groove formed by the surface 94 thus has a bottom located radially at this median position.

[0092] Concerning the surface 93 of the ring 74, this has a convexity of a shape complementary to the groove formed by the surface 85 of the ring 71. The ring 74 thus forms legs 95 and 96 which extend radially on either side of the groove formed by this ring 74 and which are directed longitudinally towards the top of figure 4.

[0093] In the example of Figure 3, each of the rings 74 and 75 of the seal 31 has a geometry identical to that which has just been described with reference to Figure 4, the preceding description applying by analogy to each of these rings.

[0094] With reference to the ring 74 adjacent to the ring 71 in Figure 3, the latter is arranged so that its longitudinally lower surface bears on the surface 85 of the ring 71, that is to say so that a longitudinally lower part of the ring 74 is received in the groove formed by the surface 85 of the ring 71.

[0095] The other rings 74 and 75 are stacked on top of each other in a similar manner and in such a way as to alternate the rings 74 and 75 (see Figure 3), so that a longitudinally lower portion of each of the rings 75 extends radially between the legs 95 and 96 of a respective ring 74.

[0096] Similarly, a longitudinally lower portion of each of the rings 74 extends radially between the legs formed by a respective one of the rings 71 and 75 (see Figure 3).

[0097] Similarly, a longitudinally lower portion of the ring 72 extends radially between the legs formed by one of the rings 74 (see Figure 3).

[0098] In this non-limiting example, the seal 31 comprises six rings 74 and five rings 75 stacked alternately.

[0099] Concerning the ring 72, this too has a generally V-shaped section, defining tabs 97 and 98 which delimit an annular cavity in which a lower end of the ring 73 is housed (see figure 3). The ring 72 has a longitudinally lower surface which has a convexity of a shape complementary to that of the groove formed by the longitudinally upper surface of the rings 74, so as to be received in the groove formed by the surface 94 of the ring 74 which is adjacent to it. The ring 73 has for its part an L-shaped section defining, opposite the surface 82, a longitudinal end bearing on the bottom of the groove constituted by the ring 72 in which it is received.

[0100] In this non-limiting example, rings 71-75 are all made of a polymeric material. More specifically, rings 71 and 73 comprise polyketone, rings 74 comprise glass fiber-filled polytetrafluoroethylene, and rings 72 and 75 comprise graphite-filled polytetrafluoroethylene.

[0101] With reference to figures 2 and 3, the device comprises a retaining member configured to bear on the surface 82 formed by the ring 73 of the seal 31.

[0102] In this example, the retaining member comprises a bronze ring 101, a shim 102 and a flange 103.

[0103] Longitudinally, the ring 101 extends between the seal 31 and the shim 102 and the shim 102 extends between the ring 101 and the flange 103.

[0104] Radially, the ring 101, the shim 102 and a longitudinally lower end of the flange 103 extend between the piston 7 and the bore 11 of the body 3.

[0105] The longitudinally lower end of the flange 103 forms a retaining surface 105 bearing on the shim 102. This retaining surface 105 is arranged opposite the surface 82 of the seal 31.

[0106] The flange 103 comprises a shouldered portion extending radially between the piston 7 and the counterbore 14 of the body 3 and bearing longitudinally on the shoulder 15 formed by the body 3.

[0107] The retaining member is in this example formed by the part 5 which is configured to keep the flange 103 resting on the shoulder 15 of the body 3.

[0108] In this example, the shim 102 comprises peelable layers stacked along the direction D1.

[0109] In a non-limiting manner, the layers of the shim 102 each have a thickness of five hundredths of a mm. The following description relates more specifically to the assembly of the seal 31 and the retaining member.

[0110] The flange 103, the shim 102 and the ring 101 are first fitted onto a dummy piston (not shown) which has an external geometry similar to the piston 7.

[0111] The seal 31 is in turn fitted onto the dummy piston, so that the surface 82 of the ring 71 comes to bear on the ring 101.

[0112] The subassembly formed by the dummy piston, the seal 31, the ring 101, the shim 102 and the flange 103 is then introduced into the body 3 to be housed in the bores 11 and 12, so that the seal 31 extends radially between the dummy piston and the bore 11, over the entire height of the seal 31.

[0113] In this example, the radial dimension between the piston - dummy piston and piston 7 - and the bore 11 is substantially equal to the width X6 of the seal 31 but it is less than the maximum width Xll of the rings 74 and 75 and of the ring 72 (see figure 4).

[0114] The insertion of the subassembly described above into the body 3 consequently causes radial crushing of the seal 31, in particular a folding back of the tabs 95 and 96 of each of the rings 74 and 75 which each grip the longitudinally lower part of a respective ring.

[0115] The seal 31 is thus deformed relative to its free state, which makes it possible to ensure the sealing function when the assembly is carried out with the piston 7. This deformation results in an increase in its height X5.

[0116] The shim 102 makes it possible to adjust, by removing one or more of its layers, the total height formed by the superposition of the seal 31, the ring 101 and the shim 102, as a function of the actual deformation of the seal 31, which is difficult to estimate by simulation.

[0117] In this example, the number of layers to be removed is determined from the total height measured when these different parts are mounted in the body 3 with the dummy piston as described above. When the desired thickness of the shim 102 is obtained by removing one or more of its layers, the seal 31, the ring 101, the shim 102 and the flange 103 are fitted onto the piston 7 and introduced into the body 3, in the same manner as with the dummy piston.

[0118] After assembly, the shoulder 13 of the body 3 prevents movement of the seal 31 in the direction S1 while the retaining member and in particular the flange 103 prevent movement of the seal 31 in the direction S2.

[0119] Of course, many variations can be made to the device described above. In particular, the seal may comprise rings in different numbers and / or having other geometries and / or made of different materials compared to the seal 31 of FIG. 3.

Claims

Claims 1. Device (1) for thermodynamic characterization of a fluid, comprising a body (3), a piston (7), a sealing joint (31) and a chamber (41) intended to receive the fluid, the body (3) forming a housing in which the piston (7) is mounted to slide along a longitudinal direction (Dl) so as to be able to modify the volume of the chamber (41), the joint (31) extending radially between the piston (7) and the body (3), characterized in that the joint (31) comprises a plurality of rings (71-75) stacked along the longitudinal direction (Dl).

2. Device (1) according to claim 1, wherein at least one of the rings (71, 72, 74, 75) comprises a groove (85, 94) configured to receive a portion of another of said rings, the groove (85, 94) preferably extending circumferentially around the longitudinal direction (D1).

3. Device (1) according to claim 2, wherein one or more of the ring(s) (74, 75) which comprise a groove (94) each have a V-shaped section.

4. Device (1) according to any one of claims 1 to 3, wherein one or more of said rings (71-75) comprise a polymeric material, preferably comprising fillers, for example a material such as polyetheretherketone or polytetrafluoroethylene.

5. Device (1) according to any one of claims 1 to 4, wherein the rings (71-75) comprise a first type of rings (74) and a second type of rings (75) stacked alternately, the rings (74) of the first type comprising for example polytetrafluoroethylene filled with glass fiber, the rings (75) of the second type comprising for example polytetrafluoroethylene filled with graphite.

6. Device (1) according to any one of claims 1 to 5, in which the body (3) comprises a shoulder (13) configured to come opposite a first longitudinal end of the seal so as to prevent movement of the seal (31) in a first direction (SI) along the longitudinal direction (Dl), the device (1) comprising a retaining member configured to come opposite a second longitudinal end of the seal so as to prevent movement of the seal (31) in a second direction (S2) along the longitudinal direction (D1).

7. Device (1) according to claim 6, wherein the retaining member comprises a flange (103) defining a retaining surface (105) opposite said second longitudinal end of the seal (31).

8. Device (1) according to claim 6 or 7, wherein the retaining member comprises a shim (102) comprising peelable layers stacked along the longitudinal direction (D1), the shim (102) extending longitudinally between the second longitudinal end of the seal (31) and the retaining surface (105 of the flange (103).

9. Device (1) according to any one of claims 6 to 8, in which the retaining member comprises a ring (101), preferably made of bronze, extending longitudinally between the shim (102) and the second longitudinal end of the seal (31).

10. Method of assembling a device (1) according to any one of claims 1 to 9, comprising inserting the seal (31) into the housing of the body (3).

11. A method according to claim 10, for assembling a device (1) including the features of claim 8, the method comprising removing one or more of said layers of the shim (102) so that the seal (31) and the shim (102) inserted into the housing (11) define a longitudinal dimension equal to a reference dimension.

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